Human MST but not MT responds to tactile stimulation

Area of Science:

• Neuroscience
• Sensory processing
• Human brain imaging

Background:

• Previous studies reported tactile responses in human visual area MT/V5 using complex stimuli.
• Complex stimuli may induce visual motion imagery, a known potent activator of MT.
• Human area MT/V5 comprises distinct areas MT and MST.

Purpose of the Study:

• To investigate tactile responses in human MT and MST independently of visual motion imagery.
• To determine if vibrotactile stimuli activate MT and MST.
• To explore somatotopic organization within MST for tactile input.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to localize human MT and MST.
• Vibrotactile stimuli, designed to minimize visual motion imagery, were applied.
• Stimulation of left/right hand and foot was performed to assess somatotopy.

Main Results:

• Strong vibrotactile responses were detected in MST, but not in MT.
• MST's vibrotactile responses were about half the magnitude of its visual motion responses.
• MST showed no spatial segregation for hand versus foot stimulation, but preferred contralateral hand input, similar to somatosensory cortex.

Conclusions:

• Evidence suggests somatosensory responses exist in human MST, independent of visual motion imagery.
• The MT area does not appear to respond to these specific vibrotactile stimuli.
• Findings differentiate MST's tactile processing from other visual areas like the lateral occipital complex.