Effect of hemispherectomy in infantile hemiplegics

Four patients with infantile hemiplegia who had undergone hemispherectomy were examined. both left (LH) and right (RH) hemidecorticates obtained borderline defective scores on IQ tests. Patients with isolated right hemispheres were found not to be aphasic or apraxic. Visuospatial and constructional capacities were compromised in all patients. Individuals with an isolated right hemisphere smiled and gestured more than did those with an isolated right hemisphere. EEG and CT scan data showed that the remaining hemisphere was not normal in these patients. Therefore, inferences regarding the functional plasticity of the remaining hemisphere must be made with caution.     

Linguistic impairment after left hemidecortication for infantile hemiplegia? A reappraisal

It is now widely accepted that patients who have undergone left hemidecortication for infantile hemiplegia have subtle linguistic deficits. It is argued that the evidence supporting this view is weak, and that many of the “deficits” of left hemidecorticates fall in the normal range of performance.     

Language acquisition following hemidecortication: Linguistic superiority of the left over the right hemisphere

The language development of three 9- and 10-year-old children possessing only a right or a left hemisphere was studied. Surgical removal of one brain half antedated the beginning of speech, so each child has acquired speech and language with only one hemisphere. Different configurations of language skill have developed in the two isolated hemispheres: phonemic and semantic abilities are similarly developed but syntactic competence has been asymmetrically acquired. In relation to the left, the right brain half is deficient in understanding auditory language, especially when meaning is conveyed by syntactic diversity; detecting and correcting errors of surface syntactic structure; repeating stylistically permuted sentences; producing tag questions which match the grammatical features of a heard statement; determining sentence implication; integrating semantic and syntactic information to replace missing pronouns; and performing judgments of word interrelationships in sentences. Language development in an isolated right hemisphere, even under seizure-free conditions, results in incomplete language acquisition.     

Right-hemisphere speech representation and comprehension of syntax after left cerebral injury

Comprehension of language and visuo-spatial abilities were studied in 12 surgical patients with left cerebral lesions and right-hemisphere speech representation verified by sodium amobarbital tests. When left-hemisphere symptoms preceded the acquisition of speech, impaired understanding of syntactically complex sentences was associated with an early, but not late, onset of convulsive seizures. Other behavioral measures did not show a similar effect of age at seizure onset. Sparing or loss of comprehension could not be related to any aspects of the neurological histories in cases with right-hemisphere speech acquired before the onset of left-hemisphere symptoms. Factors which may have influenced the development of right-hemisphere language comprehension are discussed.     

Written language acquisition after left or right hemidecortication in infancy

When written language is acquired in only one hemisphere because of hemidecortication in infancy, the left hemisphere is superior to the right at using morphophonemic rules to read and spell unfamiliar words, and at exploiting the structure of sentence units to achieve rapid reading of meaning in prose. The ability to learn names for logographs, however, is better in the right hemisphere than in the left. The greater mastery of written language in the left hemisphere is a result, not of an enhanced facility for making cross-modal associations between sounds and signs, but of a superior access to the morphophonemic rule system and the higher-order textual constraints of English.     

About face: left-hemisphere involvement in processing physiognomies

Three experiments were concluded to investigate the involvement of the two cerebral hemispheres in processing faces. Perceptual discrimination of pairs of faces was equally speedy overall when the stimuli were presented in the right visual field (RVF) or left visual field (LVF). For faces differing in one or two features, however, a qualitatively different pattern of results was obtained for the two visual fields, and an RVF advantage emerged when the difference lay in the upper part of the faces (Experiment 1). An examination of the discriminability of the facial features from which the faces were constructed (Experiment 2) showed that the processes involved in RVF comparisons of faces were not dependent on the saliency of the features but, rather, followed a top-to-bottom serial analysis of the stimuli; the speed of the processing involved in LVF presentations was a function of the degree of similarity of the different comparison faces. Evidence for a serial type of comparison faces were used (Experiment 3). It was concluded that even though comparisons were equally speedy overall in LVF and RVF presentations, qualitatively different processes take place in the two hemispheres, which prove competent at processing faces, each in its own way. Some methodological problems inherent in tachistoscopic studies are discussed, and it is proposed that the quality of the stimulus representation achieved or required for cognitive processing may be determinant in the emergence of functional hemispheric asymmetries.     

