Auditory temporal processing in children with specific reading disability with and without attention deficit/hyperactivity disorder

Internal Cognitive Load Differentially Influences Acoustic and Lexical Context Effects in Speech Perception: Evidence From a Population With Attention-Deficit/Hyperactivity Disorder

BACKGROUND

To overcome variability in spoken language, listeners utilize various types of context information for disambiguating speech sounds. Context effects have been shown to be affected by cognitive load. However, previous results are mixed regarding the influence of cognitive load on the use of context information in speech perception.

PURPOSE

We tested a population characterized by an attention-deficit/hyperactivity disorder (ADHD) to better understand the relationship between attention (or internal cognitive load) and context effects.

METHOD

The use of acoustic versus lexical properties of the surrounding signal to disambiguate speech sounds was examined in listeners with ADHD and neurotypical listeners.

RESULTS

Compared to neurotypicals, individuals with ADHD relied more strongly on lexical context for speech perception; however, reliance on acoustic context information from speech rate did not differ.

CONCLUSION

These findings confirm that cognitive load impacts the use of high-level but not low-level context information in speech and imply that speech recognition deficits in ADHD likely arise due to impaired higher order cognitive processes.

Impaired frequency selectivity and sensitivity to temporal fine structure, but not envelope cues, in children with mild-to-moderate sensorineural hearing loss

Psychophysical thresholds were measured for 8-16 year-old children with mild-to-moderate sensorineural hearing loss (MMHL; N = 46) on a battery of auditory processing tasks that included measures designed to be dependent upon frequency selectivity and sensitivity to temporal fine structure (TFS) or envelope cues. Children with MMHL who wore hearing aids were tested in both unaided and aided conditions, and all were compared to a group of normally hearing (NH) age-matched controls. Children with MMHL performed more poorly than NH controls on tasks considered to be dependent upon frequency selectivity, sensitivity to TFS, and speech discrimination (/bɑ/-/dɑ/), but not on tasks measuring sensitivity to envelope cues. Auditory processing deficits remained regardless of age, were observed in both unaided and aided conditions, and could not be attributed to differences in nonverbal IQ or attention between groups. However, better auditory processing in children with MMHL was predicted by better audiometric thresholds and, for aided tasks only, higher levels of maternal education. These results suggest that, as for adults with MMHL, children with MMHL may show deficits in frequency selectivity and sensitivity to TFS, but sensitivity to the envelope may remain intact.

Phonemes, words, and phrases: Tracking phonological processing in pre-schoolers developing dyslexia

OBJECTIVES

Individuals with dyslexia often suffer from deficient segmental phonology, but the status of suprasegmental phonology (prosody) is still discussed.

METHODS

In three passive-listening event-related brain potential (ERP) studies, we examined prosodic processing in literacy-impaired children for various prosodic units by contrasting the processing of word-level and phrase-level prosody, alongside segmental phonology. We retrospectively analysed school children's ERPs at preschool age for discrimination of vowel length (phoneme processing), discrimination of stress pattern (word-level prosody), and processing of prosodic boundaries (phrase-level prosody).

RESULTS

We found differences between pre-schoolers with and without later literacy difficulties for phoneme and stress pattern discrimination, but not for prosodic boundary perception.

CONCLUSION

Our findings complement the picture of phonological processing in dyslexia by confirming difficulties in segmental phonology and showing that prosodic processing is affected for the smaller word level, but not the larger phrase level.

SIGNIFICANCE

These findings might have implications for early interventions, considering both phonemic awareness and stress pattern training.

Language Skills, but Not Frequency Discrimination, Predict Reading Skills in Children at Risk of Dyslexia

This study evaluated the claim that auditory processing deficits are a cause of reading and language difficulties. We report a longitudinal study of 245 children at family risk of dyslexia, children with preschool language impairments, and control children. Children with language impairments had poorer frequency-discrimination thresholds than controls at 5.5 years, but children at family risk of dyslexia did not. A model assessing longitudinal relationships among frequency discrimination, reading, language, and executive function skills showed that frequency discrimination was predicted by executive skills but was not a longitudinal predictor of reading or language skills. Our findings contradict the hypothesis that frequency discrimination is causally related to dyslexia or language impairment and suggest that individuals at risk for dyslexia or who have language impairments may perform poorly on auditory processing tasks because of comorbid attentional difficulties.

