Abstract
Rats with neonatal hemidecortication exhibit fairy normal tactile placing reflex (Barth and Stanfield 1990) and reach-grasp movements (Takahashi et al. 2007) of their contralesional forelimb. The neuronal mechanism for the control of contralesional forelimb movements in these animals remains to be clarified. In the anterograde tracing experiments, we have shown that corticospinal fibers originating from the sensorimotor cortex of the remaining side issued aberrant collaterals to the contralesional spinal gray matter. The present study was designed to investigate whether the aberrant collaterals establish functional connections to contralesional forelimb motoneurons as well as ipsilesional motoneurons in the hemidecorticated rats. In the intact animals, electrical stimulation to the medullary pyramid induced no clear field response in the spinal gray matter nor EPSP/IPSP in forelimb motoneurons on the ipsilateral side to the stimulus. In the hemidecorticated rats, in contrast, stimulation of the remaining pyramid elicited negative field potential in the dorsal horn of bilateral cervical spinal cord. Oligosynaptic pyramidal excitation and/or inhibition were detected in intracellular recordings from motoneurons on both sides. The results indicated that pyramidal neurons in the remaining cortex could transmit signals to contralesional motoneurons via a few synapses. We will also describe the location of the intercalated neurons in the presentation. [J Physiol Sci. 2008;58 Suppl:S195]
