Nonlinguistic perceptual deficits associated with reading and language disorders

Variation in the normal hearing threshold predicts childhood IQ, linguistic, and behavioral outcomes

Childhood hearing level varies considerably within the range considered normal. Four classes of outcome were investigated for associations with hearing thresholds in this range: ability to identify speech in noise, neurocognitive ability, linguistic ability, and behavior. The research was conducted in a general population cohort of 711 children with mean hearing threshold of 15 dB HL or better. Some outcomes: speech in noise, intelligence, and certain linguistic abilities, were predicted in both boys and girls; effects were stronger in girls. In girls only, poorer hearing predicted worse behavior. These effects remained after statistical control for childhood socioeconomic status and otitis media. Variability in normal hearing, due to causes other than otitis media, is associated with the listening, language, and neurocognitive abilities of children, and the behavior of girls. We suggest that these effects may be present for three reasons, cochlear insults, neurodevelopmental factors, and psychological factors. We discuss how these may interact to produce the effects observed.

Membrane fatty acids, reading and spelling in dyslexic and non-dyslexic adults

Increasing evidence implicates functional deficiencies or imbalances of omega-3 and omega-6 fatty acids in dyslexia. The associations between literacy skills and omega-3 and omega-6 fatty acid status were examined. 32 dyslexics and 20 controls completed standardised tests of reading and spelling and gave venous blood samples for analysis of the polar lipid fatty acid composition of red blood cell (RBC) membranes. Relationships between literacy skills and omega-3 and omega-6 concentrations were examined using rank-order correlations. Better word reading was associated with higher total omega-3 concentrations in both dyslexic and control groups. In dyslexic subjects only, reading performance was negatively associated with the ratio of arachidonic acid/eicosapentaenoic acid (ARA/EPA) and with total omega-6 concentrations. There were no significant differences in membrane fatty acid levels between the dyslexic and control subjects. However, the finding that omega-3 status was directly related to reading performance irrespective of dyslexia supports a dimensional view of this condition, and our results also suggest that it is the omega-3/omega-6 balance that is particularly relevant to dyslexia.

Speech- and sound-segmentation in dyslexia: evidence for a multiple-level cortical impairment

Developmental dyslexia involves deficits in the visual and auditory domains, but is primarily characterized by an inability to translate the written linguistic code to the sound structure. Recent research has shown that auditory dysfunctions in dyslexia might originate from impairments in early pre-attentive processes, which affect behavioral discrimination. Previous studies have shown that whereas dyslexic individuals are deficient in discriminating sound distinctions involving consonants or simple pitch changes, discrimination of other sound aspects, such as tone duration, is intact. We hypothesized that such contrasts that can be discriminated by dyslexic individuals when heard in isolation are difficult to identify when occurring within words or structurally similar complex sound patterns. In the current study, we addressed how segments of pseudo-words and their non-speech counterparts are processed in dyslexia. We assessed the detection of long-duration differences in segments of these stimuli and identified the brain processes that could be associated with the behavioral results. Consistent with previous studies, we found no early cortical sound-duration discrimination deficit in dyslexia. However, differences between impaired and non-impaired readers were found in the brain processes associated with sound-change recognition as well as in the behavioral performance. This suggests that even when the early, automatic, sound discrimination processes are intact in dyslexic individuals, deficits in the later, attention-dependent processes may lead to impaired perception of speech and other complex sounds.

Development of structure and function in the infant brain: implications for cognition, language and social behaviour

Recent advances in cognitive neuroscience have allowed us to begin investigating the development of both structure and function in the infant brain. However, despite the rapid evolution of technology, surprisingly few studies have examined the intersection between brain and behaviour over the first years of life. Even fewer have done so in the context of a particular research question. This paper aims to provide an overview of four domains that have been studied using techniques amenable to elucidating the brain/behaviour interface: language, face processing, object permanence, and joint attention, with particular emphasis on studies focusing on early development. The importance of the unique role of development and the interplay between structure and function is stressed throughout. It is hoped that this review will serve as a catalyst for further thinking about the substantial gaps in our understanding of the relationship between brain and behaviour across development. Further, our aim is to provide ideas about candidate brain areas that are likely to be implicated in particular behaviours or cognitive domains.

Static postural control in children with developmental dyslexia

The present investigation tries to better understand potential association and causal relationship between phonological and postural impairment due to developmental dyslexia. The study included 50 boys with developmental dyslexia and selected on the basis of their overall reading difficulties, and 42 control boys. Body sway during a quite standing posture eye open and eye closed on a force platform were tested in the two groups of subjects that were between 10 and 13 years of age. Analysis of classical parameters quantifying the centre of pressure (CP) displacements along antero-posterior and lateral axes showed a significant difference between the two groups. Dyslexic children showed on average greater instability, with greater length, variability and mean power frequency of CP displacements with or without vision. Our results demonstrate that postural parameters may discriminate between children with dyslexia and age-equivalent controls.

