Identification of cognitive processes with fMRI and auditory stimulation in hearing impaired with and without hearing aids

Within this project, we will investigate the neural correlates of cognitive processes during speech intelligibility in noise. The data will be analysed according to the working memory framework of Ease of Language Understanding (ELU) developed by Rönnberg and colleagues. This model states that the demands on cognitive (‘explicit’) processing increase when speech comprehension is impaired by background noise, hearing loss, or altered by the type of signal processing in the hearing instrument.

• Staff:

Ingrid Johnsrude , PhD		Project manager		Queen's University, Kingston Ontario
Jerker Rönnberg , Prof.		PI		Behavioural Sciences and Learning
Maria Engström , Assoc. Prof.		fMRI		Radiological Sciences
Thomas Lunner , Prof.		Signal processing		Technical Audiology
Stefan Stenfelt , Prof.		Technical audiology		Technical Audiology
Örjan Dahlström , PhD		Data analysis		Behavioural Sciences and Learning
Mattias Ragnehed , PhD		Experimental set-up, data analysis		Technical Audiology
Mary Rudner , Assoc. Prof.		Cognitive hearing science		Behavioural Sciences and Learning

• Former Staff:

• Project Description:

This project is linked to the Linneus centre for research on hearing and deafness (HEAD) at Linköping University. The overall goal of the research programme is to establish a new field of investigation, Cognitive Hearing Science, which (a) addresses different hearing impairment syndromes and deafness, b) emphasizes the interaction between different kinds of signal processing and cognitive capacity, and (c) relates cognitive capacities to successes/failures of communication, aging and social life. HEAD has two major research goals within the field. The first goal is to model acoustic information transfer from the peripheral hearing organ to the auditory cortex and the second is to develop a general cognitive model for ease of language understanding that encompasses (a) through (c). The output from the acoustic model serves as an input to the cognitive model. Achievement of these goals will allow us to explain developmental trajectories and intervention outcomes as well as informing the technical development and clinical fitting of hearing aids and cochlear implant.

The working memory model for Ease of Language Understanding (ELU) accounts for the role of working memory in language understanding. The perceptual input to the model is conceptualised as multi-sensory or multi-modal linguistic information, which at a cognitive level is assumed to be rapidly and automatically bound together to form phonological streams of information (RAMBPHO).  As long as optimum conditions prevail, the RAMBPHO function mediates rapid and implicit unlocking of the lexicon by means of matching input with stored phonological representations in long-term memory. If suboptimum conditions are at hand (e.g. due to hearing impairment, suboptimal signal processing in a hearing instrument, or noisy conditions), RAMBPHO information may not readily match stored representations, and mismatch may occur. Mismatch may also arise due to slow lexical access and less precise phonological representations. When mismatch occurs, explicit processing and storage capacity is required to infer meaning, prospectively as well as retrospectively, on the basis of incomplete information.

Within this project we will examine the neural correlates of mismatch-related cognitive processes during speech comprehension in noise. This will be accomplished by using sparse sampling fMRI that enables stimuli to be presented during silent periods in the MR-scanner. In the first study, the interaction between intelligibility and cognitive capacity will be investigated both in hearing impaired and normal hearing subjects. For this purpose a set of sentences are presented auditory to the subjects during different noise conditions. The subjects are subsequently tested if they remembered words in the sentences or not. Future studies will investigate the effects cognitive capacity and hearing aids on the neural response.