Knockout Mice for Dyslexia Susceptibility Gene Homologs KIAA0319 and KIAA0319L have Unaffected Neuronal Migration but Display Abnormal Auditory Processing

Developmental dyslexia is a neurodevelopmental disorder that affects reading ability caused by genetic and non-genetic factors. Amongst the susceptibility genes identified to date, KIAA0319 is a prime candidate. RNA-interference experiments in rats suggested its involvement in cortical migration but we could not confirm these findings in Kiaa0319-mutant mice. Given its homologous gene Kiaa0319L (AU040320) has also been proposed to play a role in neuronal migration, we interrogated whether absence of AU040320 alone or together with KIAA0319 affects migration in the developing brain. Analyses of AU040320 and double Kiaa0319;AU040320 knockouts (dKO) revealed no evidence for impaired cortical lamination, neuronal migration, neurogenesis or other anatomical abnormalities. However, dKO mice displayed an auditory deficit in a behavioral gap-in-noise detection task. In addition, recordings of click-evoked auditory brainstem responses revealed suprathreshold deficits in wave III amplitude in AU040320-KO mice, and more general deficits in dKOs. These findings suggest that absence of AU040320 disrupts firing and/or synchrony of activity in the auditory brainstem, while loss of both proteins might affect both peripheral and central auditory function. Overall, these results stand against the proposed role of KIAA0319 and AU040320 in neuronal migration and outline their relationship with deficits in the auditory system.

The Effect of Attention-Deficit/Hyperactivity Disorder and Methylphenidate Treatment on the Adult Auditory Temporal Order Judgment Threshold

PURPOSE

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition notes that attention-deficit/hyperactivity disorder (ADHD) diagnosed in childhood will persist into adulthood among at least some individuals. There is a paucity of evidence, however, regarding whether other difficulties that often accompany childhood ADHD will also continue into adulthood, specifically auditory processing deficits. The aim of this study was to examine the effect of ADHD and the stimulant medication methylphenidate on auditory perception performance among adults.

METHOD

A total of 33 adults diagnosed with ADHD according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria (ADHD group) and 48 adults without ADHD (non-ADHD group) performed an auditory temporal order judgment task. Participants with ADHD performed the task twice: with and without taking methylphenidate (Ritalin), in random order.

RESULTS

Temporal order judgment thresholds of the ADHD group were significantly higher than those of the non-ADHD group. Methylphenidate significantly decreased temporal order judgment thresholds within the ADHD group, making their performance similar to the non-ADHD participants.

CONCLUSIONS

Auditory processing difficulties of those diagnosed with ADHD seem to persist into adulthood. Similar to findings with children, methylphenidate treatment improves performance on tasks requiring this ability among adults. Therefore, given the association between auditory temporal processing and linguistic skills, the beneficial effect of methylphenidate on adults' academic achievement may be accomplished by positively affecting auditory temporal processing. Further studies in this line of research are needed.

Auditory behavior and auditory temporal resolution in children with sleep-disordered breathing

OBJECTIVE

Intermittent hypoxia caused by obstructive sleep apnea syndrome (OSAS) may lead to damage in brain areas associated to auditory processing. The aim of this study was to compare children with OSAS or primary snoring (PS) to children without sleep-disordered breathing with regard to their performance on the Gaps-in-Noise (GIN) test and the Scale of Auditory Behaviors (SAB) questionnaire.

METHODS

Thirty-seven children (6-12 years old) were submitted to sleep anamnesis and in-lab night-long polysomnography. Three groups were organized according to clinical criteria: OSAS group (13 children), PS group (13 children), and control group (11 children). They were submitted to the GIN test and parents answered SAB questionnaire. The Kruskal-Wallis statistical test was used to compare the groups; p < 0.05 was considered statistically significant.

RESULTS

The OSAS group performed significantly worse than PS (p = 0.011) and Control (p = 0.029) groups on gap detection percentage, while PS and Control groups showed no significant differences. The three groups showed similar gap detection thresholds. Regarding SAB questionnaire, PS group had significantly worse scores when compared to Control (p = 0.011), but not to OSAS (p = 0.101) groups. No statistical difference between OSAS and Control groups were found.

CONCLUSION

Children with OSAS showed worse performance on GIN test in comparison to children with PS and children without sleep-disordered breathing. PS negatively affected auditory behavior in children. These findings suggest that sleep-disordered breathing may lead to auditory behavior impairment.

Perception in attention deficit hyperactivity disorder

A large body of research demonstrated that individuals with attention deficit hyperactivity disorder (ADHD) suffer from various neuropsychological deficits. In contrast, less is known and only divergent evidence exists on perceptual functions of individuals with ADHD. This is problematic as neuropsychological and perceptual functions are closely interrelated and are often difficult to disentangle in behavioral assessments. This study presents the conduct and results of a systematic literature review on perceptual functions in children and adults with ADHD. This review considers studies using psychophysical methods (objective measurements) and self- and informant reports (subjective measurements). Results indicate that individuals with ADHD have altered perceptual functions in various domains as compared to typically developing individuals. Increased perceptual functions in individuals with ADHD were found with regard to olfactory detection thresholds, whereas reduced perceptual functions were evident for aspects of visual and speech perception. Moreover, individuals with ADHD were found to experience discomfort to sensory stimuli at a lower level than typically developing individuals. Alterations of perceptual functions in individuals with ADHD were shown to be moderated by various factors, such as pharmacological treatment, cognitive functions, and symptom severity. We conclude by giving implications for daily life functioning and clinical practice.