Early experience of sex hormones as a predictor of reading, phonology, and auditory perception

Previous research has indicated possible reciprocal connections between phonology and reading, and also connections between aspects of auditory perception and reading. The present study investigates these associations further by examining the potential influence of prenatal androgens using measures of digit ratio (the ratio of the lengths of the index and ring fingers). Those with low digit ratios (shorter index finger and therefore in the masculine direction) are hypothesised to have experienced greater "masculinisation" in the uterus. ANCOVA analyses using a verbal reasoning task as a covariate showed that only phonology was influenced by digit ratio in the right hand indicating that hypothesised androgen effects were inhibiting phonology; however this effect in the left hand was reduced and instead there was an effect indicating an inhibition of androgens on reading. Furthermore, subjects with low right-hand digit ratios were also impaired compared to those with high right-hand digit ratios in an auditory saltation task. These findings are discussed in terms of the possible effects of androgens on early brain development impairing aspects of the temporal processing of sounds by the left hemisphere, which could also have a secondary influence on developing phonology and literacy skills.

Deficits in speech perception predict language learning impairment

Specific language impairment (SLI) is one of the most common childhood disorders, affecting 7% of children. These children experience difficulties in understanding and producing spoken language despite normal intelligence, normal hearing, and normal opportunities to learn language. The causes of SLI are still hotly debated, ranging from nonlinguistic deficits in auditory perception to high-level deficits in grammar. Here, we show that children with SLI have poorer-than-normal consonant identification when measured in ecologically valid conditions of stationary or fluctuating masking noise. The deficits persisted even in comparison with a younger group of normally developing children who were matched for language skills. This finding points to a fundamental deficit. Information transmission of all phonetic features (voicing, place, and manner) was impaired, although the deficits were strongest for voicing (e.g., difference between/b/and/p/). Children with SLI experienced perfectly normal "release from masking" (better identification in fluctuating than in stationary noise), which indicates a central deficit in feature extraction rather than deficits in low-level, temporal, and spectral auditory capacities. We further showed that speech identification in noise predicted language impairment to a great extent within the group of children with SLI and across all participants. Previous research might have underestimated this important link, possibly because speech perception has typically been investigated in optimal listening conditions using non-speech material. The present study suggests that children with SLI learn language deviantly because they inefficiently extract and manipulate speech features, in particular, voicing. This result offers new directions for the fast diagnosis and remediation of SLI.

Poor frequency discrimination is related to oral language disorder in children: a psychoacoustic study

Some children have difficulty in perceiving differences between sounds, even though they have normal hearing sensitivity, and it has been suggested that such problems could lead to difficulties in language and literacy development. Poor ability to distinguish sounds on the basis of frequency (perceived as pitch) has been described in poor readers on a variety of auditory processing tasks. The aim of the present study was three-fold: to determine whether children with specific language impairment (SLI) have difficulty discriminating frequency, whether this deficit is specific to the frequency domain, or part of a more general auditory impairment, and whether it is linked to reading or oral language ability. The performance of a SLI group (N = 15) and a control group with normally developing oral language matched for age and intelligence (N = 18) was compared on a frequency discrimination task and a control task testing intensity discrimination. The children with SLI consistently demonstrated significantly poorer performance on the frequency discrimination task, but not on the intensity discrimination task. Frequency discrimination thresholds were not related to reading ability in either group. This study provides evidence for a basic auditory deficit in children with SLI, regardless of their reading ability.

Auditory perceptual grouping and attention in dyslexia

Despite dyslexia affecting a large number of people, the mechanisms underlying the disorder remain undetermined. There are numerous theories about the origins of dyslexia. Many of these relate dyslexia to low-level, sensory temporal processing deficits. Another group of theories attributes dyslexia to language-specific impairments. Here, we show that dyslexics perform worse than controls on an auditory perceptual grouping task. The results show differences in performance between the groups that depend on sound frequency and not solely on parameters related to temporal processing. Performance on this task suggests that dyslexics' deficits may result from impaired attentional control mechanisms. Such deficits are neither modality nor language-specific and may help to reconcile differences between theories of dyslexia.

Individual differences in auditory processing in specific language impairment: a follow-up study using event-related potentials and behavioural thresholds

It has frequently been claimed that children with specific language impairment (SLI) have impaired auditory perception, but there is much controversy about the role of such deficits in causing their language problems, and it has been difficult to establish solid, replicable findings in this area. Discrepancies in this field may arise because (a) a focus on mean results obscures the heterogeneity in the population and (b) insufficient attention has been paid to maturational aspects of auditory processing. We conducted a study of 16 young people with specific language impairment (SLI) and 16 control participants, 24 of whom had had auditory event-related potentials (ERPs) and frequency discrimination thresholds assessed 18 months previously. When originally assessed, around one third of the listeners with SLI had poor behavioural frequency discrimination thresholds, and these tended to be the younger participants. However, most of the SLI group had age-inappropriate late components of the auditory ERP, regardless of their frequency discrimination. At follow-up, the behavioural thresholds of those with poor frequency discrimination improved, though some remained outside the control range. At follow-up, ERPs for many of the individuals in the SLI group were still not age-appropriate. In several cases, waveforms of individuals in the SLI group resembled those of younger typically-developing children, though in other cases the waveform was unlike that of control cases at any age. Electrophysiological methods may reveal underlying immaturity or other abnormality of auditory processing even when behavioural thresholds look normal. This study emphasises the variability seen in SLI, and the importance of studying individual cases rather than focusing on group means.

