Pattern of cortical connections of the ventral premotor cortex in a new world monkey: Impact of a primary motor cortex lesion

The present study aimed at describing (1) the pattern of connections of the physiologically defined ventral premotor (PMv) hand representation in squirrel monkeys and (2) the impact of a primary motor cortex (M1) lesion on this pattern of connection.;Neuroanatomical tracing methods were combined with neurophysiological and histochemical techniques to allow precise documentation of the injections cores locations and the distribution of connections in relation to the hand area of PMv, M1, the primary somatosensory cortex (S1) and the supplementary motor area. Results obtained in naive animals were compared to the one obtained from animals that recovered for several months from an ischemic infarct destroying the majority of the hand representation in M1.;In naive animals, we show that the pattern of connection with M1 is far more complex than originally expected and that connections with S1 hand area are very sparse and inconsistent across cases. Following the recovery from an M1 ischemic lesion, we show that PMv (1) ipsilesional connections reorganized at the rostral border of the lesion and form novel atypical connections with the somatosensory area 1/2 hand representation; (2) interhemispheric connections with contralesional M1 are increased; (3) that the disruption of connectivity of PMv with M1 is not the factor triggering the physiological expansion of PMv hand representation in the ipsilesional hemisphere.;Results presented provide significant improvement of our knowledge of PMv connections in naive animals. This new information challenges conventional thinking concerning the relation of PMv with M1 and S1. In addition, the extensive anatomical cortical plasticity we describe in the central nervous system (CNS) of adult animals was previously unsuspected. It reveals tremendous adaptive capacity of the CNS that could certainly be exploited for maximization of recovery following an injury, such as might occur following stroke. We thus believe that the set of data presented will have great repercussions on the diverse fields of neuroanatomy, motor control, plasticity and rehabilitation following central nervous system injury.