Anosognosia for memory deficit in amnestic mild cognitive impairment and Alzheimer's disease.

OBJECTIVE: to investigate patterns of anosognosia for memory deficit in subjects with amnestic mild cognitive impairment (MCI) and Alzheimer's disease (AD). METHODS: the study involved twenty-five subjects with MCI, 15 with mild AD and 21 normal controls (NC). Subjective rating of memory functioning was assessed with a six-items questionnaire that was administered before and after memory testing; an informant version from caregivers gave a discrepancy score (SRD). In the Objective Judgement (OJ) task, aiming to evaluate memory-monitoring abilities, subjects were requested three times to predict their memory performance in recalling words from a list of ten. Then they had to recall the words. Prediction accuracy was computed by subtracting the predicted performance from the actual performance. RESULTS: MCI and AD showed reduced awareness of memory difficulties at the SRD and did not change their rating of these difficulties after memory testing. At the OJ task, MCI and AD consistently overestimated their memory performances as compared with NC. The SRD and OJ measures were not correlated with some patients being impaired on only one measure. Only the OJ measure was significantly related to executive functioning. CONCLUSIONS: AD and MCI subjects show unawareness for memory deficit and significant memory-monitoring disorder. This confirms that anosognosia is an important symptom of MCI. Similarities of patterns of impaired awareness between AD and MCI supports the view of a continuum of the anosognosia phenomenon in MCI and AD.

Episodic future thinking in amnesic mild cognitive impairment.

Results from behavioral studies of amnesic patients and neuroimaging studies of individuals with intact memory suggest that a brain system involving direct contributions from the medial temporal lobes supports both remembering the past and imagining the future (Episodic Future Thinking). In the present study, we investigated whether amnesic Mild Cognitive Impairment (aMCI) affects EFT. Amnesic MCI is a high-risk factor for Alzheimer's disease and is characterized by a selective impairment of episodic memory, likely reflecting hippocampal malfunctioning. The present study assessed, for the first time, whether the reduction of episodic specificity for past events, evident in aMCI patients, extends also to future events. We present data on 14 aMCI patients and 14 healthy controls, who mentally re-experienced and pre-experienced autobiographical episodes. Transcriptions were segmented into distinct details that were classified as either internal (episodic) or external (semantic). Results revealed that aMCI patients produced fewer episodic, event-specific details, and an increased number of semantic details for both past and future events, as compared to controls. These results are discussed with respect to the constructive episodic simulation hypothesis, which suggests that reminiscence and future thinking are the expression of the same neurocognitive system.