[Background and evoked activity of visual cortex neurons of a mutant strain of mice]

Background and evoked activities of visual neurons were studied in mice with hereditary microphthalmia ("ocular retardation", "or/or"). Phenotypical action of the "or" gene manifested itself in underdevelopment of the optical nerve followed by full blindness of the animal. Control experiments were carried out on C57Br mice. Higher level of background activity in neurons of mutant animals as well as differences in distribution of neurons according to the type of background activity were found. In the "or/or" mice regularly firing neurons were 2.5 times as frequent while bursting cells were 2.7 times as seldom as in the control group. Mutant mice cells were more reactive to sounds. Their responses to sound and cutaneous stimulation were usually tonic and mostly of excitatory nature. Convergence of heterogeneous afferent signals was demonstrated for 42% of mutant mice cells. It is suggested that these functional properties are phenotypical manifestations of mutant gene action on cortical neurons.