Abstract not found

It is commonly assumed that innate linguistic constraints are necessary to learn a natural language, based on the apparent lack of explicit negative evidence provided to children and on Gold's proof that, under assumptions of virtually arbitrary positive presentation, most interesting classes of languages are not learnable. However, Gold's results do not apply under the rather common assumption that language presentation may be modeled as a stochastic process. Indeed, Elman (Elman, J.L., 1993. Learning and development in neural networks: the importance of starting small. Cognition 48, 71--99) demonstrated that a simple recurrent connectionist network could learn an artificial grammar with some of the complexities of English, including embedded clauses, based on performing a word prediction task within a stochastic environment. However, the network was successful only when either embedded sentences were initially withheld and only later introduced gradually, or when the network itself was given initially limited memory which only gradually improved. This finding has been taken as support for Newport's `less is more' proposal, that child language acquisition may be aided rather than hindered by limited cognitive resources. The current article reports on connectionist simulations which indicate, to the contrary, that starting with simplified inputs or limited memory is not necessary in training recurrent networks to learn pseudonatural languages; in fact, such restrictions hinder acquisition as the languages are made more English-like by the introduction of semantic as well as syntactic constraints. We suggest that, under a statistical model of the language environment, Gold's theorem and the possible lack of explicit negative evidence do not implicate i...

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.

Selective deficits in aphasics patients ’ grammatical production and comprehension are often cited as evidence that syntactic processing is modular and localizable in discrete areas of the brain (e.g., Y. Grodzinsky, 2000). The authors review a large body of experimental evidence suggesting that morphosyntactic deficits can be observed in a number of aphasic and neurologically intact populations. They present new data showing that receptive agrammatism is found not only over a range of aphasic groups, but is also observed in neurologically intact individuals processing under stressful conditions. The authors suggest that these data are most compatible with a domain-general account of language, one that emphasizes the interaction of linguistic distributions with the properties of an associative processor working under normal or suboptimal conditions. The primary purpose of this article is to provide empirical arguments in support of a new view of language deficits and their neural correlates, particularly in the realm of syntax. Selective syntactic deficits are often cited as evidence that the human brain contains a bounded and well-defined faculty or module dedicated exclusively to the representation and/or processing of syntax (Caplan & Waters, 1999; Grodzinsky, 1995a,

Where does grammar come from? How does it develop in children? Developmental psycholinguists who set out to answer these questions quickly find themselves impaled upon the horns of a dilemma, caught up in a modern variant of the ancient war between empiricists and nativists. Indeed, some of the fiercest battles in this war have been waged in the field of child language. Many reasonable individuals in this field have argued for a middle ground, but such a compromise has proven elusive thus far, in part because the middle ground is difficult to define. So let us begin with some definitions. The core of this debate is about epistemology, a branch of philosophy that we can define as “The study of knowledge, its form and source, and the process by which it comes to be. ” Within this framework, empiricism can be defined as “The belief that knowledge originates in the environment and comes into the mind/brain through the

Two sets of experiments were performed to test the perceptual benefits of enhancing consonantal regions which contain a high density of acoustic cues to phonemic contrasts. In the first set, hand-annotated consonantal regions of natural vowelconsonant vowel (VCV) stimuli were amplified to increase their salience, and filtered to stylise the cues they contained. In the second set, corresponding regions in natural semantically-unpredictable sentence (SUS) material were annotated and enhanced in the same way. Both sets of stimuli were combined with speech-shaped noise and presented to normally-hearing listeners. The VCV experiments showed statistically significant improvements in intelligibility as a result of enhancement; significant improvements were also obtained for sentence material after some adjustments in enhancement strategies and levels. These results demonstrate the benefits gained from enhancement techniques which use knowledge of acoustic cues to phonetic contrasts to improve the intelligibility of speech in the presence of background noise. <3 1998 Elsevier Science B.V. All rights reserved.

A principal observation in the study of language acquisition is that people exposed to a language as children are more likely to achieve fluency in that language than those first exposed to it as adults, giving rise to the popular notion of a critical period for language learning (Lenneberg, 1967; Long, 1990). This is perhaps surprising since children have been found to be inferior to adults in most tests of cognitive abilities. A variety of explanations have been put forth to account for the benefit of early language learning. Possibly the most prevalent view is that children possess a specific "language acquisition device" that is programmatically deactivated prior to or during adolescence (Chomsky, 1965; McNeill, 1970). Important to this view is that knowledge or processes specifically necessary for effective language learning are only available for a limited period of time. But this theory has trouble accounting for continued effects of age-of-acquisition after

Eleven children with early focal lesions were compared with 70 age-matched controls to assess their performance in repeating nonwords, in learning new words, and in immediate serial recall, a triad of abilities that are believed to share a dependence on serial ordering mechanisms (e.g., Baddeley, Gathercole, & Papagno, 1998; Gupta, in press-a). Results for the experimental group were also compared with other assessments previously reported for the same children by MacWhinney, Feldman, Sacco, and Valds-Prez (2000). The children with brain injury showed substantial impairment relative to controls in the experimental tasks, in contrast with relatively unimpaired performance on measures of vocabulary and nonverbal intelligence. The relationships between word learning, nonword repetition, and immediate serial recall were similar to those observed in several other populations. These results support previous reports that there are persistent processing impairments following early brain injury, despite developmental plasticity. They also suggest that word learning, nonword repetition, and immediate serial recall may be relatively demanding tasks, and that their relationship is a fundamental aspect of the cognitive system.

Rehabilitation of the damaged brain can foster reconnection of damaged neural circuits; Hebbian learning mechanisms play an important part in this. The authors propose a triage of post-lesion states, depending on the loss of connectivity in particular circuits. A small loss of connectivity will tend to lead to autonomous recovery, whereas a major loss of connectivity will lead to permanent loss of function; for such individuals, a compensatory approach to recovery is required. The third group have potentially rescuable lesioned circuits, but guided recovery depends on providing precisely targeted bottom-up and top-down inputs, maintaining adequate levels of arousal, and avoiding activation of competitor circuits that may suppress activity in target circuits. Empirical data are implemented in a neural network model, and clinical recommendations for the practice of rehabilitation following brain damage are made. The Clinical Problem Many tens of millions of people worldwide suffer brain damage. Hundreds of thousands of professionals treat this brain damage using a variety of rehabilitation therapies. Yet in spite of this enormous endeavor, there is no agreement as to how these therapies work, though it can be concluded that at least some have been shown to be effective (Antonucci et al., 1995; Biitefisch, Hummelsheim,

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...