Inattention of Patients with Lesions Confined to the Striatum

the Analysis of Eye-movements during a Maze Test

Abstract

Recently, it has been suggested that the striatum is involved in cognitive function, motor activity, and eye's movement. The motor loop passes largely through the putamen, which receives inputs from the sensorimotor cortex and ultimately transmits signals to certain premotor areas. The association loop passes through the caudate nucleus, which receives input from the association areas and ultimately returns signal to portions of the prefrontal cortex. In addition, the caudate nucleus occupies a significant position in the oculomotor circuit. We attempted to evaluate visual attention as one of the striatum functions using resolution of maze depicted on paper maze no. 5 of the WISC-R tests. The optimal solution of the maze requires prediction and strategy; knowing in advance where the blind alleys, especially the last one, are located, facilitates resolution of the maze. Subjects were 20 normal controls and 55 right-handed chronic stroke patients with lesions of the striatum; these included 27 patients with lesions confined to the left, and 28 to the right. They were matched for age and duration of disease. We classified the relation between visual attention and the actual solution by dividing solutions into four types: the glancing type involved a smooth resolution with only glancing at the key blind alley and exit; the haphazard type was a smooth resolution without looking at these features; the perplexed type involved stagnant resolution with looking hard throughout the experiment while not drawing; the hesitant type was an inefficient form of resolution involving looking only for the next key but not evaluating the whole maze while not drawing. There were two types among the controls; Two-third of them were of the glancing type, and the rest were of the haphazard type. The patients with left lesions were found to be the same ratio as controls except for a few with the perplexed type. By contrast, half of the patients with right-sided lesions were of the hesitant type, one-fifth were the glancing type, one-third were the haphazard type. All patients associated with unilateral spatial neglect were of the hesitant type. Our results suggest that the striatum is intimately involved visual attention during performance of a maze test. Patients with lesions confined to the left striatum sometimes have ‘restless’ inattention; patients with only right lesions frequently have ‘frozen’ inattention.