Cortical Alpha Oscillations Predict Speech Intelligibility

Abstract

Understanding speech in noise (SiN) is a complex task involving sensory encoding and cognitive resources including working memory and attention. Previous work has shown that brain oscillations, particularly alpha rhythms (8–12 Hz) play important roles in sensory processes involving working memory and attention. However, no previous study has examined brain oscillations during performance of a continuous speech perception test. The aim of this study was to measure cortical alpha during attentive listening in a commonly used SiN task (digits-in-noise, DiN) to better understand the neural processes associated with “top-down” cognitive processing in adverse listening environments. We recruited 14 normal hearing (NH) young adults. DiN speech reception threshold (SRT) was measured in an initial behavioral experiment. EEG activity was then collected: (i) while performing the DiN near SRT; and (ii) while attending to a silent, close-caption video during presentation of identical digit stimuli that the participant was instructed to ignore. Three main results were obtained: (1) during attentive (“active”) listening to the DiN, a number of distinct neural oscillations were observed (mainly alpha with some beta; 15–30 Hz). No oscillations were observed during attention to the video (“passive” listening); (2) overall, alpha event-related synchronization (ERS) of central/parietal sources were observed during active listening when data were grand averaged across all participants. In some participants, a smaller magnitude alpha event-related desynchronization (ERD), originating in temporal regions, was observed; and (3) when individual EEG trials were sorted according to correct and incorrect digit identification, the temporal alpha ERD was consistently greater on correctly identified trials. No such consistency was observed with the central/parietal alpha ERS. These data demonstrate that changes in alpha activity are specific to listening conditions. To our knowledge, this is the first report that shows almost no brain oscillatory changes during a passive task compared to an active task in any sensory modality. Temporal alpha ERD was related to correct digit identification.

Induced cortical responses require developmental sensory experience

“…Alpha activity has a key role in both sensory processing ( Haegens et al , 2015 ; Lakatos et al , 2016 ) as well as in gating cerebral activity, also between sensory systems ( Jensen and Mazaheri, 2010 ). Alpha activity may also have a role in suppressing background noise from acoustic stimuli ( Strauß et al , 2014 ; Dimitrijevic et al , 2017 ).…”

“…Neuronal oscillations or oscillatory transients (referred together as ‘oscillatory activity’ here) are involved in such interactions in different brain regions ( Lakatos et al , 2007 ; Buzsáki and Wang, 2012 ; Giraud and Poeppel, 2012 ). Oscillatory activity has been, among other functions, also related to stimulus detection and stimulus selection ( Fiebelkorn et al , 2013 ; Mercier et al , 2015 ; Lakatos et al , 2016 ; van de Nieuwenhuijzen et al , 2016 ), auditory stimulus familiarity and choice ( Handa et al , 2017 ), sound perception ( Ross et al , 2017 ), listening effort ( Dimitrijevic et al , 2017 ) and auditory attention ( Wöstmann et al , 2017 ), auditory streaming ( Riecke et al , 2015 ), and auditory decision tasks ( Strauß et al , 2014 ). Of clinical importance is that oscillatory activity is tightly related to language physiology ( Shahin et al , 2009 ; Lewis et al , 2015 a ; Dimitrijevic et al , 2017 ) and that many forms of language pathology are accompanied by abnormal oscillatory activity ( Gandal et al , 2010 ; Goswami, 2011 , 2014 ; Heim et al , 2011 ; Edgar et al , 2015 ; Murphy and Benítez-Burraco, 2017 ).…”

Noise-Induced Change of Cortical Temporal Processing in Cochlear Implant Users

“…For CI users, paying attention to sound is one solution to enhance SiN perception. Previously, in both CI users and the NH group, the attentional modulation of auditory cortical responses has been revealed during SiN perception [31,32]. In people with hearing impairment and CIs, aural rehabilitation focusing on attention-induced change has been effective in improving speech understanding with background noise [14,33].…”

An exploratory Study of EEG Alpha Oscillation and Pupil Dilation in Hearing-Aid Users During Effortful listening to Continuous Speech

“…Studies utilizing the alpha band, which is usually detected in the posterior regions of the brain, have indicated that these brain oscillations are related to attentional processes in active versus passive listening [32] or different selective attention conditions [33]. However, studies have shown contradictory outcomes with varying listening demand.…”