Time evolution of acoustic 'information' processing in the mesencephalon of Wistar rats

A traditional analysis of intra-encephalic auditory evoked potentials does not highlight the dynamical evolution of the auditory 'information' processing in neither time nor space. This work presents a method for tracing such signal evolution throughout the primary auditory pathway in the mesencephalon of adult anesthetized Wistar rats, using a unilateral 3 kHz tone burst stimulus. The results of the acoustic evoked potentials mapping are presented as conventional 20 ms recordings and re-analyzed in intervals of 1 ms-time windows. The parameter used, as an 'activity' correlate, was the maximum/minimum voltage difference obtained from each time window. The methodology used clearly indicates sequential signal propagation from the dorsal and ventral nuclei of the lateral lemniscus up to the inferior colliculus.