Parkinson's disease patient's behaviour in a covered maze learning task

A computerized maze task was constructed that allowed only partial vision of the maze structure and produced measurements for separate analysis of cognitive processes described as impaired in Parkinson's disease. Eighteen patients suffering from mild Parkinson's disease and 18 individually matched normal controls were investigated. Baseline task response times were found to be identical for both groups. Differences between patients' and controls' performance could be related to (a) a response bias in Parkinson patients that favoured repetition of the previous action and slowed down shifting and (b) an impairment of multistep plan generation. It is speculated that the response bias reflects the disinhibition of cortico-thalamo-cortical reverberation loops which results from striatal dopamine depletion.