Background noise content of evoked responses from facial nucleus of cat.

Abstract

A correlation dependent technique for determining signal: noise levels in serial evoked responses was used to measure background noise activity in acute and chronic cat preparations. In the former, topographic mapping of an area of the brain stem concerned functionally with performance of an eye blink showed no significant change in background noise over several mm of the signal space. The averaged amplitudes and signal: noise ratios of the evoked potential responses were maximal at the area of the facial nucleus, the motor nucleus through which information related to the movement was transmitted.Changes in the background noise of evoked electrical responses were observed during performance of a conditioned eye blink. These increases in background noise above levels associated with the unconditioned blink to glabella tap appeared to depend on the nature of the afferent input rather than on learning effects per se. That is, the cortically mediated input was noisier than that from the trigeminal system.Changes in background activity of less than 10 μV following the administration of Flaxedil were within the sensitivity of the measurement technique.