Effects of computer-based intervention through acoustically modified speech (Fast ForWord) in severe mixed receptive-expressive language impairment: outcomes from a randomized controlled trial

Seventy-seven children between the ages of 6 and 10 years, with severe mixed receptive-expressive specific language impairment (SLI), participated in a randomized controlled trial (RCT) of Fast ForWord (FFW; Scientific Learning Corporation, 1997, 2001). FFW is a computer-based intervention for treating SLI using acoustically enhanced speech stimuli. These stimuli are modified to exaggerate their time and intensity properties as part of an adaptive training process. All children who participated in the RCT maintained their regular speech and language therapy and school regime throughout the trial. Standardized measures of receptive and expressive language were used to assess performance at baseline and to measure outcome from treatment at 9 weeks and 6 months. Children were allocated to 1 of 3 groups. Group A (n = 23) received the FFW intervention as a home-based therapy for 6 weeks. Group B (n = 27) received commercially available computer-based activities designed to promote language as a control for computer games exposure. Group C (n = 27) received no additional study intervention. Each group made significant gains in language scores, but there was no additional effect for either computer intervention. Thus, the findings from this RCT do not support the efficacy of FFW as an intervention for children with severe mixed receptive-expressive SLI.

Improving language and literacy is a matter of time

Developmental deficits that affect speech perception increase the risk of language and literacy problems, which can lead to lowered academic and occupational accomplishment. Normal development and disorders of speech perception have both been linked to temporospectral auditory processing speed. Understanding the role of dynamic auditory processing in speech perception and language comprehension has led to the development of neuroplasticity-based intervention strategies aimed at ameliorating language and literacy problems and their sequelae.

Age and experience-related improvements in gap detection in the rat

The ability to accurately process brief, successive acoustic signals rapidly presented to the central nervous system is believed to underlie successful language development. The limits of temporal resolution of the auditory system, often assessed using gap detection tasks, has been widely studied in relation to developing and decoding speech. In the present study, a reflex modification paradigm was used to investigate potential shifts in gap detection thresholds in rats across development, with test sessions beginning on postnatal day (P) 15, P35 and P64. We found that thresholds decreased over the course of development. These thresholds were determined to lie between 10 and 20 ms for the P15 and P35 groups, and between 5 and 10 ms for the P64 group. Moreover, we observed improvements in gap detection thresholds in all age groups over 5 days of testing, including the youngest age group (P15). These later results suggest that experience-dependent plasticity mechanisms at the level of sensory processing are operational and observable both very early in development, and also in adult animals. The present findings also demonstrate maturational improvements in silent gap detection using a pre-pulse inhibition paradigm.

Sequential spatial frequency discrimination is consistently impaired among adult dyslexics

The degree and nature of dyslexics' difficulties in performing basic visual tasks have been debated for more than thirty years. We recently found that dyslexics' difficulties in detecting temporally modulated gratings are specific to conditions that require accurate comparisons between sequentially presented stimuli [Brain 124 (2001) 1381]. We now examine dyslexics' spatial frequency discrimination (rather than detection), under simultaneous (spatial forced choice) and sequential (temporal forced choice) presentations. Sequential presentation (at SOAs of 0.5, 0.75 and 2.25 s) yielded better discrimination thresholds among the majority of controls (around 0.5 c/ degrees reference), but not among dyslexics. Consequently, there was a (large and significant) group effect only for the sequential conditions. Within the same dyslexic group, performance on a sequential auditory task, two-tone frequency discrimination, was impaired in a smaller proportion of the participants. Taken together, our findings indicate that visual paradigms requiring sequential comparisons are difficult for the majority of dyslexic individuals, perhaps because deficits either in visual perception or in visual memory could both lead to difficulties on these paradigms.

Two visual motion processing deficits in developmental dyslexia associated with different reading skills deficits

Developmental dyslexia is associated with deficits in the processing of visual motion stimuli, and some evidence suggests that these motion processing deficits are related to various reading subskills deficits. However, little is known about the mechanisms underlying such associations. This study lays a richer groundwork for exploration of such mechanisms by more comprehensively and rigorously characterizing the relationship between motion processing deficits and reading subskills deficits. Thirty-six adult participants, 19 of whom had a history of developmental dyslexia, completed a battery of visual, cognitive, and reading tests. This battery combined motion processing and reading subskills measures used across previous studies and added carefully matched visual processing control tasks. Results suggest that there are in fact two distinct motion processing deficits in developmental dyslexia, rather than one as assumed by previous research, and that each of these deficits is associated with a different type of reading subskills deficit. A deficit in detecting coherent motion is selectively associated with low accuracy on reading subskills tests, and a deficit in discriminating velocities is selectively associated with slow performance on these same tests. In addition, evidence from visual processing control tasks as well as self-reports of ADHD symptoms suggests that these motion processing deficits are specific to the domain of visual motion, and result neither from a broader visual deficit, nor from the sort of generalized attention deficit commonly comorbid with developmental dyslexia. Finally, dissociation between these two motion processing deficits suggests that they may have distinct neural and functional underpinnings. The two distinct patterns of motion processing and reading deficits demonstrated by this study may reflect separable underlying neurocognitive mechanisms of developmental dyslexia.

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.

