| 1. |
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| 2. |
- Lundblad, Linda, et al.
(author)
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Processing in prefrontal cortex underlies tactile direction discrimination: An fMRI study of a patient with a traumatic spinal cord lesion.
- 2010
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In: Neuroscience letters. - : Elsevier BV. - 1872-7972 .- 0304-3940. ; 483:3, s. 197-200
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Journal article (peer-reviewed)abstract
- We have investigated cortical processing of tactile direction discrimination (TDD) in a patient with unilateral tactile disturbance due to spinal cord lesion. The patient R.A. (male, 45 years old), suffers from a traumatic dorsal column lesion at the level of Th XI-XII on the right side. He was instructed to report the direction of 2mm long skin pull stimulations applied in a proximal or distal direction on his right or left lower legs during functional magnetic resonance imaging (fMRI). Although R.A. considered himself to have nearly normal tactile sensibility, testing showed severely disturbed TDD on his right leg whereas results were within the range of healthy subjects on his left leg. For both legs TDD activated an extensive cortical network that included opercular parietal area 1 (OP1) of the second somatosensory cortex (S2), as has previously been observed in healthy subjects. However, dorsolateral prefrontal cortex (DLPFC) and anterior insular cortex (AIC) were only activated for the unaffected (left) leg where TDD was normal. A revisit of previously published data showed that healthy subjects consistently had TDD-related activations in DLPFC and AIC. However, in several healthy subjects AIC, but not DLPFC, was also activated for skin pull stimulations per se without the TDD task. Thus, the patient's data, in conjunction with the previous results from healthy subjects, suggest that DLPFC processing is important for tactile decision making based on proper tactile input.
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| 3. |
- Ydrefors, Johannes, et al.
(author)
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Automated Nociceptive Withdrawal Reflex Measurements Reveal Normal Reflex Thresholds and Augmented Pain Ratings in Patients with Fibromyalgia.
- 2020
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In: Journal of clinical medicine. - Switzerland : MDPI AG. - 2077-0383. ; 9:6
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Journal article (peer-reviewed)abstract
- The nociceptive withdrawal reflex (NWR) is used to probe spinal cord excitability in chronic pain states. Here, we used an automated and unbiased procedure for determining the NWR threshold and compared the reflex thresholds and corresponding pain ratings in a well-characterized cohort of fibromyalgia (n = 29) and matched healthy controls (n = 21). Surface electrical stimuli were delivered to the foot in a stepwise incremental and decremental manner. The surface electromyographic activity was recorded from the ipsilateral tibialis anterior muscle. Fibromyalgia patients reported significantly higher scores for psychological distress and pain-related disability and a significantly lower score for perceived state of health compared to the matched controls. The subjective pain ratings were significantly higher in patients. The NWR thresholds were similar to the controls. In the patients, but not in controls, the NWR thresholds and subjective pain ratings were significantly correlated. Our results showed an increased subjective pain sensitivity in fibromyalgia, but we found no evidence for spinal sensitization based on the reflex measures.
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| 4. |
- Ackerley, Rochelle, 1980, et al.
(author)
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An fMRI study on cortical responses during active self-touch and passive touch from others
- 2012
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In: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 6
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Journal article (peer-reviewed)abstract
- Active, self-touch and the passive touch from an external source engage comparable afferent mechanoreceptors on the touched skin site. However, touch directed to glabrous skin compared to hairy skin will activate different types of afferent mechanoreceptors. Despite perceptual similarities between touch to different body sites, it is likely that the touch information is processed differently. In the present study, we used functional magnetic resonance imaging (fMRI) to elucidate the cortical differences in the neural signal of touch representations during active, self-touch and passive touch from another, to both glabrous (plam) and hairy (arm) skin, where a soft brush was used as the stimulus. There were two active touch conditions, where the participant used the brush in their right hand to stroke either their left palm or arm. There were two similar passive, touch conditions where the experimenter used an identical brush to stroke the same palm and arm areas on the participant. Touch on the left palm elicited a large, significant, positive blood-oxygenation level dependence (BOLD) signal in right sensorimotor areas. Less extensive activity was found for touch to the arm. Separate somatotopical palm and arm representations were found in Brodmann area (BA) 3 of the right primary somatosensory cortex (SI) and in both these areas, active stroking gave significantly higher signals than passive stroking. Active, self-touch elicited a positive BOLD signal in a network of sensorimotor cortical areas in the left hemisphere, compared to the resting baseline. In contrast, during passive touch, a significant negative BOLD signal was found in the left SI. Thus, each of the four conditions had a unique cortical signature despite similarities in afferent signaling or evoked perception. It is hypothesized that attentional mechanisms play a role in the modulation of the touch signal in the right SI, accounting for the differences found between active and passive touch.
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| 5. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Human C-tactile afferents are tuned to the temperature of a skin-stroking caress
- 2014
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In: Journal of Neuroscience. - 0270-6474. ; 34:8, s. 2879-2883
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Journal article (peer-reviewed)abstract
- Human C-tactile (CT) afferents respond vigorously to gentle skin stroking and have gained attention for their importance in social touch. Pharmacogenetic activation of the mouse CT equivalent has positively reinforcing, anxiolytic effects, suggesting a role in grooming and affiliative behavior. We recorded from single CT axons in human participants, using the technique of microneurography, and stimulated a unit's receptive field using a novel, computer-controlled moving probe, which stroked the skin of the forearm over five velocities (0.3, 1, 3, 10, and 30 cm s-1) at three temperatures (cool, 18°C; neutral, 32°C; warm, 42°C). We show that CTs are unique among mechanoreceptive afferents: they discharged preferentially to slowly moving stimuli at a neutral (typical skin) temperature, rather than at the cooler or warmer stimulus temperatures. In contrast, myelinated hair mechanoreceptive afferents proportionally increased their firing frequency with stroking velocity and showed no temperature modulation. Furthermore, the CT firing frequency correlated with hedonic ratings to the same mechano-thermal stimulus only at the neutral stimulus temperature, where the stimuli were felt as pleasant at higher firing rates. We conclude that CT afferents are tuned to respond to tactile stimuli with the specific characteristics of a gentle caress delivered at typical skin temperature. This provides a peripheral mechanism for signaling pleasant skin-to-skin contact in humans, which promotes interpersonal touch and affiliative behavior. © 2014 the authors.
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| 6. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Touch perceptions across skin sites: Differences between sensitivity, direction discrimination and pleasantness
- 2014
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In: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 8:54
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Journal article (peer-reviewed)abstract
- Human skin is innervated with different tactile afferents, which are found at varying densities over the body. We investigate how the relationships between tactile pleasantness, sensitivity and discrimination differ across the skin. Tactile pleasantness was assessed by stroking a soft brush over the skin, using five velocities (0.3, 1, 3, 10, 30 cm s-1), known to differentiate hedonic touch, and pleasantness ratings were gained. The ratings velocity-profile is known to correlate with firing in unmyelinated C-tactile (CT) afferents. Tactile sensitivity thresholds were determined using monofilament force detection and the tactile discrimination level was obtained in the direction discrimination of a moving probe; both tasks readily activate myelinated touch receptors. Perceptions were measured over five skin sites: forehead, arm, palm, thigh and shin. The assessment of tactile pleasantness over the skin resulted in a preference for the middle velocities (1-10 cm s-1), where higher ratings were gained compared to the slowest and fastest velocities. This preference in tactile pleasantness was found across all the skin sites, apart from at the palm, where no decrease in pleasantness for the faster stroking velocities was seen. We find that tactile sensitivity and discrimination vary across the skin, where the forehead and palm show increased acuity. Tactile sensitivity and discrimination levels also correlated significantly, although the tactile acuity did not relate to the perceived pleasantness of touch. Tactile pleasantness varied in a subtle way across skin sites, where the middle velocities were always rated as the most pleasant, but the ratings at hairy skin sites were more receptive to changes in stroking velocity. We postulate that although the mechanoreceptive afferent physiology may be different over the skin, the perception of pleasant touch can be interpreted using all of the available incoming somatosensory information in combination with central processing. © 2014 Ackerley, Carlsson, Wester, Olausson and Backlund Wasling.
