[Formation of neuronal activity in the association area of the cortex in developing cats]

Background spike activity as well as activity evoked by photic and acoustic stimulation in units of the associative cortex (field PMSA) was investigated in experiments on curarized kittens aged from four to six hours up to 60 days. Background activity of single PMSA cells appears from the first day of the animal's life. The mean frequency of impulsation is low; it changes but slightly during the first two weeks. Evoked spike activity in response to light is recorded from the end of the first week of the animal's life. Responses to sound appear somewhat later. During the second week the number of monosensory cells increases. Later ther is a diminution of the relative number of monosensory units and an increase in the number of bisensory ones. The results are discussed in the aspect of heterochronic systemic maturing of cortical cells in ontogenesis.