Neural Mechanisms Of Prospective Memory And Its Application In The Early Diagnosis Of Alzheimer's Disease

Objective Prospective memory (PM) is an important aspect of memory outside of the laboratory, and may be regarded as one of the main factors supporting the attainment and maintenance of autonomy across the lifespan.The goal of the current study was to examine the neurocognitive processes underlying prospective memory based on the neuropsychological methods.To investigate the event-based prospective memory (EBPM) and time-based prospective memory (TBPM) in patients with lesion in prefrontal cortex (PFC) and thalamus, and test the hypothesis that prefrontal cortex and thalamus is involved in the PM network, and to find out the different mechanisms between EBPM and TBPM. In addition, to investigate the EBPM and TBPM in normal aging, patients with amnesia mild cognitive impairment (aMCI) and AD, to find out the characteristic of PM impairment and the most sensitive component of memory impairment in patients with aMCI and AD.Methods 30 patients with lesion in prefrontal cortex, 18 patients with stroke in thalamus and 30 patients with white matter ischemic lesion (WMIL) were administered with a neuropsychological battery of tests including EBPM and TBPM tasks. In addition, 40 healthy elders, 30 patients with aMCI and 20 AD patients were also tesed with EBPM and TBPM tasks. All controls were matched with age and education level.Results Compared with the healthy adults(EBPM, 6.00±1.91; TBPM, 5.30±0.92), the patients with lesion in prefrontal cortex were significantly impaired in EBPM(1.47±1.07, P<0.001),but not significantly impaired in TBPM.(4.77±1.17, P>0.05); Compared with the healthy control group (EBPM, 5.98±1.90; TBPM, 5.29±0.91), the patients with stroke in thalamus showed a various loss in TBPM, but not in EBPM. Compared with the healthy controls, WMIL patients demonstrated a selective impairment in their ability to perform TBPM, but not in EBPM tasks. In addition, Compared with healthy adults (EBPM, 6.25±1.60;TBPM,5.38±0.87), healthy elders were impaired in EBPM(2.50±0.85)as well as in TBPM(4.93±1.07) (P<0.001, P<0.05), furthermore were impaired in EBPM more significantly(P<0.001). Double dissociation between the performance of EBPM and TBPM was also found in healthy elders;Compared with healthy elders(EBPM,2.33±0.66;TBPM,4.90±1.03), patients with aMCI were impaired in EBPM(0.90±1.09)as well as in TBPM(4.23±1.14) (P<0.01, P<0.05), furthermore were impaired in EBPM more significantly (P<0.01); Compared with age and education matched healthy elders(EBPM 2.23±0.77; TBPM 4.83±1.09) and aMCI(EBPM,1.00±1.03;TBPM,3.10±1.52), AD patients were impaired in EBPM (0.20±0.41) as well as in TBPM(1.40±1.27) (P<0.05)Conclusion These results suggest that the patients with lesion in PFC were impaired in EBPM, but not in TBPM, patients with white matter ischemic lesion and stroke in thalamus were impaired in TBPM, but not in EBPM. This finding also indicats that EBPM and TBPM may have different neural substrate. It is possible that prefrontal lobe is selectively involved in EBPM, but less involved in TBPM, thalamus is selectively involved in TBPM, but less involved in EBPM. These results suggest that prospective memory is obviously impaired, and EBPM is impaired more significantly than TBPM in healthy elders. The evidence of double dissociation between EBPM and TBPM supports that EBPM and TBPM may have different neural substrate;There are mult-memory disorders in patients with aMCI and AD. But compared with RM and TBPM, EBPM is impaired more significantly in patients with aMCI and AD. This finding indicats that EBPM impairment may be as an early indicator of aMCI and AD;...