OBJECTIVE
To examine the utility of a novel “cognitive stress test” to detect subtle cognitive impairments and amyloid load within the brains of neuropsychologically normal community-dwelling elders.
DESIGN
Participants diagnosed as cognitively normal (CN), subjective memory impairment (SMI), mild cognitive impairment (MCI) and pre-clinical mild cognitive impairment (PreMCI) were administered the LASSI-L, a sensitive test of proactive semantic interference (PSI), retroactive semantic interference and uniquely, the ability to recover from the effects of PSI.
SETTING
Ninety-three subjects (31 males and 62 females) were recruited from three academic institutions in a research consortium. A subset of these individuals underwent F-18 Florbetapir PET scanning.
MEASURES
Relative percentages of impairment for each diagnostic group on the LASSI-L were calculated by chi-square and Fisher's Exact Test. Spearman's rho was employed to examine associations between amyloid load, and different cognitive measures.
RESULTS
LASSI-L deficits were identified among 89% of those with MCI, 47% with PreMCI, 33% with SMI and 13% of those classified as CN. CN subjects had no difficulties with recovery from PSI while SMI, preMCI and MCI participants evidenced deficits in recovery from PSI effects. Among a subgroup of participants with normal scores on traditional neuropsychological tests, the strong associations were between the failure to recover from theeffects of PSI and amyloid load in the brain.
CONCLUSIONS
Failure to recover or compensate for the effects of PSI on the LASSI-L distinguishes the LASSI-L from other widely used neuropsychological tests and appears to be sensitive to subtle cognitive impairments and increasing amyloid load.