An overview of what is currently known about the neurological substrates and cognitive structures involved in gesture use and how they relate to what is known about the neuropsychology of language.

Since the beginnings of psycholinguistics, gestures were considered as significant parts of the multimodal messages that are exchanged during social interactions. The first models proposed to explain production and comprehension of these messages took various forms of cognitive architectures. These information-processing models explicitly distinguished several components and processing levels, either modality-specific or “abstract”, i.e. shared by different modalities as input to production and output of comprehension. The assumption of such abstract conceptual representations underlying uses of speech and gesture was challenged in two directions. In a dynamic perspective, the notion of fixed conceptual, lexical or motor representations was criticized and meaning was supposed to emerge from temporary interactions among sub-symbolic units connected in multi-layered networks. In another, pragmatic direction, a distinction was made between monologues and dialogues. Speech and gestures in conversations are joint actions that require collaborative partners sharing a common ground. These various models have inspired experimental or quasi-experimental manipulations of several factors: the characteristics of the speakers, of the addressees, of the situational context, of the speech content, of the task demands. In this way, multiple routes were drawn to link up the verbal, motor, and social cognitive subsystems that are involved in multimodal communication.

The aim of this study was to determine whether verbal knowledge can compensate for the age-related decline in word production during a fluency test. We assessed the performance of 20 young and 20 old subjects in standard letter and semantic fluency tasks over time (T1: 0–30 s vs. T2: 31–60 s). The number of words produced, switching, and clustering components (Troyer et al. Neuropsychology, 11(1): 138–146, 1997) were investigated. Correlations between age and cognitive factors (processing speed, executive functions, and vocabulary level) were analyzed. The results revealed a knowledge compensation mechanism in elderly subjects, but only in letter fluency productions. It only occurred during the second period and was related to an increase in the clustering component and a positive correlation between age and vocabulary level. The differences between letter and semantic fluency performances are discussed in terms of the nature of the non-semantic and semantic components involved in these tasks.

The positive effects of gesturing on memory are robust but their interpretation is still controversial. To clarify the issue, recognition and cued recall of action phrases were compared in 24 younger (M=20 years) and 20 older adults (M=68 years), in three encoding conditionspurely verbal tasks (VTs), subject-performed tasks (SPTs), and experimenter-performed tasks (EPTs)for well- and poorly integrated phrases. As expected, the effects of these factors were significant, but there was no interaction between age-related differences, enactment effects, and semantic association. In particular, both SPT and EPT displayed similar advantages over VT conditions in both age groups and in the two memory tasks. These results are discussed in relation to the debate between Engelkamp on one side, and Kormi-Nouri and Nilsson on the other side, about the role of motor components in the episodic integration of verbs and nouns in action phrases.

This study analyzed reference lists in a large number of master's and doctoral theses in a university library of psychology and education sciences. It compared citation counts to other indicators of the use of periodicals. The usefulness and limitations of these statistics are discussed in relation to decision-making in subscriptions' management.

According to Hasher, Zacks, and May (Attention and performance XVII. Cognitive regulation of performance: Interaction of theory and application, pp. 653-675, MIT Press, 1999), a general age-related decline of inhibitory control affects the contents of working memory through three kinds of functions: limiting access to irrelevant information, deleting information that is no longer relevant, and restraining the production of dominant responses. Supportive evidence has been found in a wide variety of experimental tasks. In the present study, age-related changes were examined in the same group of 34 older (aged 60 to 82) and 30 younger (aged 19 to 30) adults performing the same set of tasks involving the access, deletion, or restraint function. The results indicate that age-related declines in inhibition are not uniform but vary depending on task-specific characteristics.

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BACKGROUND:Disordered discourse in cases of senile dementia of Alzheimer's type (DAT) has mainly been described in conversation and picture description tasks. The referential communication task provides researchers and clinicians with new insights on the nature of these disorders.AIMS:To study to what extent persons suffering from DAT can benefit from shared experience through trial repetition to achieve common reference.METHODS & PROCEDURES:Thirteen persons suffering from DAT at minimal or mild stage (MMSE score range = 18-27) were compared with 13 healthy elderly adults (64-86 years) in neuropsychological assessment of executive functions and in a referential communication paradigm. To study how the two partners achieve mutual understanding by progressively elaborating a common ground, the task was repeated three times.OUTCOMES & RESULTS:Persons with DAT produced a larger number of words than control participants and they benefited from the task repetition. However, they were less able to take into account previously shared information, used no definite referential expressions and were more idiosyncratic in their descriptions of the referent. This decline of communicative effectiveness was found not to relate closely to executive deficits.CONCLUSIONS:Collaborative exchanges allow healthy elderly persons to ground reference in common experience. This process is severely disturbed in persons with DAT, in relation to poor memory of preceding episodes or to other cognitive impairments.

