Dissociation of attentional processes in patients with focal frontal and posterior lesions

A location-based ('select-what, respond-where') priming task was used to ex amine three measures of selective attention (interference (INT), negative p riming (NP), and inhibition of return (IOR)) as a function of focal brain p athology and the complexity of target selection. Control subjects showed di fferent patterns of performance for the three attentional measures as a fun ction of complexity, suggesting some independence among INT, NP, and IOR. B rain-damaged subjects showed significant response slowing, as well as a num ber of lesion-specific attentional abnormalities. Right frontal (including bifrontal) damage resulted in proportionally increased interference related to task complexity. Left posterior damage increased IOR in the most comple x task, while left frontal damage reversed the control pattern of IOR as a function of complexity. Right hemisphere (right posterior and right frontal damage) pathology resulted in a virtual loss of negative priming at all le vels of task complexity; left and bifrontal damage resulted in diminished N P only related to increases in the complexity of selection. INT, NP, and IO R are mediated by different brain regions and their expression can be modul ated by the complexity of the selection task. (C) 1999 Elsevier Science Ltd . All rights reserved.