Motor cortical representation patterns reorganize following forelimb nerve injury in adult mammals
摘要
We examined the relationship between the digits before and after reorganization in the digital area of the motor cortex (MCx-digital area) in adult cats following denervations of the ulnar and median nerves. A single tungsten-in-glass microelectrode was inserted into the depths of the MCx-digital area for recording unitary spikes and intracortical microstimulation (ICMS). The receptive fields (RFs) of neurons were examined using natural stimulation. The ulnar nerve and median nerve were denervated under nembutal anesthesia (40 mg/kg, i.p.). At 1 week following denervation of the ulnar nerve, neurons within the MCx-digital area, with RFs on the III-V pads were lost. At 1 and 3 months following denervation, the number of neurons within the MCx-digital area increased and responded to touch on the I and/or II pads. A small number of neurons in the MCx-digital area responded to light touch of the metacarpal pad. In addition, a small number of neurons within the MCx-digital area responded to touch of the dorsal I and II digital skin. On the contrary, at 1 week following denervation of the medial nerve, neurons within the MCx-digital area, with RFs on the I and/or II pads were lost. At 1 and 2 months following denervation, number of neurons within the MCx-digital area increased and responded to touch on the IV and/or V pads, and II-V dorsal digits. At 1 week following denervation, with ICMS into the MCx-digital area, a small number of neurons produced flexion on the contralateral side of the I and II digits. At 2 and 3 months ICMS into the MCx-digital area produced flexion on the contralateral side of I and/or II digits. In addition; ICMS into the MCx-digital area produced extension on the contralateral side of the I and II digits. At 1 week ICMS into the MCx-digital area, neurons produced flexion on the contralateral side of the V. At 1 and 2 months ICMS into the MCx-digital area produced flexions of V, IV-V and II-V.