| 1. |
- Böhme, Rebecca, et al.
(författare)
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Anhedonia to Gentle Touch in Fibromyalgia: Normal Sensory Processing but Abnormal Evaluation
- 2020
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Ingår i: Brain Sciences. - : MDPI. - 2076-3425 .- 2076-3425. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Social touch is important for interpersonal interaction. Gentle touch and slow brushing are typically perceived as pleasant, the degree of pleasantness is linked to the activity of the C-tactile (CT) fibers, a class of unmyelinated nerves in the skin. The inability to experience pleasure in general is called anhedonia, a common phenomenon in the chronic pain condition fibromyalgia. Here, we studied the perception and cortical processing of gentle touch in a well-characterized cohort of fibromyalgia. Patients and controls participated in functional brain imaging while receiving tactile stimuli (brushing) on the forearm. They were asked to provide ratings of pleasantness of the tactile stimulus and ongoing pain. We found high distress, pain catastrophizing, and insomnia, and a low perceived state of health in fibromyalgia. Further, patients rated both slow (CT-optimal) and fast (CT-suboptimal) brushing as less pleasant than healthy participants. While there was no difference in brain activity during touch, patients showed deactivation in the right posterior insula (contralateral to the stimulated arm) during pleasantness rating and activation during pain rating. The opposite pattern was observed in healthy participants. Voxel-based morphometry analysis revealed reduced grey matter density in patients, in the bilateral hippocampus and anterior insula. Our results suggest anhedonia to gentle touch in fibromyalgia with intact early-stage sensory processing but dysfunctional evaluative processing. These findings contribute to our understanding of the mechanisms underlying anhedonia in fibromyalgia.
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| 2. |
- Böhme, Rebecca, et al.
(författare)
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Differentiating self-touch from social touch
- 2022
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Ingår i: CURRENT OPINION IN BEHAVIORAL SCIENCES. - : ELSEVIER. - 2352-1546. ; 43, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- Humans need to be able to differentiate between signals they produce themselves and signals that arise from non-self-causes. It has long been discussed that the brain uses a copy of the motor command, an efference copy, to predict the sensory outcomes of ones own action - and to attenuate these. While studies in humans suggest that cerebellum and supplementary motor area play crucial roles in the attenuation, a study in mice suggests a global suppression during self-touch. However, the sensory percepts of self-touch are not fully cancelled out. Humans touch themselves frequently suggesting a behavioral relevance of self-touch, as to refocus attention, to calm oneself down during stress, to itch or for self-enjoyment. We discuss studies on sensory attenuation as well as the behavioral relevance of self-touch and open questions for future research.
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| 3. |
- Böhme, Rebecca, et al.
(författare)
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Sharpened self-other distinction in attention deficit hyperactivity disorder
- 2020
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Ingår i: NeuroImage. - : Elsevier. - 2213-1582. ; 27
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionDifferentiation between self-produced tactile stimuli and touch by others is necessary for social interactions and for a coherent concept of “self”. In attention-deficit-hyperactivity-disorder (ADHD), tactile hypersensitivity and social cognition problems are part of the symptomatology, but pathophysiological mechanisms are largely unknown. Differentiation of self- and non-self- generated sensations might be key to understand and develop novel strategies for managing hypersensitivity. Here, we compared the neural signatures of affective self- and other-touch between adults with ADHD and neurotypical controls (NC).MethodsTwenty-eight adult ADHD participants and 30 age- and gender-matched NC performed a self-other-touch-task during functional magnetic resonance imaging: they stroked their own arm, an object, or were stroked by the experimenter. In addition, tactile detection thresholds and rubber hand illusion (RHI) were measured.ResultsADHD participants had more autistic traits than NC and reported to engage less in interpersonal touch. They also reported to be more sensitive to tactile stimuli. Compared to NC, ADHD participants showed enhanced responses to both the self- and other-touch conditions: stronger deactivation during self-touch in the anterior and posterior insula, and increased activation during other-touch in primary somatosensory cortex. ADHD participants had intact tactile detection thresholds, but were less susceptible to the RHI.ConclusionsUnaltered detection thresholds suggest that peripheral processing is intact, and that hypersensitivity might be driven by central mechanisms. This has clinical implications for managing somatosensory hypersensitivity in ADHD. The more pronounced differentiation between self- and other-touch might indicate a clearer self-other-distinction. This is of interest regarding body ownership perception in both NC and ADHD, and possibly other psychiatric conditions with altered self-experiences, like schizophrenia. A sharper boundary of the own body might relate to deficits in social cognition and tactile hypersensitivity.
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| 4. |
- Deserno, Lorenz, et al.