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| 7. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Wetness perception across body sites
- 2012
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In: Neuroscience Letters. - : Elsevier BV. - 0304-3940. ; 522:1, s. 73-77
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Journal article (peer-reviewed)abstract
- Human skin is innervated with a variety of receptors serving somatosensation and includes the sensory sub-modalities of touch, temperature, pain and itch. The density and type of receptors differ across the body surface, and there are various body-map representations in the brain. The perceptions of skin sensations outside of the specified sub-modalities, e.g. wetness or greasiness, are described as 'touch blends' and are learned. The perception of wetness is generated from the coincident activation of tactile and thermal receptors. The present study aims to quantify threshold levels of wetness perception and find out if this differs across body sites. A rotary tactile stimulator was used to apply a moving, wetted stimulus over selected body sites at a precise force and velocity. Four wetness levels were tested over eight body sites. After each stimulus, the participant rated how wet the stimulus was perceived to be using a visual analogue scale. The results indicated that participants discriminated between levels of wetness as distinct percepts. Significant differences were found between all levels of wetness, apart from the lowest levels of comparison (20 mu l and 40 mu l). The perception of wetness did not, however, differ significantly across body sites and there were no significant interactions between wetness level and body site. The present study emphasizes the importance of understanding how bottom-up and top-down processes interact to generate complex perceptions. (C) 2012 Elsevier Ireland Ltd. All rights reserved.
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| 8. |
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| 9. |
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| 10. |
- Björnsdotter, Malin, et al.
(author)
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Development of brain mechanisms for processing affective touch
- 2014
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In: Frontiers in Behavioral Neuroscience. - Lausanne, Switzerland : Frontiers Media SA. - 1662-5153. ; 8:FEB
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Journal article (peer-reviewed)abstract
- Affective tactile stimulation plays a key role in the maturation of neural circuits, but the development of brain mechanisms processing touch is poorly understood. We therefore used functional magnetic resonance imaging (fMRI) to study brain responses to soft brush stroking of both glabrous (palm) and hairy (forearm) skin in healthy children (5-13 years), adolescents (14-17 years), and adults (25-35 years). Adult-defined regions-of-interests in the primary somatosensory cortex (SI), secondary somatosensory cortex (SII), insular cortex and right posterior superior temporal sulcus (pSTS) were significantly and similarly activated in all age groups. Whole-brain analyses revealed that responses in the ipsilateral SII were positively correlated with age in both genders, and that responses in bilateral regions near the pSTS correlated significantly and strongly with age in females but not in males. These results suggest that brain mechanisms associated with both sensory-discriminative and affective-motivational aspects of touch are largely established in school-aged children, and that there is a general continuing maturation of SII and a female-specific increase in pSTS sensitivity with age. Our work establishes a groundwork for future comparative studies of tactile processing in developmental disorders characterized by disrupted social perception such as autism. © 2014 Björnsdotter, Gordon, Pelphrey, Olausson and Kaiser.
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| 11. |
- Björnsdotter, Malin, et al.
(author)
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Somatotopic organization of gentle touch processing in the posterior insular cortex.
- 2009
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In: The Journal of neuroscience : the official journal of the Society for Neuroscience. - Washington, DC, United States : Society for Neuroscience. - 1529-2401 .- 0270-6474. ; 29:29, s. 9314-20
-
Journal article (peer-reviewed)abstract
- A network of thin (C and A delta) afferents relays various signals related to the physiological condition of the body, including sensations of gentle touch, pain, and temperature changes. Such afferents project to the insular cortex, where a somatotopic organization of responses to noxious and cooling stimuli was recently observed. To explore the possibility of a corresponding body-map topography in relation to gentle touch mediated through C tactile (CT) fibers, we applied soft brush stimuli to the right forearm and thigh of a patient (GL) lacking A beta afferents, and six healthy subjects during functional magnetic resonance imaging (fMRI). For improved fMRI analysis, we used a highly sensitive multivariate voxel clustering approach. A somatotopic organization of the left (contralateral) posterior insular cortex was consistently demonstrated in all subjects, including GL, with forearm projecting anterior to thigh stimulation. Also, despite denying any sense of touch in daily life, GL correctly localized 97% of the stimuli to the forearm or thigh in a forced-choice paradigm. The consistency in activation patterns across GL and the healthy subjects suggests that the identified organization reflects the central projection of CT fibers. Moreover, substantial similarities of the presently observed insular activation with that described for noxious and cooling stimuli solidify the hypothesized sensory-affective role of the CT system in the maintenance of physical well-being as part of a thin-afferent homeostatic network.
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| 12. |
- Björnsdotter Åberg, Malin, et al.
(author)
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Grey matter correlates of autistic traits in women with anorexia nervosa
- 2018
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In: Journal of Psychiatry & Neuroscience. - : CMA-CANADIAN MEDICAL ASSOC. - 1180-4882 .- 1488-2434. ; 43:2, s. 79-86
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Journal article (peer-reviewed)abstract
- Background: Patients with anorexia nervosa exhibit higher levels of behaviours typically associated with autism-spectrum disorder (ASD), but the neural basis is unclear. We sought to determine whether elevated autistic traits in women with anorexia nervosa may be reflected in cortical morphology. Methods: We used voxel-based morphometry (VBM) to examine regional grey matter volumes in high-resolution MRI structural brain scans in women with anorexia nervosa and matched healthy controls. The Autism-spectrum Quotient (AQ) scale was used to assess autistic traits. Results: Women with anorexia nervosa (n = 25) had higher AQ scores and lower bilateral superior temporal sulcus (STS) grey matter volumes than the control group (n = 25). The AQ scores correlated negatively with average left STS grey matter volume in women with anorexia nervosa. Limitations: We did not control for cognitive ability and examined only women with ongoing anorexia nervosa. Conclusion: Elevated autistic traits in women with anorexia nervosa are associated with morphometric alterations of brain areas linked to social cognition. This finding provides neurobiological support for the behavioural link between anorexia nervosa and ASD and emphasizes the importance of recognizing autistic traits in preventing and treating-anorexia nervosa.
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| 13. |
- Böhme, Rebecca, et al.
(author)
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Distinction of self-produced touch and social touch at cortical and spinal cord levels
- 2019
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In: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 116:6, s. 2290-2299
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Journal article (peer-reviewed)abstract
- Differentiation between self-produced tactile stimuli and touch by others is necessary for social interactions and for a coherent concept of "self." The mechanisms underlying this distinction are unknown. Here, we investigated the distinction between self-and other-produced light touch in healthy volunteers using three different approaches: fMRI, behavioral testing, and somatosensory-evoked potentials (SEPs) at spinal and cortical levels. Using fMRI, we found self-other differentiation in somatosensory and sociocognitive areas. Other-touch was related to activation in several areas, including somatosensory cortex, insula, superior temporal gyrus, supramarginal gyrus, striatum, amygdala, cerebellum, and prefrontal cortex. During self-touch, we instead found deactivation in insula, anterior cingulate cortex, superior temporal gyrus, amygdala, parahippocampal gyrus, and prefrontal areas. Deactivation extended into brain areas encoding low-level sensory representations, including thalamus and brainstem. These findings were replicated in a second cohort. During self-touch, the sensorimotor cortex was functionally connected to the insula, and the threshold for detection of an additional tactile stimulus was elevated. Differential encoding of self-vs. other-touch during fMRI correlated with the individual self-concept strength. In SEP, cortical amplitudes were reduced during self-touch, while latencies at cortical and spinal levels were faster for other-touch. We thus demonstrated a robust self-other distinction in brain areas related to somatosensory, social cognitive, and interoceptive processing. Signs of this distinction were evident at the spinal cord. Our results provide a framework for future studies in autism, schizophrenia, and emotionally unstable personality disorder, conditions where symptoms include social touch avoidance and poor self-vs.-other discrimination.
