Heart-rate indices of hemispheric asymmetry in a discrete-trials Stroop-paradigm

Heart-rate changes were recorded in a discrete-trials Stroop-paradigm where slides with color-words written in an incongruent color were briefly flashed (200 msec.) either to the left or to the right of a central fixation point. Subjects were required to attend only to the color, ignoring the color-word. The logic behind the paradigm is that a greater conflict should occur for the Stroop-words presented in the right visual half-field due to the relative inability of the left hemisphere to suppress the verbal information. By recording phasic heart-rate it would be possible to elucidate 1982 findings of Walker and Sandman that changes in heart-rate are differentially related to the right and left cerebral hemispheres. The results showed a significant initial deceleration during the first trialblock only to stimuli presented in the left half-field. Asymmetrical effects were demonstrated for heart-rate.