Harry A. Whitaker

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

Abstract 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.

Language localization and variability

Abstract Language localization data from 11 neurosurgical patients undergoing cortical resection for medically intractable focal epilepsy were obtained by mapping with bipolar electrical stimulation at current levels below sensory and after-discharge thresholds, during an object-naming task. The topographical extent of language cortex in an individual subject can be wider than that proposed in the classic maps. Within this zone, language is discretely localized, with different sites variably committed to language as measured by the naming function. The naming data from the left cortex of eight patients, all left-brain-dominant, were pooled to determine the variability within the primary language zone. Only a narrow band of posterior, inferior frontal lobe, immediately anterior to motor strip, showed involvement in all of the patients in whom it was sampled. This is a motor speech area; it constitutes only a small portion of the frontal language area. Other infero-frontal, parietal, and postero-temporal sites showed considerable variability, with naming involvement in only 50–80% of the patients sampled. There is a suggestion that some of these patterns of language localization may correlate with poorer verbal abilities. Data were also obtained on language localization in the left insula in a patient who was left-hemisphere-dominant for language. Mapping of the right hemisphere in a left-brain-dominant patient demonstrated no naming function. Mapping of the right hemisphere in one and the left hemisphere in another patient, both of whom were right-hemisphere-dominant for language, suggests more diffuse language representation with right hemisphere dominance.

Early effects of normal aging on perseverative and non‐perseverative prefrontal measures

Current neuropsychological research supports a model postulating that prefrontal functions are among the first to decline in normal aging, but this model has rarely been empirically tested with subjects of 65 years or less. This study tests the following hypotheses: (a) A significant decline occurs prior to age 65 in a wide ranging set of prefrontal performance measures and (b) a significant increase occurs on measures of perseveration based on the same prefrontal tasks. A group of young adults (n = 70) aged 20 to 35 and a group of elderly adults (n = 58) aged 45 to 65, group‐matched for education and sex, were evaluated by means of six neuropsychological prefrontal tasks: the Self‐Ordered Pointing Task, the Wisconsin Card Sorting Test, the Porteus Mazes, a Verbal Fluency Task, a Design Fluency Task, and the Stroop Test. Four of the six prefrontal scores and four of six measures of perseveration manifested significant declines in the elderly group, suggesting that normal aging prior to age 65 may exhibit ...

Language Production: Electroencephalographic Localization in the Normal Human Brain

Slow negative potentials, which are at a maximum over Brocas area in the left hemisphere, were recorded when normnal subjects spontaneously produced polysyllabic words. Bilaterally symmetrical potentials were seen with analogous, nonspeech control gestures. These potentials began up to 1 second before word or gesture articulation. These results are the first demonstration of localization of language production in normal human brain.

Verbal and cognitive sequelae following unilateral lesions acquired in early childhood

Eight left-hemisphere lesioned children and eight right-hemisphere lesioned children between 18 months and 8 years of age were compared to control subjects on a battery of intelligence and language measures. Both left- and right-lesioned subjects had lower IQ scores than their controls, yet most functioned within the normal range or higher. Lexical comprehension and production were depressed in both subject groups and appeared to be depressed to a greater degree in right-lesioned subjects than in those with left lesions. In contrast, syntactic production in left-lesioned subjects was markedly deficient in comparison to controls as well as right-lesioned subjects. Although both subjects and controls included children with articulation errors, the number of misarticulating children and misarticulated sounds was greatest in the left-lesioned group. Finally, fluency disorders were observed in both right- and left-lesioned subjects but were not observed in controls. The study provides further evidence that the right and left hemispheres are not equipotential for language and that left-hemisphere lesions acquired early in childhood impair syntactic development to a greater degree than do right-hemisphere lesions.

Hemispheric Equipotentiality and Language Acquisition

Publisher Summary This chapter discusses hemispheric equipotentiality and language acquisition. Hemispheric equipotentiality refers to a supposed equivalence of the two cerebral hemispheres for basic language capacity. The condition for hemispheric equivalence is that language shall not have lateralized; a progressive loss of the equipotential characteristic is assumed to occur as linguistic skills come under the control of one side of the brain. Equipotentiality has taken two different forms: one based on proposals about the anatomical features of the two hemispheres, the other on suppositions about language behavior. Subsequently, it is possible to assert hemispheric equivalence for language functions while admitting to the facts of anatomic asymmetry: regardless of their structural differences, the left and right hemispheres are similarly good language substrates. Hemispheric equipotentiality does appear to make an untenable supposition about the brain because it neither explains nor predicts at least two facts about language–that the two perinatal hemispheres are not equally at risk for language delay or disorder and that they are not equivalent substrates for language acquisition.

