COMPARATIVE INVESTIGATION OF EVENT-RELATED POTENTIALS ELICITED BY THE STROOP EFFECT AND EVENT-RELATED POTENTIALS ELICITED BY COLOR CONFLICT

Abstract

Main interest of cognitive and experimental psychology is the human behavior system. Cognitive control is the key aspect of this system and investigating its neural mechanisms is an important objective method in such studies. One of the prominent methods of studying cognitive control is the Stroop effect. The studies we have met in the literature used different sets for congruent and incongruent stimuli, which could cause habituation effects at various ERP components. The aim of this thesis was to examine the cognitive control in the context of the Stroop task by recording event-related potentials with a standard oddball paradigm. Amplitudes and latencies of the seven ERP components were examined in the averaged data and compared between stimulus types. N1 was not different for four stimuli in terms of amplitude and latency. Latencies of P2, N2 and P3b were significantly longer for incongruent words than that of incongruent bars. These findings suggest that Stroop conflict is processed at early stages of stimulus evaluation. Incongruent bars and words enhanced significantly longer and larger P3b responses than congruent bars and words, respectively, as expected from a standard oddball paradigm. N450-LPC complex was recorded only for incongruent words as a reflector of post-perceptual mechanisms. Among the stimulus types, only congruent bars did not evoke an LPN response since they did not have any semantic dimension or a color conflict.