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PubMed2006

The structures of letters and symbols throughout human history are selected to match those found in objects in natural scenes.

Are there empirical regularities in the shapes of letters and other human visual signs, and if so, what are the selection pressures underlying these regularities? To examine this, we determined a wide variety of topologically distinct contour configurations and examined the relative frequency of these configuration types across writing systems, Chinese writing, and nonlinguistic symbols. Our first result is that these three classes of human visual sign possess a similar signature in their configuration distribution, suggesting that there are underlying principles governing the shapes of human visual signs. Second, we provide evidence that the shapes of visual signs are selected to be easily seen at the expense of the motor system. Finally, we provide evidence to support an ecological hypothesis that visual signs have been culturally selected to match the kinds of conglomeration of contours found in natural scenes because that is what we have evolved to be good at visually processing.

Cultural Evolution↗

PubMed1996

Lexical-semantic event-related potential effects in patients with left hemisphere lesions and aphasia, and patients with right hemisphere lesions without aphasia.

Lexical-semantic processing impairments in aphasic patients with left hemisphere lesions and non-aphasic patients with right hemisphere lesions were investigated by recording event-related brain potentials (ERPs) while subjects listened to auditorily presented word pairs. The word pairs consisted of unrelated words, or words that were related in meaning. The related words were either associatively related, e.g. "bread-butter', or were members of the same semantic category without being associatively related, e.g. "church-villa'. The latter relationships are assumed to be more distant than the former ones. The most relevant ERP component in this study is the N400. In elderly control subjects, the N400 amplitude to associatively and semantically related word targets is reduced relative to the N400 elicited by unrelated targets. Compared with this normal N400 effect, the different patient groups showed the following pattern of results: aphasic patients with only minor comprehension deficits (high comprehenders) showed N400 effects of a similar size as the control subjects. In aphasic patients with more severe comprehension deficits (low comprehenders) a clear reduction in the N400 effects was obtained, both for the associative and the semantic word pairs. The patients with right hemisphere lesions showed a normal N400 effect for the associatively related targets, but a trend towards a reduced N400 effect for the semantically related word pairs. A dissociation between the N400 results in the word pair paradigm and P300 results in a classical tone oddball task indicated that the N400 effects were not an aspecific consequence of brain lesion, but were related to the nature of the language comprehension impairment. The conclusions drawn from the ERP results are that comprehension deficits in the aphasic patients are due to an impairment in integrating individual word meanings into an overall meaning representation. Right hemisphere patients are more specifically impaired in the processing of semantically more distant relationships, suggesting the involvement of the right hemisphere in semantically coarse coding.

Adult↗

PubMed2005

Visual cortical activity during tactile perception in the sighted and the visually deprived.

This article reviews studies demonstrating activity in visual cortex during tactile perception in sighted participants as well as in those who have experienced visual deprivation of varying duration. This field has been very active over the last few years, with the result that a number of exciting findings have emerged, but a unifying framework is still lacking. The first section of this article deals with investigations revealing that visual cortical activity is regularly associated with the neural processing of tactile inputs in normally sighted individuals. Next, the possible reasons underlying such visual cortical recruitment are considered. The focus then shifts to the effects of visual deprivation, examining the involvement of visual cortex in sensory and language processing in the early and late blind. The final section gives an account of studies suggesting that a remarkable degree of plasticity can be observed even after quite short-lasting visual deprivation. Overall, it appears that the nature of visual cortical activity during nonvisual tasks in the sighted can be influenced by late-onset blindness and even by brief interruptions of visual input; however, the relevant neural plasticity seems to considerably more exuberant if vision is lost very early in life or was never present, which suggests that there is a critical period for the maximal expression of such plasticity.

Animals↗

PubMed1997

Verbal fluency and agrammatism.

Since the beginning of this century it has been documented that cerebellar lesions induce speech deficits but these were thought to result from lack of motor coordination in the muscular activity needed for phonation. The pure motor nature of the cerebellum has been challenged on different grounds, and cerebellar activation has been documented in language-related tasks independently from motor activity. This chapter reviews the available evidence in favor of a cerebellar contribution to linguistic processing, focusing mainly on clinical observations in patients. The clinical findings are discussed in the light of recent theories on cerebellar functions.

Cerebellar Diseases↗

PubMed2000

On the relation of speech to language.

There are two widely divergent theories about the relation of speech to language. The more conventional view holds that the elements of speech are sounds that rely for their production and perception on two wholly separate processes, neither of which is distinctly linguistic. Accordingly, the primary motor and perceptual representations are inappropriate for linguistic purposes until a cognitive process of some sort has connected them to language and to each other. The less conventional theory takes the speech elements to be articulatory gestures that are the primary objects of both production and perception. Those gestures form a natural class that serves a linguistic function and no other. Therefore, their representations are immediately linguistic, requiring no cognitive intervention to make them appropriate for use by the other components of the language system. The unconventional view provides the more plausible answers to three important questions: (1) How was the necessary parity between speaker and listener established in evolution, and how maintained? (2) How does speech meet the special requirements that underlie its ability, unique among natural communication systems, to encode an indefinitely large number of meanings? (3) What biological properties of speech make it easier than the reading and writing of its alphabetic transcription?

