Executive dysfunction contributes to verbal encoding and retrieval deficits in posterior cortical atrophy

Abstract

Posterior Cortical Atrophy (PCA) is a neurodegenerative syndrome that typically presents with predominant visual and spatial impairments. The early diagnostic criteria specify a relative sparing of functioning in other cognitive domains, including executive functions, language, and episodic memory, yet little is known of the cognitive profile of PCA as the disease progresses. Studies of healthy adults and other posterior cortical lesion patients implicate posterior parietal and temporal regions in executive functions of working memory and verbal fluency, both of which may impact episodic memory. Relatively little has been reported about these cognitive functions in PCA, and to our knowledge there has not yet been a study of the impact of such deficits on memory function in PCA. We sought to examine PCA patients' performance on tests of executive function and the associations to verbal episodic memory encoding, storage, and delayed recall. Nineteen individuals with PCA underwent neuropsychological and neuroimaging evaluations as part of a comprehensive clinical assessment. We developed a novel consensus rating method-the Neuropsychological Assessment Rating (NAR) scale-to grade the severity of test performance impairments in selected cognitive domains and subdomains. Hypothesis-driven analyses demonstrated relative deficits in working memory and lexical-semantic retrieval. Preliminary analyses suggested associations between both deficits and atrophy in the left-hemisphere inferior parietal lobule. These executive deficits were also associated with impairments in verbal encoding and delayed recall, but not with recognition discriminability. We conclude that deficits in verbal executive functions impact verbal episodic memory in PCA. Our findings also support theories emphasizing the role of the posterior parietal cortex in supporting executive and lexical-semantic contributions to verbal episodic memory.

Keywords: Cognitive impairment; Neurodegeneration; Posterior parietal atrophy; Verbal episodic memory; Working memory.