Temporal processing deficits of language-learning impaired children ameliorated by training

Intensive training in adults refines A1 representations degraded in an early postnatal critical period

The spectral, temporal, and intensive selectivity of neurons in the adult primary auditory cortex (A1) is easily degraded in early postnatal life by raising rat pups in the presence of pulsed noise. The nonselective frequency tuning recorded in these rats substantially endures into adulthood. Here we demonstrate that perceptual training applied in these developmentally degraded postcritical-period rats results in the recovery of normal representational fidelity. By using a modified go/no-go training strategy, structured noise-reared rats were trained to identify target auditory stimuli of specific frequency from a set of distractors varying in frequency. Target stimuli changed daily on a random schedule. Consistent with earlier findings, structured noise exposure within the critical period resulted in disrupted tonotopicity within A1 and in degraded frequency-response selectivity for A1 neurons. Tonotopicity and frequency-response selectivity were normalized by perceptual training. Changes induced by training endured without loss for at least 2 months after training cessation. The results further demonstrate the potential utility of perceptual learning as a strategy for normalizing deteriorated auditory representations in older (postcritical-period) children and adults.

Sensory experience determines enrichment-induced plasticity in rat auditory cortex

Our previous studies demonstrated that only a few days of housing in an enriched environment increases response strength and paired-pulse depression in the auditory cortex of awake and anesthetized rats [Engineer, N.D., Percaccio, C.R., Pandya, P.K., Moucha, R., Rathbun, D.L., Kilgard, M.P., 2004. Environmental enrichment improves response strength, threshold, selectivity, and latency of auditory cortex neurons. J Neurophysiol. 92, 73-82 and Percaccio, C.R., Engineer, N.D., Pruette, A.L., Pandya, P.K., Moucha, R., Rathbun, D.L., Kilgard, M.P., 2005. Environmental enrichment increases paired-pulse depression in rat auditory cortex. J Neurophysiol. 94, 3590-3600]. Multiple environmental and neurochemical factors likely contribute to the expression of this plasticity. In the current study, we examined the contribution of social stimulation, exercise, auditory exposure, and cholinergic modulation to enrichment-induced plasticity. We recorded epidural evoked potentials from awake rats in response to tone pairs and noise bursts. Auditory evoked responses were not altered by social stimulation or exercise. Rats that could hear the enriched environment, but not interact with it, exhibited enhanced responses to tones and increased paired-pulse depression. The degree to which enrichment increased response strength and forward masking was not reduced after a ventricular injection of 192 IgG-saporin. These results indicate that rich auditory experience stimulates physiological plasticity in the auditory cortex, despite persistent deficits in cholinergic activity. This conclusion may be beneficial to clinical populations with sensory gating and cholinergic abnormalities, including individuals with autism, schizophrenia, and Alzheimer's disease.

Developmental dyslexia: The visual attention span deficit hypothesis

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.

The notion of 'phonology' in dyslexia research: cognitivism--and beyond

Phonology has been a central concept in the scientific study of dyslexia over the past decades. Despite its central position, however, it is a concept with no precise definition or status. The present article investigates the notion of 'phonology' in the tradition of cognitive psychology. An attempt is made to characterize the basic assumptions of the phonological approach to dyslexia and to evaluate these assumptions on the basis of commonly accepted standards of empirical science. First, the core assumptions of phonological awareness are outlined and discussed. Second, the position of Paula Tallal is presented and discussed in order to shed light on an attempt to stretch the cognitive-psychological notion of 'phonology' towards auditory and perceptual aspects. Both the core assumptions and Tallal's position are rejected as unfortunate, albeit for different reasons. Third, the outcome of this discussion is a search for what is referred to as a 'vulnerable theory' within this field. The present article claims that phonological descriptions must be based on observable linguistic behaviour, so that hypotheses can be falsified by data. Consequently, definitions of 'dyslexia' must be based on symptoms; causal aspects should not be included. In fact, we claim that causal aspects, such as 'phonological deficit', both exclude other causal hypotheses and lead to circular reasoning. If we are to use terms such as 'phonology' and 'phoneme' in dyslexia research, we must have more precise operationalizations of them.

Auditory temporal processing deficits in children with reading disabilities

The role of central auditory processing in reading skill development and reading disorders is unclear. The purpose of this study was to examine whether individuals with specific reading disabilities (SRD) have deficits in processing rapidly presented, serially ordered non-speech auditory signals. To this end, we compared 12 children with SRD and 12 children without SRD on their ability to detect differences and similarities in pure tones of 1000 and 2000 Hz when these signals were presented in pairs (same or different tones, randomly ordered) with short (50 ms) versus long (500 ms) inter-stimulus intervals (ISI). Results showed that the children with SRD had significant difficulty in discriminating between pure tones with short, but not long ISI, whereas the controls performed well with both short and long ISI. The two groups did not differ significantly on measures of attention (d2) and performance IQ, and there were no significant correlations between these measures and ISI performance. There were significant correlations between the short ISI performance and phonologic awareness test results when the two groups were combined. These findings support the specific rapid auditory processing deficit hypothesis of SRD. Examination of intra-subject variability in performance indicated that children from the SRD group showed both decrement in performance with time on task and high overall variability in performance as compared to the controls. These findings underpin the importance of using time-series analyses of performance.

Auditory cortical plasticity: does it provide evidence for cognitive processing in the auditory cortex?

The past 20 years have seen substantial changes in our view of the nature of the processing carried out in auditory cortex. Some processing of a cognitive nature, previously attributed to higher-order "association" areas, is now considered to take place in auditory cortex itself. One argument adduced in support of this view is the evidence indicating a remarkable degree of plasticity in the auditory cortex of adult animals. Such plasticity has been demonstrated in a wide range of paradigms, in which auditory input or the behavioural significance of particular inputs is manipulated. Changes over the same time period in our conceptualization of the receptive fields of cortical neurons, and well-established mechanisms for use-related changes in synaptic function, can account for many forms of auditory cortical plasticity. On the basis of a review of auditory cortical plasticity and its probable mechanisms, it is argued that only plasticity associated with learning tasks provides a strong case for cognitive processing in auditory cortex. Even in this case the evidence is indirect, in that it has not yet been established that the changes in auditory cortex are necessary for behavioural learning and memory. Although other lines of evidence provide convincing support for cognitive processing in auditory cortex, that provided by auditory cortical plasticity remains equivocal.

