[Comparison of cognitive potential P300 with high and low frequency stimulus in early onset blind subjects]

Previous studies suggest that auditory stimulus frequency in normal subjects contribute to both P300 amplitude and latency measures. As occipital cortex devotes to other modalities including auditory inputs, the purpose of this study was to determine the effects of stimulus frequency in early blind subjects. Fifteen early blind subjects [8 males and 7 females] with mean age of 25.13 +/- 4.27 years were tested. Cognitive potential P300 was recorded in response to high [1000/2000Hz] and low [250/500 Hz] frequencies auditory stimuli using an oddball task in 70 dB nHL. While participants answered to target stimulus, amplitude and latency of P300 was recorded. With high frequency stimuli, mean amplitude in early onset blind subjects obtained 14.13 +/- 5.53 micro v and was 17.59 +/- 8.17 micro v with low frequency. With high and low frequency, mean latency of P300 obtained 295.60 +/- 31.33 ms and 317.38 +/- 21.71 ms respectively. Comparison of results between two stimuli showed that there were statistically significant differences between amplitudes [p=0.008] and latencies [p=0.001] of cognitive potential P300. Changing low frequency to high frequency results in decreasing both amplitude and latency. It seems that auditory stimuli frequency affect the P300 parameters in blind subjects