(författare)
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Volatility Estimates Increase Choice Switching and Relate to Prefrontal Activity in Schizophrenia
- 2020
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Ingår i: Biological Psychiatry. - : ELSEVIER. - 2451-9022. ; 5:2, s. 173-183
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Reward-based decision making is impaired in patients with schizophrenia (PSZ), as reflected by increased choice switching. The underlying cognitive and motivational processes as well as associated neural signatures remain unknown. Reinforcement learning and hierarchical Bayesian learning account for choice switching in different ways. We hypothesized that enhanced choice switching, as seen in PSZ during reward-based decision making, relates to higher-order beliefs about environmental volatility, and we examined the associated neural activity. METHODS: In total, 46 medicated PSZ and 43 healthy control subjects performed a reward-based decision-making task requiring flexible responses to changing action-outcome contingencies during functional magnetic resonance imaging. Detailed computational modeling of choice data was performed, including reinforcement learning and the hierarchical Gaussian filter. Trajectories of learning from computational modeling informed the analysis of functional magnetic resonance imaging data. RESULTS: A 3-level hierarchical Gaussian filter accounted best for the observed choice data. This model revealed a heightened initial belief about environmental volatility and a stronger influence of volatility on lower-level learning of action-outcome contingencies in PSZ as compared with healthy control subjects. This was replicated in an independent sample of nonmedicated PSZ. Beliefs about environmental volatility were reflected by higher activity in dorsolateral prefrontal cortex of PSZ as compared with healthy control subjects. CONCLUSIONS: Our study suggests that PSZ inferred the environment as overly volatile, which may explain increased choice switching. In PSZ, activity in dorsolateral prefrontal cortex was more strongly related to beliefs about environmental volatility. Our computational phenotyping approach may provide useful information to dissect clinical heterogeneity and could improve prediction of outcome.
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| 5. |
- Enmalm, Adam, et al.
(författare)
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Body Perception and Social Touch Preferences in Times of Grief
- 2024
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Ingår i: Journal of loss & trauma. - : TAYLOR & FRANCIS INC. - 1532-5024 .- 1532-5032.
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Tidskriftsartikel (refereegranskat)abstract
- Grief is a core human experience. The time following the loss of a loved one is associated with an increased risk for negative health outcomes. Yet, only a few studies investigate bodily consequences of grief and consoling behaviors, specifically the potentially supportive role of interpersonal touch during grief. We conducted an online-study where participants filled in questionnaires and rated videos of short touch gestures and interactions. People who lost a loved one within the last 2 years were asked about their grief experiences and to rate the different types of touch from the perspective of a receiver. People who had not lost a close person in the last 2 years rated the touch from the perspective of providing touch to a grieving individual. The majority of the recent-loss sample reported to have perceived their own body and bodily states less after the loss. Two-thirds reported feeling the presence of the deceased at least once. Grief-sensations were experienced mostly in the chest and upper body, the same areas where the consoling effect of a hug was perceived. Overall, the recent-loss group reported amounts of wanting of the vicarious touch gestures similar to the endorsement by people taking the active touching perspective. However, discrepancies between groups were found for some types of touch, including slow affective stroking. These results contribute to a deeper understanding of the body and bodily interactions like social touch in grief and consolation. Our findings can be seen as a first point of reference on how to interact with grieving individuals and could contribute to novel interventions for individuals with prolonged grief disorder.
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| 6. |
- Frost-Karlsson, Morgan, et al.
(författare)
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Neural processing of self-touch and other-touch in anorexia nervosa and autism spectrum condition
- 2022
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Ingår i: NeuroImage. - : Elsevier Science Ltd. - 2213-1582. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The tactile sense plays a crucial role in the development and maintenance of a functional bodily self. The ability to differentiate between self-and nonself-generated touch contributes to the perception of the bodies boundaries and more generally to self-other-distinction, both of which are thought be altered in anorexia nervosa (AN) and autism spectrum condition (AS). While it has been suggested that AN and AS are characterized by overlapping symptomatology, they might differ regarding body perception and self-other-distinction. Methods: Participants with a diagnosis of AN (n = 25), AS (n = 29), and a comparison group without diagnoses (n = 57) performed a self-other-touch task during functional brain imaging. In the experimental conditions, they stroked their own arm or were stroked on the arm by an experimenter. Results: As shown previously, the CG group showed lower activation or deactivation in response to self-touch compared to social touch from someone else. A main group effect was found in areas including somatosensory cortex, frontal and temporal gyri, insula, and subcortical regions. This was driven by increased activations in participants with AN, while participants in the AS group showed mostly comparable activations to the com-parison group. Conclusions: AN diagnosis was associated with an increased neural activity in response to both self-touch and social touch. Failure to attenuate self-touch might relate to altered predictions regarding the own body and reduced perception of bodily boundaries. Participants with an AS diagnosis were mostly comparable to the comparison group, potentially indicating unaltered tactile self-other-distinction.
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| 7. |
- Mcintyre, Sarah, 1981-, et al.
(författare)
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The Language of Social Touch Is Intuitive and Quantifiable
- 2022
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Ingår i: Psychological Science. - : Sage Publications Inc. - 0956-7976 .- 1467-9280. ; 33:9, s. 1477-1494
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Pietrzak, Michal, et al.
