According to the inhibitory deficit hypothesis, older adults have difficulties in preventing task-irrelevant materials from gaining access to working memory (Lustig, Hasher, & Zacks, 2007). Some neuroscientific evidence, however, show that the age-related inhibitory deficit disappears when task difficulty is equated. Thus, it is still not clear whether findings regarding the age-related inhibitory deficit are confounded by task-related factors or not. Additionally, although previous studies showed that event-related potentials (ERPs) to emotional material change as a function of task relevancy in the young, it is still an open question whether there are age-related differences on this issue. Combining these questions, the goal of this dissertation was to examine the effect of age on ERP correlates of inhibitory functioning by employing a selective attention task which required younger and older adults to selectively attend to either pictures (emotional or non-emotional) or to flanking line bars, concurrently presented on the screen. In the picture task, participants decided whether the picture was presented in black and white or color; in the bar task, they indicated whether the orientation of the bars matched or not. Prior to the experiment, I individually calibrated the difficulty of the non-emotional bar task such that accuracy was 75% correct. The behavioral data showed no interference from emotional material in the bar task. Accuracy in the picture task was higher for emotional relative to neutral pictures in the picture task, regardless of age. ERPs provided evidence for both emotion-based and more differentiated valence-based effect for the younger adult group in the picture task. In the bar task, there was evidence for enlarged ERPs for task-irrelevant emotional relative to task-irrelevant neutral pictures during the time windows (250-300 ms and 350-450ms) associated with the negative ERP components, but task-irrelevant emotional material was suppressed at a later stage of processing (500-700 ms). ERP results for the older adult group provided evidence for an emotional positivity effect and an emotional negativity effect in the picture task. In the bar task, although interference from positive images occurred at early stage of processing, ERPs to task-irrelevant emotional and neutral pictures were similar during later ERP components. These findings are discussed in light of theories of cognitive aging and different accounts of emotional processing in aging.
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Age-related differences in selective attention to emotional material: does task-relevance matter?