Modulation of Neural Variability in Premotor, Motor, and Posterior Parietal Cortex during Change of Motor Intention

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• The parieto-frontal system, including dorsal premotor cortex (PMd), primary motor cortex (MI), and posterior parietal cortex (PPC), is vital for planning and executing reaching movements.
• Lesions in these areas disrupt trajectory formation and correction, highlighting their critical role in motor control.

Purpose of the Study:

• To investigate the temporal dynamics of neural variability in key motor control areas (PMd, MI, PPC) during both unperturbed and perturbed reaching movements in monkeys.
• To understand how neural variability changes during the updating of motor intentions in response to unexpected events.

Main Methods:

• Monkeys performed direct reaches or reaches requiring direction changes after unexpected target shifts.
• Neural activity and variability were recorded in PMd, MI, and PPC during these tasks.
• Comparisons were made between unperturbed and perturbed reaches to analyze context-dependent neural patterns.

Main Results:

• Neural variability decreased before movement onset in both frontal and parietal areas during unperturbed reaches.
• Unexpected target changes led to complex, area-specific modulations in neural variability, with signals appearing earlier in PMd.
• Identical hand movements exhibited different variability patterns depending on the context (perturbed vs. unperturbed), indicating context-dependent neural coding.
• Neural variability in PMd was higher before reach initiation than before correction, potentially explaining faster corrections.
• Lower neural variability predicted faster reach corrections, while higher variability predicted slower corrections.

Conclusions:

• Neural variability exhibits complex, context- and area-dependent modulation during motor intention updates.
• The findings provide neural underpinnings for why movement corrections are faster than initial movements.
• Analysis of neural variability is a valuable tool for studying complex motor cognition and intention updating.