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| 14. |
- Cole, J., et al.
(author)
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Insights from A-beta or C-fibre denervated subjects
- 2016
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In: Affective Touch and the Neurophysiology of CT Afferents. Olausson H., Wessberg J., Morrison I., McGlone F. (eds.). - New York, NY : Springer. - 9781493964185 ; , s. 175-185
-
Book chapter (other academic/artistic)abstract
- CT afferents have been known for years, since 1939 when Zotterman suggested they might contribute to itch. But their study has been hampered because any low threshold tactile stimulus will also activate large numbers of Aβ afferents. To investigate the psychophysics of CT afferents has recently become possible through microneurography, allowing selective recording from groups of these nerves, (Löken et al., Nat Neurosci 12(5):547-548, 2009 and this volume), and through the study of two rare cohorts of people who have lost either large fibre afferents due to disease or have selective loss of C afferents themselves due to hereditary neuropathy. This chapter details this latter work, and though comparisons between those with neurological conditions and control subjects must always be done with caution, such work can allow some insights into the normal functioning of the CT system. Slow stroking on the hairy skin of deafferented subjects is poorly localised, but described, during forced choice experiments, as pleasant, and leads to activations in insula cortex but not sensory cortex. Since Ct activation is perceived poorly, if at all in deafferented subjects this suggests that a role for CT afferents may be to-in some way-set, or prime, information through Aβ pathways with affective valence. © 2016 Springer Science+Business Media New York.
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| 15. |
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| 16. |
- Condon, M., et al.
(author)
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Differential sensitivity to surface compliance by tactile afferents in the human finger pad
- 2014
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In: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 111:6, s. 1308-1317
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Journal article (peer-reviewed)abstract
- We undertook a neurophysiological investigation of the responses of low-threshold mechanoreceptors in the human finger pad to surfaces of differing softness. Unitary recordings were made from 26 slowly adapting type I (SAI), 17 fast-adapting type I (FAI), and 9 slowly adapting type II (SAII) afferents via tungsten microelectrodes inserted into the median nerve at the wrist. A servo-controlled stimulator applied ramp-and-hold forces (1, 2, 4 N) at a constant loading and unloading rate (2 N/s) via a flat silicone disc over the center of the finger pad. Nine discs were used, which linearly increased in stiffness across the range. Population responses of the SAI afferents showed the greatest sensitivity to compliance, with a steep monotonic increase in mean firing rate with increasing stiffness (decreasing compliance) of the surface during the loading and plateau (but not unloading) phases. FAI afferents also showed a linear increase in firing during the loading but not unloading phase, although the slope was significantly lower than that of the SAI afferents at all amplitudes. Conversely, SAII afferents were influenced by object compliance only in certain conditions. Given their high density in the finger pads and their linear relationship between firing rate and object compliance during the loading and plateau phases, SAI afferents (together with FAI afferents during the loading phase) are ideally suited to contributing information on surface compliance to the overall estimation of softness, but the SAII afferents appear to play only a minor role.
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| 17. |
- Croy, Ilona, et al.
(author)
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Gentle touch perception: From early childhood to adolescence
- 2019
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In: Developmental Cognitive Neuroscience. - : Elsevier BV. - 1878-9293 .- 1878-9307. ; 35, s. 81-86
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Journal article (peer-reviewed)abstract
- Affective touch plays an important role in children's social interaction and is involved in shaping the development of the social brain. The positive affective component of touch is thought to be conveyed via a group of unmyelinated, low-threshold mechanoreceptive afferents, known as C-tactile fibers that are optimally activated by gentle, slow, stroking touch. Touch targeting these C-tactile fibers has been shown to decrease the heart rate in infants. The current study investigated the relationship between age and psychophysical ratings in response to affective touch. A total of n = 43 participants (early childhood: aged 5-8 years, 9 girls, 12 boys; late childhood: aged 9-12 years, 12 girls, 10 boys) were presented with C-tactile optimal and sub-optimal stroking velocities and rated touch pleasantness on an affective pictorial scale. For both age groups, we found that children preferred C-tactile-targeted stimulation. A comparison with previously published data showed that the children's preference for C-tactile-targeted stimulation was similar to those obtained in adolescents and adults. We speculate that the effect of C-tactile-targeted touch, which is linked with pleasantness, shapes the children's preference for C-tactile over non-C-tactile-targeted stimulation, and that C-tactile afferent stimulation is important for social development.
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| 18. |
- Croy, Ilona, et al.
(author)
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Olfactory modulation of affective touch processing - A neurophysiological investigation
- 2016
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In: Neuroimage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 135, s. 135-141
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Journal article (peer-reviewed)abstract
- Touch can be highly emotional, and depending on the environment, it can be perceived as pleasant and comforting or disgusting and dangerous. Here, we studied the impact of context on the processing of tactile stimuli using a functional magnetic resonance imaging (fMRI) paradigm. This was achieved by embedding tactile stimulation in a variable olfactory environment. Twenty people were scanned with BOLD fMRI while receiving the following stimulus blocks: Slow stroking Touch, Civette odor (feces like), Rose odor, Touch + Civette, and Touch + Rose. Ratings of pleasantness and intensity of tactile stimuli and ratings of disgust and intensity of olfactory stimuli were collected. The impact of the olfactory context on the processing of touch was studied using covariance analyses. Coupling between olfactory processing and somatosensory processing areas was assessed with psychophysiological interaction analysis (PPI). A subjectively disgusting olfactory environment significantly reduced the perceived pleasantness of touch. The touch fMRI activation in the secondary somatosensory cortex, operculum 1 (OP1), was positively correlated with the disgust towards the odors. Decreased pleasantness of touch was related to decreased posterior insula activity. PPI analysis revealed a significant interaction between the OP1, posterior insula, and regions processing the disgust of odors (orbitofrontal cortex and amygdala). We conclude that the disgust evaluation of the olfactory environment moderates neural reactivity in somatosensory regions by upregulation of the OP1 and downregulation of the posterior insula. This adaptive regulation of affective touch processing may facilitate adaptive reaction to a potentially harmful stimulus.
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| 19. |
- Croy, Ilona, et al.
(author)
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Reduced Pleasant Touch Appraisal in the Presence of a Disgusting Odor
- 2014
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In: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 9:3
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Journal article (peer-reviewed)abstract
- Objectives: Odors are powerful emotional stimuli influencing mood, attention and behavior. Here we examined if odors change the perception of pleasant touch. In line with the warning function of the olfactory system, we proposed that especially unpleasant odors will reduce touch pleasantness, presumably through a disgust-related mechanism. Methods: Forty-five healthy participants (mean age 23.3 +/- 3years SD, 24 females) were presented to slow (3 cm/s) and fast (30 cm/s) brush stroking delivered by a robot to the forearm. Touch pleasantness under the influence of an unpleasant odor (Civette, smelling like feces) and an intensity matched pleasant odor (Rose) was compared to an odorless control condition. In a pilot study with 30 participants (mean age 25.9 +/-6 years, 21 females), the odors were matched according to their intensity, and we studied the influence of disgust sensitivity on the perception of 4 different odor qualities. Results: The unpleasant odor decreased touch pleasantness for both stroking velocities compared to the odorless control (p<0.005) whereas the rose odor did not change touch pleasantness significantly. Disgust sensitivity was correlated with the modulation of touch pleasantness. The pilot study revealed a significant correlation between disgust sensitivity and the perception of the unpleasant odor qualities (r = -0.56; p = 0.007), but not with any of the other odors. Conclusion: Unpleasant odors are powerful in modulating touch pleasantness, and disgust might be a moderating variable.
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| 20. |
- Davidovic, Monika, et al.
