Genetics and visual attention: Selective deficits in healthy adult carriers of the ɛ4 allele of the apolipoprotein E gene

The ɛ4 allele of the apolipoprotein E (APOE) gene is associated with altered brain physiology in healthy adults before old age, but concomitant deficits in cognition on standardized tests of cognitive function have not been consistently demonstrated. We hypothesized that sensitive and specific assessment of basic attentional functions that underlie complex cognition would reveal evidence of impairment in otherwise asymptomatic individuals. We found that as early as middle age, nondemented carriers of the ɛ4 allele of the APOE gene showed deficits when visual attention was spatially directed by cues in tasks of visual discrimination and visual search, in comparison to those without the ɛ4 allele (ɛ2 and ɛ3 carriers). Two component attentional operations were selectively affected: (i) shifting spatial attention following invalid location cues, and (ii) adjusting the spatial scale of attention during visual search. These changes occurred only in the presence of the ɛ4 allele and without decline in other aspects of attention (vigilance), memory, or general cognition. The results show that specific components of visual attention are affected by APOE genotype and that the course of cognitive aging is subject to selective alteration by a genetic trait.