ИСТИНА

Neural processes guiding purposeful and adaptive behavior by representing task-relevant information in brain networks are commonly referred to as cognitive control system (Botvinick et al., 2001; Yeung, 2013). Frontal midline theta rhythm (FMT) is believed to be related to cognitive control processes, and it is known to be modulated conflicts and by error commissions (Cavanagh, Shackman, 2014). The present study is aiming at investigation of relations between errors and FMT power in the auditory condensation task. This task involves high percentage of errors while producing the overall performance significantly above chance level, and it allows investigation of cognitive control during spontaneous attentional lapses. Data were obtained from 80 healthy volunteers with normal hearing (mean age - 19.6±1.4 years). Four brief (40 ms) tones were presented with equal probability. Each stimulus required pressing one or the other of two buttons; constant stimulus-to-response mapping was based exclusively on feature conjunction. The stimuli were presented with random stimulus onset asynchrony of 2500 ± 500 ms. FMT power was calculated 1000 ms before each type of response (correct response, error or omission). Participants made errors in 9.6 ± 1.1% of trials and response omissions in 5.4 ± 0.7% of trials. Average response time for errors was significantly higher than for correct responses. Group-level analysis did not reveal significant differences in prestimulus FMT power for correct and incorrect trials (errors and omissions). Individual statistics revealed that FMT power was significantly higher before errors compared to correct responses in 10 subjects, while only 1 subject demonstrated the opposite effect. Relative change in FMT power before incorrect responses pooled together as compared to correct responses was negatively correlated with the percentage of errors and positively correlated with the ratio of response times for erroneous and correct responses. Low pre-stimulus theta power was related to significantly higher number of incorrect trials grouped into uninterrupted series. Spontaneous fluctuations of attention can lead to the state characterized by higher probability of error commission. Reduced FMT power is considered a hallmark of reduced ability to monitor task performance, and, conversely, increased FMT power reflects increased activity of conflict monitoring system (Cohen et al., 2009; Cohen, Donner, 2013). Subjects with relative increase in FMT power before incorrect responses compared to correct ones had better task performance. This may mean that these subjects actually committed some of these incorrect responses during the state of increased cognitive control, which at the same time allows them to perform better in most other trials. In contrast, subjects with no FMT increase performed the task less successfully, suggesting that errors were more frequently committed during the low-control state. From this point of view, the relative increase in erroneous response time that was correlated with the FMT increase could be considered an aspect of cognitive control exertion leading to more accurate responding. The overall high power of pre-stimulus FMT could be also a correlate of the ability to quickly re-instantiate the control over task performance resulting in the absence of grouping of incorrect responses into uninterrupted series.