| 1. |
- Björnsdotter, Malin, et al.
(författare)
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A Monte Carlo method for locally multivariate brain mapping.
- 2011
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Ingår i: NeuroImage. - : Elsevier BV. - 1095-9572 .- 1053-8119.
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Tidskriftsartikel (refereegranskat)abstract
- Locally multivariate approaches to functional brain mapping offer a highly appealing complement to conventional statistics, but require restrictive region-of-interest hypotheses, or, in exhaustive search forms (such as the "searchlight" algorithm; Kriegeskorte et al., 2006), are excessively computer intensive. We therefore propose a non-restrictive, comparatively fast yet highly sensitive method based on Monte Carlo approximation principles where locally multivariate maps are computed by averaging across voxelwise condition-discriminative information obtained from repeated stochastic sampling of fixed-size search volumes. On simulated data containing discriminative regions of varying size and contrast-to-noise ratio (CNR), the Monte Carlo method reduced the required computer resources by as much as 75% compared to the searchlight with no reduction in mapping performance. Notably, the Monte Carlo mapping approach not only outperformed the general linear method (GLM), but also produced higher discriminative voxel detection scores than the searchlight irrespective of classifier (linear or nonlinear support vector machine), discriminative region size or CNR. The improved performance was explained by the information-average procedure, and the Monte Carlo approach yielded mapping sensitivities of a few percent lower than an information-average exhaustive search. Finally, we demonstrate the utility of the algorithm on whole-brain, multi-subject functional magnetic resonance imaging (fMRI) data from a tactile study, revealing that the central representation of gentle touch is spatially distributed in somatosensory, insular and visual regions.
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| 2. |
- Björnsdotter, Malin, et al.
(författare)
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Clustered sampling improves random subspace brain mapping
- 2012
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Ingår i: Pattern recognition. - : Elsevier BV. - 0031-3203 .- 1873-5142. ; 45:6, s. 2035-2040
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Tidskriftsartikel (refereegranskat)abstract
- Intuitive and efficient, the random subspace ensemble approach provides an appealing solution to the problem of the vast dimensionality of functional magnetic resonance imaging (fMRI) data for maximal-accuracy brain state decoding. Recently, efforts to generate biologically plausible and interpretable maps of brain regions which contribute information to the ensemble decoding task have been made and two approaches have been introduced: globally multivariate random subsampling and locally multivariate Monte Carlo mapping. Both types of maps reflect voxel-wise decoding accuracies averaged across repeatedly randomly sampled voxel subsets, highlighting voxels which consistently participate in high-classification subsets. We compare the mapping sensitivities of the approaches on realistic simulated data containing both locally and globally multivariate information and demonstrate that utilizing the inherent volumetric nature of fMRI through clustered Monte Carlo mapping yields dramatically improved performances in terms of voxel detection sensitivity and efficiency. These results suggest that, unless a priori information specifically dictates a global search, variants of clustered sampling should be the priority for random subspace brain mapping.
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| 3. |
- Björnsdotter, Malin, et al.
(författare)
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Development of brain mechanisms for processing affective touch
- 2014
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Ingår i: Frontiers in Behavioral Neuroscience. - Lausanne, Switzerland : Frontiers Media SA. - 1662-5153. ; 8:FEB
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Björnsdotter, Malin, et al.
(författare)
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Evaluation of Quantified Social Perception Circuit Activity as a Neurobiological Marker of Autism Spectrum Disorder.
- 2016
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Ingår i: JAMA psychiatry. - : American Medical Association (AMA). - 2168-6238 .- 2168-622X. ; 73:6, s. 614-621
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Tidskriftsartikel (refereegranskat)abstract
- Autism spectrum disorder (ASD) is marked by social disability and is associated with dysfunction in brain circuits supporting social cue perception. The degree to which neural functioning reflects individual-level behavioral phenotype is unclear, slowing the search for functional neuroimaging biomarkers of ASD.
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| 5. |
- Björnsdotter, Malin, et al.
(författare)
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Somatotopic organization of gentle touch processing in the posterior insular cortex.
- 2009
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Ingår i: 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
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Björnsdotter, Malin, et al.
