ИСТИНА

We addressed the question whether ERP parameters may be identified as correlates of spontaneous errors related to failures in information processing in alert non-clinical subjects. Relying on the behavioral data (Dyson and Quinlan, 2003; Thompson, 1994), we used the condensation task (Garner, 1975), which creates high cognitive load (Chernyshev et al., 2012, 2014). In experiment 1 four brief tones were presented with equal probability. The stimuli could be discriminated by way of conjunction of two distinct features: pitch and noisiness (high pure, high noised, low pure and low noised sounds). Participants were asked to discriminate the stimuli and to respond by pushing one of the two buttons. Evoked potentials were separately averaged for each response type. Data were obtained in 56 participants. Both manifestations of inattention (errors and omissions) produced a similar pattern of changes in the ERPs - a statistically significant increase in the P2 amplitude. Later N2 and P3 peaks were rather small in amplitude, and no effects were found within their time ranges. In experiment 2 the condensation task was integrated into the oddball task. In addition to four stimuli described above, additional pure tone was added as a frequent standard stimulus with the probability ratio of 4:1. As in experiment 1, participants were asked to discriminate the stimuli and to respond by pushing one of the two buttons. Data were obtained in 48 participants. Participants made almost no omissions, thus ERPs were measured only for correct responses and errors. N2 amplitude was higher for correct responses than for errors. Interestingly, the N2 peak in experiment 2 was observed in almost the same time-window as the P2 peak in experiment 1 (around 180 ms after stimulus onset). Taken independently, N2 effect, observed in the second experiment, hints at possible deterioration of cognitive control (Botvinick et al., 2001) preceding errors. Less clear is the role of P2 effect in the experiment 1. Current evidence suggests that increased P2 reflects discontinuation or suppression of information processing (Melara et al., 2002). We can speculate that enhanced P2 is a reflection of some processes in the auditory cortex which leads to premature termination of signal information processing, and consequently to failures in the behavioral response. This process may be similar to the “rejection positivity” described by Alho et al. (1987). Another possible explanation, suitable for both experiments, is the presence of a superimposed wave, which leads to a negative shift of the ERP preceding correct responses and thus affects both N2 and P2 amplitudes. The nature of this wave is probably similar to the processing negativity (Näätänen, 1978) reflecting shifts in the attentional state of the subjects.