Journal Article↗

PubMed1999

Numerical skills and aphasia.

The aim of this study was to investigate numerical difficulties in 50 patients with left hemispheric lesions. Aphasic patients were grouped according to their type of aphasia diagnosed by the Aachener Aphasia Test. The overall error rate in various transcoding and calculation tasks was clearly correlated with the severity of the language deficit, global aphasics being the most impaired patients. Broca's and Wernicke's aphasics scored similarly at the quantitative level, and amnesic aphasics were less impaired. Interestingly, qualitative analysis of the errors indicated that each group presented with specific difficulties, partially reflecting the nature of the language problems. In simple calculation, multiplication was found to be the most impaired operation, in particular in Broca's aphasics. This result supports the hypothesis that the retrieval of multiplication facts is preferentially mediated by verbal processing. Calculation procedures were mainly impaired in Wernicke's and global aphasics.

Adult↗

PubMed2002

Prosodic effects on word reduction.

It is widely known that English-speaking children reduce words by omitting syllables in certain predictable patterns (e.g., banána --> nána). One way to better understand the nature of phonological reductions in children is to examine adults' word reduction behavior. This study explored whether adults produce predictable output patterns when reducing words. Undergraduate participants heard a list of polysyllabic words varying systematically across syllable number and primary stress location and were asked to generate a "reduced" form, similar to common English reductions (e.g., rhinóceros --> rhino). Regardless of stress and syllable number, participants reduced the stimulus words significantly more often to left-headed disyllabic or monosyllabic feet, retaining stressed syllables and omitting unstressed syllables. The general bias found was similar to that which children exhibit in natural speech, namely, to maintain well-formed prosodic patterns and preserve salient syllables. On the other hand, a tendency to preserve word-initial instead of word-final syllables was also found, suggesting subtle differences in language processing between children and adults. The current study contributes to the psycholinguistic literature on adults' syllable omissions in abbreviations and fast-speech registers by examining the processing strategies that adults may use when reducing words.

Adult↗

PubMedDate not supplied

Pre-school visually impaired children: visual stimulation and micro-computers.

A justification is offered for using micro-computers and specially-designed programs with severely visually impaired pre-school children. It is argued that this technology optimizes the visual environment for the child and provides immediate feedback about the correctness of his responses to the stimuli displayed on the screen. Some of the problems encountered in such use are described, with examples taken from sessions in which teachers are working with children as young as 2 years of age, using teaching/learning sequences designed to promote and exercise visual perception skills. Among the issues addressed are the nature of the language interactions between child and adult, the effects of altering the complexity of the tasks, and the possible value of formal task analysis as a means of enabling the teacher to pinpoint critical stages in the learning process.

Blindness↗

PubMedDate not supplied

21st century literacy for a diverse world.

Literacy demands in the 21st century require that proficient readers do more than 'read along the lines' or decode words and know their meaning. Proficient readers must be able to 'read between the lines', making relevant inferences to interpret, analyze, and synthesize information in texts; and 'read across the lines', applying these critical reading processes to multiple texts for purposes of problem-raising and problem-solving. This article will review literature on the cognitive and linguistic skills necessary for reading along the lines in a variety of scripts; the nature of the language and cognitive skills essential for the text comprehension necessary for reading between and across the lines, and the ways that culture and language influence text comprehension.

Awareness↗

PubMed2006

Language and the aging brain: patterns of neural compensation revealed by functional brain imaging.

Human aging brings with it declines in sensory function, both in vision and in hearing, as well as a general slowing in a variety of perceptual and cognitive operations. Yet in spite of these declines, language comprehension typically remains well preserved in normal aging. We review data from functional magnetic resonance imaging (fMRI) to describe a two-component model of sentence comprehension: a core sentence-processing area located in the perisylvian region of the left cerebral hemisphere and an associated network of brain regions that support the working memory and other resources needed for comprehension of long or syntactically complex sentences. We use this two-component model to describe the nature of compensatory recruitment of novel brain regions observed when healthy older adults show the same success at comprehending sentences as their younger adult counterparts. We suggest that this plasticity in neural recruitment contributes to the stability of language comprehension in the aging brain.

Aged↗

PubMedDate not supplied

From individual differences to dynamic pathways of development.

A fruitful way to build upon French-language research on development of analogical and propositional processes in logical reasoning tasks is to use dynamic systems tools to describe and analyze relevant developmental pathways. Issues to address include (1) the characteristics of developmental transitions, such as hysteresis; (2) the nature of growth processes, such as hierarchical development or predator-prey interactions; and (3) the construction of effective scales for measuring change in logical reasoning.

Child↗

PubMed1991

Parallel distributed processing and neural networks: origins, methodology and cognitive functions.

