(2c) Chronic Electrophysiological and Behavioral Response in Rats Due to Cerebral Ischemic Stroke in the Motor Cortex

This work is the beginning of a study investigating dynamic changes of electrophysiological and correlative behavioral response in rats before, during and after stroke. Stroke was induced in the primary motor cortex area controlling forelimb movement, and an implanted microwire electrode recorded neural activity. Animals performed behavioral tests, including a cylinder test that characterizes neural damage with asymmetrical forelimb use, and the pasta manipulation test, which evaluates forepaw function while eating uncooked pasta. The rats need training to regularly perform the tests. The standard deviation of total paw touches in the cylinder test and the time needed to eat a pasta strand decreased by a factor of 1.7 and 3.6 respectively after 5 days of training (n=4).

Behaviorally, post-stroke, cylinder touches decreased by a factor of 5.6, and pasta time increased by a factor of 3.6 suggesting stroke caused impairments (n=1). The pre-stroke mean neural firing rate was 94 spikes per second (spk/s), this increased to 146 spk/s during the 20 minute stroke induction, and was only 4 spk/s 20min post-stroke. The firing increased to near pre-stroke levels in days 2-3 after stroke. These preliminary studies suggest that this technique has potential to assess the complex process of neural reorganization/rehabilitation following brain injury due to stroke.