Specific Features of Perception of Semantically Equivalent Stimuli in the Verbal and Visual Form

Response time and evoked potentials were registered for visual images related to two categories fruit and tableware as well as their verbal representations. The stimuli were presented randomly. The subjects were to attribute them regardless of the form (a word or image) to one of the categories. 11 female and 10 male subjects (average age 21.9±2.9 years) participated in the tests. 6 components of the evoked potentials were singled out: Р1 (Р66), N1 (N124), Р2 (Р180), N2 (N248), Р3 (Р331) and N3 (N456). Analysis showed that both female and male subjects demonstrated reliably longer response time for words as compared to those for corresponding images. For words, evoked potentials were registered in more complex configurations and with a shorter latency period for the early components (P1, N1) and longer latency period for the late ones (P2, N2, P3, N3). The evoked potential amplitude in response to verbal stimuli was smaller than that for visual ones. Evoked potential components in response to target stimuli (both images and words) had, in general, shorter latency. The amplitude of N1, Р2 and N2 components was lower, while that of P3 and N3 was higher for target stimuli rather than a non-target. The obtained results allow us to assume that evaluation of the type of information (verbal or visual) can be performed on early stages of stimulus perception (up to 120-150 ms). Further analysis includes either more detailed description of spatial features of the visual stimuli in parietal and occipital lobes or estimation of the semantics of a word employing the frontal and temporal areas. Decision-making on formulating a response barely depends on the manner of information presentation (visual and verbal).