The Effect of Frontal Lobe Function on Proverb Interpretation in Parkinson's Disease

Abstract

The cognitive impairment associated with PD involves a broad range of deficits including difficulty with executive functions such as working memory, inhibition, decision-making, and cognitive multitasking, learning, and visuoperceptual skills. Even early in the disease, when motor symptoms tend to predominate, there is evidence that cognitive functions can be compromised. Owing to the presence of executive-type dysfunction in PD, some researchers likened the cognitive deficit of PD to that seen with frontal lobe damage. The anatomical basis of PD, however, suggests otherwise. Dopamine depletion in the basal ganglia, and the downstream depletion of dopamine in the frontostriatal circuitry is often thought to be the foundation of the cognitive deficits associated with PD.In addition to cognitive impairments, a language deficit attends Parkinson's disease (PD) alongside the other motor and non-motor aspects of the disease. This language deficit is characterized by difficulty processing various types of figurative language, and has been associated with various PD-related cognitive deficits, such as deficits in working memory (WM). Varied assessment tools have been used to characterize the neuropsychological functions associated with this language deficit, most of which involve some measure of frontally-based cognitive skills.The purpose of this study was to examine the influence of frontal lobe function on higher-level language function in the non-demented PD (NDPD) population. To investigate this influence, the performance of two groups of participants (i.e., one NDPD group and one control group) was compared on both a proverb interpretation task and on a statistically derived measure of frontal lobe function.Results indicated a relation between performance on the measure of frontal lobe function and performance on the proverb interpretation task in the PD group only. Significant findings are discussed in relation to the neuropsychological underpinnings of the figurative language deficit in PD.