In order to study the effect of normal aging and cardiovascular disease on selective attention, a letter-identification task was proposed to younger and older healthy adults as well as patients with a recent myocardial infarction or a recent coronary artery bypass grafting. Participants had to detect either a big stimulus or a small one surrounded by flanking letters. The stimuli were displayed horizontally, either in the left (LVF) or in the right visual field (RVF). The interaction between the type of stimulus and the hemifield of presentation reached significance in all groups except in patients who underwent a coronary artery bypass. Only young normal adults showed the expected significant RVF advantage when detecting big stimuli and an LVF advantage when detecting small stimuli surrounded by flankers. In older control adults and in patients with myocardial infarction, the RVF advantage for the condition with selective attention vanished. In patients who underwent a coronary artery bypass, reaction times were increased and no hemispheric specialization for selective attention emerged. The results are discussed with regard to the hypothesis of a Hemispheric Asymmetry Reduction in Older Adults (HAROLD model) and to the presence of cognitive dysfunction consecutive to cardiovascular disease. 1. Introduction The concept of selective attention usually refers to the ability to focus on areas of visual space to facilitate target detection . Using a visual detection paradigm adapted from LaBerge and Buchsbaum , and previously shown to activate the pulvinar  we demonstrated that when selective attention is required to identify a visual target surrounded by flankers, reaction times (RTs) are shorter in the right than in the left visual field [4, 5], thus confirming a left hemisphere (LH) advantage for filtering irrelevant information and analysing the local features of a visual scene [6, 7]. Conversely, RTs are found to be shorter in the left visual field (LVF) than in the right visual field (RVF) when the to-be-identified target is presented alone and required less filtering activity, that is, less selective attention. These data were obtained in young healthy right-handed adults (average age, 28.4 years in Chokron et al. ), but as several studies have hypothesized, aging may modify both selective attention processes and the pattern of cerebral lateralization . Cabeza et al.  measured prefrontal activation in younger and older adults performing memory tasks. They found that high-functioning older adults showed strong bilateral prefrontal
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