(författare)
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A randomized controlled experimental medicine study of ghrelin in value-based decision making
- 2023
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Ingår i: Journal of Clinical Investigation. - : AMER SOC CLINICAL INVESTIGATION INC. - 0021-9738 .- 1558-8238. ; 133:12
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND. The stomach-derived hormone ghrelin stimulates appetite, but the ghrelin receptor is also expressed in brain circuits involved in motivation and reward. We examined ghrelin effects on decision making beyond food or drug reward using monetary rewards. METHODS. Thirty participants (50% women and 50% men) underwent 2 fMRI scans while receiving i.v. ghrelin or saline in a randomized counterbalanced order. RESULTS. Striatal representations of reward anticipation were unaffected by ghrelin, while activity during anticipation of losses was attenuated. Temporal discounting rates of monetary reward were lower overall in the ghrelin condition, an effect driven by women. Discounting rates were inversely correlated with neural activity in a large cluster within the left parietal lobule that included the angular gyrus. Activity in an overlapping cluster was related to behavioral choices and was suppressed by ghrelin. CONCLUSION. This is, to our knowledge, the first human study to extend the understanding of ghrelins significance beyond the canonical feeding domain or in relation to addictive substances. Contrary to our hypothesis, we found that ghrelin did not affect sensitivity to monetary reward anticipation, but rather resulted in attenuated loss aversion and lower discounting rates for these rewards. Ghrelin may cause a motivational shift toward caloric reward rather than globally promoting the value of reward. TRIAL REGISTRATION. EudraCT 2018-004829-82.
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| 9. |
- Pietrzak, Michal, 1987-, et al.
(författare)
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Ghrelin decreases sensitivity to negative feedback and increases prediction-error related caudate activity in humans, a randomized controlled trial
- 2024
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Ingår i: Neuropsychopharmacology. - : Springer Science+Business Media B.V.. - 0893-133X .- 1740-634X. ; 49, s. 1042-1049
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Tidskriftsartikel (refereegranskat)abstract
- The stomach-derived hormone ghrelin plays not only a role in feeding, starvation, and survival, but it has been suggested to also be involved in the stress response, in neuropsychiatric conditions, and in alcohol and drug use disorders. Mechanisms related to reward processing might mediate ghrelin's broader effects on complex behaviors, as indicated by animal studies and mostly correlative human studies. Here, using a within-subject double-blind placebo-controlled design with intravenous ghrelin infusion in healthy volunteers (n = 30), we tested whether ghrelin alters sensitivity to reward and punishment in a reward learning task. Parameters were derived from a computational model of participants' task behavior. The reversal learning task with monetary rewards was performed during functional brain imaging to investigate ghrelin effects on brain signals related to reward prediction errors. Compared to placebo, ghrelin decreased punishment sensitivity (t = -2.448, p = 0.021), while reward sensitivity was unaltered (t = 0.8, p = 0.43). We furthermore found increased prediction-error related activity in the dorsal striatum during ghrelin administration (region of interest analysis: t-values >= 4.21, p-values <= 0.044). Our results support a role for ghrelin in reward processing that extends beyond food-related rewards. Reduced sensitivity to negative outcomes and increased processing of prediction errors may be beneficial for food foraging when hungry but could also relate to increased risk taking and impulsivity in the broader context of addictive behaviors.
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| 10. |
- Savallampi, Mattias, et al.
(författare)
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Social Touch Reduces Pain Perception-An fMRI Study of Cortical Mechanisms
- 2023
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Ingår i: Brain Sciences. - : MDPI. - 2076-3425 .- 2076-3425. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Unmyelinated low-threshold mechanoreceptors (C-tactile, CT) in the human skin are important for signaling information about hedonic aspects of touch. We have previously reported that CT-targeted brush stroking by means of a robot reduces experimental mechanical pain. To improve the ecological validity of the stimulation, we developed standardized human-human touch gestures for signaling attention and calming. The attention gesture is characterized by tapping of the skin and is perceived as neither pleasant nor unpleasant, i.e., neutral. The calming gesture is characterized by slow stroking of the skin and is perceived as moderately to very pleasant. Furthermore, the attention (tapping) gesture is ineffective, whereas the calming (stroking) gesture is effective in activating CT-afferents. We conducted an fMRI study (n = 32) and capitalized on the previous development of touch gestures. We also developed an MR compatible stimulator for high-precision mechanical pain stimulation of the thenar region of the hand. Skin-to-skin touching (stroking or tapping) was applied and was followed by low and high pain. When the stroking gesture preceded pain, the pain was rated as less intense. When the tapping gesture preceded the pain, the pain was rated as more intense. Individual pain perception related to insula activation, but the activation was not higher for stroking than for tapping in any brain area during the stimulation period. However, during the evaluation period, stronger activation in the periaqueductal gray matter was observed after calming touch compared to after tapping touch. This finding invites speculation that human-human gentle skin stroking, effective in activating CT-afferents, reduced pain through neural processes involving CT-afferents and the descending pain pathway.
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