Pierre Goulet

Criterion-specific reduction of verbal fluency in right brain-damaged right-handers

Thirty-five vascular right brain-damaged (RBD) and 20 control (C) subjects were submitted to a verbal fluency task for which acceptability criteria were either semantic or formal. Results showed that subjects with a vascular lesion limited to the right hemisphere do show a statistically significant reduction of verbal fluency as compared to controls, that this reduction in verbal fluency is only present when the criterion is semantic, and that such a reduction is independent from the frontal or non-frontal topography of the lesion. These results tend to agree with the general conception of a--non-exclusive--right-hemisphere contribution to lexico-semantic processing, and more specifically to its semantic aspects.

Narrative Discourse in Right-Brain-Damaged Right-Handers

The interest in a possible contribution of the right “nondominant” hemisphere of right-handers to verbal communication has been popularized by the split-brain studies more than 20 years ago (Gazzaniga, 1971; Gazzaniga and Hillyard, 1971; Gazzaniga and Sperry, 1967; Sperry and Gazzaniga, 1967). This interest followed a long dark period for the right hemisphere, having begun with the contributions of Dax (1865) and Broca (1865) some 100 years before, and during which the verbal communication of right-handers was essentially attributed to the left-hemisphere functioning. The split-brain data came at the time when some clinicians were beginning to describe a certain number of “subtle” changes in the communicative behavior of right-handers having sustained an acquired lesion of the right hemisphere (RBD subjects) (Critchley, 1970; Eisenson, 1959, 1962; Weinstein, 1964). All these data pointed to either a certain potential of the right hemisphere of right-handers for verbal communication, or to a real and effective contribution of this hemisphere to verbal communication in right-handers, these two alternatives still being under discussion (Hannequin, Goulet, and Joanette, 1987; Joanette, Goulet, and Hannequin, 1989). Despite differences in results and some controversies, these studies as well as numerous other studies made since, both with these two experimental populations (split-brain and right-braindamaged subjects) and normal subjects, using techniques such as divided field studies, seem to converge toward the following characteristic: if the right hemisphere does contribute to verbal communication, or if it does have a certain potential for it, this contribution, or this potential, pertains to aspects linked with the content of language rather than with its formal output or input.

Impaired word naming in right-brain-damaged right-handers: error types and time-course analyses

The purpose of this study is to search for cues that could account for the fact that right-hemisphere lesions affect word naming when the criterion for naming is semantic. The authors analyzed the errors as well as the time course of productions of 35 vascular right-brain-damaged subjects (RBD) and 20 control subjects (C) in a semantic-based word-naming task. Results show that there are no differences between groups in terms of (a) the number of errors produced and, (b) the patterns of error types. However, results also show a reduction of verbal fluency for semantic criteria in RBD-subjects present only after the first 30 seconds of production. These results indicate that reduction of word production in RBD-subjects is not the consequence of nonspecific factors such as perseveration or spontaneity, but reflects problems with the less automatized processes permitting exploration of semantic organization, either because scanning process are affected, or because the presence of a discreet semantic impairment prevents scanning from being as efficient. Given that efficient exploration of semantic knowledge is important for lexico-semantic functioning, the present results suggest that the right hemisphere contributes to some aspects of lexico-semantic processing necessary for language production.

Word-Naming in Right-Brain-Damaged Subjects

The mere fact this book addresses the question of the right hemisphere’s contribution to lexical semantics bears in itself a strong, and widely accepted, hypothesis; that is, if the right hemisphere contributes to any of the cognitive processes necessary for language, lexicosemantic ones are probably among the most likely. This assumption proceeds from an amazingly large number of studies using different experimental paradigms. Of these, the analysis of the linguistic capacities of the right hemisphere in split-brain patients can probably be considered as having been one of the most productive. Indeed, not only did these studies provide some evidence for the linguistic capacities of the right hemisphere as far as lexical semantics are concerned, but they also stimulated research with normal subjects using, for example, hemifield studies. From studies with split-brain and normal subjects it can be inferred that the right hemisphere of right-handers has some lexicosemantic capacity which is, at least quantitatively and probably even qualitatively, different from that of the left hemisphere. One can summarize this capacity by saying that it is optimal for the comprehension of frequent and concrete lexical items (Beaumont 1982; Bradshaw et al. 1977; Bradshaw and Nettleton 1983; Chiarello 1985; Gazzaniga 1983; Gazzaniga and Hillyard 1978; Gazzaniga and Sperry 1967; Hannequin et al. 1987; Millar and Whitaker 1983; Searleman 1983; Zaidel 1983). However, all these studies point essentially to the fact that the right hemisphere of right-handers has some specific lexicosemantic potential. Given this potential, the question is whether or not the right hemisphere really contributes to lexicosemantic function when it is normally connected to the left hemisphere.

