SBNeC 2010
Resumo:F.164


Poster (Painel)
F.164THE ACUITY OF NUMERICAL REPRESENTATION IS IMPAIRED IN CHILDREN WITH MATHEMATICAL LEARNING DIFFICULTIES
Autores:Pedro Pinheiro Chagas (UFMG - Universidade Federal de Minas Gerais) ; Fernanda de Oliveira Ferreira (UFMG - Universidade Federal de Minas Gerais) ; Guilherme Wood (UNIVERSITÄT SALZBURG - Paris-Lodron Universität Salzburg) ; Jan Lohnemann (RWTH AACHEN - Rheinisch-Westfaelische Technische Hochschule Aachen) ; Helga Krinzinger (RWTH AACHEN - Rheinisch-Westfaelische Technische Hochschule Aachen) ; Klaus Willmes (RWTH AACHEN - Rheinisch-Westfaelische Technische Hochschule Aachen) ; Vitor Geraldi Haase (UFMG - Universidade Federal de Minas Gerais)

Resumo

INTRODUCTION: Developmental dyscalculia (DD) is a condition of presumed genetic origin, associated with persistent problems in learning mathematics. Several studies support the hypothesis that the core deficit underlying DD is an impairment in the analogical representation of magnitudes (ARM). According to the Triple-Code Model, numbers are represented internally in three different ways: analogic, symbolic and verbal. While the symbolic and verbal representations are cultural artifacts and depend on formal education, the ARM is considered being a learning instinct and thus necessary for the development of the other representations and also for arithmetic abilities. Recent dada strongly supports that the ARM is well described by Weber-Fechner law. METHODS: Participants were recruited from schools in BH and Mariana (MG). A total of 43 children [mean age = 10.07(2.08)] with specific mathematical learning difficulties (MLD) (defined by the performance in an arithmetic test below the 25th percentile, together with normal IQ as well as normal writing and reading abilities) and 64 controls [mean age = 9.66(1.51)] participated on the study. The psychophysical experiment was a dot comparison task in which children had to respond (fast and without counting) for the larger of the two sets of dots that appeared on a computer screen. The reference set of 32 dots (nref) was fixed and the other sets contained 20, 23, 26, 29, 35, 38, 41, 44 dots (n) and appeared 8 times each, totalizing 64 trials. To estimate the acuity of the ARM, we used a psychophysical model that assumes that numbers are represented by noisy patterns of distributions of activation on an internal continuum or mental number line, in which the tuning curves of the population of neurons dedicated are Gaussian functions of the logarithm of numerosity. The probability of respond larger then was modeled by the equation: P_maior (n,n_ref )= 1/2*(1+erf((Log(n/nref)/(√2*w))) where w is the only free parameter and correspond to the internal Weber fraction, or the degree of precision of the internal representation. RESULTS: Both groups showed an increase in the RT as a function of the distance between (nref) and (n) (distance effect) tested with a series of one-way repeated measures ANOVAs (p < 0.0001). ER did not differ significantly in the group comparison (p > 0.47), but MDL shower higher RT (p > 0.01), using T-Student tests. Collapsing across subjects by each group returned a Weber fraction of (w = 0.23) for the control and (w = 0.31) for the MLD group, showing that MLD had a higher threshold in discriminating nonsymbolic numerosities. In both groups, data were well described by the psychophysical function (R2 > 0.96). CONCLUSIONS: Children with MLD have an impairment in the ARM that could explain at least in part their persistent difficulties in learning mathematics. The w values found are similar to the ones reported recently in the literature (Cognition. 116(1):33, 2010). This result has implications to the development of more powerful pedagogical and neuropsychological strategies for rehabilitation of children with DD.


Palavras-chave:  numerical cognition, mathematics learning difficulties, neuropsychology