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This paper investigates mathematical skills in Prader–Willi Syndrome (PWS), a pathological condition because of congenital alterations of chromosome pair 15. The following questions were addressed: (1) Are mathematical skills in PWS relatively more impaired with respect to other cognitive functions (as has been repeatedly but anecdotally reported)?; and (2) What is the nature of the mathematical impairment?The first study employed the Wechsler Adult Intelligence Scale (WAIS) and an extensive battery of cognitive tasks for which norms are known. Both batteries include a mathematical section. The second study used a theoretically motivated series of mathematical tasks specifically designed to individually assess the different cognitive components underlying mathematical skills.Mathematical skills were found to be the most impaired cognitive abilities together with short-term memory capacity. No specific mathematical domain was seen to be unaffected in PWS participants. The clearest deficits observed concern‘syntactic’ processes in number transcoding, multiplication, number facts retrieval and calculation procedures.Failure of mathematical skills is the most distinctive feature in the cognitive profile of PWS. However, to determine whether this is indeed a specific pattern of performance related to PWS, results must be compared with those obtained with patients manifesting other genetic disorders. [ABSTRACT FROM AUTHOR]

Despite the high incidence of numerical deficits in neurological patients, little attention has been paid to the development of diagnostic tools. In fact, most of the published reports on acquired numerical disorders. whether single case or group studies, do not refer to standardised measures of performance providing little, if any, control data specifically collected for the examination. In this study we present data of 282 healthy controls of different age groups and educational levels in a new battery of Number Processing and Calculation (NPC). The NPC battery includes a total of 35 tasks, assessing different counting abilities, various aspects of number comprehension (such as panty and magnitude judgements), numerical transcoding, calcuIation, arithmetic reasoning and conceptual knowledge. Special attention is paid to the assessment of different calculation abilities, including simple fact retrieval, rule based processing, mental calculation and Written calculation in all four operations. Moreover, text problem solving is assessed as well as the understanding of arithmetic principles. Thus, the NPC battery differs from the EC 301battey proposed by Deloche et al., 1994 (Dellatolas, Deloche, Basso, & Claros-Salinas, 2001) and allows a more fine grained diagnosis which is relevant for planning targeted interventions. The battery is easy to administer and does not require special materials or equipment. [ABSTRACT FROM AUTHOR]

Background : Zero has a special role in calculation: indeed it is not obvious which representation may be invoked in multiplication or division by zero. In particular, zero as an operand, unlike any other operand, makes any quantity disappear. Aims : The study is intended to shed light on the mechanisms mediating the manipulation of zero. Methods & Procedures : Three neuropsychological patients, AF, FV, and FS, are described, whose specific pattern of preserved/impaired performance with single- and multi-digit multiplication shows selective problems with the use of zero ( N x 0 and 0 x N ). Outcome & Results : AF's performance in single and multi-digit multiplication showed a clear dissociation between spared fact-based problems and impaired 0 rule-based problems. FV was totally unable, in multi-digit multiplication, to apply adequately the 0 rule that he could master in simple calculation. Finally, FS showed, within the rule-based problems, a clear-cut dissociation between a preserved performance on N x 0 problems and an impaired performance on 0 x N problems, a difficulty that almost disappeared in multi-digit multiplications. Conclusions : Overall the reported dissociations indicate that a full grasp of the concept of zero may not be used in routine calculation, and that processing of zero rather appears to rely on a collection of independent, shallow representations. [ABSTRACT FROM AUTHOR]