Biomedical subjects

M Delazer

Publications and source records attributed to M Delazer.

11 recordsLinked to original sources

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↗

PubMed1999

The breakdown of calculation procedures in Alzheimer's disease.

The study investigates calculation abilities in 12 patients with probable Alzheimer's disease (AD) and compares them to calculation abilities of healthy control subjects (NC) and patients with focal left hemisphere lesions (LHL). AD patients scored significantly lower than NC in all calculation tasks and lower than LHL patients in the execution of complex written calculation, but not in the retrieval of arithmetic facts. In the AD group a subject-by-subject error analysis on the complex written calculation showed a low consistency and a high variability of error types. It is suggested that AD patients' difficulties in complex calculation arise from a monitoring deficit and not from incomplete or distorted calculation algorithms. Overall, deficits in monitoring calculation procedures may be an early and common symptom of AD.

Alzheimer Disease↗

PubMed1999

Arithmetic reasoning and implicit memory: a neuropsychological study on amnesia.

The present study investigates implicit memory and arithmetic reasoning in a group of severely amnesic patients. Priming effects have been observed in the retrieval of arithmetic facts in amnesic patients (Delazer, Ewen and Benke, 1997), but no studies have so far investigated the effect of previous experience in a pure reasoning task. Findings indicate that answering to a first numerical series (e.g, 1 3 5 7, answer "9") facilitates answering to a second numerical series (2 4 6 8, answer "10") including different numbers but sharing the same underlying algorithm (+ 2). Within the model of Langdon and Warrington (1997) priming effects are attributed to the stage of abstract formula generation.

Adult↗

PubMed1999

Numerical skills and aphasia.

The aim of this study was to investigate numerical difficulties in 50 patients with left hemispheric lesions. Aphasic patients were grouped according to their type of aphasia diagnosed by the Aachener Aphasia Test. The overall error rate in various transcoding and calculation tasks was clearly correlated with the severity of the language deficit, global aphasics being the most impaired patients. Broca's and Wernicke's aphasics scored similarly at the quantitative level, and amnesic aphasics were less impaired. Interestingly, qualitative analysis of the errors indicated that each group presented with specific difficulties, partially reflecting the nature of the language problems. In simple calculation, multiplication was found to be the most impaired operation, in particular in Broca's aphasics. This result supports the hypothesis that the retrieval of multiplication facts is preferentially mediated by verbal processing. Calculation procedures were mainly impaired in Wernicke's and global aphasics.

Adult↗

PubMed1998

The processing of compound words: a study in aphasia.

The naming difficulties of an aphasic patient (MB) are almost exclusively confined to compound words. The paraphasias in response to compounds always reflect the compound structure of the targets. Frequent semantically adequate substitution errors suggest the separate processing of single components at the lemma level. MB's specific difficulties probably arise when two lemmas are defined by one lexical entry, as we suggest for compounds. The compound structure, as well as the positions of the single lemmas within the compound, would be specified before lemmas are accessed. The lack of a positional effect in substitution errors suggests a parallel activation of the two components.

Adult↗

PubMed1998

Writing arabic numerals in an agraphic patient.

We report on the writing of Arabic numerals in a patient whose alphabetical script was restricted to graphemic jargon (Schonauer & Denes, 1994). The analysis of writing errors in Arabic script over three testing sessions (4, 10, and 13 months after stroke) confirmed the separate processing of syntactic and lexical information in number production proposed by current models. The changing error pattern over time reflected some difficulties observed in developmental studies on the acquisition of Arabic numeral writing. Errors were mostly of the syntactic type and (at a certain stage) were based on the verbal form of the numerals. As reported in neuropsychological (Noel & Seron, 1995) and developmental (Power & Dal Martello, 1990; Seron & Fayol, 1994) studies, sum relations were more difficult to transcode than product relations within complex numerals.

Agraphia↗

PubMed1997

Arithmetic facts without meaning.

The paper presents a single-case study of patient J.G. showing severe calculation problems (and also agraphia, finger agnosia, right-left disorientation and apraxia) after the surgery of a left parietal tumor. Although the patient completely lost conceptual knowledge of arithmetic, she preserved part of memorised fact knowledge (multiplications and some additions and subtractions). The study indicates that arithmetic facts can be represented at a superficial level without understanding of the operation performed. The study completes a valid double dissociation between two types of knowledge involved in calculation (memorised facts and conceptual knowledge).

Brain Neoplasms↗

PubMed1997

Priming arithmetic facts in amnesic patients.

In this study, amnesic patients showed significant repetition priming effects in arithmetic fact retrieval tasks. The results indicate that repetition priming effects in arithmetic depend not on explicit recognition, but on the activation of specific long-term representations of arithmetic facts. Processing dissociations between easy and difficult items suggest that the priming effects results from the stage of fact retrieval and not from peripheral activation. This claim is also supported by encoding and naming tasks, which showed only slight priming effects as compared to the priming found in calculation tasks. Significant priming was found for identical (5 x 6 and 5 x 6) and complement problems (5 x 6 and 6 x 5), the latter showing a smaller magnitude of priming.

Adult↗

PubMed1996

Subtraction bugs in an acalculic patient.

We report a patient, MT, who presented a specific, though not isolated, deficit in written calculation. Despite a preserved knowledge of simple arithmetic - single-digit addition and subtraction - he failed systematically in multi-digit subtraction. The nature of errors was consistent across problems and reflected the application of a disturbed underlying algorithm. Moreover, the pattern of error observed mimies a very common finding in developmental studies on arithmetical procedure acquisition (Fuson, 1990, 1992, Young and O'Shea, 1981; VanLehn, 1986, 1990). The data suggest that, within calculation skills, syntax may exist as a system of stable, but inappropriate, rules which are independent of any underlying conceptual knowledge.

Aphasia↗

PubMed1996

The representation of arithmetical facts: evidence from two rehabilitation studies.

We report the improvement following rehabilitation of two patients with a selective deficit on multiplication facts. The remediation experiments were conducted in specific designs to test a series of hypotheses about both the process of reacquisition and organisation of arithmetical facts in memory. The results show a significant and stable recovery and the pattern of reacquisition reflects the different strategy used by the patients to relearn the multiplication facts. Quantitative and qualitative changes in error patterns in the course of remediation reveal the underlying (re)organization of the memory network representing multiplication facts.

Adult↗

PubMedDate not supplied

Priming arithmetic reasoning in an amnesic patient.

The present study elucidates the role of implicit memory in problem solving by evaluating priming effects in a severely amnesic patient. An arithmetic series completion task was adopted to investigate the effects of lags, of items difficulty, as well as the influence of different distractor tasks on priming numerical reasoning. The results indicated that the priming effect was maximized in difficult trials and disappeared after long lags. On the other hand, the facilitation effect was not modulated by the nature of the distractor tasks. Critically, the experimental design controlled for peripheral facilitation of visual input and verbal output processes and a recognition task indicated that the effect may not be attributed to explicit memory. Thus, the facilitation must be located to a more central stage, possibly at the stage in which the abstract formula of the underlying algorithm are generated (Langdon & Warrington, 1997).

Adult↗