Learning problems, delayed development, and puberty

Language-based learning disorders such as dyslexia affect millions of people, but there is little agreement as to their cause. New evidence from behavioral measures of the ability to hear tones in the presence of background noise indicates that the brains of affected individuals develop more slowly than those of their unaffected counterparts. In addition, it seems that brain changes occurring at approximately 10 years of age, presumably associated with puberty, may prematurely halt this slower-than-normal development when improvements would normally continue into adolescence. The combination of these ideas can account for a wide range of previous results, suggesting that delayed brain development, and its interaction with puberty, may be key factors contributing to learning problems.

FMRI brain activation in a finnish family with specific language impairment compared with a normal control group

The aim of the present study was to investigate differences in brain activation in a family with SLI as compared to intact individuals with normally developed language during processing of language stimuli. Functional magnetic resonance imaging (fMRI) was used to monitor changes in neuronal activation in temporal and frontal lobe areas in 5 Finnish family members with specific language impairment (SLI) and 6 individuals in an intact control group. Magnetic resonance (MR) image acquisitions were made while the participants listened to series of isolated vowel sounds, pseudowords, and real words. The stimuli were digitized single Finnish vowel sounds, 3-phoneme pseudowords, and 3- and 4-phoneme real words. MR scanning was made with a 1.5 T Siemens Vision Plus scanner, and the auditory stimuli were presented according to an event-related fMRI design. The results showed significant differences between the family with SLI and the intact control group with regard to brain activation in areas in the temporal and frontal lobes. Temporal lobe activation differences were most pronounced in the middle temporal gyrus bordering the superior temporal sulcus. The control participants also activated an area in the inferior frontal lobe in BA 44. It is concluded that individuals with SLI showed reduced activation in brain areas that are critical for speech processing and phonological awareness. The present functional brain imaging data fit well with other recent imaging data that also showed structural abnormalities in the same and neighboring areas.

Die Bedeutung auditiver Wahrnehmungsschwächen für die Pathogenese der Lese-Rechtschreibstörung

Zusammenfassung: Fragestellung: Als mögliche Ursache einer Lese-Rechtschreibstörung werden auditive Verarbeitungs- und Wahrnehmungsstörungen (AVWS) angenommen und Trainingsverfahren zur Verbesserung auditiver Fähigkeiten finden in der Therapie zunehmende Verbreitung. In der vorliegenden Studie wird der Frage nachgegangen, ob sich ein Zusammenhang zwischen auditiver Wahrnehmungsfähigkeit und LRS empirisch belegen lässt. Methodik: Untersucht wurden 27 durchschnittlich intelligente und normal hörende LRS- und 31 Vergleichskinder. Die auditive Wahrnehmungsfähigkeit wurde mit nonverbalen (Tonhöhen-, Tondauer-, Geräuschdifferenzierung) und verbalen (Spracherkennen im Störgeräusch, zeitkomprimierte Sprache) Tests beurteilt. Außerdem wurden auditive Merkfähigkeit, nonverbaler IQ, Rechtschreib- und Sprachleistungen sowie anamnestische Angaben zum Verhalten erfasst. Ergebnisse: Die Gruppen unterschieden sich im Mittelwert in der Tondifferenzierungs- und auditiven Merkfähigkeit, nicht jedoch beim Erkennen von Geräuschen und in verbalen auditiven Tests. Bei Betrachtung der Einzelwerte zeigte sich jedoch, dass trotz signifikanter Mittelwertsunterschiede die Leistungen der LRS-Kinder überwiegend im Bereich der Streubreite der Vergleichskinder lagen. Eine Korrelation zwischen auditiver und Rechtschreibfähigkeit war nicht nachweisbar. Schlussfolgerungen: In verbalen auditiven Tests zeigen LRS-Kinder keine auffälligen Befunde. Basale auditive Defizite lassen sich lediglich bei einer kleineren Subgruppe von LRS-Kindern beobachten. Für eine kausale Beziehung zwischen LRS und AVWS fanden sich keine Hinweise und somit keine empirischen Belege für die Grundannahmen, auf denen ein Training auditiver Fähigkeiten im Rahmen einer LRS-Behandlung beruht.

How ‘generalized’ is the ‘slowed processing’ in SLI? The case of visuospatial attentional orienting

The study was designed to assess the speed and efficiency of visuospatial attentional orienting and the speed of visual processing and motor response in school-age children diagnosed with specific language impairment (SLI). Fifteen participants with SLI (7-15 years old) and their gender- and age-matched normally developing peers performed two formats of a simple visual discrimination task, one requiring the use of attentional orienting for accurate performance, and the other not requiring shifts of attention. The SLI group was characterized by (a) slower visual processing, and (b) slower motor response, but (c) similar attentional orienting speed, relative to the control group. The results are discussed in relation to the 'generalized slowing hypothesis' in SLI and the neural underpinning of visuospatial attentional orienting and SLI.

Comorbid Auditory Processing Disorder in Developmental Dyslexia

OBJECTIVE

The primary objective of this study was to investigate the extent of comorbid auditory processing disorder (APD) in a group of adults with developmental dyslexia. An additional objective was to compare performance on auditory tasks to results from standardized tests of reading in an attempt to generate a clinically useful profile of developmental dyslexics with comorbid APD.