Auditory processing disorders: acquisition and treatment

Auditory processing disorder (APD) describes a mixed and poorly understood listening problem characterised by poor speech perception, especially in challenging environments. APD may include an inherited component, and this may be major, but studies reviewed here of children with long-term otitis media with effusion (OME) provide strong evidence for changes in auditory processing acquired through altered experience (deprivation) and brain plasticity. Whether inherited or acquired, it is suggested that APD may be reversed by active learning. Training tunes both bottom-up and top-down neural mechanisms, some that are specific to the trained stimulus and some that reflect more generalised arousal. APD and its treatment therefore provide examples of brain plasticity working either in a negative or in a positive way to modulate listening.

LEARNING OUTCOMES

(1) Readers will be able to discuss APD in the context of inheritance and experience. (2) Readers will be able to explain how OME has been shown to alter auditory processing. (3) Readers will be able to list examples of good and bad brain plasticity. (4) Readers will be able to explain what auditory learning is, list some of its properties, and provide examples of its application in therapy for communication disorders.

Effects of computer-assisted speech training on Mandarin-speaking hearing-impaired children

The present study investigated whether moderate amounts of computer-assisted speech training can improve the speech recognition performance of hearing-impaired children. Ten Mandarin-speaking children (3 hearing aid users and 7 cochlear implant users) participated in the study. Training was conducted at home using a personal computer for half an hour per day, 5 days per week, for a period of 10 weeks. Results showed significant improvements in subjects' vowel, consonant, and tone recognition performance after training. The improved performance was largely retained for 2 months after training was completed. These results suggest that moderate amounts of auditory training, using a computer-based auditory rehabilitation tool with minimal supervision, can be effective in improving the speech performance of hearing-impaired children.

Computer-Assisted Speech Training for Cochlear Implant Patients: Feasibility, Outcomes, and Future Directions

Learning electrically stimulated speech patterns can be a new and difficult experience for cochlear implant patients. Cochlear implantation alone may not fully meet the needs of many patients, and additional auditory rehabilitation may be necessary to maximize the benefits of the implant device. A recently developed computer-assisted speech-training program provides cochlear implant patients with the means to conduct auditory rehabilitation at home. The training software targets important acoustic contrasts between speech stimuli and provides auditory and visual feedback as well as progressive training, thereby maintaining patients' interest in the auditory training exercises. Recent scientific studies have demonstrated the effectiveness of such specialized auditory training programs in improving cochlear implant patients' speech recognition performance. Provided with an inexpensive and accessible auditory training program, cochlear implant patients may find the motivation and momentum to get the most from the implant device.

Dyslexia, learning, and pedagogical neuroscience

The explosion in neuroscientific knowledge has profound implications for education, and we advocate the establishment of the new discipline of 'pedagogical neuroscience' designed to combine psychological, medical, and educational perspectives. We propose that specific learning disabilities provide the crucible in which the discipline may be forged, illustrating the scope by consideration of developmental dyslexia. Current approaches have failed to establish consensus on fundamental issues such as theoretical causes, diagnostic methods, and treatment strategies. We argue that these difficulties arise from diagnosis via behavioural or cognitive symptoms, even though they may arise from diverse causes. Rather than an inconvenience, variability of secondary symptoms within and across learning disabilities can inform both diagnosis and treatment. We illustrate how brain-based theories lead to radical restructuring of diagnostic methods and propose that there is an urgent need to develop genetic and brain-based diagnostic methods designed to lead to individually-appropriate remediation and treatment methods.

A preliminary study of speech discrimination in youth with Down syndrome

Few studies have examined the ability of individuals with learning disabilities, in general, or with Down syndrome, specifically, to discriminate speech. The purpose of this study was compare the speech discrimination abilities of eight children with Down syndrome (aged 5.7 to 12.8 years) to seven nonverbal mental-age matched controls (aged 4.0 to 5.3 years). A computer program presented the speech discrimination task using a two-cued alternative forced choice procedure. On each trial, the participants heard four successive synthesized speech syllables, with the first and last stimuli being the same and serving as the cue. The results indicated children with Down syndrome differed from their nonverbal mental-age matched peers in their ability to discriminate two of the five pairs, but not in the manner predicted. The relationship between speech discrimination, phonological memory, and speech-language development is also discussed.

Discrimination of coronal stops by bilingual adults: the timing and nature of language interaction

The current study was designed to investigate the timing and nature of interaction between the two languages of bilinguals. For this purpose, we compared discrimination of Canadian French and Canadian English coronal stops by simultaneous bilingual, monolingual and advanced early L2 learners of French and English. French /d/ is phonetically described as dental whereas English /d/ is described as alveolar. Using a categorial AXB task, the performance of all four groups was compared to chance and to the performance of native Hindi listeners. Hindi listeners performed well above chance in discriminating French and English /d/-initial syllables. The discrimination performance of advanced early L2 learners, but not simultaneous bilinguals, was consistent with one merged category for coronal stops in the two languages. The data provide evidence for interaction in L2 learners as well as simultaneous bilinguals; however, the nature of the interaction is different in the two groups.

