Influence of long-term intracortical microstimulation on the motor cortex

Long-term (0.5–1 s) stimulation of the hand region of the motor cortex in both macaque and human through a microelectrode by a series of biphasic current pulses of small amplitude evokes different complex, coordinated movements of the hand. There are two different opinions on how these movements are produced. The first hypothesis associates the movements with the presence of specific subregions in the motor cortex, which reflect different ethologically relevant categories of movement. According to the second hypothesis, these evoked complex movements are the artifacts of electrical stimulation. This article discusses the results of a number of studies in favor of each of the hypotheses. The conclusion about the validity of the first hypothesis is based on the analysis of the results of microstimulation and their comparison with the data obtained by the latest methods without the use of electric current. Moreover, this finding suggests the possibility of testing the condition changes of the monkey motor cortex through analysis the characteristics of the movements caused by long-term microstimulation.