Studies on the membrane properties of the cat parietal cortical pyramidal neurons concerning motor compensation

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The aims of this project are to investigate the electrophysiological and morphological substrates for the neural plasticity concerning the motor compensation. During the research project, we investigated the three aspects of the neuronal system. First, we examined the membrane properties of cortical neurons from slice preparations of the cat sensorimotor cortex and the parietal cortex. Second, we studied the changes of the cerebello-parietal projection after ablation of the motor cortex. Third, we revealed the time course and synaptic plasticity after the facial nerve suture. At the end of the project, we obtained several results on these three projects. Concerning slice experiments, we found that the burst firing neurons exist in the layr III of the sensorimotor cortex. When applying high frequency stimulation (tetanus stimuli) onto the white matter, layr III and V pyramidal neurons displayd long term potentiation or depression with membrane potential changes in either direction. Such synaptic plasticity may not be concerned with NMDA receptors. In the second project, we must continue the experiment, beacause the constant changes of the cerebello-parietal responses could not be obtained after the motor cortical ablation. However, in the third project, we reported the early regeneration of the sutured facial nerve. The functional recovery examined by the facial muscle EMG was detected as early as 11 days after suture. During the regeneration of the sutured facial nerve, we also found that the trigemino-facial reflex showed transient change in 1-2 weeks after operation, i.e., the reflex nerve discharges were induced not only in the main branch as normal but also in the posterior-auricular branch. Such a transient change of the reflex pattern returned normal in 3 weeks after suture. We are now planning to examine the details in such a change electrophysiologically as well as morphologically.