Auditory Brainstem Correlates of Perceptual Timing Deficits

Children with language-based learning problems often exhibit pronounced speech perception difficulties. Specifically, these children have increased difficulty separating brief sounds occurring in rapid succession (temporal resolution). The purpose of this study was to better understand the consequences of auditory temporal resolution deficits from the perspective of the neural encoding of speech. The findings provide evidence that sensory processes relevant to cognition take place at much earlier levels than traditionally believed. Thresholds from a psychophysical backward masking task were used to divide children into groups with good and poor temporal resolution. Speech-evoked brainstem responses were analyzed across groups to measure the neural integrity of stimulus-time mechanisms. Results suggest that children with poor temporal resolution do not have an overall neural processing deficit, but rather a deficit specific to the encoding of certain acoustic cues in speech. Speech understanding relies on the ability to attach meaning to rapidly fluctuating changes of both the temporal and spectral information found in consonants and vowels. For this to happen properly, the auditory system must first accurately encode these time-varying acoustic cues. Speech perception difficulties that often co-occur in children with poor temporal resolution may originate as a neural encoding deficit in structures as early as the auditory brainstem. Thus, speech-evoked brainstem responses are a biological marker for auditory temporal processing ability.

Development of inhibitory mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the auditory cortex

Although it is known that neural selectivity for species-specific vocalizations changes during development, the mechanisms underlying such changes are not known. This study followed the development of mechanisms underlying selectivity for the direction and rate of frequency-modulated (FM) sweeps in the auditory cortex of the pallid bat, a species that uses downward FM sweeps to echolocate. In the adult cortex, direction and rate selectivity arise as a result of different spectral and temporal properties of low-frequency inhibition (LFI) and high-frequency inhibition (HFI). A narrow band of delayed HFI shapes rate selectivity for downward FM sweeps. A broader band of early LFI shapes direction selectivity. Here we asked whether these differences in LFI and HFI are present at the onset of hearing in the echolocation range or whether the differences develop slowly. We also studied how the development of properties of inhibitory frequencies influences FM rate and direction selectivity. We found that adult-like FM rate selectivity is present at 2 weeks after birth, whereas direction selectivity matures 12 weeks after birth. The different developmental time course for direction and rate selectivity is attributable to the differences in the development of LFI and HFI. Arrival time and bandwidth of HFI are adult-like at 2 weeks. Average arrival time of LFI gradually becomes faster and bandwidth becomes broader between 2 and 12 weeks. Thus, two properties of FM sweeps that are important for vocalization selectivity follow different developmental time courses attributable to the differences in the development of underlying inhibitory mechanisms.

Timing in the absence of clocks: encoding time in neural network states

Decisions based on the timing of sensory events are fundamental to sensory processing. However, the mechanisms by which the brain measures time over ranges of milliseconds to seconds remain unclear. The dominant model of temporal processing proposes that an oscillator emits events that are integrated to provide a linear metric of time. We examine an alternate model in which cortical networks are inherently able to tell time as a result of time-dependent changes in network state. Using computer simulations we show that within this framework, there is no linear metric of time, and that a given interval is encoded in the context of preceding events. Human psychophysical studies were used to examine the predictions of the model. Our results provide theoretical and experimental evidence that, for short intervals, there is no linear metric of time, and that time may be encoded in the high-dimensional state of local neural networks.

Auditive Verarbeitungs- und Wahrnehmungsstörungen

The consensus statement published by the German Society for Phoniatry and Paedaudiology in the year 2000 has been revised and actualized. The revised version takes into account current scientific and clinical findings. Aspects of the definition of auditory processing disorders (APD) are described extensively. These include symptoms, anamnestic information and diagnostic steps (preliminary examinations, subjective and objective audiological procedures). APD can appear in different forms, some of which can be classified within subtypes. Furthermore, factors which need to be considered in order to differentiate between APD and other diseases are specified. Therapeutic intervention possibilities which are rated according to their prognostic values conclude the article.

Perceptual-learning evidence for separate processing of asynchrony and order tasks

Normal perception depends, in part, on accurate judgments of the temporal relationships between sensory events. Two such relative-timing skills are the ability to detect stimulus asynchrony and to discriminate stimulus order. Here we investigated the neural processes contributing to the performance of auditory asynchrony and order tasks in humans, using a perceptual-learning paradigm. In each of two parallel experiments, we tested listeners on a pretest and a posttest consisting of auditory relative-timing conditions. Between these two tests, we trained a subset of listeners approximately 1 h/d for 6-8 d on a single relative-timing condition. The trained listeners practiced asynchrony detection in one experiment and order discrimination in the other. Both groups were trained at sound onset with tones at 0.25 and 4.0 kHz. The remaining listeners in each experiment, who served as controls, did not receive multihour training during the 8-10 d between the pretest and posttest. These controls improved even without intervening training, adding to evidence that a single session of exposure to perceptual tasks can yield learning. Most importantly, each of the two groups of trained listeners learned more on their respective trained conditions than controls, but this learning occurred only on the two trained conditions. Neither group of trained listeners generalized their learning to the other task (order or asynchrony), an untrained temporal position (sound offset), or untrained frequency pairs. Thus, it appears that multihour training on relative-timing skills affects task-specific neural circuits that are tuned to a given temporal position and combination of stimulus components.

Perceptual learning of motion leads to faster flicker perception

Critical flicker fusion thresholds (CFFT) describe when quick amplitude modulations of a light source become undetectable as the frequency of the modulation increases. The threshold at which CFF occurs has been shown to remain constant under repeated testing. Additionally, CFF thresholds are correlated with various measures of intelligence, and have been regarded by clinicians as a general measure of cortical processing capacity. For these reasons, CFF is used as a cognitive indicator in drug studies, as a measure of fatigue, and has been suggested as a diagnostic measure for various brain diseases. Here we report that CFFT increases dramatically in subjects who are trained with a motion-direction learning procedure. Control tasks demonstrate that CFFT changes are tightly coupled with improvements in discriminating the direction of motion stimuli, and are likely related to plasticity in low-level visual areas that are specialized to process motion signals. This plasticity is long-lasting and is retained for at least one year after training. Combined, these results show that CFFT relates to a specialized sensory process and bring into question that CFFT is a measure of high-level, or general, processes.

