Context-Dependent Encoding in the Human Auditory Brainstem Relates to Hearing Speech in Noise: Implications for Developmental Dyslexia

SummaryWe examined context-dependent encoding of speech in children with and without developmental dyslexia by measuring auditory brainstem responses to a speech syllable presented in a repetitive or variable context. Typically developing children showed enhanced brainstem representation of features related to voice pitch in the repetitive context, relative to the variable context. In contrast, children with developmental dyslexia exhibited impairment in their ability to modify representation in predictable contexts. From a functional perspective, we found that the extent of context-dependent encoding in the auditory brainstem correlated positively with behavioral indices of speech perception in noise. The ability to sharpen representation of repeating elements is crucial to speech perception in noise, since it allows superior “tagging” of voice pitch, an important cue for segregating sound streams in background noise. The disruption of this mechanism contributes to a critical deficit in noise-exclusion, a hallmark symptom in developmental dyslexia

Signaling of noncomprehension in communication breakdowns in fragile X syndrome, Down syndrome, and autism spectrum disorder

The ability to indicate a failure to understand a message is a critical pragmatic (social) language skill for managing communication breakdowns and supporting successful communicative exchanges. The current study examined the ability to signal noncomprehension across different types of confusing message conditions in children and adolescents with fragile X syndrome (FXS), Down syndrome (DS), autism spectrum disorder (ASD), and typical development (TD). Controlling for nonverbal mental age and receptive vocabulary skills, youth with comorbid FXS and ASD and those with DS were less likely than TD controls to signal noncomprehension of confusing messages. Youth with FXS without ASD and those with idiopathic ASD did not differ from controls. No sex differences were detected in any group. Findings contribute to current knowledge of pragmatic profiles in different forms of genetically-based neurodevelopmental disorders associated with intellectual disability, and the role of sex in the expression of such profiles

Neural Correlates of Reading Ability and Their Plasticity in Response to Auditory Training

Reading is a complex communication process that relies on visual perception of letters and auditory translation of sounds. Children with reading disorders are known to have difficulty with auditory perception, and these deficits may contribute to the well-documented impairments in phonological awareness, auditory memory, speech sound discrimination, and auditory attention in this population. First, five studies were undertaken to better understand the neurological correlates of auditory processing impairments in children with reading disabilities. In the present studies, auditory brainstem responses to stop-consonant syllables were collected from children with varying reading ability. Particular measures of the auditory brainstem response to speech were found to relate to reading ability and be impaired in poor readers relative to good: the timing of the response, the representation of stimulus harmonics, the ability to enhance stimulus representations with repetition, and the consistency of the response from trial to trial. These factors uniquely predicted reading ability, even when phonological awareness skill and working memory were taken into account. The auditory brainstem response to speech is known to be malleable in response to active experience with sound, although it was found to be consistent with a lack of targeted intervention. In order to assess the impact of auditory training on reading ability and auditory neurophysiology, a study was conducted of children with reading disorders utilizing assistive listening devices in their classrooms for one year. The auditory brainstem response to speech became more consistent after using the assistive listening device, a change that was not seen for other children with reading disorders primarily in the same schools who did not wear the device. Those children with the most deficient neural encoding before training showed the greatest gains after training, even resembling typically-developing children. These studies suggest that auditory brainstem responses to speech may provide a unique, neural marker of reading ability, and that auditory training can help remediate neural deficits in children with reading disorders. The contribution of these results to the field of learning disabilities can lead to enhancements in diagnostic practices and reading remediation by focusing on deficits in auditory neural function

Biological changes in auditory function following training in children with autism spectrum disorders

Abstract Background Children with pervasive developmental disorders (PDD), such as children with autism spectrum disorders (ASD), often show auditory processing deficits related to their overarching language impairment. Auditory training programs such as Fast ForWord Language may potentially alleviate these deficits through training-induced improvements in auditory processing. Methods To assess the impact of auditory training on auditory function in children with ASD, brainstem and cortical responses to speech sounds presented in quiet and noise were collected from five children with ASD who completed Fast ForWord training. Results Relative to six control children with ASD who did not complete Fast ForWord, training-related changes were found in brainstem response timing (three children) and pitch-tracking (one child), and cortical response timing (all five children) after Fast ForWord use. Conclusions These results provide an objective indication of the benefit of training on auditory function for some children with ASD.</p

Neural Correlates of Orthographic and Phonological Consistency Effects in Children

The objective of this study was to examine the neural correlates of phonological inconsistency (relationship of spelling to sound) and orthographic inconsistency (relationship of sound to spelling) in visual word processing using functional magnetic resonance imaging (fMRI). Children (9- to 15-year-old) performed a rhyming and spelling task in which two words were presented sequentially in the visual modality. Consistent with previous studies in adults, higher phonological inconsistency was associated with greater activation in several regions including left inferior frontal gyrus and medial frontal gyrus/anterior cingulate cortex. We additionally demonstrated an effect of orthographic inconsistency in these same areas, suggesting that these regions are involved in the integration of orthographic and phonological information and, with respect to the medial frontal/anterior cingulate, greater demands on executive function. Higher phonological and orthographic consistency was associated with greater activation in precuneus/posterior cingulate cortex, the putative steady state system active during resting, suggesting lower demands on cognitive resources for consistent items. Both consistency effects were larger for the rhyming compared with the spelling task suggesting greater demands of integrating spelling and sound in the former task. Finally, accuracy on the rhyming task was negatively correlated with the consistency effect in left fusiform gyrus. In particular, this region showed insensitivity to consistency in low performers, sensitivity to inconsistency (higher activity) in moderate performers, and sensitivity to inconsistency (high activation) and to consistency (deactivation). In general, these results show that the influence of spelling-sound (and sound-spelling) correspondences on processing in fusiform gyrus develops as a function of skill. Hurt Brain Mapp 29:14161429, 2008. (C) 2007 Wiley-Liss. Inc