SELECTIVE STRENGTHENING OF POLYSYNAPTIC INTERHEMISPHERIC CONNECTIONS WITH LATENCIES WHICH ARE MULTIPLES OF GAMMA-OSCILLATION PERIODS

The high-effective polysynaptic transcallosal connections were reveale d in the motor cortex of anesthetized rats. Polysynaptic connections w ere manifested in crosscorrelation histograms as high narrow peaks of width 1-2 ms and latencies up to the end of the analyzed interval in 5 0 ms. In most cases the polysynaptic transcallosal connections were re ciprocal. The incidence of transcallosal polysynaptic connections was twice as high as of the ipsilateral. Gamma oscillations were observed in the same neural assemblies. Interhemispheric oscillations were 1.5- fold more frequent than the ipsilateral ones. The peak latencies were multiples of gamma oscillation periods. The distribution of peak laten cies was similar to the distribution of gamma oscillations. It was sug gested that synchronous discharges in neurons in a polysynaptic interh emispheric pathway in consequence of gamma oscillations cause potentia tion in efficacy of neural connections, which promotes the high-effect ive transmission of a signal from one hemisphere to another.