EFFECTS OF VASOPRESSIN ON EVENT-RELATED POTENTIAL INDICATORS OF COGNITIVE STIMULUS-PROCESSING IN YOUNG AND OLD HUMANS

Background. Vasopressin has been shown to improve electrophysiological signs of cognitive stimulus processing in young human subjects. This study compared the effects of arginine vasopressin (AVP) on central nervous stimulus processing in old and young mentally healthy subjects. To assess aspects of cognitive stimulus processing, event-related potentials (ERPs) were recorded. Method. A total of 22 old and 28 young subjects were tested on two subsequent days. Substances were administered intranasally 22, 12, and 1 hour(s) prior to experimental sessions. Prior to the first session, all subjects received placebo. Prior to the second session, 11 of the elderly and 15 of the young subjects received AVP (3 x 10 IU in each nostril) while the remaining subjects again received placebo. The study was held double blind. The subjects performed an auditory ''oddball'' task consisting of rare target tones (requiring a button press response) interspersed throughout a sequence of frequent standard tones while an electroencephalogram was recorded. Results. Differences between young and aged subjects were more pronounced for ERPs to targets than standard pips. Latencies of the N2 and P3 waves of the ERP to targets were significantly prolonged, and the P3 amplitude was diminished in the elderly subjects (p < .01). N2 amplitude was enhanced in both age groups by vasopressin (p < .05). However, AVP treatment significantly enlarged the N2-P3 difference amplitude only in young subjects. Conclusions, The results indicate that AVP improves ERP signs of stimulus processing associated with attentional mechanisms. However, the ERP signs of age-related cognitive impairment remained unimproved after AVP.