Long-Term Memory Biases Auditory Spatial Attention: Healthy and Impaired “Memory-Guided Attention”

Attention and memory may be impaired in individuals at-risk for Alzheimer’s disease (AD), though standard cognitive assessments typically study the two in parallel. In reality, attention and memory interact to facilitate processing, and thus a more integrative approach is required. Here, I used a novel auditory paradigm to assess how long-term contextual memory facilitates detection of an auditory target in healthy young adults (Study 1 and 2), and whether performance on this task is related to Apolipoprotien E4 (APOE4) genotype, a risk factor for the sporadic AD (Study 3). During an initial familiarization task, participants heard audio-clips some of which included a lateralized target (p = 50%). On each trial, participants indicated whether the target was presented from the left, right or was absent. Following a retention interval, the same audio-clips were presented, but now all included a target. Across three experiments in Study 1, young adults showed memory-based gains in response speed and accuracy associated with informative memory cues. In Study 2, auditory context facilitated speeded target detection 24 hours after learning just as well as 1 hour after learning. Differences between electrophysiological (EEG) responses associated with informative and uninformative audio-clip cues point to memory rather than attention mechanisms. In Study 3, differences in cognitive performance in carriers of APOE4 at a pre-clinical phase were observed. Notably, while memory recall was unaffected by genotype, APOE4 dose impaired memory-guided attention. A relationship between explicit memory and memory-guided attention was only observed in non-carriers, and this relationship was broken in APOE4 heterozygotes and homozygotes, indicating that APOE4 carriers rely less on explicit memory to facilitate attention. Because memory-guided attention declined with age in APOE4 carriers, it may be an early disease-related impairment rather than a life-long impairment.Ph.D