Behavioral, Electrophysiological, and Pupil-based Rhythms of Attention and Memory in Young and Older Adults

Stanford University, Stanford CA

Investigators

Abstract

ABSTRACT: The acquisition of episodic memories (EM) relies on attention mechanisms, which are affected by aging with consequences for everyday functioning. Attention can operate on nonspatial features, via feature- based attention (FA), which has been recently shown to wax and wane at a consistent temporal frequency (behavioral rhythm), likely reflecting an intrinsic rhythmicity of the underlying neural computations. Notably, while a similar behavioral rhythm has been recently observed in EM, this memory-related rhythm has been interpreted to reflect distinct mechanisms from those underlying attentional rhythms despite their overlapping frequency and the likelihood that the memory behavior depends, in part, on attention. The magnitude of EM and FA rhythms may also interact with fluctuations of states of arousal, which are known to relate to variability in attention and memory. These observations raise fundamental questions about the neurocognitive mechanisms underlying behavioral rhythms of FA and EM, and how they are altered in human aging independent of Alzheimer’s disease (AD). This project will examine attention and memory performance concurrent with simultaneous scalp electroencephalography (EEG) and pupillometry with a well-powered sample of 75 young and 75 AD-biomarker negative, cognitively unimpaired older adults. Older adults will be screened with an extensive neuropsychological battery and blood plasma-based assays of AD pathology (Aβ42:40 and p-tau217), enabling more specific conclusions about AD-independent age-related changes in behavioral and neural expressions of FA and EM. In the main experiment, participants will perform a novel, integrated attention-memory task that combines FA and EM, with a design that will sample different phases of rhythms of feature-based attention and episodic memory encoding. Neural rhythms will be characterized using a cutting-edge state-space modeling approach applied to the EEG data to maximize sensitivity and specificity to detect genuine rhythmic neural activity. Pupillometry metrics of pupil size and EEG posterior alpha power will serve as moment-to-moment and individual-difference measures of arousal/sustained attention. Our specific aims are to examine the relations between behavioral rhythms of EM and FA and their alteration in aging (Aim 1); to elucidate the neural mechanisms underlying behavioral rhythms of EM and FA and their changes in aging (Aim 2); and to investigate how FA and EM rhythms relate to changes in arousal and how these relationships are altered in aging (Aim 3). Collectively, this Exploratory / Development Research project will provide novel insights into the dynamic interactions between attention, memory, and arousal, and will elucidate pathways through which AD-independent changes with age result in memory decline and between-person memory variability. The resulting data may ultimately reveal candidate biobehavioral markers for more effective diagnostics, along with potential avenues of intervention that can be developed and explored in future research.