Development of perceptual correlates of reading performance

Performance on perceptual tasks requiring the discrimination of brief, temporally proximate or temporally varying sensory stimuli (temporal processing tasks) is impaired in some individuals with developmental language disorder and/or dyslexia. Little is known about how these temporal processes in perception develop and how they relate to language and reading performance in the normal population. The present study examined performance on 8 temporal processing tasks and 5 language/reading tasks in 120 unselected readers who varied in age over a range in which reading and phonological awareness were developing. Performance on all temporal processing tasks except coherent motion detection improved over ages 7 years to adulthood (p<0.01), especially between ages 7 and 13 years. Independent of these age effects, performance on all 8 temporal processing tasks predicted phonological awareness and reading performance (p<0.05), and three auditory temporal processing tasks predicted receptive language function (p<0.05). Furthermore, all temporal processing measures except within-channel gap detection and coherent motion detection predicted unique variance in phonological scores within subjects, whereas only within-channel gap detection performance explained unique variance in orthographic reading performance. These findings partially support the (Farmer, M.E., Klein, R.M., 1995. The evidence for a temporal processing deficit linked to dyslexia: A review. Psychon. Bull. Rev. 2, 460-493) notion of there being separable auditory and visual perceptual contributions to phonological and orthographic reading development. The data also are compatible with the view that the umbrella term "temporal processing" encompasses fundamentally different sensory or cognitive processes that may contribute differentially to language and reading performance, which may have different developmental trajectories and be differentially susceptible to pathology.

Behavioural and event-related potentials evidence for pitch discrimination deficits in dyslexic children: improvement after intensive phonic intervention

Although it is commonly accepted that dyslexic children have auditory phonological deficits, the precise nature of these deficits remains unclear. This study examines potential pitch processing deficit in dyslexic children, and recovery after specific training, by measuring event-related brain potentials (ERPs) and behavioural responses to pitch manipulations within natural speech. In two experimental sessions, separated by 6 weeks of training, 10 dyslexic children, aged 9-12, were compared to reading age-matched controls, using sentences from children's books. The pitch of the sentence's final words was parametrically manipulated (either congruous, weakly or strongly incongruous). While dyslexics followed a training focused on phonological awareness and grapheme-to-phoneme conversion, controls followed a non-auditory training. Before training, controls outperformed dyslexic children in the detection of the strong pitch incongruity. Moreover, while strong pitch incongruities were associated with increased late positivity (P300 component) in controls, no such pattern was found in dyslexics. Most importantly, pitch discrimination performance was significantly improved, and the amplitude of the late positivity to the strong pitch incongruity enhanced, for dyslexics after a relatively brief period of training, so that their pattern of response more closely resemble those of controls.

Single-neuron responses to rapidly presented temporal sequences in the primary auditory cortex of the awake macaque monkey

One fundamental process of the auditory system is to process rapidly occurring acoustic stimuli, which are fundamental components of complex stimuli such as animal vocalizations and human speech. Although the auditory cortex is known to subserve the perception of acoustic temporal events, relatively little is currently understood about how single neurons respond to such stimuli. We recorded the responses of single neurons in the primary auditory cortex of alert monkeys performing an auditory task. The stimuli consisted of four tone pips with equal duration and interpip interval, with the first and last pip of the sequence being near the characteristic frequency of the neuron under study. We manipulated the rate of presentation, the frequency of the middle two tone pips, and the order by which they were presented. Our results indicate that single cortical neurons are ineffective at responding to the individual tone pips of the sequence for pip durations of <12 ms, but did begin to respond synchronously to each pip of the sequence at 18-ms durations. In addition, roughly 40% of the neurons tested were able to discriminate the order that the two middle tone pips were presented in at durations of > or =24 ms. These data place the primate primary auditory cortex at an early processing stage of temporal rate discrimination.

Morphological processing in adult dyslexia

This study employed the masked-priming paradigm [Forster and Davis (J Exp Psychol bearn Mem Cogn 10: 680-698, 1984).], along with traditional methods of evaluation of morphological awareness and phonological processing, to obtain a finer-grained picture of the relationship between morphological abilities and reading in adult dyslexic readers. Participants were 21 dyslexic and 21 normally reading native Hebrew-speaking male college students. The results with masked priming demonstrated almost normal status of morphological knowledge in adult dyslexic readers with the presence of characteristic processing slowness. Phonological processing and morphological awareness were also shown to contribute primarily to word decoding in the regular and dyslexic group alike. At the same time, the contribution of different phonological skills to morphological priming effects (for pattern and root) dropped to zero. The findings demonstrated that weakness of dyslexic readers in morphological awareness tasks cannot be explained either by hypotheses on the structural deficit of morphological knowledge in dyslexia or by phonological deficit hypotheses. The explanation for this phenomenon seems to lie in the specific deficit of morphological processing, or even, more generally, in metalinguistic processing deficiency in dyslexia.

Individual cognitive training of reading disability improves word identification and sentence comprehension in adults with mild mental retardation

Reading therapy has been shown to be effective in treating reading disabilities (RD) in dyslexic children, but little is known of its use in subjects with mild mental retardation (MR). Twenty adult volunteers, with both RD and mild MR, underwent 60 consecutive weeks in a cognitive remediation program, and were compared with 32 untreated control subjects. The experimental group showed a significant improvement in word identification, as measured by oral production (p=0.0004) or silent reading (p=0.023), and sentence comprehension (p=0.0002). Adults with MR appear to benefit from new approaches in the field of RD.

