The Relationship between Associative Learning, Transfer Generalization, and Homocysteine Levels in Mild Cognitive Impairment
The Relationship between Associative Learning, Transfer Generalization,
and Homocysteine Levels in Mild Cognitive Impairment
Abeer Mahmoud Eissa, Egypt
Ahmed A. Moustafa1*, Doaa H. Hewedi2
, Abeer M. Eissa2
,
Catherine E. Myers3
, Hisham A. Sadek2
Previous studies have shown that high total homocysteine levels are
associated with Alzheimer’s disease (AD) and mild cognitive impairment (MCI).
Objectives: Prior studies suggest that learning and generalization of learned
rules are subserved by different brain systems, namely the basal ganglia and
hippocampus. In the current study, we test if these cognitive processes are
affected by homocysteine levels in healthy controls and individuals with MCI.
Methods: In this study, we test the relationship between cognitive function and
total homocysteine levels in healthy subjects (Global Dementia Rating, CDR =
0) and individuals with MCI (CDR = 0.5). We have used a cognitive task that
tests learning and generalization of rules, processes that have been
previously shown to rely on the integrity of the striatal and hippocampal
regions, respectively.
Results: We found that total homocysteine levels are higher in MCI individuals than in healthy controls. Unlike what we expected, we found no difference between MCI subjects and healthy controls in learning and generalization. We conducted further analysis after diving MCI subjects in two groups, depending on their Global Deterioration Scale (GDS) scores: individuals with very mild cognitive decline (vMCD, GDS = 2) and mild cognitive decline (MCD, GDS = 3). There was no difference among the two MCI and healthy control groups in learning performance. However, we found that individuals with MCD make more generalization errors than healthy controls and individuals with vMCD. We found no difference in the number of generalization errors between healthy controls and MCI individuals with vMCD. In addition, interestingly, we found that total homocysteine levels correlate positively with generalization errors, but not with learning errors.
Conclusion: Our results are in agreement with prior results showing a link between hippocampal function, generalization performance, and total homocysteine levels. Importantly, our study is perhaps among the first to test the relationship between learning (and generalization) of rules and homocysteine levels in healthy controls and individuals with MCI.
http://www.alz.co.uk/sites/default/files/dubai2013/adi-dubai-2013-abstracts.pdf