Two Distinct Systems Represent Contralateral and Ipsilateral Sensorimotor Processes in the Human Premotor Cortex: A...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Motor Control

Background:

• Animal brains integrate sensory and motor information in behaviorally committed representations.
• The premotor cortex (PM) in primates contains topographically clustered sensorimotor neurons.
• Functional cartography of the human PM is not fully understood.

Purpose of the Study:

• To explore the topographic distribution of spatially dependent sensorimotor functions in the human PM.
• To investigate how the human PM processes visual cues and controls movements across different body sides and hemispaces.

Main Methods:

• Event-related transcranial magnetic stimulation (TMS) was applied to a dense grid on the left hemiscalp covering the PM.
• Participants performed hand or foot responses to visual cues presented in left or right hemispace.
• Stimulus side, effector side, and effector type were independently manipulated.

Main Results:

• Spatially segregated hand and foot representations were identified.
• Focal representations of contralateral cues and movements were found in the dorsal PM.
• Distributed representations of ipsilateral cues and movements were observed in the ventral and dorso-medial PM.

Conclusions:

• The human PM exhibits somatotopic organization.
• The left PM contains sensorimotor representations for both hemispaces and hemibodies.
• Contralateral hemispace and hemibody representations are mapped to distinct cortical regions within the PM compared to ipsilateral ones.