Is relational reasoning dependent on language? A voxel-based lesion symptom mapping study

Abstract

Previous studies with brain-injured patients have suggested that language abilities are necessary for complex problem-solving, even when tasks are non-verbal. In the current study, we tested this notion by analyzing behavioral and neuroimaging data from a large group of left-hemisphere stroke patients (n=107) suffering from a range of language impairment from none to severe. Patients were tested on the Raven's Colored Progressive Matrices (RCPM), a non-verbal test of reasoning that requires participants to complete a visual pattern or sequence with one of six possible choices. For some items, the solution could be determined by visual pattern-matching, but other items required more complex, relational reasoning. As predicted, performance on the relational-reasoning items was disproportionately affected in language-impaired patients with aphasia, relative to non-aphasic, left-hemisphere patients. A voxel-based lesion symptom mapping (VLSM) procedure was used to relate patients' RCPM performance with areas of damage in the brain. Results showed that deficits on the relational reasoning problems were associated with lesions in the left middle and superior temporal gyri, regions essential for language processing, as well as in the left inferior parietal lobule. In contrast, the visual pattern-matching condition was associated with lesions in posterior portions of the left hemisphere that subserve visual processing, namely, occipital and inferotemporal cortex. These findings provide compelling support for the idea that language is critical for higher-level reasoning and problem-solving.

Figure 1

Examples of the types of problems tested in the RCPM: A) visual-match and B) relational reasoning. Note that due to copyright issues, these examples only portray the types of problems on the RCPM, not actual items from the test.

Figure 2

Overlay of all 107 patients’ lesions. Brighter areas represent areas of greater lesion overlap, with green representing approximately half of the sample (see color bar).

Figure 3

Map showing distribution of power, ranging from 0.4 (in magenta) to 0.8 (in red), with alpha set to p < .05.

Figure 4

Performance on the visual-match versus relational-reasoning condition on the RCPM in patients diagnosed as aphasic vs. within-normal-limits (WNL) on the language battery. The reference line shows chance performance of 16.7%.

Figure 5

Performance on the visual-match versus relational-reasoning condition on the RCPM as a factor of aphasia subtype. The reference line shows chance performance of 16.7%. WNL=within normal limits; TCS= transcortical sensory aphasia; Unclass.=unclassifiable; CA=conduction aphasia.

Figure 6

VLSM map showing lesion correlates of poor performance on the relational reasoning condition (red) and visual-match condition (blue) of the RCPM. Relational reasoning was most affected by lesions in the left middle and superior temporal gyri, as well as inferior parietal cortex. Performance on the visual-match condition was uniquely affected by lesions in left inferior temporal cortex, the optic radiations, and visual association cortex in the occipital lobe. Only significant voxels are shown based on a critical threshold determined by permutation testing (p < .05).