Encoding of Stimulus-driven and Intention-driven Actions in Monkey's Primary Motor Cortex

Actions can be divided into two modes, one is driven by intention without stimulus, another is in response to external stimulus. Previous studies have shown that these two modes of movement may be manipulated by different physiological pathways in the brain. However, the neural coding of them in motor cortex is still unknown. In this study, we trained rhesus monkeys performing external stimulus-driven and internal intention-driven arm movement tasks, and recorded neuronal activity in primary motor cortex (M1). We aimed to compare the neuronal coding between stimulus-based and intention-based action modes. We found that neurons fired in different patterns while doing internal intention-driven arm movement. These neurons show no significant difference between intention-based and stimulus-based tasks during movement execution period. We also set up a general linear model to quantify the encoding strength of M1 neurons towards movement parameters in different action modes.