Memory enhancement in healthy older adults using a brain plasticity-based training program: a randomized, controlled study

Normal aging is associated with progressive functional losses in perception, cognition, and memory. Although the root causes of age-related cognitive decline are incompletely understood, psychophysical and neuropsychological evidence suggests that a significant contribution stems from poorer signal-to-noise conditions and down-regulated neuromodulatory system function in older brains. Because the brain retains a lifelong capacity for plasticity and adaptive reorganization, dimensions of negative reorganization should be at least partially reversible through the use of an appropriately designed training program. We report here results from such a training program targeting age-related cognitive decline. Data from a randomized, controlled trial using standardized measures of neuropsychological function as outcomes are presented. Significant improvements in assessments directly related to the training tasks and significant generalization of improvements to nonrelated standardized neuropsychological measures of memory (effect size of 0.25) were documented in the group using the training program. Memory enhancement appeared to be sustained after a 3-month no-contact follow-up period. Matched active control and no-contact control groups showed no significant change in memory function after training or at the 3-month follow-up. This study demonstrates that intensive, plasticity-engaging training can result in an enhancement of cognitive function in normal mature adults.

Temporal processing and context dependency of phoneme discrimination in patients with aphasia

Standard diagnostic procedures for assessing temporal-processing abilities of adult patients with aphasia have so far not been developed. In our study, temporal-order measurements were conducted using two different experimental procedures to identify a suitable measure for clinical studies. Additionally, phoneme-discrimination abilities were tested on the word, as well as on the sentence level, as a relationship between temporal processing and phoneme-discrimination abilities is assumed. Patients with aphasia displayed significantly higher temporal-order thresholds than control subjects. The detection of an association between temporal processing and speech processing, however, depended on the stimuli and the phoneme-discrimination tasks used. Our results also suggest top-down feedback on phonemic processing.

Dynamic auditory processing, musical experience and language development

Children with language-learning impairments (LLI) form a heterogeneous population with the majority having both spoken and written language deficits as well as sensorimotor deficits, specifically those related to dynamic processing. Research has focused on whether or not sensorimotor deficits, specifically auditory spectrotemporal processing deficits, cause phonological deficit, leading to language and reading impairments. New trends aimed at resolving this question include prospective longitudinal studies of genetically at-risk infants, electrophysiological and neuroimaging studies, and studies aimed at evaluating the effects of auditory training (including musical training) on brain organization for language. Better understanding of the origins of developmental LLI will advance our understanding of the neurobiological mechanisms underlying individual differences in language development and lead to more effective educational and intervention strategies. This review is part of the INMED/TINS special issue "Nature and nurture in brain development and neurological disorders", based on presentations at the annual INMED/TINS symposium (http://inmednet.com/).

Principles underlying the design of "The Number Race", an adaptive computer game for remediation of dyscalculia

Background

Adaptive game software has been successful in remediation of dyslexia. Here we describe the cognitive and algorithmic principles underlying the development of similar software for dyscalculia. Our software is based on current understanding of the cerebral representation of number and the hypotheses that dyscalculia is due to a "core deficit" in number sense or in the link between number sense and symbolic number representations.

Methods

"The Number Race" software trains children on an entertaining numerical comparison task, by presenting problems adapted to the performance level of the individual child. We report full mathematical specifications of the algorithm used, which relies on an internal model of the child's knowledge in a multidimensional "learning space" consisting of three difficulty dimensions: numerical distance, response deadline, and conceptual complexity (from non-symbolic numerosity processing to increasingly complex symbolic operations).

Results

The performance of the software was evaluated both by mathematical simulations and by five weeks of use by nine children with mathematical learning difficulties. The results indicate that the software adapts well to varying levels of initial knowledge and learning speeds. Feedback from children, parents and teachers was positive. A companion article [1] describes the evolution of number sense and arithmetic scores before and after training.

Conclusion

The software, open-source and freely available online, is designed for learning disabled children aged 5–8, and may also be useful for general instruction of normal preschool children. The learning algorithm reported is highly general, and may be applied in other domains.

Real-time language processing in school-age children with specific language impairment

BACKGROUND

School-age children with specific language impairment (SLI) exhibit slower real-time (i.e. immediate) language processing relative to same-age peers and younger, language-matched peers. Results of the few studies that have been done seem to indicate that the slower language processing of children with SLI is due to inefficient higher-order linguistic processing and not to difficulties with more basic acoustic-phonetic processing. However, this claim requires further experimental verification.

AIMS

It was investigated whether the real-time language processing deficit of children with SLI arises from inferior acoustic-phonetic processing, inefficient linguistic processing, or both poor sensory processing and linguistic processing. If these children's impaired online language processing is due to inferior acoustic-phonetic processing, then their reaction time (RT) for recognizing words presented in list fashion should be significantly longer relative to control children's RT. If, however, their impaired language processing relates to inefficient linguistic processing, then, relative to control children, their RT for word-list-presented words should be comparable and their sentence-embedded word-recognition RT should be significantly longer.

METHODS & PROCEDURES

Sixteen school-age children with SLI, 16 age-matched (CA) typically developing children, and 16 receptive-syntax matched (RS) children completed two word-recognition RT tasks. In one task, children monitored word lists for the occurrence of a target word (isolated lexical processing task). In the second task, children monitored simple sentences for a target word (sentence-embedded lexical processing task). In both tasks, children made a timed response immediately upon recognizing the target.

OUTCOMES & RESULTS

Children with SLI and CA children showed comparable RT in the isolated lexical processing task and both were faster than RS children. In the sentence-processing task, children with SLI were slower at lexical processing than CA and RS children, with CA children demonstrating the fastest processing.

CONCLUSIONS

The real-time language processing of children with SLI appears to be attributable to inefficient higher-order linguistic processing operations and not to inferior acoustic-phonetic processing. The slower language processing of children with SLI relative to younger, language-matched children suggests that the language mechanism of children with SLI operates more slowly than what might otherwise be predicted by their linguistic competence.

Treatment of developmental dyslexia: a review

Remarkably few research articles on the treatment of developmental dyslexia were published during the last 25 years. Some treatment research arose from the temporal processing theory, some from the phonological deficit hypothesis and some more from the balance model of learning to read and dyslexia. Within the framework of that model, this article reviews the aetiology of dyslexia sub-types, the neuropsychological rationale for treatment, the treatment techniques and the outcomes of treatment research. The possible mechanisms underlying the effects of treatment are discussed.

