Functional parcellation of the human primary somatosensory cortex to natural touch.
Despite the significance of human touch, brain responses to interpersonal manual touch have been rarely investigated. We used functional magnetic resonance imaging to study brain activity in eight healthy adults whose left hand was touched by two individuals, in separate runs and in 20-s blocks, either by holding, smoothing, or poking. Acceleration was measured from both the subject's and the touching person's hands for postimaging control of the stimuli. Independent component analysis of the functional magnetic resonance imaging data unraveled three functional networks involving the primary somatosensory cortex (SI). One network comprised the contralateral and another the ipsilateral Brodmann area 3. The third network included area 2 bilaterally, left-hemisphere middle temporal gyrus and dorsolateral prefrontal regions, ventral prefrontal cortices bilaterally, and middle cingulate cortex. The response shapes and polarities varied between the three networks. The contralateral area 3 differentiated the responses between the three types of touch stimuli, and the response magnitudes depended on the variability of the touch within each block. However, the responses of the other two networks were strikingly similar to all stimuli. The subjects' reports on the pleasantness of the touch did not correlate with the characteristics of the SI responses. These findings imply area-specific processing of the natural human touch in three networks including the SI cortex, with only area 2 connected to a functional network of brain areas that may support social interaction.
Brain Research Unit, O.V. Lounasmaa Laboratory, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Espoo, Finland; Advanced Magnetic Imaging Centre, Aalto NeuroImaging, Aalto University School of Science, Espoo, Finland.
Sanna
S
Malinen
Ville
V
Renvall
Riitta
R
Hari
D000328:Adult; D001931:Brain Mapping; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D013003:Somatosensory Cortex / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult
accelerometer; independent component analysis; natural tactile stimulation; somatosensory activation; two-person neuroscience