Memory performance under varying cueing conditions in patients with Parkinson's disease

The present study is a continuation of a previous study in memory performance which showed that Parkinson's disease (PD) patients increasingly relied on explicit cues which prompt the external strategy of serial clustering, in comparison to control subjects (CS), who profited increasingly from implicit cues which prompt the internal and more effective strategy of semantic clustering. In this study, we investigated whether the recall of PD patients can be affected by adding or removing explicit cues. We manipulated the California Verbal Learning Test in two ways. First, we told the subjects under study in advance from which categories the items to be recalled were derived, thus making the implicit cue to cluster semantically explicit (explicit condition). Next, we permuted the sequence of the items in each trial, thus preventing the subjects from adhering to the serial order, i.e. to explicit cues (permuted condition). We included the data of our previous study (mixed condition) in the analysis of memory and learning performance in the three conditions. Learning of PD patients, as reflected in the semantic ratio, proved to be more affected by the cueing conditions than that of CS. Total performance and the serial ratios did not show a significant interaction between group and cueing condition. The results are discussed in terms of external and internal generation of problem-solving strategies.