Neuron Activity In Monkey's Primary Motor Cortex During Action Selection

One of the most important process in the brain control of voluntary movement is action selection.In addition to motor disorders,patients with Parkinson's disease generally show defects in action selection.Action selection can be divided into two categories.One is driven by internal intention without an external stimulus,another is in response to external stimulus.Previous studies have shown that the two kinds of action selection may be controlled by different brain regions.However,their neural coding in the motor cortex,and whether Parkinson's disease has different effects on them is still unknown.Primary motor cortex(M1)plays an important role in motor control of brain,but we know little much about the neuronal coding pattern of this brain area in action selection at present.In order to compare the coding similarities and differences between the stimulus driven and intention driven action selection in M1,in this study we trained rhesus monkey to perform stimulus-driven and intention-driven action selection tasks.We recorded the neuronal activity of M1 from one monkey and behavioral signals in the task simultaneously.Then we analyzed the neuronal activity of task-related single-unit and population data.Furthermore,we set up a general linear model(GLM)to detect the neuron coding strength of kinematic parameters in different action selection modes.We found that in different action selection modes,there are extensive heterogeneity among M1 neurons with many different response patterns.According to the population data,the difference between the two modes of action selection is mainly reflected in the preparation stage of the movement.After analyzing the coding pattern of kinematic parameters in general linear model,we found two peaks in the movement preparation stage and the execution stage in the intention driven mode,and there are some neurons whose GLM coefficients in intention-driven mode are obviously higher than the coefficients in stimulus-driven mode,suggesting that the M1 may have different coding processes in different driven modes of action selection.In summary,we analyzed the neural signals of the primary motor cortex of rhesus monkey while performing intention-and stimulus-driven action selection tasks,and discuss the relationship between M1 activity and kinematics parameters in different modes of action selection qualitatively and quantitatively.The understanding of the neural mechanism of M1 may help us to deeply comprehend the neural circuits in diseases related to the brain motor control system,such as Parkinson's disease,and provide new insights for the treatment.