SPECTRAL-ANALYSIS OF EVENT-RELATED POTENTIALS

Event-related brain potentials (ERPs) of twenty normal subjects with no sign of neurologic diseases were measured by applying nontarget and target stimuli as green and red lights respectively. ERPs were recorded in two experimental conditions that the target stimulus was counted (Test 1) or uncounted (Test 2). The spectral analysis of ERPs recorded for Test 1 and Test 2 were computed by using the Transient Responses Frequency Characteristics (TRFC) method. Amplitude maxima were observed in the frequency bands as indicated: 1-2, 3-4, 5-6, 7-8, 8-12, 13-20, 20.5-36, 36 Hz and higher. When we compared Test 2 with the results of Test 1, we observed a significant decrease in the amplitude mean (decibel) of 1-2 Hz frequency band (p < .05). Repeated measures ANOVAs also showed that dB values of 1-2 Hz between counted and uncounted stimuli were significantly different (p < .04). When the number of subjects displaying amplitude maximum in each frequency band was considered, we have found important differences in 1-2, 3-4 Hz and 5-6 Hz bands.