Concept identification as a function of preceding negative or positive spontaneous shifts in slow brain potentials.

Abstract

ABSTRACTThe stimuli of a concept identification experiment (N = 20) were presented such that each stimulus was preceded by either a negative or a positive spontaneous slow potential shift in the EEG (C3 to mastoid). The stimuli were presented visually for 4 sec. The subject's task was to learn a concept consisting of one vertical and one slanted line. He or she responded by pressing a key within 2 sec after stimulus offset to indicate whether the stimulus belonged to the concept or not, with immediate feedback. Slow potential shifts were automatically detected by a computer and were used to trigger the stimuli. The results indicated that the concept was learned significantly faster when the stimulus was preceded by a negative shift (minimum of ‐ 25 μ V) than when it was preceded by a positive shift (minimum of + 25 μ V).