(author)
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Abnormal brain processing of gentle touch in anorexia nervosa
- 2018
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In: Psychiatry Research : Neuroimaging. - : Elsevier BV. - 0925-4927 .- 1872-7506. ; 281, s. 53-60
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Journal article (peer-reviewed)abstract
- Body image disturbance is a core symptom in anorexia nervosa (AN). Recent research suggests that abnormalities in touch perception may contribute to the disease mechanisms in AN. Here, we used functional magnetic resonance imaging (fMRI) to study possible abnormalities in cortical processing of affective touch in AN. Gentle skin strokes were applied to the right forearm during fMRI scanning in women diagnosed with AN (n=25) and in matched healthy controls (HC; n=25). Blocks of skin stroking were alternated with blocks of static skin indentation. Participants provided ratings of the pleasantness of skin stroking stimulation. AN participants perceived skin stroking as significantly less pleasant than HC. We observed no group differences for the contrast between skin stroking and skin indentation in primary tactile regions. We did find, however, significantly less activity in the AN group in areas including left caudate nucleus. Also, we found less activity in the AN group in bilateral lateral occipital cortex for the main effect of skin stroking. Our results suggest that abnormal functioning of the dorsal striatum could affect evaluation of pleasant tactile stimuli, and that abnormal functioning of the lateral occipital cortex might be related to disturbed body image perception.
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| 21. |
- Davidovic, Monika, et al.
(author)
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Processing of affective and emotionally neutral tactile stimuli in the insular cortex
- 2019
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In: Developmental Cognitive Neuroscience. - : Elsevier BV. - 1878-9293 .- 1878-9307. ; 35, s. 94-103
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Journal article (peer-reviewed)abstract
- The insula is important for the processing of pleasant aspects of touch whereas its role in the processing of emotionally neutral touch has been less explored. Here, we used a network approach to investigate the insular processing of pleasant stroking touch and emotionally neutral vibratory touch, analysing functional magnetic resonance imaging data from 23 healthy adult participants. Vibration and skin stroking activated areas in the posterior, middle and anterior insula. Psychophysiological interaction analyses suggested that skin stroking increased functional connectivity between the posterior and ventral anterior insula. Vibration instead increased functional connectivity between the posterior and dorsal anterior insula, and induced a stronger decrease of the default mode network activity compared to stroking. These results confirmed findings from previous studies showing that the posterior insula processes affective touch information. We suggest that this is accomplished by relaying tactile information from the posterior insula to ventral anterior insula, an area tightly connected to the emotional parts of the brain. However, our results also suggested that the insula processes tactile information with less emotional valence. A central hub in this processing seemed to be the right dorsal anterior insula.
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| 22. |
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| 23. |
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| 24. |
- Ellingsen, Dan-Mikael, 1985, et al.
(author)
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In touch with your emotions: Oxytocin and touch change social impressions while others' facial expressions can alter touch
- 2014
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In: Psychoneuroendocrinology. - : Elsevier BV. - 0306-4530. ; 39, s. 11-20
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Journal article (peer-reviewed)abstract
- Interpersonal touch is frequently used for communicating emotions, strengthen social bonds and to give others pleasure. The neuropeptide oxytocin increases social interest, improves recognition of others' emotions, and it is released during touch. Here, we investigated how oxytocin and gentle human touch affect social impressions of others, and vice versa, how others' facial expressions and oxytocin affect touch experience. In a placebo-controlled crossover study using intranasal oxytocin, 40 healthy volunteers viewed faces with different facial expressions along with concomitant gentle human touch or control machine touch, while pupil diameter was monitored. After each stimulus pair, participants rated the perceived friendliness and attractiveness of the faces, perceived facial expression, or pleasantness and intensity of the touch. After intranasal oxytocin treatment, gentle human touch had a sharpening effect on social evaluations of others relative to machine touch, such that frowning faces were rated as less friendly and attractive, whereas smiling faces were rated as more friendly and attractive. Conversely, smiling faces increased, whereas frowning faces reduced, pleasantness of concomitant touch the latter effect being stronger for human touch. Oxytocin did not alter touch pleasantness. Pupillary responses, a measure of attentional allocation, were larger to human touch than to equally intense machine touch, especially when paired with a smiling face. Overall, our results point to mechanisms important for human affiliation and social bond formation. (C) 2013 Elsevier Ltd. All rights reserved.
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| 25. |
- Ellingsen, Dan-Mikael, 1985, et al.
(author)
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Placebo improves pleasure and pain through opposite modulation of sensory processing
- 2013
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 110:44, s. 17993-17998
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Journal article (peer-reviewed)abstract
- Placebo analgesia is often conceptualized as a reward mechanism. However, by targeting only negative experiences, such as pain, placebo research may tell only half the story. We compared placebo improvement of painful touch (analgesia) with placebo improvement of pleasant touch (hyperhedonia) using functional MRI and a crossover design. Somatosensory processing was decreased during placebo analgesia and increased during placebo hyperhedonia. Both placebo responses were associated with similar patterns of activation increase in circuitry involved in emotion appraisal, including the pregenual anterior cingulate, medial orbitofrontal cortex, amygdala, accumbens, and midbrain structures. Importantly, placebo-induced coupling between the ventromedial prefrontal cortex and periaqueductal gray correlated with somatosensory decreases to painful touch and somatosensory increases to pleasant touch. These findings suggest that placebo analgesia and hyperhedonia are mediated by activation of shared emotion appraisal neurocircuitry, which down-or upregulates early sensory processing, depending on whether the expectation is reduced pain or increased pleasure.
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| 26. |
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| 27. |
- Hudson, K. M., et al.
(author)
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Effects of changing skin mechanics on the differential sensitivity to surface compliance by tactile afferents in the human finger pad
- 2015
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In: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 114:4, s. 2249-2257
-
Journal article (peer-reviewed)abstract
- It is not known how changes in skin mechanics affect the responses of cutaneous mechanoreceptors in the finger pads to compression forces. We used venous occlusion to change the stiffness of the fingers and investigated whether this influenced the firing of low-threshold mechanoreceptors to surfaces of differing stiffness. Unitary recordings were made from 10 slowly adapting type I (SAI), 10 fast adapting type I (FAI) and 9 slowly adapting type II (SAII) units via tungsten microelectrodes inserted into the median nerve at the wrist. A servocontrolled stimulator applied ramp-and-hold forces (1, 2, and 4 N) at a constant loading and unloading rate (2 N/s) via a flat 2.5-cmdiameter silicone disk over the center of the finger pad. Nine silicone disks (objects), varying in compliance, were used. Venous occlusion, produced by inflating a sphygmomanometer cuff around the upper arm to 40±5 mmHg, was used to induce swelling of the fingers and increase the compliance of the finger pulp. Venous occlusion had no effect on the firing rates of the SAI afferents, nor on the slopes of the relationship between mean firing rate and object compliance at each amplitude, but did significantly reduce the slopes for the FAI afferents. Although the SAII afferents possess a poor capacity to encode changes in object compliance, mean firing rates were significantly lower during venous occlusion. The finding that venous occlusion had no effect on the firing properties of SAI afferents indicates that these afferents preserve their capacity to encode changes in object compliance, despite changes in skin mechanics. © 2015 the American Physiological Society.
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| 28. |
- Jönsson, Emma H., et al.
