Heterogeneity of cingulate contributions to spatial attention

Functional magnetic resonance imaging was used to investigate activation pa tterns within the cingulate region during tasks based on spatial attention. Subjects were asked to detect targets which appeared either at the site in dicated by a cue or on the opposite side. A "cue effect" was identified by the presence of shorter reaction times to validly than invalidly cued targe ts, showing that an anticipatory bias had been generated in the direction o f the cue. Target detection accuracy was consistently above 90% although cu e effects and reaction times displayed substantial variations, from one tas k session to another, Activation within the anterior cingulate region was s een in 16 of the 26 sessions but showed no correlation with reaction time. Posterior cingulate activation was seen in only 16 of the 26 sessions. Howe ver, a random effects analysis showed that the task-related signal change i n this region was strongly correlated with the speed of target detection. A post hoc analysis indicated that this correlation was significant only whe n cue effects were present. No other part of the cerebral cortex displayed significant correlations with reaction times or cue effects. These results suggest that the cingulate component of the attentional network has at leas t two functionally segregated sectors, an anterior one in BA 24/32 and a po sterior cingulo-retrosplenial one in BA 23/29/30, The posterior sector appe ars to be associated with the speed of detecting spatial targets, especiall y when attention is under the influence of a cue-induced anticipatory bias. The anterior cingulate focus did not display such a relationship in our ta sks and is likely to mediate other aspects of attentional deployment such a s performance monitoring, response selection or target identification. (C) 2001 Academic Press.