Pb exposure prolongs the time period for postnatal transient uptake of 5-HT by murine LSO neurons

Pb exposure is associated with cognitive deficits including Attention Deficit Hyperactivity Disorder (ADHD) in children and alters auditory temporal processing in humans and animals. Serotonin has been implicated in auditory temporal processing and previous studies from our laboratory have demonstrated that developmental Pb decreases expression of serotonin (5-HT) in the adult murine lateral superior olive (LSO). During development, certain non-serotonergic sensory neurons, including auditory LSO neurons, transiently take up 5-HT through the serotonin reuptake transporter (SERT). The uptake of 5-HT is important for development of sensory systems. This study examines the effect of Pb on the serotonergic system in the LSO of the early postnatal mouse. Mice were exposed to moderate Pb (0.01mM) or high Pb (0.1mM) throughout gestation and postnatal day 4 (P4) and P8. We found that Pb exposure prolongs the normal developmental expression of 5-HT by LSO neurons and this is correlated with expression of SERT on LSO cell bodies. The prolonged expression of 5-HT by postnatal LSO neurons is correlated with decreased synaptic immunolabeling within the LSO. This Pb-associated decrease in synaptic density within the LSO could contribute to the auditory temporal processing deficits and cognitive deficits associated with developmental Pb exposure.

Present and past: Can writing abilities in school children be associated with their auditory discrimination capacities in infancy?

Literacy acquisition is highly associated with auditory processing abilities, such as auditory discrimination. The event-related potential Mismatch Response (MMR) is an indicator for cortical auditory discrimination abilities and it has been found to be reduced in individuals with reading and writing impairments and also in infants at risk for these impairments. The goal of the present study was to analyze the relationship between auditory speech discrimination in infancy and writing abilities at school age within subjects, and to determine when auditory speech discrimination differences, relevant for later writing abilities, start to develop. We analyzed the MMR registered in response to natural syllables in German children with and without writing problems at two points during development, that is, at school age and at infancy, namely at age 1 month and 5 months. We observed MMR related auditory discrimination differences between infants with and without later writing problems, starting to develop at age 5 months-an age when infants begin to establish language-specific phoneme representations. At school age, these children with and without writing problems also showed auditory discrimination differences, reflected in the MMR, confirming a relationship between writing and auditory speech processing skills. Thus, writing problems at school age are, at least, partly grounded in auditory discrimination problems developing already during the first months of life.

Improving reading skills in students with dyslexia: the efficacy of a sublexical training with rhythmic background

The core deficit underlying developmental dyslexia (DD) has been identified in difficulties in dynamic and rapidly changing auditory information processing, which contribute to the development of impaired phonological representations for words. It has been argued that enhancing basic musical rhythm perception skills in children with DD may have a positive effect on reading abilities because music and language share common mechanisms and thus transfer effects from the former to the latter are expected to occur. A computer-assisted training, called Rhythmic Reading Training (RRT), was designed in which reading exercises are combined with rhythm background. Fourteen junior high school students with DD took part to 9 biweekly individual sessions of 30 min in which RRT was implemented. Reading improvements after the intervention period were compared with ones of a matched control group of 14 students with DD who received no intervention. Results indicated that RRT had a positive effect on both reading speed and accuracy and significant effects were found on short pseudo-words reading speed, long pseudo-words reading speed, high frequency long words reading accuracy, and text reading accuracy. No difference in rhythm perception between the intervention and control group were found. Findings suggest that rhythm facilitates the development of reading skill because of the temporal structure it imposes to word decoding.

Music and Sound in Time Processing of Children with ADHD

ADHD involves cognitive and behavioral aspects with impairments in many environments of children and their families' lives. Music, with its playful, spontaneous, affective, motivational, temporal, and rhythmic dimensions can be of great help for studying the aspects of time processing in ADHD. In this article, we studied time processing with simple sounds and music in children with ADHD with the hypothesis that children with ADHD have a different performance when compared with children with normal development in tasks of time estimation and production. The main objective was to develop sound and musical tasks to evaluate and correlate the performance of children with ADHD, with and without methylphenidate, compared to a control group with typical development. The study involved 36 participants of age 6-14 years, recruited at NANI-UNIFESP/SP, subdivided into three groups with 12 children in each. Data was collected through a musical keyboard using Logic Audio Software 9.0 on the computer that recorded the participant's performance in the tasks. Tasks were divided into sections: spontaneous time production, time estimation with simple sounds, and time estimation with music.

