Authors:

Hodgson, T.L., Tiesman, B., OWEN, A.M. & Kennard, C.

Reference:

Year of publication:

2002

CBU number:

4144

Abstract:

We have taken a novel approach to the study of problem solving involving the detailed analysis of natural scanning eye movements during the Ñone touchâ Tower of London task. Control subjects and patients with idiopathic ParkinsonÇs disease (PDs) viewed a series of pictures depicting two arrangements of coloured balls in pockets within the upper and lower halves of a computer display. The task was to plan (but not execute) the shortest movement sequence required to rearrange the balls in one half of the display (the Workspace) to match the arrangement in the opposite half (the Goalspace) and indicate the minimum number of moves required for problem solution. As problem complexity increased control subjects spent proportionally more time fixating the Workspace region. This pattern is found regardless of whether subjects were instructed to solve problems by rearranging balls in the lower or upper visual fields. The distribution of gaze within the Workspace was also found to be problem dependent, with gaze being selectively directed towards the problem critical balls. In contrast, PDs made more errors in the task and also failed to show any dissociation in the amount of time fixating the two halves of the display. There was also no evidence for consistent problem dependent modulation in gaze in the PD group. We conclude that the patients have difficulty in encoding and / or maintaining current goals during problem solving. This is consistent with a role for fronto-striatal circuits in mechanisms of working memory and attention.