Covert orienting of attention and overt eye movements activate identical brain regions

This study investigated the anatomical relationship between covert and overt shifts of attention. Previous studies have found that the areas of the brain activated by covert and overt shifts of attention are very similar. However, despite a general agreement between studies there are a few issues that merit closer inspection. Primarily, the tasks aiming to produce covert or overt shifts of attention were not always comparable. Secondly, the previous studies disagreed on whether greater neural activity is elicited by covert shifts or overt shifts of attention. Thirdly, the previous studies differed on whether the shifts of attention were exogenously or endogenously driven. Finally, the statistical analyses used by all previous studies failed to account for between subject variability. The present study was designed to address all these issues. Twelve healthy subjects performed either covert or overt shifts of attention while the functional magnetic resonance imaging (fMRI) signal was continuously measured. In line with the previous studies, the present study showed a virtually complete overlap between areas of the brain recruited during covert shifts of attention and areas of the brain recruited during overt shifts of attention. Furthermore, using endogenously driven shifts of attention this study found that overt shifts of attention resulted in higher levels of activation in the brain than covert shifts of attention. The results of this study provide support for the premotor theory of attention that posits that the attentional and motor systems are the result of neural activation in the same areas of the brain. (C) 2008 Elsevier B.V. All rights reserved.