Population interactions between parietal and primary motor cortices during reach

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• Understanding cortico-cortical interactions is crucial for deciphering motor control mechanisms.
• Previous studies often focused on single neuron activity, potentially missing population-level dynamics.

Purpose of the Study:

• To investigate neural interactions between parietal area 2/5 and primary motor cortex (M1).
• To determine the timing and behavioral relevance of these cortico-cortical interactions.
• To introduce and validate a novel population-level analysis method for studying neural communication.

Main Methods:

• Simultaneous neural recordings from areas 2/5 and M1 using microelectrode arrays in rhesus monkeys during a center-out reach task.
• Introduction of partial spike-field coherence (PSFC) to quantify phase locking between neural ensembles and local field potentials (LFPs).
• Spectral analysis of M1 LFPs and PSFC in different frequency bands (1-10 Hz, 10-40 Hz, 60-200 Hz).

Main Results:

• M1 LFPs showed distinct power changes during movement preparation and performance across different frequency bands.
• Partial spike-field coherence (PSFC) was strongest in the 1-10 Hz band and present in the 10-40 Hz band during movement preparation.
• Ensemble PSFC revealed stronger parietal-motor interactions than single cell-LFP pairings, peaking around 500 ms after movement onset and carrying movement direction information.

Conclusions:

• Parietal area 2/5 contributes movement direction information to M1 through cortico-cortical communication.
• Ensemble-level analysis, specifically PSFC, is more effective than single neuron analysis for detecting neural interactions.
• Cortico-cortical communication is more readily observed at the ensemble level, highlighting the importance of population dynamics in motor control.