Feeling of knowing, verb processing and executive functions in non-demented Parkinson's disease patients

Abstract

The aim of this present study was to explore whether feeling-of-knowing (FOK) judgments are related with executive functioning of the frontal lobes in non-demented Parkinson’s Disease (PD) patients and to compare noun versus verb processing at three different levels (memory, metamemory and word generation). It was predicted that PD patients would be impaired in episodic memory and metamemory and they would perform worse for verb targets than nouns. An episodic task of paired associate learning for 32 word pairs was used in this study. It was found that PD patients were impaired in recall and recognition as compared to controls. Only the PD group performed worse on verb recognition implying an episodic memory deficit for verbs as a lexical category. Accuracy of FOK judgments was not above the chance level implying that metamemory monitoring is significantly impaired in this patient population. To explore the relationship between FOK accuracy and executive functions, two tests of executive functioning were used: Verbal fluency (semantic, lexical and action fluency) and Wisconsin Card Sorting Test (WCST). PD patients were impaired in all tests of verbal fluency but magnitude of difference was greater for the action fluency test which supports existing literature that verb generation tasks are especially sensitive to PD related cognitive changes. For the PD group neither WCST nor verbal fluency composite scores significantly correlated with FOK accuracy measures. However for healthy controls, WCST performance is a strong predictor of FOK accuracy.