Biomedical subjects

X Seron

Publications and source records attributed to X Seron.

At least 19 recordsLinked to original sources

PubMed2001

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.

Adult↗

PubMed2001

Involvement of short-term memory in complex mental calculation.

The aim of this study was to examine the involvement of the short-term memory system in complex mental addition by manipulating the phonological and visual similarity of two numbers to be added. The phonological similarity of the problems appeared to have a major effect on both speed and accuracy. However, the manipulation of visual similarity failed to have any measurable impact. This suggests that the phonological loop, rather than the visual-spatial sketch pad, would be used preferably for temporary storage of addends. An interpretation of these results in terms of the nature of the internal code underlying this task is discussed.

Adult↗

PubMed2000

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.

Agnosia↗

PubMed2000

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.

Aphasia↗

PubMed2000

Neuroanatomical substrates of arabic number processing, numerical comparison, and simple addition: a PET study.

Positron emission tomography was used to localize the cerebral networks specifically involved in three basic numerical processes: arabic numeral processing, numerical magnitude comparison, and retrieval of simple addition facts. Relative cerebral blood flow changes were measured while normal volunteers were resting with eyes closed, making physical judgment on nonnumerical characters or arabic digits, comparing, or adding the same digits. Processing arabic digits bilaterally produced a large nonspecific activation of occipito-parietal areas, as well as a specific activation of the right anterior insula. Comparison and simple addition fact retrieval revealed a fronto-parietal network involving mainly the left intraparietal sulcus, the superior parietal lobule and the precentral gyrus. Comparison also activated, but to a lesser extent, the right superior parietal lobe, whereas addition also activated the orbito-frontal areas and the anterior insula in the right hemisphere. Implications for current anatomo-functional models of numerical cognition are drawn.

Adult↗

PubMed2000

The odd-even effect in multiplication: parity rule or familiarity with even numbers?

This study questions the evidence that a parity rule is used during the verification of multiplication. Previous studies reported that products are rejected faster when they violate the expected parity, which was attributed to the use of a rule (Krueger, 1986; Lemaire & Fayol, 1995). This experiment tested an alternative explanation of this effect: the familiarity hypothesis. Fifty subjects participated in a verification task with contrasting types of problems (even x even, odd x odd, mixed). Some aspects of our results constitute evidence against the use of the parity rule: False even answers were rejected slowly, even when the two operands were odd. We suggest that the odd-even effect in verification of multiplication could not be due to the use of the parity rule, but rather to a familiarity with even numbers (three quarters of products are indeed even).

Adolescent↗

PubMed1998

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.

Aged↗

PubMed1995

Lexicalization errors in writing arabic numerals: a single-case study.

This paper presents a single-case study of a patient suffering from several impairments in number processing. The main focus of the paper is to describe and interpret the patient's errors in verbal to arabic transcoding. The errors were of the syntactical type and consisted of partial lexicalizations appearing mainly in response to items with Thousand in sum relationships and less frequently with Hundred in sum relationships. The Discussion section compares three models in their ability to account for the patient's dissociation. It was suggested that models such as that of McCloskey, Caramazza, and Basili (1985), postulating a semantic representation for numbers built up on a base-ten system, are unable to account for the patient's errors. By contrast, Power et al.'s perspective (Power & Longuet-Higgins, 1978; Power & Dal Martello, 1990), which posits a semantic representation of numbers reflecting the structure of the verbal numeral system, could provide an economical interpretation for the dissociation observed between the mastery of sum and product relationships. Similarly, the asemantic transcoding model developed by Deloche and Seron (1987) gives a valid account for the patient's profile.

Aged↗

PubMed1995

[A case of metamorphopsia restricted to faces and different familiar objects].

The case of a 19-year old patient suffering of transient metamorphopsia restricted to familiar faces and familiar objects is reported. This clinical sign resulted from a small right occipitotemporal haemorrhage due to a sub-cortical metastasis. The patient claimed that faces are distorted and look more pleasant. There were neither visual field defects nor visual agnosia. MRI revealed a small high signal area in the right fusiform gyrus. The structural and functional aspects of the metamorphopsia are documented and discussed in relation to aperceptive prosopagnosia. More specifically, it is suggested that facial metamorphopsia and aperceptive prosopagnosia express the same underlying disorder differing only in terms of severity.

Adult↗

PubMed1994

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.

Adult↗

PubMed1994

Calculation and number processing: assessment battery; role of demographic factors.

This paper describes the structure and contents of EC301, a standardized testing battery for the evaluation of brain-damaged adults in the area of calculation and number processing. The battery was administered to 180 normal subjects stratified by education (3 levels), age (3) and gender. EC301 is composed of a large variety of tasks dealing with basic arithmetic skills, and their linguistic, spatial, and mnesic dimensions. The three main notational systems for numbers--Arabic digits, written verbal, and spoken verbal number forms--are explored. Analysis of error rates indicated the effect of some demographic factors (principally, education; incidentally, gender) on normal performance in some tasks.

Adult↗

PubMed1993

Patterns of line bisection in patients suffering from unilateral spatial neglect.

Thirteen patients suffering from Unilateral Spatial Neglect and 6 Right Brain Damaged Control Patients were tested on a line bisection task in order to verify peculiar patterns of error. Stimuli were arranged in order to avoid confounding the effects of line length and line position in the space. Two parameters of rightward displacement of setting point were used: 1) the distance of patient's setting point from actual line midpoint, and 2) the deduced left end-point of the line that patient took into account. Results showed that: 1) the rightward extension of lines did not lead to a consistent rightward displacement of setting point; 2) error significantly increased as lines extended more than 10 cm in the left hemispace; 3) the USN severity amplified the degradation of leftmost portion of stimuli until the deduced left endpoint of all space/length conditions was aligned on the left of patient's sagittal midplane. The interpretation of these results points to the particular arrangement of neurons directing attention on specific portions of the visual field.

Attention↗

PubMed1992

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.

Adult↗

PubMed1991

Dot counting by brain damaged subjects.

In this study, we examine how brain damaged adults (aphasics, right-brain lesioned subjects (RBD), and demented subjects) perform a basic education skill: determining the cardinality of different sets of objects (dots). The RBD subjects encountered more difficulty with the spatial correspondence components of the task (correct pointing to the dots), while the aphasics experienced more difficulty with the verbal components (the production of the correct number-word sequence). The deficit evidenced by the demented patients was less systematic. However, qualitative analyses of patients' behavior suggested an organization that tended to minimize the impact of their cognitive deficits on the object-counting task, and an analysis of their counting indicates that the basic counting principles proposed by Gelman (1982) and Fuson (1988) may be preserved.

Aphasia↗

PubMed1988

Aphasia and personality.

A critical review of the data in the literature and their interpretations is given. There are three main lines of interpretation: --The neuropsychological point of view interprets personality disorders as a reaction to the language deficit; --the anatomical point of view tries to relate personality disorders to the location and extent of brain lesions; --the historical point of view links personality disorders to the pre-morbid personality. All of them seem to have shortcomings and to be based at least in part on inadequate scientific methods including the principle problems of psychologically testing aphasics, of not having pre-morbid personality tests or using tests which are developed outside the field of neuropsychology. We suggest the development of multifactorial approaches which take into account biological, sociological and psycho-individual variables in an interactive way.

Adaptation, Psychological↗

PubMed1988

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.

Adult↗

PubMed1987

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.

Adolescent↗

PubMed1986

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.

Adult↗