Abstracts

Rationale: The human brain executes cognitive control, such as selection of relevant information in the presence of competing irrelevant information, and cognitive control is essential for us to yield a series of optimal behaviors in our daily life. The present study assessed electrocorticographic gamma-oscillations elicited by cognitive control in the context of the Stroop color-naming paradigm, with a temporal resolution of 10 msec and spatial resolution of 1 cm. Methods: We studied a consecutive series of five native English-speaking patients with a diagnosis of medically-uncontrolled focal seizures (age range: 10 - 17 years; three females), who underwent extraoperative electrocorticography recording. Subjects were instructed to overtly read a color word printed in an incongruent color in the reading task (e.g.: to answer Red when a word Red printed in blue ink was presented), and to overtly name the ink color of a color word printed in an incongruent color in the Stroop color-naming task (e.g.: to answer Blue when a word Red printed in blue ink was presented). Results: The Stroop color-naming task specifically elicited larger gamma-augmentations in the dorsolateral-premotor, dorsolateral-prefrontal and supplementary motor areas with considerable inter-subject spatial variability. Such Stroop color-naming-specific gamma-augmentations occurred approximately 500 to 200 msec prior to overt responses. Electrical stimulation of the sites showing Stroop color-naming-specific gamma-augmentations resulted in temporary naming impairment more frequently than that of the remaining sites. Conclusions: This study has provided direct evidence that a critical process of cognitive control in the context of Stroop color-naming paradigm consists of recruitment of neurons essential for naming located in variable portions of the dorsolateral premotor and prefrontal areas.