DESIGN

A group of eleven persons with developmental dyslexia and 14 age- and intelligence-matched controls participated in the study. Behavioral audiograms, 226-Hz tympanograms, and word recognition scores were obtained binaurally from all subjects. Both groups were administered the frequency-pattern test (FPT) and duration-pattern test (DPT) monaurally (30 items per ear) in both the left and right ear. Gap detection results were obtained in both groups (binaural presentation) using narrowband noise centered at 1 kHz in an adaptive two-alternative forced-choice (2-AFC) paradigm. The FPT, DPT, and gap detection results were analyzed for interaural (where applicable), intergroup, and intragroup differences. Correlations between performance on the auditory tasks and the standardized tests of reading were examined. Additive logistic regression models were fit to the data to determine which auditory tests proved to be the best predictors of group membership.

RESULTS

The persons with developmental dyslexia as a group performed significantly poorer than controls on both the FPT and DPT. Furthermore, the group differences were significant in both monaural conditions. On the FPT and DPT, five of the eleven participants with dyslexia performed below the widely used clinical criterion for APD of 70% correct in either ear. All five of these participants performed below criterion on the FPT, whereas four of the five additionally performed below 70% on the DPT. The data also were analyzed by fitting a series of stepwise logistic regression models, which indicated that gap detection did not significantly predict group membership, whereas the FPT and DPT were significant predictors. The addition of the FPT score after the DPT did not result in a significant change in the residual deviance.

CONCLUSIONS

Approximately half of the participants with developmental dyslexia showed clinically significant diminished performance on the FPT and DPT indicative of APD. These results indicate that the percentage of persons with developmental dyslexia and comorbid APD may be substantial enough to warrant serious clinical considerations.

Balance and gait in children with dyslexia

Tests of postural stability have provided some evidence of a link between deficits in gross motor skills and developmental dyslexia. The ordinal-level scales used previously, however, have limited measurement sensitivity, and no studies have investigated motor performance during walking in participants with dyslexia. The purpose of this study was to investigate if continuous-scaled measures of standing balance and gait could discriminate between groups of impaired and normal readers when investigators were blind to group membership during testing. Children with dyslexia ( n=22) and controls ( n=18), aged 10-12 years, performed walking tests at four different speeds (slow-preferred-fast-very fast) on an even and an uneven surface, and tests of unperturbed and perturbed body sway during standing. Body movements were registered by a triaxial accelerometer over the lower trunk, and measures of reaction time, body sway, walking speed, step length and cadence were calculated. Results were controlled for gender differences. Tests of standing balance with eyes closed did not discriminate between groups. All unperturbed standing tests with eyes open showed significant group differences ( P<0.05) and classified correctly 70-77.5% of the subjects into their respective groups. Mean walking speed during very fast walking on both flat and uneven surface was > or =0.2 m/s ( P< or =0.01) faster for controls than for the group with dyslexia. This test classified 77.5% and 85% of the subjects correctly on flat and uneven surface, respectively. Cadence at preferred or very fast speed did not differ statistically between groups, but revealed significant group differences when all subjects were compared at a normalised walking speed ( P< or =0.04). Very fast walking speed as well as cadence at a normalised speed discriminated better between groups when subjects were walking on an uneven surface compared to a flat floor. Continuous-scaled walking tests performed in field settings may be suitable for motor skill assessment as a component of a screening tool for developmental dyslexia.

Developmental dyslexia: specific phonological deficit or general sensorimotor dysfunction?

Dyslexia research now faces an intriguing paradox. It is becoming increasingly clear that a significant proportion of dyslexics present sensory and/or motor deficits; however, as this 'sensorimotor syndrome' is studied in greater detail, it is also becoming increasingly clear that sensory and motor deficits will ultimately play only a limited role in a causal explanation of specific reading disability.

Impaired processing of brief, rapidly presented auditory cues in infants with a family history of autoimmune disorder

Studies have shown that individuals with language disorders, such as developmental dyslexia and specific language impairment, exhibit impairments in the processing of brief, successive, or rapidly changing auditory information. It is also the case that a higher rate of autoimmune disorders have been identified in those with language-based learning disorders and, conversely, that individuals with autoimmune disorders show a higher incidence of language-related disorders. The rapid auditory processing (RAP) deficits described for older individuals with language impairments may also be used as a behavioral marker to identify infants at higher risk for language delays. Thus, we were interested in examining RAP abilities in a subset of infants with a positive family history of autoimmune disorders. Eleven infants from our ongoing prospective longitudinal studies were identified based on parental response to a question about the presence of a family history of autoimmune disease and compared to 11 matched controls. The RAP threshold of each infant was assessed at 6 and 9 months of age using a conditioned head-turn procedure (using tone pairs with brief interstimulus intervals) and an auditory-visual habituation-recognition memory task using computer-generated consonant-vowel syllables (/ba/ vs. /da/). A visual habituation-recognition memory task that did not require processing of brief temporal cues was also administered. Group differences emerged on the infant RAP tasks, and on language outcome measures at 12 and 16 months of age. Infants from families with a history of autoimmune disorder had significantly higher (i.e., poorer) RAP thresholds and lower language scores than did control infants, whereas visual discrimination scores did not differ between family history infants and controls. Moreover, when brief auditory cues were necessary for the discrimination of /ba/ vs. /da/, infants with a family history of autoimmune disorder performed significantly more poorly than did controls. These findings lend support to the hypothesis that a similar mechanism, perhaps a neural-immune interaction, may underlie the observed co-occurrence of autoimmune disorders and learning impairments.

