The ability to recognize faces and words is crucial for social communication. A close relationship between the face recognition and the word recognition has been documented in numerous studies involving EEG, evoked potentials, functional MRI, as well as clinical data in patients with impaired face perception who suffered from some word recognition inability. Therefore, identifying common mechanisms underlying the recognition of verbal and non-verbal stimuli is relevant not only for normal physiology and cognitive neuroscience, but also for the clinical conditions of agnosia of various etiologies.
We hypothesized that EEG patterns related to the recognition of words and faces might be influenced by both the stimulus-type factor (word or face) and the factor of familiarity.
The aim of the study is to identify the EEG patterns responsible for the perception and recognition of a visual stimulus, regardless of its specificity, i.e. the common patterns for verbal (words) and non-verbal (faces) stimuli.
Materials and Methods. The EEG data were obtained from 26 volunteers who were presented with complex visual stimuli, i.e., photos of people with words superimposed on them, where familiar (known) and unfamiliar people and words were combined in equal parts. Firstly, the tested subjects were asked to classify the faces into familiar or unfamiliar (with the attention only to faces); secondly - to classify the words in the same way (the attention only to words).
Results. We found a pronounced effect of familiarity on the EEG patterns: the amplitude of the N250 component of evoked potentials detected in the frontal areas was significantly greater in the responses to unfamiliar stimuli (both faces and words) compared to familiar ones. We also found an effect of instruction on the responses: the N400 component amplitude was greater in responses followed the "attention to words" instruction as compared to the "attention to faces" instruction; this effect was also best detectable in the frontal sites.
Conclusion. At the early stages of the visual stimuli recognition, the evoked potentials responses are modulated by the familiarity of the stimuli (that is, by their representation in long-term memory), and not by their type (face or word). The categorization of stimuli by their modality (verbal or non-verbal), apparently, occurs at later stages of their processing.
Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)