Directional information from neuronal ensembles in the primate orofacial sensorimotor cortex

Area of Science:

• Neuroscience
• Motor Control
• Sensory Processing

Background:

• Neurons in the sensorimotor cortex exhibit directional tuning during limb and facial movements.
• Population-level directional encoding in the orofacial sensorimotor cortex remains poorly understood compared to the arm motor cortex.

Purpose of the Study:

• To investigate and compare the directional information encoded by neuronal populations in the orofacial primary motor (MIo) and somatosensory (SIo) cortices during tongue protrusion.
• To analyze the differences in directional tuning strength, information content, and temporal dynamics between MIo and SIo.

Main Methods:

• Simultaneous recording of single-neuron spiking activity from MIo and SIo in monkeys (Macaca mulatta) using microelectrode arrays.
• Analysis of neuronal responses during voluntary tongue protrusion in various directions.
• Application of a discrete decoder to predict tongue protrusion direction from population activity.

Main Results:

• Over 60% of task-modulated neurons in both MIo and SIo showed differential modulation to tongue protrusion direction, with SIo showing stronger modulation.
• Mutual information between direction and spiking activity was significantly higher in SIo than MIo.
• Accurate trial-by-trial decoding of tongue protrusion direction was achieved from both MIo and SIo populations, with distinct temporal profiles: MIo showed late-onset, phasic decoding, while SIo exhibited early-onset, sustained decoding.

Conclusions:

• Both MIo and SIo play crucial roles in representing tongue protrusion direction.
• These areas differ in the amplitude and temporal characteristics of directional information processing.
• SIo appears to provide earlier and more sustained directional signals, while MIo contributes later, phasic directional information.