Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - AUDADAPT (The listening challenge: How ageing brains adapt)

Teaser

Humans in principle adapt well to sensory degradations. In order to do so, our cognitive strategies need to adjust accordingly (a process we term “adaptive control”). The auditory sensory modality poses an excellent, although under-utilised, research model to understand...

Summary

Humans in principle adapt well to sensory degradations. In order to do so, our cognitive strategies need to adjust accordingly (a process we term “adaptive control”). The auditory sensory modality poses an excellent, although under-utilised, research model to understand these adjustments, their neural basis, and their large variation amongst individuals. Hearing abilities begin to decline already in the fourth life decade, and our guiding hypothesis is that individuals differ in the extent to which they are neurally, cognitively, and psychologically equipped to adapt to this sensory decline.

Our project pursues three specific aims: (1) We will first specify the neural dynamics of “adaptive control” in the under-studied target group of middle-aged listeners compared to young listeners. We will employ advanced multi-modal neuroimaging (EEG and fMRI) markers and a flexible experimental design of listening challenges. (2) Based on the parameters established in (1), we will explain inter-individual differences in adaptive control in a large-scale sample of middle-aged listeners, and aim to re-test each individual again after approximately two years. These data will lead to (3) where we will employ statistical models that incorporate a broader context of audiological, cognitive skill, and personality markers and reconstructs longitudinal “trajectories of change” in adaptive control over the middle-age life span.

Pursuing these aims will help establish a new theoretical framework for the adaptive ageing brain. The project will further break new ground for future classification and treatment of hearing difficulties, and for developing individualised hearing solutions. Profiting from an excellent research environment and the principle investigator’s pre-established laboratory, this research has the potential to challenge and to transform current understanding and concepts of the ageing human individual.

Work performed

In April 2016, following the assembly of the initial project team that included experts in the fields of audiology, linguistics, system neuroscience, as well as EEG and fMRI, the team began working on WP1 (approx. 2-month delay relative to Description of Action).
As detailed in the Description of action, the main objective of WP1 was to identify and validate a set of neural markers that are functionally relevant for the processing of speech (or other auditory signals) under challenging conditions. Building on existing findings in younger adults, our primary focus was on two key neurophysiological measures: i) slow cortical oscillations in the delta/theta frequency range (1–7 Hz) that emanate from auditory cortex and are known to neurally track or “entrain to” slow amplitude and spectral fluctuations in speech, and ii) more domain-general dynamic changes in alpha oscillations (8–13 Hz) often found to be involved in functional inhibition and control of attention.
Meanwhile, as a secondary focus, a more systems-neuroscience perspective was additionally undertaken to investigate brain networks (and their signatures) underlying auditory processing. In the absence of a gold-standard approach in analyzing large-scale brain networks, first methodological efforts were dedi¬cated to design and implement network analysis and modeling streams. Here, a particular emphasis was given to investigating brain network dynamics both on the scale of seconds (trial-by-trial) and conditions (reconfiguration of resting state brain networks in adaptation to listening).
To test whether the proposed functional relevance of the aforementioned neural markers in auditory processing would also extend to our population of interest, that is, healthy middle-aged and older adults between 40 to 70 years of age, we built on and extended existing experimental paradigms known to reliably tap into selective auditory processing, hence invoking the neural markers of interest. More precisely, in the second half of 2016, we tested and compared two different experimental paradigms in order to arrive at the most suitable experimental design to be used for the large-scale data acquisition planned for WP2.
We implemented the first experiment (EEG paradigm A) that was specifically designed to probe the spatiotemporal dynamics of lateralized alpha power as a neural marker of auditory spatial attention. An earlier version thereof had been previously tested in the lab in healthy younger adults (Wöstmann et al., PNAS 2016). Since one of the main objectives of WPs 2 and 3 would be to investigate the complex interactions and correlations between the key neural markers and other non-neural measures of adaptive control, we also decided on a battery of cognitive tests, personality profiling and audiometric measurement that would complement EEG (and fMRI) measurements.
We recruited an initial sample of ~40 healthy, middle-aged adults who each underwent two separate sessions of behavioural and EEG recording using paradigm A. As one of the key results, we were able to replicate the findings by Wöstmann et al. (2016) who reported a lateralization of alpha power that was not only temporally synchronized to rhythm of speech but also spatially specific. In our cohort of middle-aged and older listeners, we found that auditory spatial attention induced a comparable lateralisation of alpha power synchronised to the speech rate. However, the observed relationship between this alpha lateralisation and task performance did not co-vary with age. In bringing together the neural parameters with our additionally collected behavioural measures, we instead found that task performance was strongly related to an individual’s attentional and working memory capacity. A first set of multivariate analyses revealed a separation of neural and behavioural variables independent of age.
A tentative conclusion that will shape our analyses of the large-sample WP2 data is that the lateralization of al

Final results

Where are we / where have we been moving beyond the state of the art with this project?
1. PUSHING THE ENVELOPE OF AUDITION IN MIDDLE-AGE ADULTHOOD: Our work is characterized by a wholesome view on audition: It does entail audiological testing on one end, and it does entail a large-scale, whole-brain characterization of even resting state characteristics and brain dynamics on the other end. Crucially, however, this project is amongst the first to model the sensory and cognitive processes in middle-aged adult, prior to or in the absence of major hearing problems, as a process that entails all these variables. Our multi-modal neuroimaging approach that not only uses EEG and fMRI but looks at various, very different measures in each of these,

2. FUSING PSYCHOLOGICAL AND NEUROSCIENTIFIC MODELLING OF AUDITION IN MIDDLE-AGE ADULTHOOD: As part of a still ongoing examination that also marks the seamless transition from ongoing WP2 into WP3, we have started to model the neural results along with the data on cognitive fitness, personality structure, as well as objective and subjective measures of hearing acuity in a multivariate, structural equation modelling framework. This modelling work will allow us to better understand the interplay of neural and psychological mechanisms which determine how well an ageing listener adapts to sensory decline. In the coming months, we hope to further elucidate the most important factors that underlie the considerable degree of inter-individual variation in the ability to adapt to challenging listening situations.

3. PROVIDING A LONGITUDINAL PERSPECTIVE. Longitudinal data are of the essence in any form of life-span research. Any attempt at causal inference is greatly facilitated if temporal precedence and observed changes can be substantiated by repeated measures over time in the same cohort. Thus, We deem the ERC AUDADAPT cohort, which we have started to establish (currently approx. N=120 listeners aged 40 to 80) an important contribution to the field. All data will be made publicly available. As the project is still under way, the cohort is still growing and will be re-tested in the years to come using behavior, audiometry, brain stem measures, cortical EEG and fMRI plus a host of cognitive, lifestyle, and personality profiles.

Website & more info

More info: http://auditorycognition.com.