Authors:

WOOLGAR, A., Parr, A., CUSACK, R., THOMPSON, R., NIMMO-SMITH, I., Torralva, T., Roca, M., Antoun, N., Manes, F. & DUNCAN, J.D.

Reference:

Year of publication:

2009

CBU number:

7069

Abstract:

A network of frontoparietal “multiple-demand” (MD) brain regions is involved in a wide variety of tasks. In human functional imaging, activity in these regions is produced by cognitive demands including increased perceptual difficulty, novelty, response conflict, working memory, episodic memory, and semantic memory. Given the generality of this pattern, we have previously suggested that the MD regions represent a neural substrate of a general cognitive function, such as that measured by tests of fluid intelligence. In a group of 90 patients with focal cortical lesions, we tested the hypothesis that the MD regions are critical for fluid intelligence. For each patient we calculated a “fluid intelligence deficit” from comparison of estimated pre- and post- morbid function. Postmorbid fluid intelligence was measured using two conventional tests of novel problem-solving. Premorbid score on each test was estimated from a multiple regression equation, derived from healthy controls, predicting fluid intelligence score from patient age and reading vocabulary. We applied correlational analyses to identify the lesion characteristics that predicted fluid intelligence loss. The data indicated that the extent of MD damage was a critical factor in determining fluid intelligence deficit. In the whole group and in the frontal group alone, the extent of MD damage was a significant predictor of behavioral deficit even after total lesion volume was accounted for. A similar trend was seen in the smaller parietal group. In the occipitotemporal group, where MD cortex was spared, there was no correlation between lesion volume and behavioral deficit. In this group fluid intelligence was also preserved relative to the frontal group, even after differences in total lesion volume were accounted for. Elsewhere, we have proposed that selective MD representations are crucial in the effective organization of diverse forms of behavior (Duncan, 2006). Consistent with this, our data suggest a central role for the MD regions in supporting fluid intelligence.

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