Complex Movements for Voluntary Actions Evoked by Electrical Stimulation in the Motor Cortex of Rats

Electrical intracortical microstimulation (ICMS) has been widely used to study the functional organization of the motor cortex. The ICMS with longer stimulus trains of about 500 ms (long-duration ICMS) evoked complex and coordinated movement, similar to those of natural behaviour. A recent paper (Ramanathan et al., 2006) have reported that long-duration ICMS in rat motor cortex can result in complex, multijoint forelimb movements organized in a roughly topography. We pose the question if different features of motor control (e.g. body map, movement patterns, target location in space) can develop overlapping maps in the forelimb region of the rat’s M1. We performed long-duration ICMS to evoke complex, multijoint forelimb movements and we used 3D motion analysis tools to measure kinematic variables of electrically-evoked movements. The analysis was aimed to define the classes of movement and their topography across the cortical surface. Then, the following kinematic parameters, related to the limb and the paw component, were determined from the analysis: maximal displacement in XYZ, latency, duration, peak velocity, mean velocity, number of peak velocity , trajectory, vector, path index. According to our methode, the repertoire of the limb movement included: abduction, adduction, extension, retraction and elevation while paw movements included: opening, closure, opening/closure sequence and supination. To analyze our data, multivariate test for difference in means (MANOVA), one-way ANOVA and Tukey’s test were performed.