Effects of distracter novelty on attentional orienting in healthy aging and Parkinson's disease: An event-related potential (ERP) study

Novel events are preferentially processed in the brain in order to facilitate adaptive responses to a dynamic, changing world. However, much is still unknown about the mechanisms that give rise to attentional orienting toward novel events in the brain. Healthy aging and Parkinson's disease (PD) have been previously associated with deficits in novelty processing, which is mediated by neural networks that give rise to preferential processing for novel distracters. In order to better characterize the nature of these attentional mechanisms, two event-related potential (ERP) experiments were conducted in young adults, older adults, and PD patients. The experiments manipulated the novelty characteristics of task-irrelevant distracters that were presented in the context of a three-stimulus oddball task. This task allowed for the examination of both distracter- and target-related processing as a function of distracter novelty. As expected, novel distracters differentially engaged the visual attention system in ways that were not seen for non-novel distracters. However, older adults and PD patients showed impairments in their attentional orienting responses toward novel stimuli. These deficits in distracter processing were associated with a number of other cognitive and emotional symptoms, and further gave rise to impairments in target-related processing. Notably, older adults and PD patients exhibited weaker processing of attentional targets and a frontal shift in their ERP reflections of target processing, which is consistent with a frontally-mediated deficit in memory updating for the targets. Taken together, the results of these experiments provide strong evidence that novel events receive preferential neural processing in ways that are influenced by the stimulus features that characterize the event, as well as the functional integrity of specialized attentional orienting networks in the brain. Older adults and PD patients appear to be less engaged with new information, yet more susceptible to the interfering effects of novel distracters. These findings help to clarify the ways in which stimulus characteristics affect attentional orienting to unexpected events, along with the impacts that healthy aging and PD have on this process.