ИСТИНА

Mechanisms of cognitive control include monitoring and regulation of both task-specific attentional processes and non-specific motor threshold. Failures in one or the other of these two mechanisms may lead to different kinds of responses, post-response adaptations and, importantly, distinctive behavioral correlates. Slow responses can be interpreted as responses committed after attentional lapses and, therefore, during the state of uncertainty, while fast responses can be interpreted as responses committed in conditions of lowered motor threshold. Thus, slow and fast errors have different nature and require different brain adaptations. The aim of the current study was to confirm the idea that modulations in oscillatory brain activity can distinguish between these two types of responses. EEG was recorded during performance of the auditory two-choice condensation task, which requires sustained attention and does not require inhibition of prepotent responses. Increased frontal midline theta (FMT) power was observed during pre-response time interval for both correct responses and errors. Enhanced error-related FMT power was found in post-response and post-feedback time intervals. Increased frontal beta power was observed in post-feedback time interval. We also observed significant positive trial-to-trial correlation between pre-response FMT power and response time (RT) for both correct responses and errors, negative trial-to-trial correlation between post-response FMT power and RT for errors, and positive trial-to-trial correlation between post-feedback frontal beta power and RT. Thus, slow erroneous responses characterized by high uncertainty were accompanied by increased FMT power before the response and by increased frontal beta power following the feedback; these effects, presumably, reflect enhanced cognitive effort and feedback processing, respectively. On the contrary, fast erroneous responses characterized by low uncertainty led to increased post-response FMT power, which, presumably, reflects internal error detection. Thus, this study confirmed the idea that RT can be a valid index of uncertainty level, with high uncertainty occurring due to attentional lapses and low uncertainty occurring due to failures to keep a sufficiently high motor threshold.