Curso temporal de la amplitud del potencial evocado auditivo de estado estable en ratas

Abstract

Auditory steady state response (ASSR) generated by amplitude-modulated tones has been used during
the last decades for the assessment of hearing in humans. This response is obtained by averaging successive epochs
(segments) of a recording in order to remove the background electrical activity. One of the theoretical assumptions of
averaging states that both the amplitude and phase of the response remain stable over time. However, a decrease of the
ASSR amplitude during averaging has been recently demonstrated. In accordance with the theoretical assumption noted
above, this fall of amplitude would correspond with the background noise cancelation. In the present study, the time
course of ASSR during averaging was analyzed. Concurrently, the amplitude of the independent epoch (not averaged
segments) as a function of time was also analyzed in order to elucidate whether the decrease of the ASSR amplitude during
averaging also resulted from physiological process occurring in the neural circuits involved in the auditory response.
Results obtained demonstrated a decreased of amplitude in the individual epoch corresponding with the first seconds
of recording. The fall of the amplitude depended on both intensity and carrier frequency of the stimulus. These results
suggest that physiological processes that occur in the neural populations responding to the stimulation are associated
with the decrease of the ASSR amplitude during averaging. Up to now, this phenomenon has not been taken into account
for obtaining the ASSR. Therefore, results presented here could have clinical implications, changing the ASSR-based
procedure used at present to estimate the psychophysical auditory response.