The development of reading skill and bases of developmental dyslexia were explored using connectionist models. Four issues were examined: the acquisition of phonological knowledge prior to reading, how this knowledge facilitates learning to read, phonological and non phonological bases of dyslexia, and effects of literacy on phonological representation. Compared with simple feedforward networks, representing phonological knowledge in an attractor network yielded improved learning and generalization. Phonological and surface forms of developmental dyslexia, which are usually attributed to impairments in distinct lexical and nonlexical processing “routes,” were derived from different types of damage to the network. The results provide a computationally explicit account of many aspects of reading acquisition using connectionist principles.

this paper. We thank Marshall Fong for technical assistance.

Studies of developmental dyslexia using functional imaging techniques have found disrupted activation of the left angular gyrus, and functional connectivity analyses have demonstrated functional disconnection of this region in dyslexia. I review evidence suggesting that this disconnection may reflect disruption of white-matter tracts in the brain, which subserve communication between disparate regions of the cerebral cortex. A novel magnetic resonance imaging technique known as diffusion tensor imaging has been used to demonstrate a correlation between white matter structure and reading ability in both dyslexic and normal adults. These results could reflect either epigeneticallydetermined differences in white-matter structure or experience-dependent plasicity of white matter structure. The relation of white matter structure and reading ability may be mediated by the role of myelinated white matter in the rapid transmission of neural signals. Poldrack -- DTI and dyslexia 3 Reading is...

this paper will be to review the scientific studies that led to 5 the development of these new remediation techniques, based on neuroplasticity research, as well as the outcome data derived from controlled laboratory studies and field trials aimed at assessing the efficacy of these new training methods. Early studies focusing on the etiology of developmental language impairments date back to the early 1960s. In a classic paper, Benton (1964) hypothesized that central auditory processing deficits may characterize many children with developmental dysphasia, now referred to as specific language impairment (SLI). Subsequent studies focused on one aspect of central auditory processing, that is, sequencing or temporal order judgement (TOJ) deficits. Pursuing these early studies, Tallal and Piercy (1973 a; 1973 b) set out to investigate further the auditory perceptual abilities of children with developmental dysphasia. In addition to an experimental temporal order judgement (TOJ) task, they included a frequency discrimination task as a control condition. In both the TOJ and the frequency discrimination task the identical set of stimuli were presented. Stimuli consisted of two 75 msec duration complex tones that differed in fundamental frequency (100Hz vs 305Hz). All possible combinations of these two stimuli were presented in pairs. The two tones in the pair were separated by a silent interval of varying duration (inter-stimulus interval -- ISI). In the TOJ task the child was trained to press two response buttons, to indicate the temporal order of the two tones. If the same tone was presented twice, the button representing that tone was pressed twice. If two different 6 tones were presented, the child was trained to indicate which one came first and which second, using the...

Four children demonstrating speech and language impairments were examined with respect to their ability to learn to identify certain auditory temporal perceptual information. These children listened to six-element temporal patterns and made judgments about the temporal proximity of two of the elements. Subjects listened to the patterns over a number of exposures ranging from 6 to 14, depending on the subject. Performance on the task improved significantly with repeated exposures. However, the disordered subjects ’ best performance was still significantly poorer than normal children who had only 1 exposure to the task. These results suggest that, in part, performance differences on temporal perceptual tasks between speech and language disordered children and normal children can be accounted for by diITerences in perceptual learning. However, because the disordered children never reached normal levels, learning differences may be associated with a fundamental deficit in temporal processing or some other mechanism such as impaired attention. 8 1989 Academic Press, Inc. Numerous investigations have documented the presence of auditory temporal processing deficits in subjects with language and learning problems