RESULTS

(1) performance of ADHD groups in temporal estimation of simple sounds in short time intervals (30 ms) were statistically lower than that of control group (p < 0.05); (2) in the task comparing musical excerpts of the same duration (7 s), ADHD groups considered the tracks longer when the musical notes had longer durations, while in the control group, the duration was related to the density of musical notes in the track. The positive average performance observed in the three groups in most tasks perhaps indicates the possibility that music can, in some way, positively modulate the symptoms of inattention in ADHD.

Evidence for a general auditory processing deficit in developmental dyslexia from a discrimination paradigm using speech versus nonspeech sounds matched in complexity

PURPOSE

It is unknown whether phonological deficits are the primary cause of developmental dyslexia or whether they represent a secondary symptom resulting from impairments in processing basic acoustic parameters of speech. This might be due, in part, to methodological difficulties. Our aim was to overcome two of these difficulties: the comparability of stimulus material and task in speech versus nonspeech conditions.

METHOD

In this study, the authors (a) assessed auditory processing of German vowel center stimuli, spectrally rotated versions of these stimuli, and bands of formants; (b) used the same task for linguistic and nonlinguistic conditions; and (c) varied systematically temporal and spectral parameters inherent in the German vowel system. Forty-two adolescents and adults with and without reading disabilities participated.

RESULTS

Group differences were found for all linguistic and nonlinguistic conditions for both temporal and spectral parameters. Auditory deficits were identified in most but not all participants with dyslexia. These deficits were not restricted to speech stimuli-they were also found for nonspeech stimuli with equal and lower complexity compared with the vowel stimuli. Temporal deficits were not observed in isolation.

CONCLUSION

These results support the existence of a general auditory processing impairment in developmental dyslexia.

Phonological, temporal and spectral processing in vowel length discrimination is impaired in German primary school children with developmental dyslexia

It is still unclear whether phonological processing deficits are the underlying cause of developmental dyslexia, or rather a consequence of basic auditory processing impairments. To avoid methodological confounds, in the current study the same task and stimuli of comparable complexity were used to investigate both phonological and basic auditory (temporal and spectral) processing in dyslexia. German dyslexic children (Grades 3 and 4) were compared to age- and grade-matched controls in a vowel length discrimination task with three experimental conditions: In a phonological condition, natural vowels were used, differing both with respect to temporal and spectral information (in German, vowel length is phonemic, and vowel length differences are characterized by both temporal and spectral information). In a temporal condition, spectral information differentiating between the two vowels of a pair was eliminated, whereas in a spectral condition, temporal differences were removed. As performance measure, the sensitivity index d' was computed. At the group level, dyslexic children's performance was inferior to that of controls for phonological as well as temporal and spectral vowel length discrimination. At an individual level, nearly half of the dyslexic sample was characterized by deficits in all three conditions, but there were also some children showing no deficits at all. These results reveal on the one hand that phonological processing deficits in dyslexia may stem from impairments in processing temporal and spectral information in the speech signal. On the other hand they indicate, however, that not all dyslexic children might be characterized by phonological or auditory processing deficits.

The relationship between phonological and auditory processing and brain organization in beginning readers

We employed brain-behavior analyses to explore the relationship between performance on tasks measuring phonological awareness, pseudoword decoding, and rapid auditory processing (all predictors of reading (dis)ability) and brain organization for print and speech in beginning readers. For print-related activation, we observed a shared set of skill-correlated regions, including left hemisphere temporoparietal and occipitotemporal sites, as well as inferior frontal, visual, visual attention, and subcortical components. For speech-related activation, shared variance among reading skill measures was most prominently correlated with activation in left hemisphere inferior frontal gyrus and precuneus. Implications for brain-based models of literacy acquisition are discussed.

Altered neuronal response during rapid auditory processing and its relation to phonological processing in prereading children at familial risk for dyslexia

Developmental dyslexia (DD) is a learning disability affecting 5-17% of children. Although researchers agree that DD is characterized by deficient phonological processing (PP), its cause is debated. It has been suggested that altered rapid auditory processing (RAP) may lead to deficient PP in DD and studies have shown deficient RAP in individuals with DD. Functional neuroimaging (fMRI) studies have implicated hypoactivations in left prefrontal brain regions during RAP in individuals with DD. When and how these neuronal alterations evolve remains unknown. In this article, we investigate functional networks during RAP in 28 children with (n = 14) and without (n = 14) a familial risk for DD before reading onset (mean: 5.6 years). Results reveal functional alterations in left-hemispheric prefrontal regions during RAP in prereading children at risk for DD, similar to findings in individuals with DD. Furthermore, activation during RAP in left prefrontal regions positively correlates with prereading measures of PP and with neuronal activation during PP in posterior dorsal and ventral brain areas. Our results suggest that neuronal differences during RAP predate reading instruction and thus are not due to experience-dependent brain changes resulting from DD itself and that there is a functional relationship between neuronal networks for RAP and PP within the prereading brain.

