Brain Advance Access originally published online on May 8, 2009
Brain 2009 132(7):1889-1897; doi:10.1093/brain/awp109
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Implicit representation and explicit detection of features in patients with hemispatial neglect
1 Veterans Administration, Northern California Health Care System, Martinez, CA, USA 2 Psychology Department, University of California, Berkeley, CA, USA
Correspondence to: Thomas M. Van Vleet, Psychology Department, 3210 Tolman Hall #1650, University of California, Berkeley, CA 94720, USA E-mail: tomvanvleet{at}gmail.com
Despite profound inattention to the side of space opposite a brain lesion in patients with unilateral neglect, priming studies demonstrate that undetected stimuli are capable of influencing subsequent behaviour. However, the nature of implicit processing of neglected stimuli is poorly understood. In the current study, we examined implicit processing in five patients with neglect using both visual search and priming methods. A psychophysical staircase method varying time of presentation was first used to establish a high (75%) and low (25%) detection probability for targets in both a feature and a conjunction search array. The arrays were then used in a priming task to examine how a difference in the level of overt detection of a feature or a conjunction presented in neglected space influenced subsequent discrimination speed to a single probe presented at fixation. The results showed that priming effects with feature primes were independent of their explicit detection rates (high versus low), but priming effects with conjunction primes reflected the pattern of explicit detection. These findings are discussed as they relate to availability versus accessibility of neglected stimuli.
Key Words: neglect; attention; preconscious; feature; conjunction
Received November 3, 2008. Revised March 17, 2009. Accepted March 24, 2009.