engleski

Electrophysiological study of the Stroop effect

Unveiling the basic processes of human cognition, Stroop test is a frequently used psychodiagnostic and research tool (Macleod, 1991). As depression in dementias may interfere with neuro-psychological testing (Nacmias, 2001), event-related potentials (ERPs) have been proposed as a more objective electrophysiological tool of assessing cognitive processes (Pirtosek, 2001). We performed Stroop test simultaneously with ERPs (P300) recordings. Six healthy volunteers (4 male, 2 female), aged 28-45 years were tested using computer version of the Stroop task. The task was to press one of the keyboard keys designed red, green or blue, as soon as possible after the presentation of the stimulus on the computer screen. The color stimuli could be either words with no meaning (neutral situation), color words matching the color they were printed in (congruent situation) or color words not matching the color they were printed in (incongruent situation). EEG was recorded at the Fz, Cz, Pz sites (EEG 10-20). The P300 was recorded at the Cz, Pz sites. As expected, the reaction times were longer in the congruent situation, and in the congruent situation somewhat shorter than in the neutral situation. No effect on P300 could be seen. Reaction times showed the effect of Stroop interference and facilitation in incongruent and congruent situation, respectively, while P300 was not influenced by any of the tasks. As already shown (Duncan-Johnson and Kopell, 1981), the latencies of P300 are not affected by any of the Stroop test conditions.

dementia; Stroop task; cognitive neurophysiology; event-related potentials

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