Re-examining overlap between tactile and visual motion responses within hMT+ and STS

Area of Science:

• Neuroscience
• Sensory Processing
• Human Brain Imaging

Background:

• The human MT+ complex (hMT+) is known for visual motion processing.
• Previous studies suggested overlapping tactile motion responses in hMT+, but relied on group analyses.
• The role of visual imagery in these tactile responses remained unclear.

Purpose of the Study:

• To replicate findings of tactile motion responses in hMT+.
• To investigate whether tactile responses in hMT+ are restricted to subregions.
• To determine if tactile responses in hMT+ are influenced by visual imagery or attention.

Main Methods:

• Individual functional magnetic resonance imaging (fMRI) mapping of MT and MST using visual field localizers.
• Examined brain responses to passive tactile motion on the arm.
• Assessed tactile responses during an unrelated visual task at fixation to minimize visual imagery.

Main Results:

• Weak tactile motion responses were found in MT (6% of voxels) and MST (2% of voxels) without a visual task.
• These responses in MST were reduced to less than 1% when an unrelated visual task withdrew attention.
• Tactile responses were observed in STS regions, superior and anterior to hMT+.
• Group-averaged data showed spurious overlap in hMT+, mimicking previous findings.

Conclusions:

• hMT+ does not appear to be a supramodal motion processing module.
• Tactile motion responses in hMT+ are minimal and attention-dependent.
• Group analyses can lead to inaccurate conclusions regarding overlapping sensory processing in hMT+.