Neural correlates of temporal auditory processing in developmental dyslexia during German vowel length discrimination: an fMRI study

This fMRI study investigated phonological vs. auditory temporal processing in developmental dyslexia by means of a German vowel length discrimination paradigm (Groth, Lachmann, Riecker, Muthmann, & Steinbrink, 2011). Behavioral and fMRI data were collected from dyslexics and controls while performing same-different judgments of vowel duration in two experimental conditions. In the temporal, but not in the phonological condition, hemodynamic brain activation was observed bilaterally within the anterior insular cortices in both groups and within the left inferior frontal gyrus (IFG) in controls, indicating that the left IFG and the anterior insular cortices are part of a neural network involved in temporal auditory processing. Group subtraction analyses did not demonstrate significant effects. However, in a subgroup analysis, participants performing low in the temporal condition (all dyslexic) showed decreased activation of the insular cortices and the left IFG, suggesting that this processing network might form the neural basis of temporal auditory processing deficits in dyslexia.

The relationship between brainstem temporal processing and performance on tests of central auditory function in children with reading disorders

PURPOSE

Studies using speech stimuli to elicit electrophysiologic responses have found approximately 30% of children with language-based learning problems demonstrate abnormal brainstem timing. Research is needed regarding how these responses relate to performance on behavioral tests of central auditory function. The purpose of the study was to investigate performance of children with dyslexia with and without abnormal brainstem timing and children with no history of learning or related disorders on behavioral tests of central auditory function.

METHOD

Performance of 30 school-age children on behavioral central auditory tests in common clinical use was examined: Group 1 (n = 10): dyslexia, abnormal brainstem timing; Group 2 (n = 10): dyslexia, normal brainstem timing; Group 3 (n = 10): typical controls.

RESULTS

Results indicated that all participants in Group 2 met diagnostic criteria for (central) auditory processing disorder [(C)APD], whereas only 4 participants in Group 1 met criteria. The Biological Marker of Auditory Processing (BioMARK) identified 6 children in Group 1 who did not meet diagnostic criteria for (C)APD but displayed abnormal brainstem timing.

CONCLUSIONS

Results underscore the importance of central auditory assessment for children with dyslexia. Furthermore, the BioMARK may be useful in identifying children with central auditory dysfunction who would not have been identified using behavioral methods of (C)APD assessment.

Medio-frontal and anterior temporal abnormalities in children with attention deficit hyperactivity disorder (ADHD) during an acoustic antisaccade task as revealed by electro-cortical source reconstruction

BACKGROUND

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent disorders in children and adolescence. Impulsivity is one of three core symptoms and likely associated with inhibition difficulties. To date the neural correlate of the antisaccade task, a test of response inhibition, has not been studied in children with (or without) ADHD.

METHODS

Antisaccade responses to visual and acoustic cues were examined in nine unmedicated boys with ADHD (mean age 122.44 ± 20.81 months) and 14 healthy control children (mean age 115.64 ± 22.87 months, three girls) while an electroencephalogram (EEG) was recorded. Brain activity before saccade onset was reconstructed using a 23-source-montage.

RESULTS

When cues were acoustic, children with ADHD had a higher source activity than control children in Medio-Frontal Cortex (MFC) between -230 and -120 ms and in the left-hemispheric Temporal Anterior Cortex (TAC) between -112 and 0 ms before saccade onset, despite both groups performing similarly behaviourally (antisaccades errors and saccade latency). When visual cues were used EEG-activity preceding antisaccades did not differ between groups.

CONCLUSION

Children with ADHD exhibit altered functioning of the TAC and MFC during an antisaccade task elicited by acoustic cues. Children with ADHD need more source activation to reach the same behavioural level as control children.

Speech perception among school-aged skilled and less skilled readers

This study investigated the relationship between speech perception, phonological processing and reading skills among school-aged children classified as 'skilled' and 'less skilled' readers based on their ability to read words, decode non-words, and comprehend short passages. Three speech perception tasks involving categorization of speech continua differing in voicing, place and manner of articulation were administered and compared to phonological processing skills in phonological awareness, speeded naming and verbal short-term memory. The results obtained suggested that (a) speech categorization among skilled readers differed from that of less skilled readers, (b) speech perception skills were associated with both reading and phonological processing skills among both skilled and less skilled readers, however, (c) a strong association between speeded naming and both word and passage reading skills found among skilled readers was absent among less skilled readers. These results suggested that phonological representations and/or activation may not be as well developed in less skilled readers.