(författare)
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Support Vector Machine Diagnosis of Acute Abdominal Pain
- 2010
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Ingår i: Communications in Computer and Information Science. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 1865-0929. ; 52:4, s. 347-355, s. 347-355
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the feasibility of a decision-support system for patients seeking care for acute abdominal pain, and, specifically the diagnosis of acute diverticulitis. We used a linear support vector machine (SVM) to separate diverticulitis from all other reported cases of abdominal pain and from the important differential diagnosis non-specific abdominal pain (NSAP). On a database containing 3337 patients, the SVM obtained results comparable to those of the doctors in separating diverticulitis or NSAP from the remaining diseases. The distinction between diverticulitis and NSAP was, however, substantially improved by the SVM. For this patient group, the doctors achieved a sensitivity of 0.714 and a specificity of 0.963. When adjusted to the physicians’ results, the SVM sensitivity/specificity was higher at 0.714/0.985 and 0.786/0.963 respectively. Age was found as the most important discriminative variable, closely followed by C-reactive protein level and lower left side pain.
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| 7. |
- Björnsdotter Åberg, Malin, et al.
(författare)
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Grey matter correlates of autistic traits in women with anorexia nervosa
- 2018
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Ingår i: Journal of Psychiatry & Neuroscience. - : CMA-CANADIAN MEDICAL ASSOC. - 1180-4882 .- 1488-2434. ; 43:2, s. 79-86
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Bunketorp Käll, Lina, 1975, et al.
(författare)
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Regional estimates of cortical thickness in brain areas involved in control of surgically restored limb movement in patients with tetraplegia.
- 2020
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Ingår i: The journal of spinal cord medicine. - : Informa UK Limited. - 2045-7723 .- 1079-0268. ; 43:4, s. 462-469
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Tidskriftsartikel (refereegranskat)abstract
- Spinal cord injury (SCI) causes atrophy of brain regions linked to motor function. We aimed to estimate cortical thickness in brain regions that control surgically restored limb movement in individuals with tetraplegia.Cross-sectional study.Sahlgrenska University hospital, Gothenburg, Sweden.Six individuals with tetraplegia who had undergone surgical restoration of grip function by surgical transfer of one elbow flexor (brachioradialis), to the paralyzed thumb flexor (flexor pollicis longus). All subjects were males, with a SCI at the C6 or C7 level, and a mean age of 40 years (range=31-48). The average number of years elapsed since the SCI was 13 (range=6-26).We used structural magnetic resonance imaging (MRI) to estimate the thickness of selected motor cortices and compared these measurements to those of six matched control subjects. The pinch grip control area was defined in a previous functional MRI study.Compared to controls, the cortical thickness in the functionally defined pinch grip control area was not significantly reduced (P=0.591), and thickness showed a non-significant but positive correlation with years since surgery in the individuals with tetraplegia. In contrast, the anatomically defined primary motor cortex as a whole exhibited substantial atrophy (P=0.013), with a weak negative correlation with years since surgery.Individuals with tetraplegia do not seem to have reduced cortical thickness in brain regions involved in control of surgically restored limb movement. However, the studied sample is very small and further studies with larger samples are required to establish these findings.
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| 9. |
- Davidovic, Monika, et al.
(författare)
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Abnormal brain processing of gentle touch in anorexia nervosa
- 2018
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Ingår i: Psychiatry Research : Neuroimaging. - : Elsevier BV. - 0925-4927 .- 1872-7506. ; 281, s. 53-60
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Davidovic, Monika, et al.
(författare)
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Posterior Superior Temporal Sulcus Responses Predict Perceived Pleasantness of Skin Stroking
- 2016
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Ingår i: Frontiers in Human Neuroscience. - : Frontiers Media SA. - 1662-5161. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Love and affection is expressed through a range of physically intimate gestures, including caresses. Recent studies suggest that posterior temporal lobe areas typically associated with visual processing of social cues also respond to interpersonal touch. Here, we asked whether these areas are selective to caress-like skin stroking. We collected functional magnetic resonance imaging data from 23 healthy participants and compared brain responses to skin stroking and vibration. We did not find any significant differences between stroking and vibration in the posterior temporal lobe; however, right posterior superior temporal sulcus (pSTS) responses predicted healthy participants perceived pleasantness of skin stroking, but not vibration. These findings link right pSTS responses to individual variability in perceived pleasantness of caress-like tactile stimuli. We speculate that the right pSTS may play a role in the translation of tactile stimuli into positively valenced, socially relevant interpersonal touch and that this system may be affected in disorders associated with impaired attachment.
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