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

The auditory temporal deficit hypothesis predicts that children with specific reading disability (RD) will exhibit a deficit in the perception of auditory temporal cues in nonspeech stimuli. Tasks assessing perception of auditory temporal and nontemporal cues were administered to children with (a) RD without attention-deficit/hyperactivity disorder (RD/no-ADHD, n = 40), (b) ADHD alone (ADHD/no-RD, n = 33), (c) RD and ADHD (RD/ADHD, n = 36), and (d) no impairment (NI, n = 41). The presence of RD was associated with a specific deficit in detection of a tone onset time asynchrony, but no reduction in performance on other tasks assessing perception of temporal or nontemporal acoustic cues. The presence of ADHD was associated with a general reduction in performance across tasks. The pattern of results did not indicate a pervasive deficit in auditory temporal function in children with RD, but did suggest a possible sensitivity to backward masking in this group. Results also indicated that the comorbid presence of ADHD is a significant factor in the performance of children with RD on psychoacoustic tasks.

The perception of "sine-wave speech" by adults with developmental dyslexia

Numerous studies have shown that, as a group, children or adults with developmental dyslexia perceive isolated syllables or words abnormally. Continuous speech containing reduced acoustic information also might prove perceptually difficult to such listeners. They might, however, exploit the intact syntactic and semantic features present in whole utterances, thereby compensating fully for impaired speech perception. "Sine-wave speech" sentences afford a test of these competing possibilities. The sentences contain only 4 frequency-modulated sine waves, lacking many acoustic cues present in natural speech. Adults with and without dyslexia were asked to orally reproduce 9 sine-wave utterances, each occurring in 4 immediately successive trials. Participants with dyslexia reported fewer words than did control listeners. Practice, phonological contrasts, and word position affected both groups similarly. Comprehension of sine-wave sentences seems impaired in many, but not all, adults with dyslexia. A reduced auditory memory capacity may contribute to this deficit.

[Reliability, trainability and stability of auditory discrimination performance in 2 computer-assisted assessment and training methods]

OBJECTIVES

The present study focuses on the possibilities and effects of training dyslexic children in tone and phoneme discrimination tasks.

METHODS

A computer program was developed to train dyslexic children to discriminate between tone and speech stimuli. The correlation between auditory discrimination and reading and orthography performance was then tested in a preliminary study of n = 63 children. In a prospective study 44 children were assigned to one of three paralyzed groups: tone training, phoneme training or a control group. Upon completion of the initial diagnostics for all groups, the two training groups received four weeks of discrimination training, after which all three groups were immediately re-tested for the first time. Parallel thereto all children underwent specific training in reading and orthography at their school. Six months later all were re-tested a second time.

RESULTS

Both test methods showed a high reliability (rn = .94; .95). Significant correlations between auditory discrimination and reading and orthography performance were confirmed. Auditory discrimination was significantly trainable. Specific training effects, as well as independent developmental effects were found. While the training effects of phoneme discrimination were stable over six months, those of tone discrimination were not.

CONCLUSION

The central auditory discrimination between tone and phoneme stimuli can be trained successfully in dyslexic children and might also affect their reading and orthography performance.

On the relationship between dynamic visual and auditory processing and literacy skills; results from a large primary-school study

Three hundred and fifty randomly selected primary school children completed a psychometric and psychophysical test battery to ascertain relationships between reading ability and sensitivity to dynamic visual and auditory stimuli. The first analysis examined whether sensitivity to visual coherent motion and auditory frequency resolution differed between groups of children with different literacy and cognitive skills. For both tasks, a main effect of literacy group was found in the absence of a main effect for intelligence or an interaction between these factors. To assess the potential confounding effects of attention, a second analysis of the frequency discrimination data was conducted with performance on catch trials entered as a covariate. Significant effects for both the covariate and literacy skill was found, but again there was no main effect of intelligence, nor was there an interaction between intelligence and literacy skill. Regression analyses were conducted to determine the magnitude of the relationship between sensory and literacy skills in the entire sample. Both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills.

Separate influences of acoustic AM and FM sensitivity on the phonological decoding skills of impaired and normal readers

Developmental dyslexia is associated with deficits in the processing of basic auditory stimuli. Yet it is unclear how these sensory impairments might contribute to poor reading skills. This study better characterizes the relationship between phonological decoding skills, the lack of which is generally accepted to comprise the core deficit in reading disabilities, and auditory sensitivity to amplitude modulation (AM) and frequency modulation (FM). Thirty-eight adult subjects, 17 of whom had a history of developmental dyslexia, completed a battery of psychophysical measures of sensitivity to FM and AM at different modulation rates, along with a measure of pseudoword reading accuracy and standardized assessments of literacy and cognitive skills. The subjects with a history of dyslexia were significantly less sensitive than controls to 2-Hz FM and 20-Hz AM only. The absence of a significant group difference for 2-Hz AM shows that the dyslexics do not have a general deficit in detecting all slow modulations. Thresholds for detecting 2-Hz and 240-Hz FM and 20-Hz AM correlated significantly with pseudoword reading accuracy. After accounting for various cognitive skills, however, multiple regression analyses showed that detection thresholds for both 2-Hz FM and 20-Hz AM were significant and independent predictors of pseudoword reading ability in the entire sample. Thresholds for 2-Hz AM and 240-Hz FM did not explain significant additional variance in pseudoword reading skill. It is therefore possible that certain components of auditory processing of modulations are related to phonological decoding skills, whereas others are not.

