Cortical auditory evoked potentials and hemispheric specialization of speech in individuals with learning disability and healthy controls: A preliminary study

Abstract

Background: Dichotic listening (DL) technique is a behavioral non-invasive tool which is used in studying hemispheric lateralization. Previous studies using behavioral DL have hypothesized that individuals with learning disabilities (LD) exhibit a lack of cortical specialization for processing speech stimulus. However, there is no event related potential (ERP) evidence, hence the main objective of the study is to explore hemispheric asymmetry using cortical auditory evoked potential (CAEPs) in normal hearing adults and also to compare the same in children with LD and healthy controls. Methods: CAEPs were recorded in 16 normal hearing young adults, eight right-handed children with LD and their age matched controls. Two stop constants (/Pa/ – voiceless, bilabial, stop: /Ta/ - voiceless, alveolar, stop) were chosen for this experiment and presented in each ear and dichotically in two different orders (/pa-ta/, /ta-pa/). ERPs were processed using a standard pipeline, and electrodes readings over the left and right hemispheres were averaged to create left and right regions of interest (ROI). The CAEPs were analyzed for mean amplitude and peak latency of P1-N1-P2 components. Results: The current study results suggest no statistically significant difference between the two stimulus in monaural condition and absence of order effect in dichotic condition. In healthy controls the CAEP latencies were shorter over the left hemisphere in both monaural and dichotic conditions in adults and control children. However, it was very evident that such a difference was lacking in children with LD. Conclusions: Hemispheric asymmetry can be detected using CAEPs for speech stimulus. The measures are consistent and void of stimulus or order effect. Taken together, the findings of current study, both monaural and dichotic condition illustrates the hemispheric differences in processing speech stimuli in normal hearers. Absence of latency differences between hemispheres in children with LD indicate a lack of hemispheric asymmetry.

Left Lateralization of the Cortical Auditory-Evoked Potential Reflects Aided Processing and Speech-in-Noise Performance of Older Listeners With a Hearing Loss

“…Determining how well left lateralized speech processing is preserved in individual listeners might then be of clinical relevance for differentiating patients in need of features that aggressively enhance speech signals from those who might prefer a more natural/neutral sounding device. To the extent that such lateralization can be modified/restored, its measurement may also serve as a useful index for evaluating the efficacy of different hearing aid technologies, interventions, and/or rehabilitation programs especially in young infants/children (Purdy et al 2005;Chang et al 2012;Bhat et al 2018) or other populations where assessing hearing aid benefits for speech-perception are difficult (e.g., Van Dun et al 2015). Speaking to this possibility, Philibert et al (2003) showed that naive hearing aid wearers demonstrated improved performance on a phonemic categorization task at 4 months after first fit.…”

Potenciais evocados auditivos de longa latência em crianças com alterações de leitura e escrita

“…O padrão acústico destes estímulos difere, sendo de grande importância a realização destes exames com os dois tipos de estímulos, para que seja feita a comparação da forma de processamento destes diferentes estímulos acústicos no Sistema Nervoso Auditivo Central (SNAC) (Massa et al, 2011), uma vez que estímulos diferentes geram respostas corticais distintas (Matas, 2015). A maioria dos estudos foca apenas na avaliação com estímulo não verbal, sendo raros os estudos que utilizam o estímulo verbal para eliciar os PEALL (Bhat et al, 2018).…”

“…Segundo Picton O padrão acústico dos estímulos TB e de Fala diferem, sendo de grande importância a realização destes exames com os dois tipos de estímulos para que seja feita a comparação da forma de processamento destes diferentes estímulos acústicos no SNAC, uma vez que estímulos diferentes geram respostas corticais distintas (Matas et al, 2011;Matas, 2015). Na literatura, a maioria dos estudos focam apenas na avaliação com estímulo TB e foi encontrado apenas um estudo em crianças com alterações de leitura e escrita em que o estímulo verbal foi utilizado para eliciar os PEALL (Bhat et al, 2018).…”

“…Sugere-se que novos estudos sejam realizados envolvendo avaliações eletrofisiológicas e comportamentais do processamento auditivo, com estímulos verbais e não verbais, em um número maior de indivíduos com alterações de leitura e escrita, bem como que utilizem estes potenciais para investigar a plasticidade neuronal frente à intervenção terapêutica (Visioli-Melo e Rotta, 2000; Purdy et al, 2002;Soares et al, 2011;Alvarenga et al, 2013;Regaçone et al, 2014;Bhat et al, 2018;Mırıcı et al, 2018;Cunha et al, 2019).…”