Word segmentation, detecting word boundaries in continuous speech, is a critical aspect of language learning. Previous research in infants and adults demonstrated that a stream of speech can be readily segmented based solely on the statistical and speech cues afforded by the input. Using functional magnetic resonance imaging (fMRI), the neural substrate of word segmentation was examined on-line as participants listened to three streams of concatenated syllables, containing either statistical regularities alone, statistical regularities and speech cues, or no cues. Despite the participants ’ inability to explicitly detect differences between the speech streams, neural activity differed significantly across conditions, with left-lateralized signal increases in temporal cortices observed only when participants listened to streams containing statistical regularities, particularly the stream containing speech cues. In a second fMRI study, designed to verify that word segmentation had implicitly taken place, participants listened to trisyllabic combinations that occurred with different frequencies in the streams of speech they just heard (“words, ” 45 times; “partwords, ” 15 times; “nonwords, ” once). Reliably greater activity in left inferior and middle frontal gyri was observed when comparing words with partwords and, to a lesser extent, when comparing partwords with nonwords. Activity in these regions, taken to index the implicit detection of word boundaries, was positively correlated with participants ’ rapid auditory processing skills. These findings provide a neural signature of on-line word segmentation in the mature brain and an initial model with which to study developmental changes in the neural architecture involved in processing speech

The current review constitutes the first comprehensive look at the possibility that the mismatch negativity (MMN, the deflection of the auditory ERP/ERF elicited by stimulus change) might be generated by so-called fresh-afferent neuronal activity. This possibility has been repeatedly ruled out for the past 30 years, with the prevailing theoretical accounts relying on a memory-based explanation instead. We propose that the MMN is, in essence, a latency- and amplitude-modulated expression of the auditory N1 response, generated by fresh-afferent activity of cortical neurons

& Individuals with developmental language disabilities, including developmental dyslexia and specific language impairment (SLI), exhibit impairments in processing rapidly presented auditory stimuli. It has been hypothesized that these deficits are associated with concurrent deficits in speech perception and, in turn, impaired language development. Additionally, postmortem analyses of human dyslexic brains have revealed the presence of focal neocortical malformations such as cerebrocortical microgyria. In an initial study bridging these research domains, we found that male rats with induced microgyria were impaired in discriminating rapidly presented auditory stimuli. In order to further assess this anatomical-- behavioral association, we designed two experiments using auditory-reflex modification. These studies were intended to assess whether auditory processing deficits in microgyric male rats would be seen in threshold detection of a silent gap in white noise, and in oddball detection of a two-tone stimulus of variable duration. Results showed no differences between sham and microgyric subjects on gap detection, but did show that microgyric subjects were impaired in the discrimination of two-tone stimuli presented in an oddball paradigm. This impairment was evident for stimuli with total duration of 64 msec or less, while both groups were able to discriminate stimuli with duration of 89 msec or greater. The current results further support the relationship between malformations of the cerebral cortex and deficits in rapid auditory processing. They also suggest that the parameters characterizing rapid auditory processing deficits for a specific task may be influenced by stimulus features and/or cognitive demand of that particular task. &

Melissa Bowerman was my teacher and mentor during my doctoral studies. If I remember correctly, I formally enrolled in three courses that she taught, and there probably were independent study enrollments to cover the time she devoted to my dissertation project. Most important, however, were the many occasions on which she devoted time to substantive conversations with me about the many questions and observations I wanted to discuss with her regarding children’s language acquisition. In retrospect, I am deeply impressed by her ability to convey respect for what surely were naïve and poorly formed contributions on my part. I recall a formative discussion in which I shared with her my hope that my studies of normative language acquisition would provide benchmarks to help identify children who deviate from the expected course of acquisition. My recollection is that she was somewhat horrified that I had such an unrealistic expectation. She helped me apprehend that it is the nature of the questions asked of the available literature that determine the nature of the answers to be discovered. Simply put,

If one was to ask a lay person to describe a symptom of a language disorder, the typical answer would probably focus on a phonological error (“wabbit ” for rabbit); on a problem related to academic performance, such as difficulty in learning to read; or on a specific named disorder that is associated also with deficits in areas other than language, such as autism-spectrum