(author)
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Affective and non-affective touch evoke differential brain responses in 2-month-old infants
- 2018
-
In: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 169, s. 162-171
-
Journal article (peer-reviewed)abstract
- Caressing touch is an effective way to communicate emotions and to create social bonds. It is also one of the key mediators of early parental bonding. The caresses are generally thought to represent a social form of touching and indeed, slow, gentle brushing is encoded in specialized peripheral nerve fibers, the C-tactile (CT) afferents. In adults, areas such as the posterior insula and superior temporal sulcus are activated by affective, slow stroking touch but not by fast stroking stimulation. However, whether these areas are activated in infants, after social tactile stimulation, is unknown. In this study, we compared the total hemoglobin responses measured with diffuse optical tomography (DOT) in the left hemisphere following slow and fast stroking touch stimulation in 16 2-month-old infants. We compared slow stroking (optimal CT afferent stimulation) to fast stroking (non-optimal CT stimulation). Activated regions were delineated using two methods: one based on contrast between the two conditions, and the other based on voxel-based statistical significance of the difference between the two conditions. The first method showed a single activation cluster in the temporal cortex with center of gravity in the middle temporal gyrus where the total hemoglobin increased after the slow stroking relative to the fast stroking (p = 0.04 uncorrected). The second method revealed a cluster in the insula with an increase in total hemoglobin in the insular cortex in response to slow stroking relative to fast stroking (p = 0.0005 uncorrected; p = 0.04 corrected for multiple comparisons). These activation clusters encompass areas that are involved in processing of affective, slow stroking touch in the adult brain. We conclude that the infant brain shows a pronounced and adult-like response to slow stroking touch compared to fast stroking touch in the insular cortex but the expected response in the primary somatosensory cortex was not found at this age. The results imply that emotionally valent touch is encoded in the brain in adult-like manner already soon after birth and this suggests a potential for involvement of touch in bonding with the caretaker.
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| 29. |
- Jönsson, Emma H., et al.
(author)
-
The relation between human hair follicle density and touch perception
- 2017
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Journal article (peer-reviewed)abstract
- Unmyelinated low threshold C-tactile fibers moderate pleasant aspects of touch. These fibers respond optimally to stroking stimulation of the skin with slow velocities (1-10 cm/s). Low threshold mechanoreceptors are arranged around hair follicles in rodent skin. If valid also in humans, hair follicle density (HFD) may relate to the perceived pleasantness of stroking tactile stimulation. We conducted two studies that examined the relation between HFD and affective touch perception in humans. In total, 138 healthy volunteers were stroked on the forearm and rated the pleasantness and intensity. Stimulation was performed by a robotic tactile stimulator delivering C-tactile optimal (1, 3, 10 cm/s) and non-optimal (0.1, 0.3, 30 cm/s) stroking velocities. Additionally, a measure of discriminative touch was applied in study 2. HFD of the same forearm was determined using the Cyanoacrylate Skin Stripping Method (CSSM), which we validated in a pretest. Women had higher HFD than men, which was explained by body size and weight. Furthermore, women rated affective touch stimuli as more pleasant and had higher tactile acuity. Depilation did not affect touch perception. A weak relationship was found between the C-tactile specific aspects of affective touch perception and HFD, and the hypothesis of HFD relating to pleasant aspects of stroking only received weak support.
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| 30. |
- Jönsson, Emma H., et al.
(author)
-
Unmyelinated Tactile Cutaneous Nerves Signal Erotic Sensations
- 2015
-
In: Journal of Sexual Medicine. - : Oxford University Press (OUP). - 1743-6095 .- 1743-6109. ; 12:6, s. 1338-1345
-
Journal article (peer-reviewed)abstract
- IntroductionIntrapersonal touch is a powerful tool for communicating emotions and can among many things evoke feelings of eroticism and sexual arousal. The peripheral neural mechanisms of erotic touch signaling have been less studied. C tactile afferents (unmyelinated low-threshold mechanoreceptors), known to underpin pleasant aspects of touch processing, have been posited to play an important role. MethodIn two studies, we investigated the relationship between C tactile activation and the perception of erotic and pleasant touch, using tactile brushing stimulation. In total, 66 healthy subjects (37 women, age range 19-51 years) were examined. In study 1 (n=20), five different stroking velocities were applied to the forearm and the inner thigh. The participants answered questions about partnership, mood, and touch. In study 2 (n=46), the same five stroking velocities were applied to the forearm. The participants answered questions about partnership, touch, and sexuality. ResultsBoth touch eroticism and pleasantness were rated significantly higher for C tactile optimal velocities compared with suboptimal velocities. No difference was found between the ratings of the thigh and the forearm. The velocity-dependent rating curves of pleasantness, intensity, and eroticism differed from each other. Pleasantness was best explained by a quadratic fit, intensity by a linear fit, and eroticism by both. A linear transformation of pleasantness and intensity predicted the observed eroticism ratings reliably. Eroticism ratings were negatively correlated with length of relationship. ConclusionTouch was rated most erotic when perceived as pleasant and weak. In human hairy skin, perception of pleasantness is correlated with the firing rate of C tactile afferents, and perception of intensity is correlated with the firing rate of A afferents. Accordingly, eroticism may be perceived most readily for touch stimuli that induce high activity in C tactile fibers and low activity in A fibers. Jonsson EH, Backlund Wasling H, Wagnbeck V, Dimitriadis M, Georgiadis JR, Olausson H, and Croy I. Unmyelinated tactile cutaneous nerves signal erotic sensations. J Sex Med 2015;12:1338-1345.
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| 31. |
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| 32. |
- Lee, Ye Seul, et al.
(author)
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Visual and physical affective touch delivered by a rotary tactile stimulation device: A human psychophysical study
- 2018
-
In: Physiology and Behavior. - : Elsevier BV. - 0031-9384 .- 1873-507X. ; 185, s. 55-60
-
Journal article (peer-reviewed)abstract
- The discovery that pleasant touch is coded by C-tactile fibers has generated considerable research interest and increased understanding of the skin as a channel for social information via cutaneous senses. However, no study has differentiated between the pleasant response to visual and tactile non-human stimulations. Our study investigated pleasant touch in which the visual and haptic touch information was obtained from an affective, but non-social experience, by a custom-built non-human device. Participants (n = 19) received soft brush strokes on their lower left arm delivered by a rotary tactile stimulator (physical session) or watched a video of an arm being stroked by a rotary tactile stimulator (visual session). The brush strokes were delivered at the same velocities (0.3, 1, 3, 10, 30 cm/s) and force (0.4 N) in both sessions. After each trial, participants rated the pleasantness of the touch. Analysis of variance was used to assess the effects of velocity and modality (visual touch vs. physical touch) on the pleasantness rating. Participants rated strokes between 1 and 10 cm/s as most pleasant under both conditions. The pleasantness rating patterns differed significantly among velocities; however, no significant differences were found between modalities. Visual and physical (without human-to-human interaction) touch elicited similar behavioral responses, including an inverted U-shaped perception of pleasantness. These findings suggest that the pleasantness of touch is influenced by the velocity of the strokes in both visual and physical touch with a non-human stimulation.
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| 33. |
- Leknes, Siri, et al.
(author)
-
Oxytocin enhances pupil dilation and sensitivity to 'hidden' emotional expressions.
- 2013
-
In: Social cognitive and affective neuroscience. - : Oxford University Press (OUP). - 1749-5024 .- 1749-5016. ; 8:7, s. 741-749
-
Journal article (peer-reviewed)abstract
- Sensing others' emotions through subtle facial expressions is a highly important social skill. We investigated the effects of intranasal oxytocin treatment on the evaluation of explicit and 'hidden' emotional expressions and related the results to individual differences in sensitivity to others' subtle expressions of anger and happiness. Forty healthy volunteers participated in this double-blind, placebo-controlled crossover study, which shows that a single dose of intranasal oxytocin (40IU) enhanced or 'sharpened' evaluative processing of others' positive and negative facial expression for both explicit and hidden emotional information. Our results point to mechanisms that could underpin oxytocin's prosocial effects in humans. Importantly, individual differences in baseline emotional sensitivity predicted oxytocin's effects on the ability to sense differences between faces with hidden emotional information. Participants with low emotional sensitivity showed greater oxytocin-induced improvement. These participants also showed larger task-related pupil dilation, suggesting that they also allocated the most attentional resources to the task. Overall, oxytocin treatment enhanced stimulus-induced pupil dilation, consistent with oxytocin enhancement of attention towards socially relevant stimuli. Since pupil dilation can be associated with increased attractiveness and approach behaviour, this effect could also represent a mechanism by which oxytocin increases human affiliation.
