Project summary A key observation in intelligence research is that individual differences in perceptual abilities are positively related to high-level cognition. The precise mechanisms underlying covariation between intelligence and perception remain unclear, but cognitive aging offers a clue because correlations between perception and intelligence increase over the adult lifespan, particularly in the auditory modality. This project focuses in-depth on auditory perception, but also measures vision and olfaction. A leading hypothesis is that a “common cause” factor that contributes to both perception and high-level cognition declines with age, but the common factor is unknown. This project tests the central hypothesis that attention control and effort, which are supported by frontal circuits vulnerable to aging, are mechanisms that link perception and cognition. We also test an alternative hypothesis, called “sensory deprivation”, where chronic auditory processing deficits induce central plasticity that impairs high-level cognition. Defining mechanisms for hearing and cognition relations has clinical importance, such as understanding cognitive influences on psychoacoustic tests and why hearing loss is a risk factor for dementia. The project uses a multimodal approach that includes structural equation modeling (SEM), EEG measures of auditory brain stem and cortical activity, and psychophysiological measures of effort. Attention control (also termed “executive function”) flexibly coordinates perceptual, cognitive, and motor functions to achieve a goal, and is accompanied by attentional effort, which reflects the intensity of mental exertion. Aim 1 tests the common cause hypothesis in young and older adults by using SEM to model data from batteries of hearing, attention, and cognitive tests. It will determine if attention control and/or effort are common mechanisms used in hearing and cognitive tests, and define the role of attention in age differences in test performance. Aim 2 further examines the common cause hypothesis by using behavioral and psychophysiological measures to test relations among multiple dimensions of listening effort to hearing and cognition. Aim 3 evaluates the sensory deprivation hypothesis by using EEG to image auditory processing in the brainstem and cortex under passive listening conditions designed to minimize auditory attention, and compares the results to when the same stimuli are actively attended. We predict that relations between auditory processing and high-level cognition will strengthen with age, and will define specific mechanisms at different levels of the neuroaxis. Statistical modeling in Aim 3 includes a head-to-head comparison of the common cause and sensory deprivation hypotheses. After completing this project, we will have learned whether attention is a common cause mechanism for relations among perception and high-level cognition, and if sensory deprivation is a mechanism in older people. The results have clinical relevance by defining influences of attention on hearing tests, and by clarifying overlap between cognition and hearing, particularly in older people at risk for both hearing and cognitive decline.

Project narrative The project is relevant to neurological and psychiatric disorders that have attentional impairments (e.g. autism, attention deficit disorder, PTSD, schizophrenia, stroke), and age-related cognitive disorders such as dementia. Hearing loss is a major risk factor for dementia (~40% relative-risk), and is greatly reduced with hearing aids. Mechanisms for hearing aid risk-reductions are unknown, but leading candidates are tested in this study (common cause, sensory deprivation), as secondary psychosocial effects of hearing aids (e.g. greater socialization, less loneliness, less depression) account for < ~11% of the effect. The project can inform hearing clinical practice by identifying cognitive influences on psychoacoustic testing, particularly in older people at risk for both hearing and cognitive decline.