Vasopressin and electrophysiological signs of attention in man

Seventeen pairs of monozygotic twins, females and males, were tested in a dichotic listening task, containing several types of pips: standard and deviating target pips, which the subject either attended to, or not. Averaged auditory evoked potentials (AEPs) to the pips provided measures of different attentional processes. Furthermore, EEG power spectra, heart rate and blood pressure and behavioral performance were measured. Subjects received treatments (20 I.U. lysine-vasopressin vs. placebo) intranasally 48, 24, and 1 hour prior to the experimental sessions according to a co-twin control design. Whereas measures of voluntary selective attention remained unchanged by lysine-vasopressin (LVP) the peptide primarily affected an attentional mechanism responding in an automatic fashion to stimulus deviance. This effect was indicated by a substantial negative shift of the AEP amplitudes following deviating stimuli within the latency range of the N2/P2 components (about 200 msec post-stimulus). The effect seemed to be unrelated to modulations of cortical arousal after LVP.