Mental calculation in a prodigy is sustained by right prefrontal and medial temporal areas.

Calculating prodigies are individuals who are exceptional at quickly and accurately solving complex mental calculations. With positron emission tomography (PET), we investigated the neural bases of the cognitive abilities of an expert calculator and a group of non-experts, contrasting complex mental calculation to memory retrieval of arithmetic facts. We demonstrated that calculation expertise was not due to increased activity of processes that exist in non-experts; rather, the expert and the non-experts used different brain areas for calculation. We found that the expert could switch between short-term effort-requiring storage strategies and highly efficient episodic memory encoding and retrieval, a process that was sustained by right prefrontal and medial temporal areas.

[Cognitive rehabilitation]. / La rééducation cognitive.

During these last 30 years, cognitive rehabilitation has accomplished dramatic improvement. In this paper, we review progress in four main domains: the development of pragmatic and ecological approaches in neuropsychological rehabilitation; the development of computerised rehabilitation; rehabilitation of executive functions; cognitive rehabilitation in degenerative dementia. Finally, we present a single-case study, recently published elsewhere, showing the effectiveness of rehabilitation of verbal working memory in a patient with left hemisphere stroke. In addition, future issues for rehabilitation research are presented. The development of bottom-up rehabilitation strategies as well as the use of inter-hemispheric interactions appears as future promising tracks for clinical rehabilitation.

Non-algorithmic access to calendar information in a calendar calculator with autism.

The possible use of a calendar algorithm was assessed in DBC, an autistic "savant" of normal measured intelligence. Testing of all the dates in a year revealed a random distribution of errors. Re-testing DBC on the same dates one year later shows that his errors were not stable across time. Finally, DBC was able to answer "reversed" questions that cannot be solved by a classical algorithm. These findings favor a non-algorithmic retrieval of calendar information. It is proposed that multidirectional, non-hierarchical retrieval of information, and solving problems in a non-algorithmic way, are involved in savant performances. The possible role of a functional rededication of low-level perceptual systems to the processing of symbolic information in savants is discussed.

[Right hemisphere lesion and directional indication in a visuoconstructive task]. / Lésion hémisphérique droite et indiçage directionnel dans une tâche visuoconstructive.

We test the hypothesis that the divergences between Hecaen and Assal (1970) and Gianotti et al (1977) as regards the efficiency of indications supplied together with drawings to patients with unilateral lesion are due to the topological or directional nature of these indicators. We submit subjects with cerebral damage to a test involving copying cubes and non-significant drawings by opposing these two types of indication and also resorting to the procedure of Pillon and Lhermitte (1978). The results demonstrate that the topological or directional character of the indicators used can account for the differences between these two sets of findings. Finally, the results tend to show that the left hemisphere basically controls the manipulatory or executive side of the visuo-constructive task, whilst the right takes over its executive and perceptive aspects in conjunction.

The operativity effect in naming: a re-analysis.

According to Howard Gardner (1973), operativity, i.e. the extent to which it is possible to act with or upon an object, influences picture naming by aphasic subjects. In the present study, this influence is analysed with three purposes: (1) to replicate the Gardner's observation, (2) to avoid methodological biases and to extend the analyses, and (3) to look for alternative explanations. Sixty-four pictures corresponding to high- and low-frequency nouns rated as high or low in operativity were presented to 18 aphasic subjects. Frequency and operativity were found to significantly affect naming performance. More particularly, fewer semantic paraphasias were observed in confrontation with operative items and fewer phonemic paraphasias in the production of frequent nouns. However, the influence of operativity on the reduction of errors disappeared when age-of-acquisition and picture familiarity were introduced as co-variables. These dimensions were found to be better predictors of aphasic performance than operativity.

Images of numbers, or "When 98 is upper left and 6 sky blue".

Some people declare that they possess a personal visual representation of numbers: some automatically "see" the numbers they are confronted with in a precise location in a structured mental space, others "associate" specific colours with given numbers. Such visuo-spatial representations of numbers were first described by Galton in 1880 but have since received little attention from psychologists. It is the aim of this article to describe these mental representations and discuss their role in number processing. The authors first review Galton's observations, and then present their own. Finally, they discuss the relevance of these visuo-spatial representations in relation to contemporary debates on number representation and calculation.

Physostigmine results in an increased decrement in brain glucose consumption in Alzheimer's disease.

