Neural and Behavioral Perturbations via Optogenetic Inhibition of the Posterior Parietal Cortex during Motor Planning

Deciphering neural mechanisms underlying neurostimulation is essential for developing targeted neurorehabilitation strategies, yet understanding the neural perturbations to behavior-related neural activity remains an area of active exploration. This study investigates the use of optogenetic inhibition to perturb motor activity and understand modulations to task-related neural activity in the posterior parietal cortex (PPC) of non-human primates (NHPs). Multiple regions of the PPC near the interparietal sulcus (IPS) were transfected with the inhibitory opsin JAWS. Inhibition was applied during a center-out reaching task, leveraging a large-scale optogenetic interface that allowed for simultaneously monitoring of local field potentials (LFPs) during optical stimulation. Optogenetic inhibition induced significant behavioral effects, including prolonged reach times. Analysis of task-related neural features during the motor planning period revealed significantly increased theta power, theta-gamma phase amplitude coupling (PAC), and trends of increased coherence near the IPS and in the 7a/7b regions of the PPC. Optogenetic inhibition resulted in distinct perturbations to task-related neural activity including increased theta and gamma power, decreased gamma coherence, and diminished theta-gamma PAC in opsin-expressing regions, with minimal effects in opsin-deficient regions. These findings highlight that optogenetic inhibition induces local network decoupling of task-related neural activity. Furthermore, this study demonstrates the potential of this large-scale optogenetic interface to unravel the neural mechanisms underlying neurostimulation and its impact on task-relevant brain dynamics.Clinical Relevance-This work provides insight into how targeted optogenetic inhibition may be used to ameliorate pathological brain activity related to neurological disorders.