Les relations temporelles entre le début d'un geste et d'un énoncé ont été analysées dans deux expériences utilisant un paradigme de doubles tâches. Dans les conditions de tâches simples, les participants répondent à la présentation d'images soit par un geste référentiel prédéfini, soit par un énoncé oral. Dans les conditions de doubles tâches, les deux réponses doivent être fournies. La difficulté de la tâche orale est manipulée lors de la sélection de la réponse (Expérience 1: ensembles de 2 ou de 8 stimuli) ou de sa préparation (Expérience 2: énoncés de 1 ou 5 mots). Comme prévu, ces manipulations affectent les latences des réponses orales. Les effets d'interférence (différences entre tâches simples et doubles) se produisent dans les deux modalités de réponse. Le début du geste précède celui de l'énoncé oral mais il est retardé quand la difficulté de planification de cet énoncé augmente. Ces résultats sont discutés en relation avec les modèles de la performance en doubles tâches; ils sont en accord un modèle de l'administrateur central qui suppose une postposition stratégique des réponses dans les conditions de doubles tâches.

Through a series of experiments, Cohen and Otterbein (1992) found that sentences presented together with pantomimes or with representational gestures were more often recalled than sentences presented without gestures. However, the mechanism underlying this mnemonic effect of a multimodal presentation was not fully specified. It may depend on activation of mental images and/or on increased distinctiveness of gestured utterances. The present study compared memory for sentences accompanied by different kinds of gestures—representational and nonrepresentational—to assess the role of meaning in remembering the verbal material. The results of the first experiment indicated that presentation of nonrepresentational gestures did not increase sentence recall as representational gestures did. These representational gestures also influenced performance in a sentence recognition task. In the second experiment, videotapes were edited to create mismatches and when sentences were presented with incongruent representational gestures, recall was not facilitated. Thus, in this study, memory scores did not depend on the distinctiveness of sentences presented with meaningless or mismatching gestures. These findings are discussed in relation to the literature on memory for actions in experimenter-performed tasks (EPTs).

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Pierre Feyereisena*a Fonds National de la Recherche Scientifique, Université catholique de Louvain, Louvain-la-Neuve, Belgium

Cognitive aging is a mosaic of selective deficits and spared abilities. To account for such discrepancies, it has been assumed that age-related differences in memory tasks were mainly observed in conditions that require executive control and activation of the prefrontal cortex. The present theoretical note examines this frontal hypothesis by contrasting a strong and a weak version. The strong version explains memory declines in normal aging by a specific deficit of inhibition mechanisms. The weak version invokes more general links between some strategic memory processes and executive control. The note proceeds in three steps. First, it briefly surveys the different formulations of the hypothesis, which focus on various aspects of human cognition. Second, it considers the diversity of inhibition mechanisms and of memory processes. Third, it examines empirical evidence about age-related changes in memory performance and executive functions : analysis of individual differences, experimental investigations, and studies using neuro-imagery techniques. In conclusion, the literature does not support tentative explanations of cognitive aging that rely on a single factor called inhibitory deficit.

Summary : Episodic memory, inhibition deficit, and cognitive aging : An examination of the frontal hypothesis Cognitive aging is a mosaic of selective deficits and spared abilities. To account for such discrepancies, it has been assumed that age-related differences in memory tasks were mainly observed in conditions that require executive control and activation of the prefrontal cortex. The present theoretical note examines this frontal hypothesis by contrasting a strong and a weak version. The strong version explains memory declines in normal aging by a specific deficit of inhibition mechanisms. The weak version invokes more general links between some strategic memory processes and executive control. The note proceeds in three steps. First, it briefly surveys the different formulations of the hypothesis, which focus on various aspects of human cognition. Second, it considers the diversity of inhibition mechanisms and of memory processes. Third, it examines empirical evidence about age-related changes in memory performance and executive functions : analysis of individual differences, experimental investigations, and studies using neuro-imagery techniques. In conclusion, the literature does not support tentative explanations of cognitive aging that rely on a single factor called inhibitory deficit. Key words : memory, cognitive aging, inhibition.