Trends in Neurosciences
ReviewCommon regions of the human frontal lobe recruited by diverse cognitive demands
Section snippets
Clustering of frontal activations
A general impression of clustering in the frontal activations associated with widely different cognitive demands is easy to obtain from the imaging literature. Fig ure 1 provides an initial illustration. To produce this figure, reported peak activation foci were taken from six studies that concerned, respectively, auditory discrimination18, visual divided attention19, self-paced response production20, task switching21, spatial problem solving22 and semantic processing of words23. Studies were
Systematic comparison of five cognitive demands
To address these problems requires some more systematic comparison of activation patterns associated with different cognitive demands. For this purpose it is especially useful to find studies in which a well-specified demand has been manipulated in the context of an otherwise identical task. In recent years, a number of reviews of imaging data have appeared in an attempt to compare regional recruitment for different cognitive demands. Often, however, results have been disappointing: combining
Finer functional specializations
Of course, the finding of frequent co-recruitment of mid-dorsolateral, mid-ventrolateral and dorsal anterior cingulate regions does not rule out finer specializations within this network. Three variants of this possibility might be considered.
The first is specialization within each of these regions at a level of scale beyond the resolution of functional imaging. For example, if several, interdigitated subregions of dorsolateral prefrontal cortex were recruited to solve problems in any given
Other prefrontal regions
What then of the large frontal regions outside the active zones revealed by our analysis – including the majority of the medial and orbital surfaces, and much of the superior frontal gyrus from the anterior limit of premotor cortex to the frontal pole? Again there are interesting hints in the imaging literature. Many authors, for example, have noted the affective and motivational changes that can follow frontal-lobe injury. In imaging studies, correspondingly, both dorsomedial and orbitomedial
Concluding remarks
Certainly functional imaging contributes something new to our understanding of regional specialization within prefrontal cortex. On the one hand, there is strong evidence for such specialization: very specific prefrontal regions are repeatedly recruited by simple cognitive demands. On the other hand, specialization takes an unexpected form: very much the same regions are recruited by different demands, suggesting a specific prefrontal network recruited in solution of diverse cognitive problems.
Acknowledgements
We are indebted to Matthew Brett for development of image creation software, and to Ian Nimmo-Smith for statistical assistance.
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