Signals from posterior parietal area 5 to motor cortex during locomotion

Area of Science:

• Neuroscience
• Motor Control
• Parietal Cortex

Background:

• Area 5 of the parietal cortex is crucial for processing visual information for action within the dorsal stream.
• The specific signals transmitted from area 5 to the motor cortex, which controls spinal cord output, remain largely unknown.

Purpose of the Study:

• To investigate the activity of corticocortical neurons (CCs) in area 5 projecting to the motor cortex during locomotion.
• To compare the activity of CCs with neighboring unidentified neurons (noIDs).
• To understand how neuronal signals change with visual dependency during locomotion.

Main Methods:

• Analysis of area 5 neuronal activity in cats during vision-independent (flat surface) and vision-dependent (horizontal ladder) locomotion.
• Focus on corticocortical neurons (CCs) projecting to motor cortex from different cortical layers.
• Comparison of CC activity with unidentified neurons (noIDs).

Main Results:

• CCs in layer V doubled their low discharge rate and showed an increased proportion of 2 bursts per stride during vision-dependent locomotion.
• Layer V 2-bursters exhibited two activity peaks synchronized with gaze shifts.
• Neurons in supragranular layers and 1-bursters did not transmit clear stride-related signals.
• CC activity patterns often differed from those of noIDs.

Conclusions:

• Specific corticocortical neurons in area 5 layer V play a role in transmitting visually guided locomotion signals to the motor cortex.
• The activity patterns suggest these neurons are involved in coordinating gaze and limb movements.
• Area 5 CCs with specific receptive fields show phase opposition with motor cortex pyramidal tract neurons, indicating distinct roles in motor output control.