Perceptual asymmetry in psychosis-prone college students: evidence for left-hemisphere overactivation.

The hypothesis that psychosis-prone students demonstrate a pattern of exaggerated perceptual asymmetry across both left- and right-hemisphere dichotic-listening tasks (consonant-vowel [CV] and tonal contour discrimination) was investigated. Subjects who scored high on the Perceptual Aberration or Magical Ideation scale or both (n = 20) demonstrated a significantly exaggerated right-ear advantage on a CV task in relation to normal control subjects (n = 27) but showed a reduced left-ear advantage on a tone task. The hypothesis of exaggerated functional lateralization across hemispheres in the psychosis-prone subjects was not supported, but the results are consistent with a hypothesis of left hemisphere overactivation in this sample.     

Mental number line disruption in a right-neglect patient after a left-hemisphere stroke

A right-neglect patient with focal left-hemisphere damage to the posterior superior parietal lobe was assessed for numerical knowledge and tested on the bisection of numerical intervals and visual lines. The semantic and verbal knowledge of numbers was preserved, whereas the performance in numerical tasks that strongly emphasize the visuo-spatial layout of numbers (e.g. number bisection) was impaired. The behavioral pattern of error in the two bisection tasks mirrored the one previously described in left-neglect patients. In other words, our patient misplaced the subjective midpoint (numerical or visual) to the left as function of the interval size. These data, paired with the patient's lesion site are strictly consistent with the tripartite organization of number-related processes in the parietal lobes as proposed by Dehaene and colleagues. According to these authors, the posterior superior parietal lobe on both hemispheres underpins the attentional orientation on the putative mental number line, the horizontal segment of the intraparietal sulcus is bilaterally related to the semantic of the numerical domain, whereas the left angular gyrus subserves the verbal knowledge of numbers. In summary, our results suggest that the processes involved in the navigation along the mental number line, which are related to the parietal mechanisms for spatial attention, and the processes involved in the semantic and verbal knowledge of numbers, are dissociable.     

The syntax of event structure.

In this paper we examine the role of events within a theory of lexical semantics. We propose a configurational theory of event structure and examine how it contributes to a lexical semantic theory for natural language. In particular, we argue that an event structure can provide a distinct and useful level of representation for linguistic analysis involving the aspectual properties of verbs, adverbial scope, the role of argument structure, and the mapping from the lexicon to syntax.     

Incidence of infantile cerebral lesions in children with behavioral disorders]

The delimitation of behavioural disturbances predominantly due to organic brain lesions from those caused by reactions due to environmental factors has practical importance for drug therapy and pedagogic guidance. Figures on the incidence of infantile brain lesions among children with behavioural disorders range from between 20 to 90%. However, comparison of the results is difficult, because different authors followed different aspects for the evaluation of their material. The authors have collected data from 497 children from the 3 to 15 year-old age group who suffer from behavioural disturbances: history, neurological and psychological findings, electroencephalogram, native x-ray picture of the skull, pneumo-encephalogram and echoencephalogram were reviewed for signs and findings suggesting infantile brain damage. Certain signs of intantile brain lesion were found in 28.6% of the children. Among the apparative diagnostic procedures without impairment to the patients, the electroencephalogram proved particularly suited for the support of the diagnosis. The most accurate data on the localization and extent of the lesion are provided by the pneumo-encephalogram. However, its performance is not possible or justified in each child.     

Comprehension disorders in aphasia: a historical review.