Chronic low-level Pb exposure during development decreases the expression of the voltage-dependent anion channel in auditory neurons of the brainstem

Lead (Pb) exposure is a risk factor for neurological dysfunction. How Pb produces these behavioral deficits is unknown, but Pb exposure during development is associated with auditory temporal processing deficits in both humans and animals. Pb disrupts cellular energy metabolism and efficient energy production is crucial for auditory neurons to maintain high rates of synaptic activity. The voltage-dependent anion channel (VDAC) is involved in the regulation of mitochondrial physiology and is a critical component in controlling mitochondrial energy production. We have previously demonstrated that VDAC is an in vitro target for Pb, therefore, VDAC may represent a potential target for Pb in the auditory system. In order to determine whether Pb alters VDAC expression in central auditory neurons, CBA/CaJ mice (n=3-5/group) were exposed to 0.01mM, or 0.1mM Pb acetate during development via drinking water. At P21, immunohistochemistry reveals a significant decrease for VDAC in neurons of the Medial Nucleus of the Trapezoid Body. Western blot analysis confirms that Pb results in a significant decrease for VDAC. Decreases in VDAC expression could lead to an upregulation of other cellular energy producing systems as a compensatory mechanism, and a Pb-induced increase in brain type creatine kinase is observed in auditory regions of the brainstem. In addition, comparative proteomic analysis shows that several proteins of the glycolytic pathway, the phosphocreatine circuit, and oxidative phosphorylation are also upregulated in response to developmental Pb exposure. Thus, Pb-induced decreases in VDAC could have a significant effect on the function of auditory neurons.

Directional effects between rapid auditory processing and phonological awareness in children

BACKGROUND

Deficient rapid auditory processing (RAP) has been associated with early language impairment and dyslexia. Using an auditory masking paradigm, children with language disabilities perform selectively worse than controls at detecting a tone in a backward masking (BM) condition (tone followed by white noise) compared to a forward masking (FM) condition (tone preceded by white noise). Tallal's (1980) auditory processing hypothesis posits that abnormal RAP leads to reduced (or impaired) phonological awareness (PA), resulting in reading and language difficulties. Alternative theories suggest that impaired PA may have more of a top-down effect on auditory processing.

METHODS

The current study examines RAP in children tested at two time points, average age 5.6 and average age 8.3, in order to test causal relations between RAP and PA in a path analysis. Additional hierarchical regressions examine how well RAP predicts reading ability when accounting for PA and vocabulary.

RESULTS

The path analysis indicates a top-down effect, such that PA has a larger impact on BM over time than the reverse. Regressions indicate no direct impact of RAP on reading ability.

DISCUSSION

The path analysis provides evidence against the auditory processing hypothesis and instead suggests that between the ages of 5 and 8 it is variability in early phonological representations that predicts subsequent lower-level rapid auditory processing.

[Significance of auditory perceptual disorders for pediatric and adolescent psychiatric disorders]

The clinical relevance of central auditory processing disorders (CAPD) is highly controversial. The paper explicates different concepts of CAPD and reviews empirical studies of the relationship between auditory deficits and learning or psychiatric disorders. The overview of the available literature reveals that numerous authors have described subnormal auditory abilities in groups of children with developmental language disorders, dyslexia or ADHD. However, little or no relationship between the severity of clinical impairment and auditory deficits has been found. Thus auditory deficits do not appear to be causally related to learning disorders or conduct disorders. With respect to the diagnostic process the review makes clear that the validity of the diagnosis CAPD is low. There is no agreement about diagnostic criteria, and the reliability of most auditory tests in insufficient. Moreover, while an auditory training can only improve the directly trained auditory functions, there is no transfer effect to learning ability of behavior. Altogether there is little evidence for a significant relevance of CAPD in Child and Adolescent Psychiatry.

Use of auditory learning to manage listening problems in children

This paper reviews recent studies that have used adaptive auditory training to address communication problems experienced by some children in their everyday life. It considers the auditory contribution to developmental listening and language problems and the underlying principles of auditory learning that may drive further refinement of auditory learning applications. Following strong claims that language and listening skills in children could be improved by auditory learning, researchers have debated what aspect of training contributed to the improvement and even whether the claimed improvements reflect primarily a retest effect on the skill measures. Key to understanding this research have been more circumscribed studies of the transfer of learning and the use of multiple control groups to examine auditory and non-auditory contributions to the learning. Significant auditory learning can occur during relatively brief periods of training. As children mature, their ability to train improves, but the relation between the duration of training, amount of learning and benefit remains unclear. Individual differences in initial performance and amount of subsequent learning advocate tailoring training to individual learners. The mechanisms of learning remain obscure, especially in children, but it appears that the development of cognitive skills is of at least equal importance to the refinement of sensory processing. Promotion of retention and transfer of learning are major goals for further research.

Stimulus, task, and learning effects on measures of temporal resolution: implications for predictors of language outcome

PURPOSE

Some studies find that temporal processing ability predicts language outcome whereas other studies do not. Resolution of this debate is hindered by the variety of temporal measures used, nonsensory loading of the tasks, and differential amounts of practice across studies. The goal of this study was to examine the effects of stimulus properties, experimental task, and perceptual learning on listeners' gap detection performance.