Amplitude envelope onsets and developmental dyslexia: A new hypothesis

A core difficulty in developmental dyslexia is the accurate specification and neural representation of speech. We argue that a likely perceptual cause of this difficulty is a deficit in the perceptual experience of rhythmic timing. Speech rhythm is one of the earliest cues used by infants to discriminate syllables and is determined principally by the acoustic structure of amplitude modulation at relatively low rates in the signal. We show significant differences between dyslexic and normally reading children, and between young early readers and normal developers, in amplitude envelope onset detection. We further show that individual differences in sensitivity to the shape of amplitude modulation account for 25% of the variance in reading and spelling acquisition even after controlling for individual differences in age, nonverbal IQ, and vocabulary. A possible causal explanation dependent on perceptual-center detection and the onset-rime representation of syllables is discussed.

Enhanced response of the left frontal cortex to slowed down speech in dyslexia: an fMRI study

Language difficulties of dyslexic subjects may result partly from a basic deficit in processing rapidly changing sensory inputs. In this fMRI study, we compared brain activities in adult dyslexics and controls during implicit categorical perception of phonemes with normal and slowed down stimuli. Perception of phonemic contrasts activated a frontal parietal network (Broca's area and the left supramarginal gyrus) in which the frontal component was down-regulated by slowed speech in controls and enhanced in dyslexic subjects. No modulation by speech rate was observed in the left supra-marginal gyrus. Enhancement of activity in Broca's area for slowed speech in dyslexic subjects might represent a neural basis of the improvement of performance that has been observed after remediation using this type of stimuli.

A major susceptibility locus for specific language impairment is located on 13q21

Children who fail to develop language normally-in the absence of explanatory factors such as neurological disorders, hearing impairment, or lack of adequate opportunity-are clinically described as having specific language impairment (SLI). SLI has a prevalence of approximately 7% in children entering school and is associated with later difficulties in learning to read. Research indicates that genetic factors are important in the etiology of SLI. Studies have consistently demonstrated that SLI aggregates in families. Increased monozygotic versus dizygotic twin concordance rates indicate that heredity, not just shared environment, is the cause of the familial clustering. We have collected five pedigrees of Celtic ancestry that segregate SLI, and we have conducted genomewide categorical linkage analysis, using model-based LOD score techniques. Analysis was conducted under both dominant and recessive models by use of three phenotypic classifications: clinical diagnosis, language impairment (spoken language quotient <85) and reading discrepancy (nonverbal IQ minus non-word reading >15). Chromosome 13 yielded a maximum multipoint LOD score of 3.92 under the recessive reading discrepancy model. Simulation to correct for multiple models and multiple phenotypes indicated that the genomewide empirical P value is <.01. As an alternative measure, we also computed the posterior probability of linkage (PPL), obtaining a PPL of 53% in the same region. One other genomic region yielded suggestive results on chromosome 2 (multipoint LOD score 2.86, genomic P value <.06 under the recessive language impairment model). Our findings underscore the utility of traditional LOD-score-based methods in finding genes for complex diseases, specifically, SLI.

The importance of rapid auditory processing abilities to early language development: evidence from converging methodologies

The ability to process two or more rapidly presented, successive, auditory stimuli is believed to underlie successful language acquisition. Likewise, deficits in rapid auditory processing of both verbal and nonverbal stimuli are characteristic of individuals with developmental language disorders such as Specific Language Impairment. Auditory processing abilities are well developed in infancy, and thus such deficits should be detectable in infants. In the studies presented here, converging methodologies are used to examine such abilities in infants with and without a family history of language disorder. Behavioral measures, including assessments of infant information processing, and an EEG/event-related potential (ERP) paradigm are used concurrently. Results suggest that rapid auditory processing skills differ as a function of family history and are predictive of later language outcome. Further, these paradigms may prove to be sensitive tools for identifying children with poor processing skills in infancy and thus at a higher risk for developing a language disorder.

Brain mechanisms in normal and dyslexic readers

Developmental dyslexics, individuals with an unexplained difficulty reading, have been shown to have deficits in phonological processing -- the awareness of the sound structure of words -- and, in some cases, a more fundamental deficit in rapid auditory processing. In addition, dyslexics show a disruption in white matter connectivity between posterior and frontal regions. These results give continued support for a neurobiological etiology of developmental dyslexia. However, more research will be required to determine the possible causal relationships between these neurobiological disruptions and dyslexia.

