Semantic dementia shows both storage and access disorders of semantic memory.

Yumi Takahashi,Satoshi Yamaguchi,Kenichi Meguro,Kyoko Akanuma,Masahiro Nakatsuka,Mari Kasai

doi:10.1155/2014/508960

Abstract

Objective. Previous studies have shown that some patients with semantic dementia (SD) have memory storage disorders, while others have access disorders. Here, we report three SD cases with both disorders. Methods. Ten pictures and ten words were prepared as visual stimuli to determine if the patients could correctly answer names and select pictures after hearing the names of items (Card Presentation Task, assessing memory storage disorder). In a second task, the viewing time was set at 20 or 300 msec (Momentary Presentation Task, evaluating memory access disorder) using items for which correct answers were given in the first task. The results were compared with those for 6 patients with Alzheimer's disease (AD). Results. The SD patients had lower scores than the AD group for both tasks, suggesting both storage and access disorders. The AD group had almost perfect scores on the Card Presentation Task but showed impairment on the Momentary Presentation Task, although to a lesser extent than the SD cases. Conclusions. These results suggest that SD patients have both storage and access disorders and have more severe access disorder than patients with AD.

Highlights

Semantic dementia (SD) is a progressive degenerative disease in which phonology and syntax of speech are retained, but semantic memory of speech is selectively impaired [1,2,3]
Presentation of items without storage disorder for a short period caused a marked reduction in correct answers, suggesting the additional presence of access disorder
Correct answers were reduced by shortening the duration of presentation in the Alzheimer’s disease (AD) group, but the effect was smaller than that in the SD patients

Summary

Introduction

Semantic dementia (SD) is a progressive degenerative disease in which phonology and syntax of speech are retained, but semantic memory of speech is selectively impaired [1,2,3]. Semantic memory is a subclass of long-term memory that was introduced into cognitive psychology as a concept in contrast to episodic memory [4]. Semantic memory represents memory of socially shared knowledge and concepts independent from personal experience and temporal context. Semantic memory disorders include “storage disorder,” in which stored information is lost [5], and “access disorder,” in which access to stored memory is impaired [6]. In Alzheimer’s disease (AD), semantic memory disorder is not required for clinical diagnosis but often appears in the disease course [5, 7, 8].

Methods

Results

Conclusion