title: Frequency-dependent patterns of somatosensory cortical responses to vibrotactile stimulation in humans: a fMRI study.
abstract: In the human mechanosensation system, rapidly adapting afferents project sensory signals of flutter (5-50Hz) to the contralateral primary somatosensory cortex (S1) and bilateral secondary somatosensory cortex (S2) whereas Pacinian afferents project sensory signals of vibration (50-400Hz) to bilateral S2. However, it remains largely unknown how somatosensory cortical activity changes as a function of vibrotactile frequency. This functional magnetic resonance imaging (fMRI) study investigated frequency dependency of somatosensory cortical activity in humans by applying vibrotactile stimulation with various frequencies (20-200Hz) to the index finger. We found more frequency-dependent voxels in the upper bank of the lateral sulcus (LS) of S2 than in S1 and the posterior parietal cortex of S2. Our statistical spatial clustering analysis showed that two groups of positively or negatively frequency-dependent voxels formed distinct clusters, most clearly in the LS. Using a cortical separability index, we reaffirmed that somatosensory cortical activity was most separable at 50Hz, previously known to demarcate flutter and vibration. Our results suggest that the LS (S2) may play an important role in processing vibrotactile frequency information and that the somatosensory cortex may include spatially localized neural assemblies specialized to higher or lower vibrotactile frequency.
authors: Department of Brain and Cognitive Engineering, Korea University, Seoul, 136-713, Republic of Korea.
authors: Yoon Gi
authors: YG
authors: Chung
authors: Junsuk
authors: J
authors: Kim
authors: Sang Woo
authors: SW
authors: Han
authors: Hyung-Sik
authors: HS
authors: Kim
authors: Mi Hyun
authors: MH
authors: Choi
authors: Soon-Cheol
authors: SC
authors: Chung
authors: Jang-Yeon
authors: JY
authors: Park
authors: Sung-Phil
authors: SP
authors: Kim
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005260:Female; D005385:Fingers / Q000294:innervation; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010812:Physical Stimulation / Q000379:methods; D013003:Somatosensory Cortex / Q000502:physiology*; D014110:Touch; D055698:Touch Perception / Q000502:physiology*; D014732:Vibration; D055815:Young Adult