Effects of focal brain lesions on visual problem-solving

In this study, the relative contributions of different brain regions to visual problem-solving were explored using a new test of divergent thinking. Seventy-three patients with focal brain lesions and 20 normal control subjects performed a set of matchstick problems, similar to those described by Guilford [15] as a measure of adaptive flexibility. For each problem, subjects were to demonstrate as many ways as possible of removing a particular number of sticks from a two-dimensional geometric design to achieve a specified resultant shape. Patients with left temporal-occipital, right temporal-occipital, or left frontal lesions displayed no significant difficulty. Evidence of general deficiencies in the ability to manipulate this visual material was seen in patients with parietal and/or central-area lesions (right worse than left). In contrast, patients with right frontal-lobe damage demonstrated a selective impairment in the ability to shift strategy. The results confirm the importance of the right suprasylvian region in the ability to process and act on visual information. They also provide evidence of the specific role played by the right frontal lobe, and particularly the ventral region, in permitting a flexible approach to visual problem-solving.