Sensitivity to semantic cuing: an index of episodic memory dysfunction in early Alzheimer disease

Alzheimer disease (AD) is characterized by episodic memory impairment. This study was aimed at assessing various aspects of episodic memory, and particularly sensitivity to semantic cuing, in patients with various degrees of cognitive deterioration, compared with normal elderly subjects. One hundred thirty-one patients, subdivided into four subgroups as a function of their Mini-Mental State Examination score, were included. All subjects, including 20 normal elderly subject, were given an episodic memory test with controlled encoding and selective reminding. The subgroups of patients were homogeneous in terms of free recall and recognition, but differed in terms of responsiveness to cuing by semantic categories corresponding to the to-be-remembered items. The data confirmed that a severe amnesic syndrome occurs very early in AD, even in a subgroup of patients who did not meet the criteria for dementia. The data indicated that free recall performance, characterized in all subgroups by a floor effect, is not likely to be an appropriate index in pharmacological trials. By contrast, sensitivity to semantic cuing seemed relatively preserved in the early stages, and decreased with the progression of the disease. This index would be the most sensitive index of episodic memory in AD.