Parallel Distributed Processing (PDP), a computational methodology with origins in Associationism, is used to provide empirical information regarding neurobiological systems. Recently, supercomputers have enabled neuroscientists to model brain behavior-relationships. An overview of supercomputer architecture demonstrates the advantages of parallel over serial processing. Histological data provide physical evidence of the parallel distributed nature of certain aspects of the human brain, as do corresponding computer simulations. Whereas sensory networks follow more sequential neural network pathways, in vivo brain imaging studies of attention and rudimentary language tasks appear to involve multiple cortical and subcortical areas. Controversy remains as to whether associative models or Artificial Intelligence symbolic models better reflect neural networks of cognitive functions; however, considerable interest has shifted towards associative models.

Artificial Intelligence↗

PubMed1984

Prosodic disturbance in aphasia: vowel length in Thai.

The aim of this study is to determine to what extent a phonologically contrastive function of the prosodic feature of length is resistant to impairment in aphasia. The language chosen for investigation is Thai, a language which contrasts short and long vowels. Subjects included two Broca aphasics, one transcortical motor aphasic, one Wernicke aphasic, one conduction aphasic, one nonaphasic right-brain-damaged patient, one nonaphasic cerebellar dysarthric patient, and five normal controls. The subjects read a list of words containing short and long vowels. Vowel durations were measured from spectrograms. The results showed that the timing of vowel duration for signaling the contrast between short and long vowels remains relatively intact in nonfluent as well as fluent aphasic patients. These data are brought to bear on issues concerning the specialization of the left hemisphere for temporal processing, the contribution of the right hemisphere to the processing of nonaffective components of prosody, the nature of prosodic disturbance in Broca's aphasia and cerebellar dysarthria, and the separate disruption of prosodic features.

Adult↗

PubMed2003

The dynamic nature of language lateralization: effects of lexical and prosodic factors.

In dichotic listening, a right ear advantage for linguistic tasks reflects left hemisphere specialization, and a left ear advantage for prosodic tasks reflects right hemisphere specialization. Three experiments used a response hand manipulation with a dichotic listening task to distinguish between direct access (relative specialization) and callosal relay (absolute specialization) explanations of perceptual asymmetries for linguistic and prosodic processing. Experiment 1 found evidence for direct access in linguistic processing and callosal relay in prosodic processing. Direct access for linguistic processing was found to depend on lexical status (Experiment 2) and affective prosody (Experiment 3). Results are interpreted in terms of a dynamic model of hemispheric specialization in which right hemisphere contributions to linguistic processing emerge when stimuli are words, and when they are spoken with affective prosody.

Analysis of Variance↗

PubMed1986

Subcortical transfer of cognitive information in subjects with complete forebrain commissurotomy.

Three complete commissurotomy subjects were tested for the ability to integrate cognitive information presented for a prolonged duration to opposite visual hemi-fields. A sample stimulus was projected to one hemi-field and a three-choice array to the other, with one choice related to the sample on an abstract or concrete basis. All subjects performed the non-verbal matching task at well above chance level, with scores comparable to those attained when the task was performed completely within one or the other hemisphere. Transfer was equally successful in the two directions, though the pathway originating in the right and terminating in the left hemisphere may be more sensitive to affective components of the stimulus. The information relayed subcortically is neither verbal nor imagic in nature, but appears to correspond to contextual or connotative associates of the stimulus. The results are discussed in terms of a cognitive system common to the two hemispheres and involving associational networks but not lateralized functions such as language and complex visuospatial processes.

Adult↗

PubMed1984

Generality in the verbal tacting of autistic children as a function of "naturalness" in antecedent control.

Two autistic children were taught to emit verbal tacts under two conditions--one employing verbal antecedent stimuli in the training process and the other employing so-called naturalistic antecedent stimuli. Although acquisition was more rapid when verbal antecedents were used, the generality of learning was substantially better for language taught under naturalistic stimulus control. Implications of these findings for the instruction of autistic children are considered in the context of current information on stimulus control.

Autistic Disorder↗

PubMed2002

Biology, context, and developmental inquiry.

This chapter summarizes some of the conceptual changes in developmental research over the last half-century. These advances include an acknowledgment of the role of maturation; also recognized have been the need for positing distinct psychological structures, the influence of temperament, the malleability of the infant, the role of the local context, and the dynamic nature of the categories describing human psychological types.

Adolescent↗

PubMed2007

Routes are trees: the parsing perspective on protein folding.

An important puzzle in structural biology is the question of how proteins are able to fold so quickly into their unique native structures. There is much evidence that protein folding is hierarchic. In that case, folding routes are not linear, but have a tree structure. Trees are commonly used to represent the grammatical structure of natural language sentences, and chart parsing algorithms efficiently search the space of all possible trees for a given input string. Here we show that one such method, the CKY algorithm, can be useful both for providing novel insight into the physical protein folding process, and for computational protein structure prediction. As proof of concept, we apply this algorithm to the HP lattice model of proteins. Our algorithm identifies all direct folding route trees to the native state and allows us to construct a simple model of the folding process. Despite its simplicity, our model provides an account for the fact that folding rates depend only on the topology of the native state but not on sequence composition.

Algorithms↗