METHOD

Gap detection thresholds were obtained from adults with normal hearing and language ability. The effects of marker frequency similarity and marker duration on thresholds were examined in yes-no, two-interval forced-choice (2IFC), and dual-pair comparison tasks (which vary in nonsensory loading) over 4 days of testing.

RESULTS

Thresholds were highest for gaps defined by markers with disparate frequencies (1000 and 4000 Hz; i.e., between-channel gap detection), and with longer (300 ms) trailing markers, obtained using yes-no and 2IFC tasks. However, these effects were attenuated with training or the initial use of the dual-pair comparison task.

CONCLUSIONS

These results suggest that gap detection thresholds reflect a variety of sensory and nonsensory factors. Understanding these underlying factors is critical to any evaluation of the relation between temporal processing and language outcome.

Auditory processing disorders: an update for speech-language pathologists

PURPOSE

Unanswered questions regarding the nature of auditory processing disorders (APDs), how best to identify at-risk students, how best to diagnose and differentiate APDs from other disorders, and concerns about the lack of valid treatments have resulted in ongoing confusion and skepticism about the diagnostic validity of this label. This poses challenges for speech-language pathologists (SLPs) who are working with school-age children and whose scope of practice includes APD screening and intervention. The purpose of this article is to address some of the questions commonly asked by SLPs regarding APDs in school-age children. This article is also intended to serve as a resource for SLPs to be used in deciding what role they will or will not play with respect to APDs in school-age children.

METHOD

The methodology used in this article included a computerized database review of the latest published information on APD, with an emphasis on the work of established researchers and expert panels, including articles from the American Speech-Language-Hearing Association and the American Academy of Audiology.

CONCLUSIONS

The article concludes with the authors' recommendations for continued research and their views on the appropriate role of the SLP in performing careful screening, making referrals, and supporting intervention.

Resolução temporal: análise em pré-escolares nascidos a termo e pré-termo

TEMA: processamento auditivo. OBJETIVO: verificar o comportamento auditivo de resolução temporal de crianças na faixa etária de cinco a seis anos, nascidas pré-termo, sem evidências de alterações neurológicas e compará-lo com o mesmo comportamento auditivo de crianças na mesma faixa etária, nascidas a termo, com baixo risco para alteração do desenvolvimento, considerando as variáveis: limiar de detecção de intervalo de tempo por freqüência sonora pré-estabelecida apresentada na forma binaural e monoaural por ordem de orelha que iniciou o teste e gênero. MÉTODO: 70 sujeitos: 44 nascidos a termo reunidos em grupos de 20 indivíduos do sexo feminino e 24 do sexo masculino, denominado Grupo 1, e 26 nascidos pré-termo, sendo 12 indivíduos do sexo feminino e 14 do sexo masculino, denominado Grupo 2, foram submetidos a avaliação audiológica composta por audiometria tonal limiar, limiar de reconhecimento de fala, imitânciometria e aplicação do teste de fusão auditiva denominado de Random Gap Detection. RESULTADOS: os nascidos a termo apresentaram menores limiares de detecção de intervalo de tempo no teste de fusão auditiva, nas formas de apresentação binaural e monoaural em todas as freqüências sonoras pré-estabelecidas, do que os nascidos pré-termo com diferença estatisticamente significante. As médias dos limiares de detecção de intervalo de tempo do Grupo 1 aumentaram conforme a freqüência sonora aumentou. No Grupo 2 não foram encontradas diferenças estatisticamente significantes quanto as médias de limiares de detecção de intervalo de tempo na forma de apresentação binaural e monoaural. CONCLUSÃO: os nascidos pré-termo se diferenciam dos nascidos a termo quanto ao comportamento auditivo de resolução temporal e o teste de fusão auditiva utilizado pode servir como ferramenta para a avaliação do processamento auditivo, uma vez que a detecção precoce de alteração dos processos temporais indica uma intervenção para minimizar ou evitar futuros prejuízos de linguagem.

Behavioural and neurophysiological correlates of dyslexia in the continuous performance task

OBJECTIVE

To investigate whether attentional difficulties are a "core" feature of developmental Dyslexia.

METHODS

Behavioural indices and event related potentials (ERPs) were recorded from 10 dyslexic participants (ages 15.5-17.4) and 10 control participants (ages 14.4-18.3) in the Continuous Performance Task (CPT), an established test of attentional performance. Participants were screened to ensure that none was diagnosable as attention deficit (ADHD).

RESULTS

There were no significant differences in mean reaction time, error rate or sustained attention between the groups. By contrast, the P3 amplitude was significantly smaller and its latency significantly longer for the dyslexic group. This component was significantly lateralised in controls, whereas in dyslexics it was symmetrical.

