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Amplitude modulations (AMs) are important for speech intelligibility, and deficits in speech intelligibility are a leading source of impairment in childhood listening difficulties (LiD). The present study aimed to explore the relationships between AM perception and speech-in-noise (SiN) comprehension in children and to determine whether deficits in AM processing contribute to childhood LiD. Evoked responses were used to parse the neural origins of AM processing. Forty-one children with LiD and 44 typically developing children, ages 8-16 years, participated in the study. Behavioral AM depth thresholds were measured at 4 and 40 Hz. SiN tasks included the Listening in Spatialized Noise-Sentences Test (LiSN-S) and a coordinate response measure (CRM)-based task. Evoked responses were obtained during an AM change detection task using alternations between 4 and 40 Hz, including the N1 of the acoustic change complex, auditory steady-state response (ASSR), P300, and a late positive response (late potential [LP]). Maturational effects were explored via age correlations. Age correlated with 4-Hz AM thresholds, CRM separated talker scores, and N1 amplitude. Age-normed LiSN-S scores obtained without spatial or talker cues correlated with age-corrected 4-Hz AM thresholds and area under the LP curve. CRM separated talker scores correlated with AM thresholds and area under the LP curve. Most behavioral measures of AM perception correlated with the signal-to-noise ratio and phase coherence of the 40-Hz ASSR. AM change response time also correlated with area under the LP curve. Children with LiD exhibited deficits with respect to 4-Hz thresholds, AM change accuracy, and area under the LP curve. The observed relationships between AM perception and SiN performance extend the evidence that modulation perception is important for understanding SiN in childhood. In line with this finding, children with LiD demonstrated poorer performance on some measures of AM perception, but their evoked

Auditory perceptual deficits are widely observed among children with developmental language disorder (DLD). Yet the nature of these deficits and the extent to which they explain speech and language problems remain controversial. In this study, we hypothesise that disruption to the maturation of the basilar membrane may impede the optimisation of the auditory pathway from brainstem to cortex, curtailing high-resolution frequency sensitivity and the efficient spectral decomposition and encoding of natural speech. A series of computational simulations involving deep convolutional neural networks that were trained to encode, recognise, and retrieve naturalistic speech are presented to demonstrate the strength of this account. These neural networks were built on top of biologically truthful inner ear models developed to model human cochlea function, which – in the key innovation of the current study – were scheduled to mature at different rates over time. Delaying cochlea maturation qualitatively replicated the linguistic behaviour and neurophysiology of individuals with language learning difficulties in a number of ways, resulting in: (i) delayed language acquisition profiles; (ii) lower spoken word recognition accuracy; (iii) word finding and retrieval difficulties; (iv) ‘fuzzy’ and intersecting speech encodings and signatures of immature neural optimisation; and (v) emergent working memory and attentional deficits. These simulations illustrate the many negative cascading effects that a primary maturational frequency discrimination deficit may have on early language development, and generate precise and testable hypotheses for future research into the nature and cost of auditory processing deficits in children with language learning difficulties.

Auditory perceptual deficits are widely observed among children with developmental language disorder (DLD). Yet the nature of these deficits and the extent to which they explain speech and language problems remain controversial. In this study, we hypothesise that disruption to the maturation of the basilar membrane may impede the optimisation of the auditory pathway from brainstem to cortex, curtailing high-resolution frequency sensitivity and the efficient spectral decomposition and encoding of natural speech. A series of computational simulations involving deep convolutional neural networks that were trained to encode, recognise, and retrieve naturalistic speech are presented to demonstrate the strength of this account. These neural networks were built on top of biologically truthful inner ear models developed to model human cochlea function, which – in the key innovation of the current study – were scheduled to mature at different rates over time. Delaying cochlea maturation qualitatively replicated the linguistic behaviour and neurophysiology of individuals with language learning difficulties in a number of ways, resulting in: (i) delayed language acquisition profiles; (ii) lower spoken word recognition accuracy; (iii) word finding and retrieval difficulties; (iv) ‘fuzzy’ and intersecting speech encodings and signatures of immature neural optimisation; and (v) emergent working memory and attentional deficits. These simulations illustrate the many negative cascading effects that a primary maturational frequency discrimination deficit may have on early language development, and generate precise and testable hypotheses for future research into the nature and cost of auditory processing deficits in children with language learning difficulties.

This thesis examines auditory selective attention as a possible cause of Auditory Processing Disorder (APD). APD is a diagnosis based on the clinical needs of the 5% of children who present with listening difficulties but demonstrate normal hearing. This thesis will focus on developmental APD, which affects children with no known infection, trauma or primary cause inducing their listening difficulties. It will seek to address the current lack of understanding of the root causes of APD, which leads to significant variation in clinical referral routes, resulting in inconsistent methods of diagnosis and treatment. APD has historically been approached via a bottom-up route of assessing auditory processing skills, such as temporal-spatial abilities. The inconsistent results of bottom-up studies has led to debate regarding the diagnosis and treatment of APD, resulting in extensive batteries of tests being conducted on children. However, recent evidence suggests that studies on the causality of APD should be refocused on top-down processes such as auditory attention and memory – hence the focus of this thesis on auditory selective attention. The thesis begins by assessing a new test of auditory selective attention, the Test of Attention in Listening (TAiL), to ensure that it measures auditory rather than supramodal attention. Having established the modality-specificity of TAiL, the thesis examines the development of auditory selective attention to both spatial and non-spatial auditory stimulus features, across tasks of varying levels of perceptual demand. Finally, the thesis assesses the selective attention ability of children with listening difficulties. Specifically, listeners’ selective attention is assessed in both the auditory and visual domains, using both spatially- and non-spatially-based tasks. If auditory selective attention deficits are found in those with listening difficulties, this will provide a basis for the diagnosis and treatment of APD to be constructed

This thesis examines auditory selective attention as a possible cause of Auditory Processing Disorder (APD). APD is a diagnosis based on the clinical needs of the 5% of children who present with listening difficulties but demonstrate normal hearing. This thesis will focus on developmental APD, which affects children with no known infection, trauma or primary cause inducing their listening difficulties. It will seek to address the current lack of understanding of the root causes of APD, which leads to significant variation in clinical referral routes, resulting in inconsistent methods of diagnosis and treatment. APD has historically been approached via a bottom-up route of assessing auditory processing skills, such as temporal-spatial abilities. The inconsistent results of bottom-up studies has led to debate regarding the diagnosis and treatment of APD, resulting in extensive batteries of tests being conducted on children. However, recent evidence suggests that studies on the causality of APD should be refocused on top-down processes such as auditory attention and memory – hence the focus of this thesis on auditory selective attention. The thesis begins by assessing a new test of auditory selective attention, the Test of Attention in Listening (TAiL), to ensure that it measures auditory rather than supramodal attention. Having established the modality-specificity of TAiL, the thesis examines the development of auditory selective attention to both spatial and non-spatial auditory stimulus features, across tasks of varying levels of perceptual demand. Finally, the thesis assesses the selective attention ability of children with listening difficulties. Specifically, listeners’ selective attention is assessed in both the auditory and visual domains, using both spatially- and non-spatially-based tasks. If auditory selective attention deficits are found in those with listening difficulties, this will provide a basis for the diagnosis and treatment of APD to be constructed