Electrophysiological analysis of deafferentation effect on visual cortex in rats

Abstract

Abstract: : Purpose: Temporary deafferentation (TD) by local anesthesia in small part of the body induces an immediate and reversible reorganization of the receptive field (RF). It is thought that the adaptation for the deafferentation would occur in the visual system. Therefore, in this study, we have carried out simultaneous multi–single unit recording (SMSUR) from visual cortex (VI cortex) of rats to characterize 1) the TD–induced changes of populational activities of single neurons, 2) the alteration of neural network among neurons in each area during TD, and 3) the synaptic mechanism underlying neuronal plasticity of the visual system. Methods: Using four channels of multi–electrode made with tungsten microwire, we have investigated the neuronal activities (evoked responses and spontaneous activities) and networks in the VI cortex of anesthetized rats. In this study, TD has been induced by retrobulbar injection of lidocaine (2%, 0.1 ml). Results: After TD, cortical neurons have shown opposite changes in evoked reoponses. TD induced the suppression of activities of the target cells in VI cortex. However, TD caused the facilitation of activities of the neighbor neurons. The spontaneous activities of neighbor neurons were also gradually facilitated after TD and then recovered gradually to initial value of control period. Conclusions: Results from the present study suggest that 1) TD–induced plasticity of central visual system involving VI cortex may be due to the disinhibition of the lateral inhibition, and 2) spontaneous activities of VI cortical neurons, as well as evoked responses, may be involved in TD–induced visual plasticity of anesthetized rats.

Keywords: visual cortex • plasticity • electrophysiology: non–clinical