Subjective cognitive impairment (SCI) is defined by a state of subjective complaint, without objective cognitive deterioration. Amnestic mild cognitive impairment (A-MCI), which characterizes a syndrome between normal cognitive aging and early Alzheimer's disease (E-AD), is preceded by A-MCI from many years. SCI expresses a metacognitive impairment. A cohort of 51 subjects [7 normal controls (NC), 28 SCI, 12 A-MCI and 5 E-AD] was followed up during 24 months, with a neuropsychological evaluation each 6 months during 1 year (V1, V2, V3), then 1 year later (V4). Among the 28 SCI, 6 converted to A-MCI at V4 (21.42%), 1 to A-MCI-A at V3, then to E-AD at V4. These results suggest a continuum from SCI to A-MCI, and E-AD. Progressive SCI differed from non-progressive SCI on verbal episodic memory and executive functions tests at the initial examination. MRI showed anterior cingular atrophy in all SCI patients but hippocampal atrophy was only observed in 20 patients. Our results suggest that metacognition impairment is the expression of a dysfunction in the anterior pre-frontal cortex, in correlation with a syndrome of hyper-attention.
Keywords: Alzheimer's disease; amnestic mild cognitive impairment; anterior cingular cortex; memory complaint; metacognition; subjective cognitive impairment.