ИСТИНА

The causal mechanisms of spontaneous attentional performance lapses in healthy alert individuals during purposeful responses to complex auditory stimuli remain largely unknown. In order to investigate this question, two versions of the auditory condensation task were used, which involves both stimuli feature binding and response selection. In the first experiment, 56 participants performed the task in which four auditory tones were presented, each having two distinct features: "low" or "high" (500 Hz or 2000 Hz sinusoidal signal), "noised" or "pure" (with or without broadband noise admixed). Participants were asked to press one or the other button depending on the conjunction of the two features. The instruction didn’t prompt the participants to respond quickly or to respond in the event of uncertainty. Event-related potentials (ERPs) were separately measured for the three outcomes (correct responses, errors, and a response omission). Both manifestations of inattention (errors and omissions) produced the 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 the second experiment, which combined odd-ball and classical condensation tasks, frequent distractors were presented amongst four target stimuli (target stimuli were the same as in experiment 1). In experiment 2 participants (N=48) made almost no omission, thus ERPs were obtained only for correct responses and errors. No difference was found between correct responses and errors in P2 amplitude. Amplitude of mismatch negativity (MMN), calculated for correct responses was slightly, still significantly bigger than the MMN for errors. Late deflections (such as N2 and P3) were clearly seen, and P3 amplitude was also bigger for correct responses. Since the participants had no problems in understanding the response rules, and they apparently had no problems in recognizing the stimuli in pretest series, the behavioral lapses could be hypothetically explained by reallocation of the attentional resources to some covert activity. The ERPs pattern for erroneous responses hints the idea that such reallocation of resources first of all affects the relatively early stages of auditory processing (reflected in P2 and MMN).