Intensity dependence of auditory evoked potentials (AEPs) as biological marker for cerebral serotonin levels: effects of tryptophan depletion in healthy subjects

Abstract

The results indicate, in contrast to earlier indirect studies, that the intensity dependence of AEPs is not a specific marker of central serotonergic activity.

Serotonin Modulates Early Cortical Auditory Processing in Healthy Subjects. Evidence from MEG with Acute Tryptophan Depletion

“…Reduced serotonin function leads to higher intensity dependence of N1/P2 amplitude and vice versa. However, Dierks et al (1999) were not able to confirm these findings using ATD in healthy subjects. In contract, this study showed that ATD decreases the intensity dependence of N1/P2 amplitudes.…”

“…Several clinical and experimental studies using EEG have suggested that AEPs could be modulated by serotonin (Hegerl and Juckel 1993;Juckel et al 1997;Dierks et al 1999). EEG detects particularly the radial currents generated by activity in the cortical gyri, but also the tangential ones in the sulci.…”

“…The earliest cortical AEFs, the middlelatency AEFs (MAEFs), occur at about 20-70 ms from stimulus onset. The MAEFs are composed of several distinct deflections, with Pam peaking at approximately 30 ms and Nbm at about 45 ms.There is evidence to suggest that serotonergic activity may modulate auditory evoked potentials (Hegerl and Juckel 1993;Juckel et al 1997;Dierks et al 1999) and background EEG frequencies (Knott et al 1999). The sound intensity dependence of auditory N1/P2 amplitude has been suggested to be a specific indicator of serotonin function (Hegerl and Juckel 1993;Juckel et al 1997).…”

“…It is likely that in our study the ATD caused a reduction of serotonin synthesis in the temporal cortex, which is shown to modulate the MAEF responses. Thus, our MEG results suggest that serotonin transmission modulates the early phase of cortical auditory processing in the human brain.Several clinical and experimental studies using EEG have suggested that AEPs could be modulated by serotonin (Hegerl and Juckel 1993;Juckel et al 1997;Dierks et al 1999). EEG detects particularly the radial currents generated by activity in the cortical gyri, but also the tangential ones in the sulci.…”

Electrophysiological predictors of clinical response to antidepressants

“…Moreover, acute depletion of serotonin in healthy adults during administration of tryptophan did not alter LDAEP (Debener et al, 2002;Dierks et al, 1999;O'Neill et al, 2008b).…”