Semantic Confusions by Aphasic Patients

Summary Verbal paraphasias occur in a number of aphasic syndromes; they can provide some information about the organization of the lexicon or ‘mental dictionary.’ Analysis suggests that there is both phonological and semantic structure to the neurological representations of words. A classification of semantic confusions based upon a literature survey is offered and it is shown that these paraphasias are by no means random substitutions. Semantic confusions were then compared to published data on word associations (normal subjects) and it was noted that the two kinds of data are remarkably similar. Apparently word association experiments on normal subjects and semantic confusions by aphasic patients follow analogous semantic organizational patterns of the lexicon. A preliminary classification of some of these semantic structures is presented in which it is noted that there are generally features common to the confusion pair as well as features which differentiate them. Some possible explanations for the basis of the confusion are offered.

Cognitive Disturbances in Parkinson's Disease

To test the hypothesis that the cognitive impairments that accompany Parkinsons disease (PD) arise from frontal lobe dys function, patients with idiopathic PD and controls were tested on a neuropsychological battery that included measures of anterograde memory, visuospatial perception, and naming, as well as several tests that are known to be sensitive to lesions of the frontal lobes. PD patients of normal mental status as measured by the Mini-Mental State Examination performed normally on the naming, line orientation, and verbal recognition memory tests but exhibited deficits on verbal recall. On tests of frontal lobe function, these patients showed mild deficits on a category fluency task and on the Wisconsin Card Sorting Test. However, their errors on the latter were not typical of patients with frontal lesions, and they performed nor mally on a letter fluency task and exhibited normal release from proactive interference. Patients of lower than normal mental status performed poorly on nearly all of the cognitive tasks including confrontational naming, line orientation, and recognition memory, suggesting that their cerebral dysfunction extended beyond subcortical-frontal circuits. The present study supports the usefulness of the Mini-Mental State Examination for cognitive screening of PD patients, but does not support the hypothesis that the cognitive impairments in PD arise principally from disruption of frontal lobe functioning. (J Geriatr Psychiatry Neurol 1989;2:22-33).

Spoken syntax in children with acquired unilateral hemisphere lesions.

The spoken syntax of eight left hemisphere lesioned and eight right hemisphere lesioned children were compared to matched controls. The childrens lesions were acquired between 0.08 and 6.17 years of age (mean = 1.33 years), and at the time of testing they were between 1.67 and 8.15 years of age (mean = 4.19). Based on analyses of spontaneous language samples, left hemisphere lesioned subjects performed more poorly than did their controls on most measures of simple and complex sentence structure. In contrast right lesioned subjects performed similarly to their controls on these measures, except for a tendency to make more errors in simple sentence structures. These findings provide further evidence that the left and right hemispheres are not comparable in supporting syntactic abilities.

NEUROLINGUISTIC ASPECTS OF LANGUAGE ACQUISITION AND BILINGUALISM

Two general questions are addressed in this paper: (a) Have the parameters of brain maturation contributed to our understanding of either monolingual or bilingual language acquisition? and (b) What do the current data on language representation in the brains of adult monolingual and multilingual speakers suggest by way of a neurolinguistic model? To anticipate the gist of this paper, the outlook is somewhat on the bleak side. First, brain maturation does not appear to be a monolithic event to which the milestones of language acquisition can be correlated easily. Second, nonlocalizationist models of brain-language relationships simply are a silly way to do neurolinguistic science; unfortunately, most current localizationist models do not do an adequate job of accounting for the known facts. On the other hand, the fact that we have at least this much understanding of neurolinguistic aspects of language acquisition and bilingualism is rather direct testimony to the progress that has been made in the field. In 1967 Lenneberg assembled an extensive body of research and ideas and proposed a number of now-familiar hypotheses concerning the neurological aspects of 1anguage.l He suggested that the two cerebral hemispheres initially are equipotential for language, that cerebral lateraliiation gradually develops until it is complete at puberty, and that there is a critical period for language acquisition from two years of age to puberty that is limited and determined by the maturation of the brain. The specific concomitants of physical maturation of the brain to which he referred were changes in cellbody volume, in neurodensity, and in some of the neurochemical components of the brain. Lenneberg’s analysis of these criteria led him to postulate a rapid rate of growth until age two, followed by a slow rise, asymptoting at puberty. His view of brain maturation as a single process was quite explicit: “Since the various aspects of cerebral maturation are so highly correlated we may think of maturation of the brain as a relatively unitary phenomenon.” The hypotheses of equipotentiality, the developnient of lateralization or dominance (currently being discussed in terms of both specialization and