Background:
Neuroimaging evidence shows the ε4 allele of the apolipoprotein E (APOE) gene is related to brain-functional differences during memory tasks in young, middle-aged and elderly adults. Developmental studies, however, indicate that the ε4 allele confers a cognition-enhancing/protective effect in children and young adults. This study uses a new measure of spatiotemporal wave activity that has shown greater sensitivity and larger effect sizes than EEG power measures.
Methods:
About 415 normal subjects were genotyped and divided into three APOE status groups: ε2 (ε2/ε2 or ε2/ε3), ε3 (ε3/ε3) and ε4 (ε3/ε4 or ε4/ε4) and four age bands: 6–15, 16–30, 31–50 and 51–65 years old. The ε3 ‘controls’ were age and gender matched to the ε2 and ε4 subjects. Subjects were tested on the Brain Resource International Databa cognitive battery. EEG was measured during a visual working-memory task and analyzed using measures of event-related power and spatiotemporal wave activity.
Results:
Analysis of covariance (controlling for age) showed no differences for APOE status on most cognitive tests. However, the ε4 group had improved performance on two tests of verbal fluency, compared with ε3, across all age bands. ε4 subjects showed less spatiotemporal wave activity in the theta band at ∼200 ms poststimulus, but no power differences.
Conclusions:
This study confirms previous findings of brain-functional differences between ε3 and ε4 subjects across a broad range of ages. However, the verbal fluency results, supported by previous studies showing developmental benefits of ε4, suggest that brain-functional differences do not necessarily imply deficits prior to the risk period for dementia.