Deficits and recovery of body stabilization during acrobatic locomotion after focal lesion to the somatosensory cortex: a kinematic analysis combined with cortical mapping.

Abstract

We used a kinematic analysis for assessing locomotor impairments and evaluating the time course of recovery after focal injury to the forepaw area of the primary somatosensory cortex (SI) in rats. The animals were trained to traverse a beam that was rotated at various speeds. Changes in orientation of the body and independent movement of the anterior and posterior parts of the body were reconstructed using a 3D motion analysis. In addition, we used electrophysiological cortical mapping to search for neurophysiological changes within the spared cortical zones surrounding the lesion. Neuronal recordings were performed in the same animals prior to and 3 weeks after the lesion induction. Our findings show that a focal lesion that destroyed about 60% of the forepaw representational zone was sufficient to cause conspicuous impairments in the rats' ability to produce adequate motor adjustments to compensate for the lateral shift of the beam and to avoid falling. The main deficits were reflected in a lack of appropriate coordination between the anterior and posterior parts of the body and an inability to maintain a regular gait during locomotion. Skilled locomotion was fully recovered within a 2-3 week period. Functional recovery cannot be ascribed to a restitution of the lost sensory representations. A permanent decrease of forepaw representation was recorded despite the re-emergence of restricted representational sectors in the peri-lesion zone. We suggest that alterations may have occurred in other cortical and subcortical areas interconnected with the injured area. It is also conceivable that the functional recovery involved an increased reliance on all the available sources of sensorimotor regulation as well as the use of behavioral strategies.