The responsibility of cerebral cholinergic lesions for the weak clinical response to cholinergic neurotransmission enhancement of Alzheimer's disease (AD) was studied by measuring the effects of physostigmine on glucose consumption and neuropsychological tests. Ten AD and ten aged normals (AN) were examined twice, under placebo and under maximal tolerated dose of physostigmine, in randomized order and blind fashion. Under physostigmine, both groups showed better performances in tests measuring attention (P < 0.05-0.001) but not long-term memory, and cerebral glucose consumption was regionally modified (P < 0.0001). We observed a regional decrease in AD and in AN which was larger in AD, where each patient exhibited a mean metabolic decrease. With normalized values, AD and AN showed a similar decrease in the metabolic values of prefrontal cortex and striatum (P = 0.0003). These findings suggest that cholinergic neurotransmission enhancement depresses glucose consumption and increases selective attention in similar ways in both groups, but to a larger extent in AD. This suggests that brain metabolism in AD over-responds to enhancement of cholinergic neurotransmission. The observed weak response of clinical symptomatology to anticholinesterase agents does not appear to be due to the failure to enhance the activity of the cholinergic system in AD.

Implicit processing of grammatical rules in a classical case of agrammatism.

The speech production of an agrammatic patient is viewed as the output of a syntactic filter which allows only nouns, verbs, and adjectives to pass. In this paper, we study the behavior of this filter in the processing of grammatically ambiguous words. Our results indicate that these words are either uttered or not as a function of their syntactic role in the sentence. Thus, the patient's oral reading of a sentence is not a concatenation of isolated words, but depends on an implicit, context-sensitive analysis. These observations bring to light a new aspect of the agrammatic's syntactic competence and may contribute to the study of psycholinguistic processes in normals.

Noncommutability of the N + 0 arithmetical rule: a case study of dissociated impairment.

It has been shown that some arithmetical problems are stored in the form of individual facts representations (e.g., 3 x 4 = 12) whereas others are solved by general stored rules (e.g., 0 x N = 0). We describe the performance of a brain-damaged subject who presented a mild impairment in arithmetical fact retrieval. Although her performance was almost perfect for rule-based problems in all arithmetical operations, she was severely impaired for 0 + n problems in contrast with her relatively good performance for the corresponding n + 0 problems. This dissociation extends to addition the noncommutability of arithmetical rules described in multiplication.

Selective impairment as evidence for mental organisation of arithmetical facts: BB, a case of preserved subtraction?

We report here the case of a patient (BB), suffering from a precocious evolving dementia with impaired arithmetic performance, who showed specific and theoretical pertinent dissociations in basic mental arithmetic. First, in a task involving production of answers to simple arithmetic problems, a strong dissociation was found among operation: while multiplication was severely impaired, addition was moderately and subtraction only slightly impaired. A second dissociation was found between problems potentially solvable by rules and the others, with the former being better preserved. Finally, in multiplication verification tasks, the rate and distribution of errors among problems were not different from those observed in the multiplication production task. This pattern of performance like the one presented by the patient RG (Dagenbach and McCloskey, 1992), suggests first that stored arithmetical fact representations are segregated by arithmetic operation and second that a distinction has to be drawn between arithmetical rules and arithmetical facts. Last, the parallelism of performance observed here in verification and production tasks suggests that the same deficit(s) is (are) responsible for errors in both tasks.

Number processing and calculation in a case of visual agnosia.

We describe the performance of a brain-damaged subject who suffered from visual agnosia leading to major difficulties in generating and exploiting visual representations from long-term memory. His performance in a physical judgement task in which he was required to answer questions about the visual shapes of Arabic numerals reflected his agnosic problems. However, he showed no impairment in usual number processing and calculation tasks. This case shows that, despite some commonalities in number and object processing, actual numerical processes are not affected by visual agnosia and can be preserved even when fine visual processes are impaired.

Syntactical knowledge in a case of agrammatism: evidence from transcoding Roman and Arabic numerals.

The ability of an aphasic subject with agrammatism in both comprehension and production to transcribe quantities from Roman numerals to Arabic and the reverse was investigated. Systematic errors in the transcoding processes were observed that could not be accounted for by the peculiarities of the two ideographic coding systems or by difficulties with direct transcoding rules. The results are discussed in the framework of the current debate on preserved/impaired hierarchical syntactical knowledge of agrammatic subjects. The findings paralleled the results of previous studies on the transcoding skills of agrammatics from/to alphabetic numerals to/from digital forms. In the case of this particular patient, it is therefore tentatively concluded in favor of preserved syntactical knowledge.

Semantic errors reconsidered in the procedural light of stack concepts.

The purpose of this paper is to demonstrate the relevance of the stack concept in neuropsycholinguistics, a stack being a file with serially ordered elements. Number names (one, two, three, . . .) and the names of the days in the week may be viewed in this way. In a stack structure, any element is identified by two pieces of information: the particular stack to which it belongs and its position within that stack. Two experiments are reported that demonstrate a double dissociation. A deep dyslexic patient with agrammatism was found to sort stack elements on the basis of identity of position-within-stacks, while a fluent aphasic with semantic verbal paraphasias used another criterion, grouping together the items of the same stack. First revealed when handling number names, the two psycholinguistic procedures are also shown to be differentially operative with other linguistic material. Introducing the stack concept thus permits a procedural reinterpretation of some "semantic confusions," particularly but not exclusively those dealing with quantities.

