Biology subjects

Voola, M. W. R.

Publications and source records attributed to Voola, M. W. R..

3 recordsLinked to original sources

bioRxiv2022

Event-Related Potentials of Single Sided Deaf Cochlear Implant Users - Using a Semantic Oddball Paradigm in Noise

ObjectiveIn individuals with single sided deafness (SSD), which is characterised by a profound hearing loss in one ear and normal hearing in the contralateral ear, binaural input is no longer present. A cochlear implant (CI) is the only way to restore functional hearing in the profoundly deaf ear, with previous literature demonstrating improvements in speech in noise intelligibility with the provision of a CI. However, we currently have a limited understanding of the neural processes involved (e.g., how the brain integrates the electrical signal produced by the CI with the acoustic signal produced by the normal hearing ear) and how the modulation of these processes with CI contributes to improved speech in noise intelligibility. Using a semantic oddball paradigm presented in the presence of background noise, this study aims to investigate how the provision of CI impacts speech in noise perception of SSD CI users. MethodHigh density electroencephalography (EEG) from twelve SSD-CI participants was recorded whilst they completed a semantic acoustic oddball task. All participants completed the oddball task in three different free field conditions with the speech and noise coming from different speakers. The three tasks were 1) with the CI-On in background noise, 2) with the CI-Off in background noise and 3) with the CI-On without background noise (Control). We examined task-performance (RT, subjective listening effort, and accuracy) and measured N2N4 and P3b event-related brain potentials (ERPs) linked to the discrimination and evaluation of task relevant stimuli. Speech in noise and sound localisation abilities was also measured. ResultsReaction time was significantly different between all tasks with CI-On (M(SE) = 809(39.9) ms) having faster RTs than CI-Off (M(SE) = 845(39.9) ms) and Control (M(SE) = 785(39.9) ms) being the fastest condition. The Control condition exhibited a significantly shorter N2N4 and P3b area latency when compared to the other two conditions. However, despite these differences noticed in RTs and area latency, we observed similar results between all three conditions for N2N4 and P3b difference area. ConclusionThe inconsistency between the behavioural and neural results suggest that EEG may not be a reliable measure of cognitive effort. This rationale is further supported by the different explanations used in past studies to explain N2N4 and P3b effects. Future studies should look to alternative measures of auditory processing (e.g., pupillometry) to get a deeper understanding of the underlying auditory processes that facilitate speech in noise intelligibility.

neuroscience↗

bioRxiv2022

Odd-Even Oddball Task: Evaluating Event-Related Potentials (ERPs) during Word Discrimination Compared to Speech-Token and Tone Discrimination.

The use of tonal and speech token auditory oddball tasks has been used abundantly in past literature; however, it has been argued that tasks using non-word sounds fail to capture the higher-level ability to interpret and discriminate stimuli based on meaning which are critical to language comprehension. As such this study aims to examine how neural signals associated with discrimination and evaluation-processes (P3b) from semantic stimuli compare with those elicited by pure tones and speech tokens. This study comprises of two experiments, both containing thirteen adults (Exp 1: (Mean(SD)age = 25.20(3.89) years and Exp 2: Mean(SD)age = 25.3(3.79) years) with normal hearing in both ears (PTA [≤] 20dB HL). Scalp electroencephalography and auditory event related potentials was recorded in free field whilst they completed three different oddball tasks: 1) Tones, 2) Speech tokens and 3) Odd/Even numbers. In experiment two, the duration of each stimulus was the same. P3b peak latency was significantly different between all three tasks, in both experiments. P3b amplitude was identified to be sensitive to reaction time, with tasks that have a large reaction time variability resulting in the P3b amplitude to be smeared out, thereby reducing the amplitude size. The findings from this study highlight the need to take into consideration all factors of the task before attributing any effects to any additional process such as semantic processing and mental effort. Furthermore, it highlights the need for more cautious interpretation of P3b results in auditory oddball tasks.

neuroscience↗

bioRxiv2022

A Study of Event-Related Potentials during Monaural and Bilateral Hearing in Single Sided Deaf Cochlear Implant Users

ObjectiveSingle sided deafness (SSD) is characterized by a profoundly deaf ear and normal hearing in the contralateral ear. A cochlear implant (CI) is the only method to restore functional hearing in a profoundly deaf ear. In a previous study, we identified that the cortical processing of a CI signal differs from the normal hearing ear (NHE) when directly compared using an auditory oddball paradigms consisting of pure tones. However, it is unclear how the electrical and acoustic signals from each ear are combined. This study aims to understand how the provision of the CI in combination with the NHE may improve SSD CI users ability to discriminate and evaluate auditory stimuli. DesignElectroencephalography (EEG) from ten SSD-CI participants (four participated in the previous pure-tone study) were recorded during a semantic acoustic oddball task, where they were required to discriminate between odd and even numbers. Stimuli were presented in four hearing conditions: directly through the CI, directly to the NHE, or in free field with the CI switched on and off. We examined task-performance (response time and accuracy) and measured N1, P2, N2N4 and P3b event-related brain potentials (ERPs) linked to the detection, discrimination, and evaluation of task relevant stimuli. Sound localization and speech in noise comprehension was also examined. ResultsIn direct presentation, task performance was superior during NHE compared to CI (Shorter and less varied RTs [[~]720 vs. [~]842 ms], higher target accuracy [[~]93 vs. [~]70%]) and early neural responses (N1 and P2) were enhanced for NHE suggesting greater signal saliency. However, the size of N2N4 and P3b target-standard effects did not differ significantly between NHE and CI. In free field, target accuracy was similarly high for both FF-on and -off ([~]95%), with some evidence of CI interference during FF-on (more variable and slightly but significantly delayed RTs [[~]737 vs. [~]709 ms]). Early neural responses and late effects were also greater during FF-on. Performance on sound localization and speech in noise comprehension (SCINNHE configuration only) was significantly greater during CI-on. ConclusionBoth behavioral and neural responses in the semantic oddball task were sensitive to CI in both direct and free-field presentations. Direct conditions revealed that participants could perform the task with the CI alone, although performance was sub-optimal and early neural responses was reduced when compared to the NHE. For free-field, the addition of the CI was associated with enhanced early and later neural responses but did not improved task performance. Enhanced neural responses show that the additional input from the CI is modulating relevant perceptual and cognitive processes, but the benefit of binaural hearing on behavior may not be realized in simple oddball tasks which can be adequately performed with the NHE. Future studies interested in binaural hearing should examine performance under noisy conditions and/or employ spatial cues to allow headroom for the measurement of binaural benefit.

neuroscience↗