EEG-Correlates of Mental Attention are Modified by Presence of Specifying Visual Signals

This work continues the study of EEG-correlates of cognitive states with different contributions of sensory and mental attention. The design of the experiments was similar to that used for investigations of evoked EEG activity, but we analyzed spectral power parameters of quasi-stationary EEGs. Tests for sensory attention and for mental attention (productive and reproductive imaginary) were presented in blocks of 80 probes each. Each probe contained 2 signals: visually presented words designated an object of sensory or mental task in the probe, then a presentation of an image started a process of memorization, a presentation of a white screen started either a process of recollection, or a process of imaging. The evaluations of EEG spectral power in the states of sensory and mental attention and their comparison with the reference state of rest showed that the very scheme of a test with multiple inclusions of visual stimuli to trigger and to direct mental activities produced a specific functional state of rapid switching between the dominants of external and internal attention. The EEG correlates of mental states were rather different as compared with the EEG correlates obtained in extended uninterrupted states of mental attention.