Training-induced plasticity of auditory localization in adult mammals

Accurate auditory localization relies on neural computations based on spatial cues present in the sound waves at each ear. The values of these cues depend on the size, shape, and separation of the two ears and can therefore vary from one individual to another. As with other perceptual skills, the neural circuits involved in spatial hearing are shaped by experience during development and retain some capacity for plasticity in later life. However, the factors that enable and promote plasticity of auditory localization in the adult brain are unknown. Here we show that mature ferrets can rapidly relearn to localize sounds after having their spatial cues altered by reversibly occluding one ear, but only if they are trained to use these cues in a behaviorally relevant task, with greater and more rapid improvement occurring with more frequent training. We also found that auditory adaptation is possible in the absence of vision or error feedback. Finally, we show that this process involves a shift in sensitivity away from the abnormal auditory spatial cues to other cues that are less affected by the earplug. The mature auditory system is therefore capable of adapting to abnormal spatial information by reweighting different localization cues. These results suggest that training should facilitate acclimatization to hearing aids in the hearing impaired.

Auditory temporal resolution in normal-hearing preschool children revealed by word recognition in continuous and interrupted noise

The purpose of this study was to examine temporal resolution in normal-hearing preschool children. Word recognition was evaluated in quiet and in spectrally identical continuous and interrupted noise at signal-to-noise ratios (S/Ns) of 10, 0, and -10 dB. Sixteen children 4 to 5 years of age and eight adults participated. Performance decreased with decreasing S/N. At poorer S/Ns, participants demonstrated superior performance or a release from masking in the interrupted noise. Adults performed better than children, yet the release from masking was equivalent. Collectively these findings are consistent with the notion that preschool children suffer from poorer processing efficiency rather than temporal resolution per se.

Programmed Instruction to teach pointing with a computer mouse in preschoolers with developmental disabilities

Programmed Instruction combined with experimenter-provided prompts (physical, verbal, and gesturing) was used to teach pointing with a computer mouse. Three preschoolers who scored at least 1 year below their chronological age levels participated. During the pre-assessment, none of the participants demonstrated pointing. However, they could press and release the mouse button. Programmed Instruction consisted of three stages, based on an analysis of the behavioral prerequisites for pointing. Stage 1 was designed to teach participants to move the mouse. Stage 2 was designed to teach participants to move the on-screen cursor onto specific items on the screen. Stage 3 was designed to teach participants to click on specific items on the screen. Experimenter-provided prompts were used to facilitate skill acquisition at each stage. The post-assessment showed that all participants learned pointing after intervention. The intervention package consisting of Programmed Instruction and experimenter-provided prompts was effective for teaching the hand-eye coordination required for pointing.

Temporal processing deficits in Hebrew speaking children with reading disabilities

The purpose of this study was to assess to what extent specific reading disabilities and poor phonologic processing in children who read Hebrew, a primarily consonant orthography, are related to central auditory temporal processing deficits (TPDs).Twenty-four Hebrew-speaking children (ages 10-13) with and without reading disabilities were asked to discriminate auditorily pairs of syllables (/ba/ vs. /pa/) that differ by voice onset time (VOT) only. Two paradigms were used, 1 with a short interstimulus interval (ISI) (50 ms) and 1 with a long ISI (500 ms). Event-related potentials (ERPs) were measured in response to the two syllables in an auditory oddball task. Results showed significantly lowered accuracy, longer reaction times, and prolonged P3 latency among the group with reading disabilities compared with the control group. No significant differences were found between the short ISI task and the long ISI task. However, significant correlations were found between the phonologic processing tasks and the short ISI task. These findings in the Hebrew language are consistent with findings from other languages and add support to the central TPD hypothesis of reading disabilities. The discussion highlights how investigating different orthographic systems can deepen our understanding of the role TPD plays in reading.

Does successful training of temporal processing of sound and phoneme stimuli improve reading and spelling?

OBJECTIVE

The aim of this study was to measure and train auditory temporal processing in children with dyslexia and to examine whether there was a transfer of improved auditory temporal processing to reading and spelling skills.

METHODS

Computer-based procedures to measure and train temporal processing of sound and phoneme stimuli were developed. Test-scores for a normal control group consisting of 8-year-olds were established. Second graders with dyslexia were included in the training condition and divided into three groups: a control group, a group specifically trained in sound processing, and a third group specifically trained in phoneme processing. After an initial diagnostic procedure, both training groups received specific training every day for 4 weeks. All children, regardless of the group, received the same standard reading training programme designed for children with dyslexia at school. Outcome measures were assessed immediately after training as well as 6 and 12 months later.

RESULTS

Tests for temporal processing of sound and phoneme stimuli proved to be highly reliable. Children with dyslexia (N = 44) showed impaired auditory processing of sound and phoneme stimuli compared to normal controls (N = 51). There was a specific significant improvement in sound, respectively phoneme, processing for the training groups immediately after the end of training. The improvement of phoneme processing remained stable after 6 months and as a trend after 12 months. After 6 and 12 months of training, children of all three groups improved significantly in reading no matter what group. In spelling, the sound training group had a slight advantage after 6 months, which was not stable after 12 months.

CONCLUSIONS

Auditory temporal processing could be trained effectively at the sound and phoneme levels. However, no significant stable transfer of these improved abilities on reading and spelling exceeding the effect of the school-based standard training was demonstrated.

Time and the brain: how subjective time relates to neural time

Most of the actions our brains perform on a daily basis, such as perceiving, speaking, and driving a car, require timing on the scale of tens to hundreds of milliseconds. New discoveries in psychophysics, electrophysiology, imaging, and computational modeling are contributing to an emerging picture of how the brain processes, learns, and perceives time.

