Time series analysis of neural facilitation of muscle activation recorded using chronically implanted microwire arrays

The role that neurons in the motor and premotor cortical regions have in facilitating muscle activation during reaching and grasping tasks can be detected through cross-correlative techniques such as spike triggered averaging (SpTA). The use of chronically implanted electrodes can provide information regarding the dynamics of this functional role over time. Using chronically implanted microwire arrays with electrode insertion lengths of 1.5 mm, 2 mm and 2.5 mm, recording from the motor and premotor regions, this study examines the effects that the initial depth of electrode implantation has on 1) the total number of units facilitating muscle activity over time; 2) the total number of units detected over time; and 3) the total number of units correlated with task-dependant parameters over time. To determine the facilitative role that recorded units play in activation of muscles during task performance, the EMGs recorded during movement from the center holding pad to the target are cross correlated with the recorded spike activity using SpTA. The results suggest that the initial depth of implantation has a significant effect on the total number of facilitating units detected, the total number of units detected, and total number of units correlated with target direction and target orientation in the specific reach to grasp task. Results also suggest that a significant increase in the number of units is detected at initial depths greater than 1.5 mm. In most cases, initial depths of 2 mm produce a significantly greater number of total units compared to initial depths of 2.5 mm.