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| 34. |
- Liljencrantz, Jaquette, et al.
(author)
-
Altered C-tactile processing in human dynamic tactile allodynia
- 2013
-
In: Pain. - : Ovid Technologies (Wolters Kluwer Health). - 0304-3959 .- 1872-6623. ; 154:2, s. 227-234
-
Journal article (peer-reviewed)abstract
- Human unmyelinated (C) tactile afferents signal the pleasantness of gentle skin stroking on hairy (nonglabrous) skin. After neuronal injury, that same type of touch can elicit unpleasant sensations: tactile allodynia. The prevailing pathophysiological explanation is a spinal cord sensitization, triggered by nerve injury, which enables Aβ afferents to access pain pathways. However, a recent mouse knockout study demonstrates that C-tactile afferents are necessary for allodynia to develop, suggesting a role for not only Aβ but also C-tactile afferent signaling. To examine the contribution of C-tactile afferents to the allodynic condition in humans, we applied the heat/capsaicin model of tactile allodynia in 43 healthy subjects and in 2 sensory neuronopathy patients lacking Aβ afferents. Healthy subjects reported tactile-evoked pain, whereas the patients did not. Instead, patients reported their C-touch percept (faint sensation of pleasant touch) to be significantly weaker in the allodynic zone compared to untreated skin. Functional magnetic resonance imaging in 18 healthy subjects and in 1 scanned patient indicated that stroking in the allodynic and control zones evoked different responses in the primary cortical receiving area for thin fiber signaling, the posterior insular cortex. In addition, reduced activation in the medial prefrontal cortices, key areas for C-tactile hedonic processing, was identified. These findings suggest that dynamic tactile allodynia is associated with reduced C-tactile mediated hedonic touch processing. Nevertheless, because the patients did not develop allodynic pain, this seems dependent on Aβ signaling, at least under these experimental conditions.
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| 35. |
- Liljencrantz, Jaquette, et al.
(author)
-
Discriminative and affective touch in human experimental tactile allodynia
- 2014
-
In: Neuroscience Letters. - : Elsevier BV. - 0304-3940. ; 563, s. 75-79
-
Journal article (peer-reviewed)abstract
- Recently, several studies have suggested a role for unmyelinated (C-tactile, CT) low-threshold mechanoreceptive afferents in the allodynic condition. In this psychophysical study we explored the integrity of both Aβ and CT afferent processing following application of the heat capsaicin model of tactile allodynia on the left forearm in healthy subjects (n= 40). We measured tactile direction discrimination (TDD) to target the integrity of Aβ processing (n= 20). The TDD accuracy was significantly lower in the allodynic compared to a control zone. In addition, we measured the perceived pleasantness and pain of brush stroking at CT targeted (slow) and CT sub-optimal (fast) stroking velocities to investigate the integrity of CT processing (n= 20). When comparing touch pleasantness in the allodynic and control zone, there was a significantly larger difference in ratings for CT targeted compared to CT suboptimal stimulation. The results suggest a disturbance in both Aβ-mediated discriminative and CT-mediated affective touch processing in human experimental tactile allodynia. Our findings support the canonical view that tactile allodynia is signaled by Aβ afferents but that CTs seem to contribute by the loss of a pain inhibiting role. © 2014 Elsevier Ireland Ltd.
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| 36. |
- Liljencrantz, J., et al.
(author)
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Pain and touch: Roles for c-tactile afferents in pain inhibition and tactile allodynia
- 2016
-
In: Affective Touch and the Neurophysiology of CT Afferents. Olausson H., Wessberg J., Morrison I., McGlone F. (eds.). - New York : Springer. - 9781493964185 ; , s. 409-420
-
Book chapter (other academic/artistic)abstract
- In humans there is a positive correlation between the pleasantness perception of soft skin stroking and the firing rate of unmyelinated C-low-threshold mechanoreceptive afferents (often abbreviated C-LTMR in animals and C-tactile and CT afferents in humans). CT-targeted touch reduces heat pain in humans suggesting that activation of the CT system modulates pain perception. This finding is supported by animal work which has shown that C-LTMRs inhibit nociceptive signaling at the spinal cord level, release a protein (TAFA4) with analgesic effects, and have positively reinforcing and anxiolytic behavioral effects. However, under pathophysiological conditions, research in mice and humans instead suggests a role for CLTMRs and CTs in tactile allodynia. There is a divergence in results with some studies pointing to CLTMRs/CTs driving tactile allodynia, whereas others suggest a modulatory role. © 2016 Springer Science+Business Media New York.
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| 37. |
- Liljencrantz, Jaquette, et al.
(author)
-
Slow brushing reduces heat pain in humans
- 2017
-
In: European Journal of Pain. - : Wiley. - 1090-3801 .- 1532-2149. ; 21:7, s. 1173-1185
-
Journal article (peer-reviewed)abstract
- Background: C-tactile (CT) afferents are unmyelinated low-threshold mechanoreceptors optimized for signalling affective, gentle touch. In three separate psychophysical experiments, we examined the contribution of CT afferents to pain modulation. Methods: In total, 44 healthy volunteers experienced heat pain and CT optimal (slow brushing) and CT sub-optimal (fast brushing or vibration) stimuli. Three different experimental paradigms were used: Concurrent application of heat pain and tactile (slow brushing or vibration) stimulation; Slow brushing, applied for variable duration and intervals, preceding heat pain; Slow versus fast brushing preceding heat pain. Results: Slow brushing was effective in reducing pain, whereas fast brushing or vibration was not. The reduction in pain was significant not only when the CT optimal touch was applied simultaneously with the painful stimulus but also when the two stimuli were separated in time. For subsequent stimulation, the pain reduction was more pronounced for a shorter time interval between brushing and pain. Likewise, the effect was more robust when pain was preceded by a longer duration of brush stimulation. Strong CT-related pain reduction was associated with low anxiety and high calmness scores obtained by a state anxiety questionnaire. Conclusions: Slow brushing - optimal for CT activation - is effective in reducing pain from cutaneous heating. The precise mechanisms for the pain relief are as yet unknown but possible mechanisms include inhibition of nociceptive projection neurons at the level of the dorsal horn as well as analgesia through cortical mechanisms.
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| 38. |
- Liljencrantz, Jaquette, et al.
(author)
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Tactile C fibers and their contributions to pleasant sensations and to tactile allodynia
- 2014
-
In: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 8
-
Research review (peer-reviewed)abstract
- In humans converging evidence indicates that affective aspects of touch are signaled by low threshold mechanoreceptive C tactile (CT) afferents. Analyses of electrophysiological recordings, psychophysical studies in denervated subjects, and functional brain imaging, all indicate that CT primary afferents contribute to pleasant touch and provide an important sensory underpinning of social behavior. Considering both these pleasant and social aspects of gentle skin-to-skin contact, we have put forward a framework within which to consider CT afferent coding properties and pathways-the CT affective touch hypothesis. Recent evidence from studies in mice suggest that CTs, when activated, may have analgesic or anxiolytic effects. However, in neuropathic pain conditions, light touch can elicit unpleasant sensations, so called tactile allodynia. In humans, tactile allodynia is associated with reduced CT mediated hedonic touch processing suggesting loss of the normally analgesic effect of CT signaling. We thus propose that the contribution of CT afferents to tactile allodynia is mainly through a loss of their normally pain inhibiting role.
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| 39. |
- Linde, Mattias, 1966, et al.
(author)
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Sumatriptan (5-HT1B/1D-agonist) causes a transient allodynia.
