Article

Several psychophysical investigations, expanding the classical introspective
observations by Galton, have suggested that the mental representation of numbers
takes the form of a number line along which magnitude is positioned in ascending
order according to reading habits, i.e. from left to right in Western cultures.
In keeping with the evidence, pathological rightward deviations in the bisection
of number intervals due to right brain damage are generally interpreted as
originating from a purely spatial-attentional deficit in the processing of the
left side of number intervals. However, consistent double dissociations between
defective processing of the left side of physical and mental number space have
called into question the universality of this interpretation. Recent evidence
suggests a link between rightward deviations in number space and defective memory
for both spatial and non-spatial sequences of items. Here we describe the case of
a left brain-damaged patient exhibiting right-sided neglect for extrapersonal and
representational space, and left-sided neglect on the mental number line.
Accurate neuropsychological examination revealed that the apparent left-sided
neglect in the bisection of number intervals had a purely non-spatial origin and
was based on mnemonic difficulties for the initial items of verbal sequences
presented visually at an identical spatial position. These findings show that
effective position-based verbal working memory might be crucial for numerical
tasks that are usually considered to involve purely spatial representation of
numerical magnitudes.
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Langue : ANGLAIS