Impaired visual recognition memory predicts Alzheimer's disease in amnestic mild cognitive impairment.

BACKGROUND: In the common form of Alzheimer's disease (AD), neurofibrillary tangles, which are associated with cognitive dysfunction, initially develop in the anterior subhippocampal (perirhinal/entorhinal) cortex before reaching the hippocampus. This area plays a key role in visual recognition memory (VRM). Impaired VRM could therefore be an early marker of AD. METHODS: An extensive neuropsychological assessment including VRM tasks was performed in 26 patients with single-domain amnestic mild cognitive impairment at baseline. We evaluated the diagnostic accuracy of neuropsychological tests using ROC curve analyses in a prospective longitudinal study until conversion to probable AD or with a follow-up of at least 6 years. RESULTS: VRM performance predicted conversion to AD with a sensitivity of 80% and a specificity of 90.9%. Combining the assessment of VRM with a verbal memory task increased diagnostic accuracy. CONCLUSIONS: Cognitive 'biomarkers' evaluating the function of brain areas that are the target of degenerative change should be considered for the early diagnosis of AD.