Aphasics' sensitivity to contextual appropriateness conditions for pragmatic indicators.

Twenty normal and twenty aphasic subjects were tested for their understanding of implicit meanings of the French adverbs même (even), aussi (also), and surtout (mainly). Their sensitivity to the contextual appropriateness conditions of such items was analyzed in a multiple-choice paradigm requiring them to select from three figures the one which was best described by a sentence like "Show me the figure that is même (aussi, surtout) red." A global quantitative comparison indicates that aphasics' performance was inferior to that of the normal controls. Yet, the analysis of individual responses allowed the identification of three different subgroups of aphasics: the first produced responses identical to the normals' responses; the second seemed to ignore the adverb and systematically selected the figure with the highest amount of the asserted color; and the third produced responses identical to the normals' responses for surtout but had difficulties with même or aussi. As concerns the relationship between aphasics' performance and their scores on literal language comprehension tests, the data favor the dissociation between literal and pragmatic factors in comprehension. Finally, no clear relationship was observed between aphasia type and aphasics' performance, although three points are noted in the discussion: (1) all the conduction aphasics performed like normals, (2) among the Broca's aphasics, the one with the clearest agrammatic verbal output produced responses similar to those of the normals, and (3) there was no anomic patient in the second subgroup.

Right hemisphere language processing: lateral difference with imageable and nonimageable ambiguous words.

Influence of imageability on hemispheric processing difference is studied in a lexical decision task with semantic priming. Homographs and ambiguous words were biased according to the prime toward their low or high imageable meanings and unilaterally presented in the visual field. A right visual field (RVF) superiority was observed; it was nonsignificant for the high imageable (HI) meaning but significant for the low imageable (LI) meaning of the ambiguous words. Thus the results seem to favor a bilateral hemispheric representation of HI words and a unilateral left representation of LI words. Theoretical implications of the results are discussed to the various models of ambiguous word access processing.

[Absence of signs of deconnection in four cases of partial anterior and median callosal lesions of vascular and neurosurgical origin (author's transl)]. / Absence de signe de déconnexion lors d'un examen neuro-psychologique différé dans quatre cas de lésions callosales antérieures et médianes partielles d'origine vasculaire et neurochirurgicale.

Three cases of partial anterior and median callosal vascular lesions and one surgical case are presented. Some months later a neuropsychological examination did not show any signs of deconnection. Two interpretations are equally plausible: either the limited extension of the lesions as well as their location explain the absence of signs of deconnection, or these signs had existed but were regressive.

[Hemineglect after right lesion. A report on three cases (author's transl)]. / Héminégligence par lésion frontale droite. A propos de trois observations.

This paper is concerned with the observation of three cases of hemineglect after right frontal lesion. A review of cases indicates clear predominance of that semiology in subjects with right hemispheric damage. The observations are discussed with regards to facts and theoretical interpretations about the role of frontal areas in the determinism of hemineglect.

[Programmed rehabilitation of a case of agraphia (author's transl)]. / Rééducation programmée d'un cas d'agraphie

The authors describe a programmed method of rehabilitation suitable for patients with writing disorders resulting from cerebral lesions. The use of a visual display screen permits differential display and the immediate correction of errors. The application of the method is illustrated in the case of a patient with aphasic agraphia, and its general utility is briefly discussed in relation to the nature of various graphic disorders.

Decoding paralinguistic signals: effect of semantic and prosodic cues on aphasics' comprehension.

A matching task between sentences voiced with joyful, angry, or sad intonation and pictures of facial expressions representing the same emotions is proposed to 27 aphasics and 20 normal subjects. Semantic contents are either meaningless, neutral, or affectively loaded. In the affective-meaning condition, content is redundant with prosody or conflicting with it. Results are 1. a greater number of nonprosodic choices in the aphasic group; 2. an identical influence of the congruence/conflict variable on aphasic and control subjects; 3. an identical influence of the semantic content of the conflict sentences on both groups. Aphasic impairment is interpreted as purely quantitative, since affective semantic content influences the decoding of the sentences.

[Rehabilitation of patients with frontal lesions]. / Rééducation de patients atteints de lésions frontales

Two patients with frontal lesions underwent re-education of the mental processes. The material used was the PM 38 test, WAIS cubes and visuo-spatial problems. The method used was based on Luria's re-education technique supplemented by a process of phasing out the controlling aids and cutting out facts for analysis. Results obtained before and after re-education in responses are described and compared. The problem of reansferring the skill acquired to other activities is discussed. The authors found that skills developed in the re-education situation to cope with a given task are not spontaneously utilised by the patient when he is again placed in a similar situation, but that a simple verbal cue from the tester is sufficient to cause this skill to be transferred. Finally, when faced with a new situation, the patient does not work out how to solve the problem, but he accepts more readily what is suggested to him by the tester.