Visual memory in Parkinson's Disease: a non-graphomotor approach to assessment.

Abstract

Parkinson's disease (PD) is a progressive motor disorder with multiple motor and non-motor symptoms. Cognitive decline, particularly memory deficits are well documented phenomenon due to its importance as potential biomarkers. While substantial research has explained mechanisms and findings related to deficits in verbal learning and memory, deficits across visual learning and memory are comparatively under-documented. They are often inconsistent due to the reliance on traditional paper-pencil based tests which are susceptible to confounding by motor symptoms and graphomotor deterioration seen in PD. This study aims to explore the usefulness of the Wechsler Memory Scale-IV (WMS-IV) as a non-graphomotor method to testing visual memory profiles in PD. Performance on subtests of the WMS-IV was compared between 113 patients with PD and 90 education-matched healthy controls (HC) with stratification based on literacy into literate, functional illiterate and illiterate. Significant differences were observed on sub-tests of Symbol Span and Designs I(Content) scores between the PD groups and their corresponding HC irrespective of education level. Only the literate PD group showed significant differences from their HC on spatial addition subtests. On the Designs I and II spatial scores, functional illiterates, did not differ from their corresponding HC while the literate and illiterate Groups continued to differ. These findings highlight the need to adapt traditional visual learning and memory tests to PD in order to elicit truly representative deficits, and the need to develop alternative versions that are not driven by education with localised education-based norms. These will permit accurate and equitable profiling across literacy backgrounds.