- 2004
-
In: Cephalalgia : an international journal of headache. - : SAGE Publications. - 0333-1024. ; 24:12, s. 1057-66
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Journal article (peer-reviewed)abstract
- Unpleasant sensory symptoms are commonly reported in association with the use of 5-HT1B/1D-agonists, i.e. triptans. In particular, pain/pressure symptoms from the chest and neck have restricted the use of triptans in the acute treatment of migraine. The cause of these triptan induced side-effects is still unidentified. We have now tested the hypothesis that sumatriptan influences the perception of tactile and thermal stimuli in humans in a randomized, double-blind, placebo-controlled cross-over study. Two groups were tested; one consisted of 12 (mean age 41.2 years, 10 women) subjects with migraine and a history of cutaneous allodynia in association with sumatriptan treatment. Twelve healthy subjects (mean age 38.7 years, 10 women) without migraine served as control group. During pain- and medication-free intervals tactile directional sensibility, perception of dynamic touch (brush) and thermal sensory and pain thresholds were studied on the dorsal side of the left hand. Measurements were performed before, 20, and 40 min after injection of 6 mg sumatriptan or saline. Twenty minutes after injection, sumatriptan caused a significant placebo-subtracted increase in brush-evoked feeling of unpleasantness in both groups (P < 0.01), an increase in brush-evoked pain in migraineurs only (P = 0.021), a reduction of heat pain threshold in all participants pooled (P = 0.031), and a reduction of cold pain threshold in controls only (P = 0.013). At 40 min after injection, no differences remained significant. There were no changes in ratings of brush intensity, tactile directional sensibility or cold or warm sensation thresholds. Thus, sumatriptan may cause a short-lasting allodynia in response to light dynamic touch and a reduction of heat and cold pain thresholds. This could explain at least some of the temporary sensory side-effects of triptans and warrants consideration in the interpretation of studies on migraine-induced allodynia.
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| 40. |
- Lundblad, Linda, et al.
(author)
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Cortical processing of tactile direction discrimination based on spatiotemporal cues in man.
- 2011
-
In: Neuroscience letters. - : Elsevier BV. - 1872-7972 .- 0304-3940. ; 501:1, s. 45-9
-
Journal article (peer-reviewed)abstract
- Tactile direction discrimination (TDD), the ability to determine the direction of an object's movement across the skin, is used clinically to detect and quantify tactile dysfunction. We have previously identified a cortical network for TDD based on skin stretch information that includes the second somatosensory, anterior insular and dorsolateral prefrontal cortices. In the present study we investigated cortical processing of TDD based on spatiotemporal cues. Sixteen healthy subjects (8 females; mean age, 25.5 years; range, 23-32 years) were stimulated with a low-friction, spatiotemporal rolling wheel on the right thigh during functional magnetic resonance imaging (fMRI). The subjects were instructed to indicate the distal or proximal rolling direction of the stimulus. The fMRI contrast between rolling wheel stimulation and rest showed activations in several areas which included the left (contralateral) primary somatosensory, bilateral second somatosensory, bilateral anterior insular, and bilateral dorsolateral prefrontal cortices. We conclude that, spatiotemporal TDD is processed in a largely similar distributed cortical network as skin stretch TDD. Further, spatiotemporal TDD activated primary somatosensory cortex whereas a role for this area in processing of skin stretch TDD has not been demonstrated.
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| 41. |
- Lundblad, Linda, et al.
(author)
-
Tactile direction discrimination in humans after stroke
- 2020
-
In: Brain Communications. - : Oxford University Press (OUP). - 2632-1297. ; 2:2
-
Journal article (peer-reviewed)abstract
- Sensing movements across the skin surface is a complex task for the tactile sensory system, relying on sophisticated cortical processing. Functional MRI has shown that judgements of the direction of tactile stimuli moving across the skin are processed in distributed cortical areas in healthy humans. To further study which brain areas are important for tactile direction discrimination, we performed a lesion study, examining a group of patients with first-time stroke. We measured tactile direction discrimination in 44 patients, bilaterally on the dorsum of the hands and feet, within 2 weeks (acute), and again in 28 patients 3 months after stroke. The 3-month follow-up also included a structural MRI scan for lesion delineation. Fifty-nine healthy participants were examined for normative direction discrimination values. We found abnormal tactile direction discrimination in 29/44 patients in the acute phase, and in 21/28 3 months after stroke. Lesions that included the opercular parietal area 1 of the secondary somatosensory cortex, the dorsolateral prefrontal cortex or the insular cortex were always associated with abnormal tactile direction discrimination, consistent with previous functional MRI results. Abnormal tactile direction discrimination was also present with lesions including white matter and subcortical regions. We have thus delineated cortical, subcortical and white matter areas important for tactile direction discrimination function. The findings also suggest that tactile dysfunction is common following stroke.
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| 42. |
- Löken, Line Sofie, 1977, et al.
(author)
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Coding of pleasant touch by unmyelinated afferents in humans.
- 2009
-
In: Nature neuroscience. - : Springer Science and Business Media LLC. - 1546-1726 .- 1097-6256. ; 12:5, s. 547-8
-
Journal article (peer-reviewed)abstract
- Pleasant touch sensations may begin with neural coding in the periphery by specific afferents. We found that during soft brush stroking, low-threshold unmyelinated mechanoreceptors (C-tactile), but not myelinated afferents, responded most vigorously at intermediate brushing velocities (1-10 cm s(-1)), which were perceived by subjects as being the most pleasant. Our results indicate that C-tactile afferents constitute a privileged peripheral pathway for pleasant tactile stimulation that is likely to signal affiliative social body contact.
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| 43. |
- Löken, Line Sofie, 1977, et al.
(author)
-
Tactile direction discrimination and vibration detection in diabetic neuropathy.
- 2009
-
In: Acta neurologica Scandinavica. - : Hindawi Limited. - 1600-0404 .- 0001-6314. ; 121:5, s. 302-308
-
Journal article (peer-reviewed)abstract
- Löken LS, Lundblad LC, Elam M, Olausson HW. Tactile direction discrimination and vibration detection in diabetic neuropathy. Acta Neurol Scand: DOI: 10.1111/j.1600-0404.2009.01282.x. (c) 2009 The Authors Journal compilation (c) 2009 Blackwell Munksgaard.Objective - To evaluate the clinical usefulness of quantitative testing of tactile direction discrimination (TDD) in patients with diabetic neuropathy. Materials and methods - TDD and vibration detection were examined on the dorsum of the feet in 43 patients with type 1 diabetes mellitus and clinical signs and symptoms indicating mild neuropathy, and abnormal results for neurography, temperature detection, or heart rate variability. Test-retest examination of TDD was performed in nine of the patients. Results - Twenty-six of the patients had abnormal TDD (sensitivity 0.60) and 20 had abnormal vibration detection (sensitivity 0.46). Ten of the patients had abnormal TDD and normal vibration detection. Four of the patients had abnormal vibration detection and normal TDD. Test-retest examination of TDD showed a high degree of reproducibility (r = 0.87). Conclusion - TDD seems more useful than vibration detection in examination of diabetic neuropathy.
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| 44. |
- Mayo, Leah, et al.
(author)
-
Putting a good face on touch: Facial expression reflects the affective valence of caress-like touch across modalities
- 2018
-
In: Biological Psychology. - : ELSEVIER SCIENCE BV. - 0301-0511 .- 1873-6246. ; 137, s. 83-90
-
Journal article (peer-reviewed)abstract
- Touch plays a central role in interpersonal behavior, especially in its capacity to convey-and induce- changes in affect. Previous research has established that slow, caress-like stroking over the skin elicits positive subjective affective responses, with higher ratings of "pleasantness" compared to a faster-moving touch stimulus. Ratings of pleasantness are associated with increased activity of a distinct class of nerve fibers: C-tactile (CT) afferents. Here, we used facial electromyography (EMG) to determine if touch that optimally activates CT afferents also influences facial muscle activity believed to reflect changes in affect. We found that less pleasant, fast-moving stroking (30 cm/s) elicited robustly negative facial EMG responses, as indexed by stronger contraction of the corrugator muscle. In contrast, pleasant, slow-moving stroking (3 cm/s) that optimally activates CT afferents resulted in decreased negative facial affective responses, manifested as significant corrugator relaxation compared to fast stroking. Moreover, the facial tracking of affective valence during touch was supra-modal, with similar effects during both directly-experienced touch and viewing of touch videos. The results of this EMG study imply that touch that fails to optimally activate CT afferent produces a negative affective response, whereas pleasant, caress-like touch has not only subjective but expressive correlates, reflected in net positive affective changes in facial expression.
