Functional Architecture and Encoding of Tactile Sensorimotor Behavior in Rat Posterior Parietal Cortex

Area of Science:

• Neuroscience
• Systems Neuroscience
• Sensorimotor Integration

Background:

• The posterior parietal cortex (PPC) connects to somatosensory and motor cortices, suggesting a role in integrating sensory information and motor commands.
• Understanding the layer-specific information processing within the PPC during complex sensorimotor behaviors like whisking is crucial but largely unknown.

Purpose of the Study:

• To investigate the sensorimotor features encoded across different layers of the PPC during voluntary whisking and object touch in rats.
• To elucidate the computational role of PPC microcircuitry in sensorimotor behavior.

Main Methods:

• Loose-patch and extracellular recordings of neuronal activity across all PPC layers in anesthetized and awake, behaving rats.
• Single-cell receptive field mapping to identify somatosensory representations.
• Analysis of spiking activity modulation during whisking and object touch, and decoding of movement parameters from population activity.

Main Results:

• A coarse somatotopy was identified along the mediolateral axis in the PPC.
• Spiking activity during whisking was modulated in PPC layers 2-4 and layer 6, but not layer 5.
• Population activity preceded movement and allowed decoding of whisker trajectory, indicating a role in motor planning.
• Active whisker touch increased spiking activity specifically in PPC layers 2-4.

Conclusions:

• The PPC exhibits layer-specific processing, with layers 2-4 integrating both motor and sensory information, and layer 6 primarily representing motor information.
• PPC activity predicts future motor output, supporting its role in motor planning during sensorimotor tasks.
• These findings enhance our understanding of how the PPC computationally processes sensory input and motor output, with implications for brain-machine interfaces.