Nd and P300 in Healthy Volunteers

We attempted to standardize values of the attention-related negative potential (Nd) and the P300 in 100 healthy volunteers (50 females, 50 males) who were given the task of making dichotic syllable discriminations requiring key-press responses. Ages ranged between 18 and 59 years. Nd was found to be maximum in the Fz region, P300 being maximum in the Pz region. The means and standard deviations of the Nd and P300 areas in their maximum regions were 554.1 ± 307.8 μV • msec and 2148.5 ± 1261.5 μV • msec, respectively. After being transformed into logarithmic values, the distribution patterns of the Nd and P300 areas followed a Gaussian distribution. When the lower limit of normal values was tentatively assigned to mean − 2 SD using logarithmically transformed data for both Nd and P300, 94% of the subjects were found to display values above the lower normal limit for Nd, and 95% for P300. Neither Nd nor P300 areas correlated with age, while P300 latencies displayed a weak positive correlation with age. Females displayed relatively larger values than males for Nd and P300 areas and P300-peak amplitudes. Females and males showed nearly equal P300-peak latencies.