CONCLUSIONS

Under the relatively light workload conditions of the CPT, "pure" dyslexic participants showed no behavioural signs of attentional difficulties. The attenuated, delayed and symmetrical ERPs in our dyslexic group may reflect abnormal information processing in the right parietal lobe and abnormal interhemispheric asymmetry in Dyslexia.

SIGNIFICANCE

The behavioural data suggest that abnormal attentional performance is not a "core" feature of developmental Dyslexia, and highlight the importance of distinguishing between dyslexic participants with and without ADHD symptoms. The presence of electrophysiological markers of Dyslexia in CPT revealed the atypical brain organisation that characterises "pure" Dyslexia.

Effect of attentional state on frequency discrimination: a comparison of children with ADHD on and off medication

Debate continues over the hypothesis that children with language or literacy difficulties have a genuine auditory processing deficit. Several recent studies have reported deficits in frequency discrimination (FD), but it is unclear whether these are genuine perceptual impairments or reflective of the comorbid attentional problems that exist in many children with language and literacy difficulties. The present study investigated FD in children with attention deficit hyperactivity disorder (ADHD) when their attentional state was altered with stimulant medication. Auditory thresholds were obtained using FD and frequency modulation detection (FM) tasks. In the FD task, participants judged which of 2 pairs contained a high-low frequency sound, and in the FM task, children judged which of two tones "wobbled" (i.e., modulated). Children with ADHD had significantly poorer and more variable FD performance when off compared to on stimulant medication, and did significantly worse than controls on all FD runs when off but not on stimulant medication. However, children with ADHD did not differ from controls on the FM task. These findings demonstrate that certain auditory discrimination tasks are influenced by the child's attentional status. In addition, significant relationships between FD and measures of language and reading were abolished when comorbid attentional difficulties were taken into account. The study has implications for design and interpretation of studies investigating links between auditory discrimination and difficulties in language and literacy.

Temporal information processing in ADHD: Findings to date and new methods

The ability to perceive and represent time is a fundamental but complex cognitive skill that allows us to perceive and organize sequences of events and actions, and to anticipate or predict when future events will occur. It is a multidimensional construct, and a variety of methods have been used to understand timing performance in ADHD samples, which makes it difficult to integrate findings across studies. While further replication is needed, growing evidence links ADHD to problems in several aspects of temporal information processing, including duration discrimination, duration reproduction, and finger tapping. Neuroimaging studies of ADHD have also implicated cerebellar, basal ganglia, and prefrontal regions of the brain, which are believed to subserve temporal information processing. This line of research implicates more basic cognitive mechanisms than previously linked with ADHD and challenges researchers to develop and utilize innovative, multidisciplinary, scientific methods to dissect the various components of temporal information processing. Recent advances in neuroimaging, such as magnetoencephalography in collaboration with structural magnetic resonance imaging, can discriminate temporal processing at the level of a millisecond. This approach can lay the groundwork to provide a more precise understanding of neural network activity during different aspects and stages of temporal information processing in ADHD.

Sensory processing, reading, IQ, and attention

Detection thresholds for two visual- and two auditory-processing tasks were obtained for 73 children and young adults who varied broadly in reading ability. A reading-disabled subgroup had significantly higher thresholds than a normal-reading subgroup for the auditory tasks only. When analyzed across the whole group, the auditory tasks and one of the visual tasks, coherent motion detection, were significantly related to word reading. These effects were largely independent of ADHD ratings; however, none of these measures accounted for significant variance in word reading after controlling for full-scale IQ. In contrast, phoneme awareness, rapid naming, and nonword repetition each explained substantial, significant word reading variance after controlling for IQ, suggesting more specific roles for these oral language skills in the development of word reading.

Functional MRI of visual–spatial processing in neurofibromatosis, type I

Visual-spatial impairment and neuroanatomical abnormalities are considered hallmark features of neurofibromatosis, type I (NF-I). Numerous studies have demonstrated visual-spatial deficits in children with NF-I, but few relations between these deficits and neuroanatomical abnormalities have been identified. We compared the functional neuroanatomy of cerebral regions involved in the spatial transformation of alphanumeric stimuli in individuals with NF-I and healthy control participants using functional magnetic resonance imaging (fMRI). Given the prevalence of visual pathway abnormalities and visual-spatial deficits in NF-I, we hypothesized that less neuronal hemodynamic activity would be found in occipital and parietal cortices in this group compared with controls. However, NF-I participants relied to a greater degree than controls on posterior cortex (including occipital, parietal, and middle temporal cortices) relative to lateral and inferior frontal regions during visual-spatial analysis. This pattern was significantly related to their behavioral performance on the fMRI task, which in turn was also positively correlated with reading scores. These findings support evidence of frontal cortical anomalies in NF-I and may provide a pathophysiological basis for cognitive deficits in NF-I.