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| 45. |
- McGlone, Francis, et al.
(author)
-
Discriminative and Affective Touch: Sensing and Feeling.
- 2014
-
In: Neuron. - : Elsevier BV. - 1097-4199 .- 0896-6273. ; 82:4, s. 737-755
-
Research review (peer-reviewed)abstract
- The multimodal properties of the human somatosensory system continue to be unravelled. There is mounting evidence that one of these submodalities-touch-has another dimension, providing not only its well-recognized discriminative input to the brain, but also an affective input. It has long been recognized that touch plays an important role in many forms of social communication and a number of theories have been proposed to explain observations and beliefs about the "power of touch." Here, we propose that a class of low-threshold mechanosensitive C fibers that innervate the hairy skin represent the neurobiological substrate for the affective and rewarding properties of touch.
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| 46. |
- McGlone, Francis, et al.
(author)
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Discriminative touch and emotional touch.
- 2007
-
In: Canadian journal of experimental psychology = Revue canadienne de psychologie expérimentale. - : American Psychological Association (APA). - 1196-1961 .- 1878-7290. ; 61:3, s. 173-83
-
Research review (peer-reviewed)abstract
- Somatic sensation comprises four main modalities, each relaying tactile, thermal, painful, or pruritic (itch) information to the central nervous system. These input channels can be further classified as subserving a sensory function of spatial and temporal localization, discrimination, and provision of essential information for controlling and guiding exploratory tactile behaviours, and an affective function that is widely recognized as providing the afferent neural input driving the subjective experience of pain, but not so widely recognized as also providing the subjective experience of affiliative or emotional somatic pleasure of touch. The discriminative properties of tactile sensation are mediated by a class of fast-conducting myelinated peripheral nerve fibres--A-beta fibres--whereas the rewarding, emotional properties of touch are hypothesized to be mediated by a class of unmyelinated peripheral nerve fibres--CT afferents (C tactile)--that have biophysical, electrophysiological, neurobiological, and anatomical properties that drive the temporally delayed emotional somatic system. CT afferents have not been found in the glabrous skin of the hand in spite of numerous electrophysiological explorations of this area. Hence, it seems reasonable to conclude that they are lacking in the glabrous skin. A full understanding of the behavioural and affective consequences of the differential innervation of CT afferents awaits a fuller understanding of their function.
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| 47. |
- Mcintyre, Sarah, 1981-, et al.
(author)
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The Effects of Ageing on Tactile Function in Humans
- 2021
-
In: Neuroscience. - : Elsevier. - 0306-4522 .- 1873-7544. ; 464, s. 53-58
-
Research review (peer-reviewed)abstract
- Ageing is accompanied by a steady decline in touch sensitivity and acuity. Conversely, pleasant touch, such as experienced during a caress, is even more pleasant in old age. There are many physiological changes that might explain these perceptual changes, but researchers have not yet identified any specific mechanisms. Here, we review both the perceptual and structural changes to the touch system that are associated with ageing. The structural changes include reduced elasticity of the skin in older people, as well as reduced numbers and altered morphology of skin tactile receptors. Effects of ageing on the peripheral and central nervous systems include demyelination, which affects the timing of neural signals, as well as reduced numbers of peripheral nerve fibres. The ageing brain also undergoes complex changes in blood flow, metabolism, plasticity, neurotransmitter function, and, for touch, the body map in primary somatosensory cortex. Although several studies have attempted to find a direct link between perceptual and structural changes, this has proved surprisingly elusive. We also highlight the need for more evidence regarding age-related changes in peripheral nerve function in the hairy skin, as well as the social and emotional aspects of touch.
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| 48. |
- Mcintyre, Sarah, 1981-, et al.
(author)
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The Language of Social Touch Is Intuitive and Quantifiable
- 2022
-
In: Psychological Science. - : Sage Publications Inc. - 0956-7976 .- 1467-9280. ; 33:9, s. 1477-1494
-
Journal article (peer-reviewed)abstract
- Touch is a powerful communication tool, but we have a limited understanding of the role played by particular physical features of interpersonal touch communication. In this study, adults living in Sweden performed a task in which messages (attention, love, happiness, calming, sadness, and gratitude) were conveyed by a sender touching the forearm of a receiver, who interpreted the messages. Two experiments (N = 32, N = 20) showed that within close relationships, receivers could identify the intuitive touch expressions of the senders, and we characterized the physical features of the touches associated with successful communication. Facial expressions measured with electromyography varied by message but were uncorrelated with communication performance. We developed standardized touch expressions and quantified the physical features with 3D hand tracking. In two further experiments (N = 20, N = 16), these standardized expressions were conveyed by trained senders and were readily understood by strangers unacquainted with the senders. Thus, the possibility emerges of a standardized, intuitively understood language of social touch.
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| 49. |
- Middleton, Steven J, et al.
(author)
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Nav1.7 is required for normal C-low threshold mechanoreceptor function in humans and mice.
- 2022
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In: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 145:10, s. 3637-3653
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Journal article (peer-reviewed)abstract
- Patients with bi-allelic loss of function mutations in the voltage-gated sodium channel Nav1.7 present with congenital insensitivity to pain (CIP), whilst low threshold mechanosensation is reportedly normal. Using psychophysics (n = 6 CIP participants and n = 86 healthy controls) and facial EMG (n = 3 CIP participants and n = 8 healthy controls) we have found that these patients also have abnormalities in the encoding of affective touch which is mediated by the specialised afferents; C-low threshold mechanoreceptors (C-LTMRs). In the mouse we found that C-LTMRs express high levels of Nav1.7. Genetic loss or selective pharmacological inhibition of Nav1.7 in C-LTMRs resulted in a significant reduction in the total sodium current density, an increased mechanical threshold and reduced sensitivity to non-noxious cooling. The behavioural consequence of loss of Nav1.7 in C-LTMRs in mice was an elevation in the von Frey mechanical threshold and less sensitivity to cooling on a thermal gradient. Nav1.7 is therefore not only essential for normal pain perception but also for normal C-LTMR function, cool sensitivity and affective touch.
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- Morrison, India, 1972, et al.
(author)
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Reduced C-afferent fibre density affects perceived pleasantness and empathy for touch.
- 2011
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In: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 134:Pt 4, s. 1116-26
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Journal article (peer-reviewed)abstract
- We examined patients with a heritable disorder associated with a mutation affecting the nerve growth factor beta gene. Their condition has been classified as hereditary sensory and autonomic neuropathy type V. Carriers of the mutation show a reduction in density of thin and unmyelinated nerve fibres, including C afferents. A distinct type of unmyelinated, low-threshold mechanoreceptive C fibre, the C-tactile afferent, is present in hairy but not glabrous skin of humans and other mammals. They have been implicated in the coding of pleasant, hedonic touch of the kind that occurs in affiliative social interactions. We addressed the relationship between C fibre function and pleasant touch perception in 10 individuals from a unique population of mutation carriers in Sweden. We also investigated the effect of reduced C-fibre density on patients' evaluation of observed interpersonal touch (empathy). Results showed that patients perceived gentle, slow arm stroking, optimal for eliciting C-tactile afferent responses (1-10 cm/s), as less pleasant than did matched controls and also differed in their rating patterns across stimulation velocities. Further, patients' blood-oxygen-level-dependent responses in posterior insular cortex--a target for C afferents--were not modulated by stimulation optimal for activating C-tactile afferents. Hence, perception of the hedonic aspect of dynamic touch likely depends on C-tactile afferent density. Closely similar patterns between individuals' ratings of felt and seen touch suggest that appraisal of others' touch is anchored in one's own perceptual experience, whether typical or atypical.
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