This paper reviews the clinical reports and theoretical inferences made by early scientists in regard to the impairment of auditory comprehension so often found in aphasics. It first presents an analysis of the literature on and the interpretation of comprehension disorders in aphasia up to the time of Pierre Marie and Arnold Pick. It then reviews early attempts to assess and quantify receptive impairment. Finally, it discusses the historical origin of some of the questions on comprehension currently under investigation by contemporary researchers.     

A left cerebral hemisphere’s superiority in processing spatial-categorical information in a non-verbal semantic format

It has been shown that the left and right cerebral hemispheres (LH and RH) respectively process qualitative or “categorical” spatial relations and metric or “coordinate” spatial relations. However, categorical spatial information could be thought as divided into two types: semantically-coded and visuospatially-coded categorical information. We examined whether a LH’s advantage in processing semantic-categorical information is observed in a non-verbal format, and also whether semantic- and visuospatial-categorical processing are differentially lateralized. We manipulated the colors and positions of the standard traffic light sign as semantic- and visuospatial-categorical information respectively, and tested performance with the divided visual field method. In the semantic-categorical matching task, in which the participants judged if the semantic-categorical information of a successive cue and target was the same, a right visual field advantage was observed, suggesting a LH’s preference for processing semantic-categorical information in a non-verbal format. In the visuospatial-categorical matching task, in which the participants judged if the visuospatial-categorical information of a successive cue and target was identical, a left visual field advantage was obtained. These results suggest that the processing of semantic-categorical information is lateralized in LH, and we discuss the dissociation between the two types of categorical information.     

The word order problem in agrammatism : I. Comprehension

The results of a picture-pointing comprehension test show that agrammatic aphasics have difficulty understanding sentences in which the underlying semantic roles are marked by the order of noun phrases around a verbal element. Agrammatic patients performed poorly on reversible constructions involving spatial prepositions (e.g., “The square is above the circle”) and verbs (e.g., “The dancer applauds the clown”). These results have significance for the interpretation of the underlying disturbance in agrammatism—whether the deficit is syntactic or purely phonological.     

Making syntax of sense: number agreement in sentence production

Grammatical agreement flags the parts of sentences that belong together regardless of whether the parts appear together. In English, the major agreement controller is the sentence subject, the major agreement targets are verbs and pronouns, and the major agreement category is number. The authors expand an account of number agreement whose tenets are that pronouns acquire number lexically, whereas verbs acquire it syntactically but with similar contributions from number meaning and from the number morphology of agreement controllers. These tenets were instantiated in a model using existing verb agreement data. The model was then fit to a new, more extensive set of verb data and tested with a parallel set of pronoun data. The theory was supported by the model's outcomes. The results have implications for the integration of words and structures, for the workings of agreement categories, and for the nature of the transition from thought to language.     

Songs to syntax: the linguistics of birdsong

Unlike our primate cousins, many species of bird share with humans a capacity for vocal learning, a crucial factor in speech acquisition. There are striking behavioural, neural and genetic similarities between auditory-vocal learning in birds and human infants. Recently, the linguistic parallels between birdsong and spoken language have begun to be investigated. Although both birdsong and human language are hierarchically organized according to particular syntactic constraints, birdsong structure is best characterized as 'phonological syntax', resembling aspects of human sound structure. Crucially, birdsong lacks semantics and words. Formal language and linguistic analysis remains essential for the proper characterization of birdsong as a model system for human speech and language, and for the study of the brain and cognition evolution.     

Emergence of syntax: commonalities and differences across children

This paper presents the results of a longitudinal examination of syntactic skills, starting at the age of emergence of simple sentences and continuing through the emergence of complex sentences. We ask whether there is systematic variability among children from different socioeconomic backgrounds in the early stages of sentence production. The results suggest a different answer for simple versus complex sentences. We found a striking similarity across SES groups on the measures tapping early mastery of basic syntactic rules of simple sentences. At the same time, there was a significant difference between SES groups in the mastery of complex sentence structures. This difference emerged at the earliest stages of production of multi-clause sentences and persisted throughout the period of observation. The implications of these findings for the understanding of mechanisms of syntactic development are discussed.