Project 2: Central Auditory Integration and Plasticity

PROJECT 2: ABSTRACT Project 2 investigates auditory cognitive mechanisms that contribute to the variability in CI outcome based on speech-in-noise (SiN) understanding. Understanding SiN is a complex task that requires multiple steps including the abstraction of the target from crowded auditory scenes, auditory working memory, and attention. Variation in any of these could affect SiN performance. However, most previous work focused on the status of the peripheral auditory system, the effect of time and CI usage on adaptation to the new listening device, or general cognitive and demographic factors. Project 2 aims to fill this gap in our understanding by assessing the auditory cognitive mechanisms that are responsible for perceiving and attending to acoustic patterns over frequency and time. These mechanisms operate at a level between the auditory periphery and high-level language processing, so that Project 2 bridges a gap between Projects 1 and 3. First, we will carry out cross-sectional cognitive studies that assess auditory cognition over the timescales of words and sentences. At the scale of words, in users of traditional CIs (fully electric hearing) we replicate our initial work that demonstrates correlation between a measure of figure-ground (FG) detection and SiN performance. We will also test whether adding measures of auditory cognition at the timescale of sentences allows better prediction of detection of sentences in noise. In addition, for CI users that integrate acoustic and electric hearing, we also test FG detection in the acoustic and electric frequency ranges and between these ranges. We will calculate the correlation between these and SiN to assess the importance of grouping within and across acoustic and electric aspects of hearing. Second, we will identify cortical bases for the auditory cognitive processes we identified in Aim 1 determine SiN ability in CI users. We carry out cross-sectional neuroimaging EEG studies to ask if EEG responses improve the prediction of SiN based on the cognitive measures of Aim 1. We will test a new EEG measure to predict sentence-in-noise listening based on endogenous attention. Finally, a study using O-15 water PET will test a model of SiN perception based on grouping mechanisms in left auditory cortex, and test whether these occur in the same part of auditory cortex in CI users and normal controls. Third, we will examine acoustic+electric CI users longitudinally to test the hypothesis that cognitive and brain mechanisms for grouping within the electric hearing ranges occur earlier after implantation than grouping between the A and E ranges. Overall, this project will establish cognitive and brain mechanisms for auditory cognition over different timescales and different frequency ranges that explain SiN detection in CI users. The cognitive measures and EEG measures are realistic potential clinical tools for identifying non-auditory factors that are related to outcomes in real world listening.