Abstract
Objectives:To investigate cognitive components and mechanisms of learning and memory in primary progressive aphasia (PPA) using a simple clinical measure, the Three Words Three Shapes Test (3W3S).Background:PPA patients can complain of memory loss and may perform poorly in standard tests of memory. The extent to which these signs and symptoms reflect dysfunction of the left hemisphere language versus limbic memory network remains unknown.Methods:3W3S data from 26 patients with a clinical diagnosis of PPA were compared with previously published data from patients with typical dementia of the Alzheimer type (DAT) and cognitively healthy elders.Results:PPA patients showed two bottlenecks in new learning. First, they were impaired in the effortless (but not effortful) on-line encoding of verbal (but not non-verbal) items. Second, they were impaired in the retrieval (but not retention) of verbal (but not non-verbal) items. In contrast, DAT patients had impairments also in effortful on-line encoding and retention of verbal and nonverbal items.Conclusions:PPA selectively interferes with spontaneous on-line encoding and subsequent retrieval of verbal information. This combination may underlie poor memory test performance and is likely to reflect the dysfunction of the left hemisphere language rather than medial temporal memory network.
Highlights
The diagnosis of progressive aphasia (PPA) is based on the presence of aphasia in the earliest stages of illness and on the absence of impairment in other cognitive domains, including episodic memory, reasoning, and visuospatial functions [1,2,3,4,5]
For purposes of comparison with data from the present study, the 15-minute delayed recall condition was used from the original cohort since it was closest in duration to our 20-minute average for the PPA participants
The present study investigated episodic memory in patients with primary progressive aphasia (PPA) using the 3W3S Test, a simple test of verbal and non verbal retentive memory that can be used during routine outpatient clinic assessments
Summary
The diagnosis of PPA is based on the presence of aphasia in the earliest stages of illness and on the absence of impairment in other cognitive domains, including episodic memory, reasoning, and visuospatial functions [1,2,3,4,5]. The MMSE has served to characterize severity in a variety of clinical dementia syndromes where language is not the primary deficit, it may overestimate the extent of functional impairment in PPA. This dissociation between test scores and daily function was demonstrated in a study comparing patients with PPA, patients with dementia of the Alzheimer type (DAT) and patients with behavioral variant frontotemporal dementia on the Activities of Daily Living Questionnaire (ADLQ) [7], an informant completed assessment of activities of daily living. The principled assessment of memory and learning in PPA has important implications for the rigorous confirmation of the diagnosis and for the comprehensive assessment of functional capacity
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