Differential Frontal Activation during Exogenous and Endogenous Orientation of Visuospatial Attention

Abstract

Aims: The aim was to measure the prefrontal cortical activity involved in shifting spatial attention to visual stimuli in the left or right visual field using near-infrared spectroscopy. Methods: Eleven participants performed a simple vigilance task, an endogenous attention task and an exogenous attention task. In the endogenous task, the left or the right side of the center diamond brightened, indicating the side for subsequent target appearance (controlled shift of attention). In the exogenous task, the peripheral squares brightened, indicating the appearance of target in those squares (reflexive shift of attention). Results: Stimuli at validly cued locations were responded to faster than stimuli at invalidly cued locations. Increases in oxyhemoglobin (oxy-Hb) were observed in the right prefrontal cortex throughout the 3 tasks, and in the left prefrontal cortex during the vigilance and the exogenous tasks. In the exogenous task, marked decreases in oxy-Hb were observed in the bilateral ventrolateral prefrontal cortex. Conclusions: These results suggest that the left and the right prefrontal cortices mediate distinct cognitive processes during the performance of visuospatial attentional tasks.