Stimulus-dependent processing of temporal order

Two distinct conceptualisations of processing mechanisms have been proposed in the research on the perception of temporal order, one that assumes a central-timing mechanism that is involved in the detection of temporal order independent of modality and stimulus type, another one assuming feature-specific mechanisms that are dependent on stimulus properties. In the present study, four different temporal-order judgement tasks were compared to test these two conceptualisations, that is, to determine whether common processes underlie temporal-order thresholds over different modalities and stimulus types or whether distinct processes are related to each task. Measurements varied regarding modality (visual and auditory) and stimulus properties (auditory modality: clicks and tones; visual modality: colour and position). Results indicate that the click and the tone paradigm, as well as the colour and position paradigm, correlate with each other. Besides these intra-modal relationships, cross-modal correlations show dependencies between the click, the colour and the position tasks. Both processing mechanisms seem to influence the detection of temporal order. While two different tones are integrated and processed by a more independent, possibly feature-specific mechanism, a more central, modality-independent timing mechanism contributes to the click, colour and position condition.

Can learning a frequency discrimination task occur without discrimination?

Following a recent report by Moore (Auditory learning: implications for speech perception. Proceedings of ISCA Workshop on Plasticity in Speech Perception [PSP2005], London, UK, 2005), showing in a frequency discrimination task that perceptual learning can occur in the absence of perceived stimuli, we further investigated the effects of training with identical stimuli (i.e. no perceptual difference between the stimuli) on frequency discrimination thresholds (DLF) and evaluated the influence of task demands on the degree of improvement following such training. A total of 20 adult normal-hearing participants were randomly assigned into three experimental groups: a "DLF-task" group, a "DLI-task" group, and a control group. For all groups, three DLF thresholds were obtained using an adaptive technique with feedback. For the two experimental groups, training was provided using two intervals of identical tone pairs. The participants in the "DLF-task" group were asked to select the tone with the higher pitch, whereas the participants in the "DLI-task" group, were instructed to select the louder of two tones. For the control group, DLF threshold-seeking tests were separated by two time intervals with no training. The results showed that: (1) training on a DLF task with identical stimuli can improve performance; (2) limited exposure to the stimuli and task in a group of naive listeners can already induce significant fast changes in performance; and (3) changing the task demands (i.e. to a DLI task) reduced improvement compared to the control group, which may suggest an interference with DLF learning. These results support the notion that perceptual learning can occur even in the absence of perceived stimuli. These findings shed light on the mechanisms that are involved in and influence auditory perceptual learning.

Resistance of grammatical impairment to computerized comprehension training in children with specific and non-specific language impairments

BACKGROUND

Receptive language impairments in school-age children have a poor prognosis, yet there is a dearth of research on effective interventions.

AIMS

Children's responses to a computerized grammatical training program were evaluated to consider whether repeated responding to spoken sentences with variable semantic content and the same syntactic structure would lead to consistent and fluent comprehension.

METHODS & PROCEDURES

Children with receptive language impairments aged from 8 to 13 years were randomly assigned to three groups: Group S (n = 12) responded to reversible sentences in a computerized game, using speech stimuli with pauses before critical phrases. Group M (n = 12) had the same stimuli acoustically modified to lengthen and amplify dynamic portions of the signal. Group U (n = 9) was an untrained control group. On average, children in groups S and M completed over 1000 training trials, focusing on training comprehension of reversible sentences.

OUTCOMES & RESULTS

Although responses speeded up over the course of training, and most children performed well above chance, accuracy typically remained below 95% correct for constructions such as above/below and reversible active/passive. Trained groups did not differ from untrained children on language or auditory outcomes. There was no evidence that acoustically modified speech input enhanced comprehension.

CONCLUSIONS

Rote training of comprehension of reversible sentences does not seem to be an effective approach to remediating such problems. For most children, the pattern of performance suggested that the problem was not a lack of syntactic knowledge, bur rather limited processing capacity that led to failures of on-line computation of meaning.

Neurobiologische Grundlagen der Lese-Rechtschreib-Schwäche

Zusammenfassung: Diese Überblicksarbeit stellt die wichtigsten neurobiologischen Theorien zu Ursachen der entwicklungsbedingten Lese-Rechtschreib-Schwäche und daraus abgeleitete Therapieansätze vor. Es wird zunächst ein kurzer Überblick über die Symptomatik und die vermuteten genetischen Grundlagen der Störung gegeben. Die phonologische Defizithypothese als eine allgemein akzeptierte, auf der kognitiven Ebene angesiedelte Theorie wird vorgestellt. Neurobiologische Modelle versuchen zu erklären, auf welchen neuroanatomischen/physiologischen Ursachen das phonologische Defizit beruht. Die magnozelluläre Defizithypothese, die Hypothese eines grundlegenden Verarbeitungsdefizits für sich zeitlich schnell verändernde Reize, die cerebelläre Defizithypothese sowie neuroanatomische Unterschiede zwischen normalen und legasthenen Lesern werden vorgestellt. Neurobiologisch fundierte Therapieansätze der Lese-Rechtschreib-Schwäche versuchen, in Ergänzung zu traditionellen, eher linguistisch orientierten Therapien die betroffenen neuronalen Systeme in ihrer Funktionsfähigkeit zu trainieren und dadurch die Voraussetzungen für die betroffenen Kinder zu schaffen, vom normalen Lese- und Schreibunterricht zu profitieren. Einige dieser Ansätze werden dargestellt. Abschließend wird darauf hingewiesen, dass eine differenzielle Zuweisung von Patienten zu bestimmten Therapieprogrammen auf der Basis einer fundierten (Ursachen-)Diagnostik in der Praxis stärker als bislang üblich durchgeführt werden sollte.