Auditory processing and the development of language and literacy

This paper considers evidence for basic auditory processing impairments associated with dyslexia and specific language impairment, against a back-drop of findings from studies of the normal development of auditory and phonological processing. A broad range of auditory impairments have been implicated in the aetiology of these language-learning disorders, including deficits in discriminating the temporal order of rapid sequences of auditory signals, elevated thresholds for frequency discrimination and for detection of amplitude and frequency modulation, impaired binaural processing and increased susceptibility to backward masking. Current evidence is inconsistent, but suggests that not all children with language difficulties have non-verbal auditory processing impairments, and for those that do, the impact on language development is poorly understood. Some implications for clinical practice are discussed.

Impaired processing of rapid stimulus sequences in dyslexia

Apart from their reading difficulties, dyslexic subjects often suffer from a variety of subtle sensory and motor deficits. Whether these deficits have a causal relationship to the reading disorder, form additional risk factors, or are totally independent of the reading problem, is under vivid debate. In this article, we review the evidence and suggest that 'sluggish attentional shifting' (SAS) can account for the impaired processing of rapid stimulus sequences in dyslexia. Within this novel framework attention-related prolongation of input chunks is decisive for many small deficits found in dyslexic subjects.

Relations between the neural bases of dynamic auditory processing and phonological processing: evidence from fMRI

Functional magnetic resonance imaging (fMRI) was used to examine how the brain responds to temporal compression of speech and to determine whether the same regions are also involved in phonological processes associated with reading. Recorded speech was temporally compressed to varying degrees and presented in a sentence verification task. Regions involved in phonological processing were identified in a separate scan using a rhyming judgment task with pseudowords compared to a lettercase judgment task. The left inferior frontal and left superior temporal regions (Broca's and Wernicke's areas), along with the right inferior frontal cortex, demonstrated a convex response to speech compression; their activity increased as compression increased, but then decreased when speech became incomprehensible. Other regions exhibited linear increases in activity as compression increased, including the middle frontal gyri bilaterally. The auditory cortices exhibited compression-related decreases bilaterally, primarily reflecting a decrease in activity when speech became incomprehensible. Rhyme judgments engaged two left inferior frontal gyrus regions (pars triangularis and pars opercularis), of which only the pars triangularis region exhibited significant compression-related activity. These results directly demonstrate that a subset of the left inferior frontal regions involved in phonological processing is also sensitive to transient acoustic features within the range of comprehensible speech.

Auditory perceptual processing in people with reading and oral language impairments: current issues and recommendations

A popular hypothesis holds that specific reading disability (SRD) and specific language impairment (SLI) result from an impaired ability to process rapid and brief sounds. However, the results of experiments that have tested this hypothesis are incongruous. A number of factors could explain these contradictory findings, including the questionable reliability and validity of rapid auditory processing tasks, individual differences in the auditory processing abilities of SRD and SLI populations, the age of listeners, the quality of control groups, and the relationship between verbal and non-verbal auditory processing abilities. These issues highlight the need for future studies to (1) establish the reliability and validity of psychophysical tasks used to assess rapid auditory processing; (2) report the rapid auditory processing scores of individuals rather than just group means; (3) include a wide range of reading and spoken language tests to determine the literacy and oral language profile of people who demonstrate an auditory processing deficit; (4) include clinical comparison groups to determine whether a rapid auditory processing deficit is related specifically to written and spoken language impairments; and (5) examine the relationship between low-level non-verbal, verbal, and phonological processing abilities.

Neuropsychologische Interventionsstrategien am Beispiel der umschriebenen Entwicklungsstörungen der Sprache und der Motorik

Zusammenfassung. Für höhere mentale Funktionen ist das unbeeinträchtigte Zusammenwirken mehrerer einzelner Prozesse erforderlich. Mittels neuropsychologischer Interventionsansätze bei Kindern wird versucht, bei Funktionsbeeinträchtigungen, die sich auf in Entwicklung befindliche Systeme auswirken, gestörte Prozesse sowie deren Zusammenwirken spezifisch zu beeinflussen. Eine neuropsychologische Interventionsstrategie bei umschriebenen Entwicklungsstörungen beinhaltet die Erfassung des Profils von Stärken und Schwächen, die Identifizierung des oder der gestörten Prozesse des betreffenden funktionellen Systems, die Anwendung spezifischer neuropsychologischer Interventionen unter Verwendung geeigneter Instruktionsstrategien und verhaltensmodifzierender Maßnahmen sowie den kompensatorischen Einsatz intakter Prozesse oder Funktionen. Bei Patienten mit umschriebenen Entwicklungsstörungen der Sprache wurde eine Beeinträchtigung der auditiven Verarbeitung kurzer bzw. in schneller Abfolge präsentierter Stimuli gezeigt. Mittels computergestützter neuropsychologischer Trainingsprogramme konnten auditive Diskrimination und Segmentierung, Phonemverarbeitung und Sprachverständnis deutlich verbessert werden ( Merzenich et al., 1996 ; Tallal et al., 1996 ). Zur Behandlung von Kindern mit umschriebenen Entwicklungsstörungen der Motorik wurden sensorische Integration und Kinästhetisches Training eingesetzt. Für beide Behandlungsverfahren wird zwar postuliert, daß Funktionsverbesserungen über die Veränderung spezifischer Prozesse erreicht werden, es konnte auch eine gewisse Effektivität belegt werden, welche jedoch weitgehend unspezifisch ist und wahrscheinlich auf allgemeinen Wirkfaktoren beruht.