[Event related potentials and reaction time on auditory discrimination tasks (2nd report)--a study by trial-to-trial...

Latency variability for single trial in the 4 components (N100, P200, N200 and P300) of the auditory event related potentials (ERP) and the temporal relationship to the choice reaction time (RT) were investigated in 11 normal subjects. Identification of each latency on single trials was derived by using a correlational-template procedure. Results showed that the mean value of the single trial latency in the 4 components was close to the peak latency in the averaged waveform. Significantly larger coefficient of variation was obtained for the N100 component and RT, when compared to the other components. Higher correlation between single trial latency and RT was found for N200 and P300 components. The P300 component latency yielded a significant temporal effect across trials (p < 0.05) showing increases in its latency in the later trials, whereas none of the RT did. These results may indicate that the P300 component latency is influenced directly by subtle changes in cerebral activities during an initial stage of human cognitive function occurring in each trial, whereas RT is additionally influenced by greater functional fluctuation during the process of motor execution for making responses.