Electrophysiological Analysis of Deafferentation Effect on Visual Cortex in Rats

ABSTRACT

PURPOSE: Temporary deafferentation (TD) by local anesthesia in small parts of the body induces an immediate and reVersible reorganization of the receptive field (RF). It is thought that an adaptation for deafferentation would occur in the visual system. Therefore, in this study, simultaneous multi-single unit recording (SMSUR) from visual cortex (VI cortex) of rats have been carried out to characterize; 1) the TD-induced changes in the populational activities of single neurons, 2) the alteration of the neural network among neurons in each area during TD and 3) the synaptic mechanism underlying the neuronal plasticity of the visual system. METHODS: Using four channels of a multi-electrode made from tungsten microwire, the neuronal activities (evoked responses and spontaneous activities) and networks in the VI cortex of anesthetized rats have been investigated. In this study, TD was induced by a retrobulbar injection of lidocaine (2%, 0.1 ml). RESULTS: After the induction of TD, the cortical neurons showed reversed changes in their evoked reoponses. The induction of TD suppressed the activities of the target cells in the VI cortex. However, TD also caused facilitation of the activities of the neighboring neurons. The spontaneous activities of the neighboring neurons were also gradually facilitated after the induction of TD and then gradually recovered to their initial control period values. CONCLUSIONS: The results from the present study suggest that; 1) TD-induced plasticity of the central visual system involving the VI cortex may be due to disinhibition of the lateral inhibition and 2) the spontaneous activities of the VI cortical neurons, as well as evoking responses, may be involved in the TD-induced visual plasticity of anesthetized rats.