Word fluency after a right-hemisphere lesion.

Joanette and Goulet (Neuropsychologia, 1986, 24, 875-879) reported that right-handed patients suffering from a right-hemisphere stroke were impaired on semantic but not on orthographic criteria when they were submitted to a word fluency task. The interpretation of this dissociation was that the right hemisphere would subtend a particular contribution to the semantic component of word processing in right handers. The goal of the research reported here was to challenge this dissociation. In contrast with the first study, the production criteria were presented randomly and their level of productivity was a controlled factor. The semantic-orthographic dissociation was not replicated under these conditions.

The effects of left- versus right-hemisphere lesions on the sensitivity to intra- and interconceptual semantic relationships

Studies on split-brain, normal and brain-damaged subjects suggest differences in the processing of semantic relationships by the two hemispheres. Various authors have conceived of this distinction in terms of the paradigmatic/syntagmatic dissociation, and the connotative and denotative meanings of words, and as reflecting different types of links between words. Drews has suggested that a left-hemisphere lesion would affect the processing of intraconceptual relationships, while a right-hemisphere lesion would impair the processing of interconceptual relationships. The goal of this study was to test this hypothesis, using a number of intra- and interconceptual semantic relationships. Pairs of common words were submitted to left-hemisphere brain-damaged and right-hemisphere brain-damaged subjects. The task required subjects to indicate whether or not there was any relationship between the words. The results only partially support the hypothesis. The right/left opposition applied to only one of three types of intraconceptual relationships (whole-part relation) and to one of two types of interconceptual relationship (same location relation). This partially unexpected result is discussed in reference to other studies.

Text-level representations as one determinant for lexical retrieval and sentence production deficits in aphasia: comments on L. B. Zingeser and R. Sloan Berndt "Retrieval of nouns and verbs in agrammatism and anomia".

This note discusses the explanation put forward by Zingeser and Berndt (1990) in their attempt to account for agrammatism by reference to word-level representations. These authors have suggested that agrammatism could be the expression of some particular difficulties with the lexical retrieval of verbs. The present discussion suggests an alternative explanation making reference to text-level representations, and particularly to the lexicalization of predicates.

Age-related evolution of the contribution of the right hemisphere to language: absence of evidence

The age difference observed between Wernickes and Brocas aphasics has been understood by some authors as an indication of a progressive diminution of the contribution of the right hemisphere to language throughout the life span. To test this hypothesis, 24 right-hemisphere-damaged (RHD) and 24 normal control adults were submitted to six tasks looking at different aspects of language abilities. Results showed that RHDs performed less well than normal subjects on 3 of these tasks, but that this difference was not linked with age (younger than 55 versus older than 65 years). Consequently, these results do not support models of functional brain organization suggesting a decreasing contribution of the right hemisphere to language abilities with age.

Activation of the Lexical-semantic System in Right-brain-damaged Right-handers

A right hemisphere lesion can be the source of difficulties in the processing of words in right-handed individuals (Joanette, Goulet & Hannequin 1990). The research that have attempted to shed light on the nature of these difficulties have taken two orientations. One such orientation is the stream of research that has investigated the semantic nature of the lexical deficits among right-brain-damaged (RBD) subjects (Chiarello & Church 1986; Gainotti, Caltagirone & Miceli 1979, 1983; Gainotti, Caltagirone, Miceli & Masullo 1981; Joanette & Goulet 1986; Lesser 1974). These studies have tried to specify the semantic components that were affected following a right hemisphere lesion, such as the nonliteral meanings of words (Brownell, Potter, Michelow & Gardner 1984; Gardner & Denes 1973). Most of the time they have used tasks that required controlled or conscious processing of the lexical-semantic knowledge (e.g. written or oral comprehension tasks for single words, semantic judgment tasks, word fluency tasks, etc). Therefore, a second stream of research became more interested in the root cause of the semantic deficiencies found among RBD subjects than in the kind of semantic word components that were affected (Brownell & Molloy 1990; Joanette, Goulet & LeDorze 1988; Tompkins 1990). More precisely, these studies have attempted to determine whether the deficit in RBD subjects is attributable to difficulties in the use of the semantic knowledge or to a disruption of its organization.

Discourse analysis in neuropsychology: Comment on Chapman and Ulatowska☆

This paper discusses a recent article by Chapman and Ulatowska (1989, Brain and Language, 36, 651-658) on discourse analysis in aphasia. As such, the research in this area is interdisciplinary drawing from neuropsychology, as well as cognitive psychology, and, in part, aging. We illustrate problems that can arise when theoretical constructs and methodological considerations in this interdisciplinary approach are not rigorously observed. It is argued that definitive conclusions regarding the functional organization of the brain and discourse can be offered only when discourse analysis uses the state of the art from neuropsychology and cognitive psychology.