Effects of unconscious perception of acoustic stimuli on event-related potential parameters

Abstract

The influence of unconscious perception of acoustic stimuli on the event-related electrical activity of the human brain was determined. For this purpose, the event-related potentials (ERPs) evoked by the acoustic stimuli presented in the unconscious priming paradigm were recorded in the subjects. Monosyllabic Russian words with a single vowel letter substitution (‘sad’ and ‘sud’) and the pseudoword ‘sid’ were chosen as stimuli for priming. It was found that repetition and alternative priming significantly and similarly affected the ERP component amplitude with 200 ms latency after target application in the central, parietal, and temporal leads. Under the conditions of alternative priming, the direction of the potential amplitude modification with a latency of 400 ms was altered for the word and pseudoword targets. Alternative priming significantly increased the amplitude of this component with a pseudoword target and decreased it if the word existing in the language was used as a target stimulus. Since none of the participants was able to distinguish the applied prime stimuli, the changes in the ERP amplitude parameters might have been evoked by unconscious perception of acoustic stimuli by the subjects. The ERP amplitude dynamics revealed in this study demonstrates the possibility that subliminal acoustic stimuli modulate the electrical activity evoked by verbal acoustic stimulation.