Brain plasticity and functional losses in the aged: scientific bases for a novel intervention

Aging is associated with progressive losses in function across multiple systems, including sensation, cognition, memory, motor control, and affect. The traditional view has been that functional decline in aging is unavoidable because it is a direct consequence of brain machinery wearing down over time. In recent years, an alternative perspective has emerged, which elaborates on this traditional view of age-related functional decline. This new viewpoint--based upon decades of research in neuroscience, experimental psychology, and other related fields--argues that as people age, brain plasticity processes with negative consequences begin to dominate brain functioning. Four core factors--reduced schedules of brain activity, noisy processing, weakened neuromodulatory control, and negative learning--interact to create a self-reinforcing downward spiral of degraded brain function in older adults. This downward spiral might begin from reduced brain activity due to behavioral change, from a loss in brain function driven by aging brain machinery, or more likely from both. In aggregate, these interrelated factors promote plastic changes in the brain that result in age-related functional decline. This new viewpoint on the root causes of functional decline immediately suggests a remedial approach. Studies of adult brain plasticity have shown that substantial improvement in function and/or recovery from losses in sensation, cognition, memory, motor control, and affect should be possible, using appropriately designed behavioral training paradigms. Driving brain plasticity with positive outcomes requires engaging older adults in demanding sensory, cognitive, and motor activities on an intensive basis, in a behavioral context designed to re-engage and strengthen the neuromodulatory systems that control learning in adults, with the goal of increasing the fidelity, reliability, and power of cortical representations. Such a training program would serve a substantial unmet need in aging adults. Current treatments directed at age-related functional losses are limited in important ways. Pharmacological therapies can target only a limited number of the many changes believed to underlie functional decline. Behavioral approaches focus on teaching specific strategies to aid higher order cognitive functions, and do not usually aspire to fundamentally change brain function. A brain-plasticity-based training program would potentially be applicable to all aging adults with the promise of improving their operational capabilities. We have constructed such a brain-plasticity-based training program and conducted an initial randomized controlled pilot study to evaluate the feasibility of its use by older adults. A main objective of this initial study was to estimate the effect size on standardized neuropsychological measures of memory. We found that older adults could learn the training program quickly, and could use it entirely unsupervised for the majority of the time required. Pre- and posttesting documented a significant improvement in memory within the training group (effect size 0.41, p<0.0005), with no significant within-group changes in a time-matched computer using active control group, or in a no-contact control group. Thus, a brain-plasticity-based intervention targeting normal age-related cognitive decline may potentially offer benefit to a broad population of older adults.

Nonmodularity of the Central Auditory Nervous System

This response to A. T. Cacace and D. J. McFarland (2005) identifies points of agreement and disagreement regarding the concept of modularity in the diagnosis of (central) auditory processing disorder [(C)APD]. We concur that the evaluation of (C)APD must take into consideration the influence of higher order global or pansensory issues on performance on tests of central auditory function. To accomplish this goal, multidisciplinary (e.g., multimodal) testing is an integral part of differential diagnosis of (C)APD. We also agree that the efficiency of diagnostic tests of (C)APD should not be evaluated by imprecise criteria [e.g., "presumed" or "suspected" (C)APD], which do not provide accurate measures of the true sensitivity and specificity of these tests. Our conceptualization and recommendations for clinical practice in this area diverge, however, from that of Cacace and McFarland in a number of pivotal ways. Based on the current limitations of multimodal assessment relative to issues related to scope of practice and test efficiency, as well as the accumulated basic science and clinical literature that demonstrates the nonmodularity and interactive organization of the brain, we recommend use of the sensitized test battery of the central auditory nervous system (CANS) in combination with multidisciplinary testing to differentially diagnose (C)APD and to guide treatment of the disorder. We assert that sensitivity and specificity measures derived from individuals with well-circumscribed lesions of the CANS provide an important guide to establishing the validity of central auditory diagnostic tests. We note that researchers in the area of auditory science and (C)APD must acknowledge the challenges of the clinical arena, and we encourage their continued help to develop diagnostic tools that are both efficient and practical for the differential diagnosis of (C)APD. We conclude that our approach, which combines multidisciplinary evaluation and specific tests of central auditory function that have demonstrated sensitivity and specificity for disorders of the CANS, allows us to identify (and thus rehabilitate) the auditory deficits present in individuals with (C)APD in its "purest" form. It also permits the identification and rehabilitation of auditory deficits in individuals who exhibit auditory perceptual problems that coexist with other processing problems, while ruling out those who perform poorly on auditory tests because of a global, supramodal problem involving cognition, attention, language, memory, or related skills.

Myelination: an overlooked mechanism of synaptic plasticity?

Myelination of the brain continues through childhood into adolescence and early adulthood--the question is, Why? Two new articles provide intriguing evidence that myelination may be an underappreciated mechanism of activity-dependent nervous system plasticity: one study reported increased myelination associated with extensive piano playing, another indicated that rats have increased myelination of the corpus callosum when raised in environments providing increased social interaction and cognitive stimulation. These articles make it clear that activity-dependent effects on myelination cannot be considered strictly a developmental event. They raise the question of whether myelination is an overlooked mechanism of activity-dependent plasticity, extending in humans until at least age 30. It has been argued that regulating the speed of conduction across long fiber tracts would have a major influence on synaptic response, by coordinating the timing of afferent input to maximize temporal summation. The increase in synaptic amplitude could be as large as neurotransmitter-based mechanisms of plasticity, such as LTP. These new findings raise a larger question: How did the oligodendrocytes know they were practicing the piano or that their environment was socially complex?

Effects of lengthening the speech signal on auditory word discrimination in kindergartners with SLI

In the present study, it was investigated whether kindergartners with specific language impairment (SLI) and normal language achieving (NLA) kindergartners can benefit from slowing down the entire speech signal or part of the speech signal in a synthetic speech discrimination task. Subjects were 19 kindergartners with SLI and 24 NLA controls. Results showed both types of speech manipulation to positively influence word discrimination for the entire group of children. Further analysis made clear that the effects were due to the improvement of the scores of the lowest 25% scorers (8 SLI, 3 NLA).

LEARNING OUTCOMES

As a result of this activity, the reader will be able to: (1) give an overview on the effects of speech manipulation on discrimination abilities of children with SLI, (2) be able to look with more nuance at the reported effects of the FFW software program.