Neural correlates of auditory perceptual awareness under informational masking.
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ABSTRACT:
SUBMITTER: Gutschalk A
PROVIDER: S-EPMC2422852 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Bistability occurs when two alternative percepts can be derived from the same physical stimulus. To identify the neural correlates of specific subjective experiences we used a bistable auditory stimulus and determined whether the two perceptual states could be distinguished electrophysiologically. Fourteen participants underwent magnetoencephalography while reporting their perceptual experience while listening to a continuous bistable stream of auditory tones. Participants reported bistability with a similar overall proportion of the two alternative percepts (52% vs 48%). At the individual level, sensor space electrophysiological discrimination between the percepts was possible in 9/14 participants with canonical variate analysis (CVA) or linear support vector machine (SVM) analysis over space and time dimensions. Classification was possible in 14/14 subjects with non-linear SVM. Similar effects were noted in an unconstrained source space CVA analysis (classifying 10/14 participants), linear SVM (classifying 9/14 subjects) and non-linear SVM (classifiying 13/14 participants). Source space analysis restricted to a priori ROIs showed discrimination was possible in the right and left auditory cortex with each classification approach but in the right intraparietal sulcus this was only apparent with non-linear SVM and only in a minority of particpants. Magnetoencephalography can be used to objectively classify auditory experiences from individual subjects.
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Project description:Background: Regarding the strong auditory spatial plasticity capability of the central auditory system and the effect of short-term and long-term rehabilitation programs in elderly people, it seems that an auditory spatial training can help this population in informational masking release and better track speech in noisy environments. The main purposes of this study are developing an informational masking measurement test and an auditory spatial training program. Protocol: This study will be conducted in two parts. Part 1: develop and determine the validity of an informational masking measurement test by recruiting two groups of young (n=50) and old (n=50) participants with normal hearing who have no difficulty in understanding speech in noisy environments. Part 2 (clinical trial): two groups of 60-75-year-olds with normal hearing, who complain about difficulty in speech perception in noisy environments, will participate as control and intervention groups to examine the effect of auditory spatial training. Intervention: 15 sessions of auditory spatial training. The informational masking measurement test and Speech, Spatial and Qualities of Hearing Scale will be compared before intervention, immediately after intervention, and five weeks after intervention between the two groups. Discussion: Since auditory training programs do not deal with informational masking release, an auditory spatial training will be designed, aiming to improve hearing in noisy environments for elderly populations. Trial registration: Iranian Registry of Clinical Trials ( IRCT20190118042404N1) on 25 th February 2019.
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Project description:In recent years there has been growing interest in masking that cannot be attributed to interactions in the cochlea-so--called informational masking (IM). Similarity in the acoustic properties of target and masker and uncertainty regarding the masker are the two major factors identified with IM. These factors involve quite different manipulations of signals and are believed to entail fundamentally different processes resulting in IM. Here, however, evidence is presented that these factors affect IM through their mutual influence on a single factor-the information divergence of target and masker given by Simpson-Fitter's da [Lutfi et al. (2012). J. Acoust. Soc. Am. 132, EL109-113]. Four experiments are described involving multitone pattern discrimination, multi-talker word recognition, sound-source identification, and sound localization. In each case standard manipulations of masker uncertainty and target-masker similarity (including the covariation of target-masker frequencies) are found to have the same effect on performance provided they produce the same change in da. The function relating d(') performance to da, moreover, appears to be linear with constant slope across listeners. The overriding dependence of IM on da is taken to reflect a general principle of perception that exploits differences in the statistical structure of signals to separate figure from ground.
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