Article

There is evidence that humans represent numbers in the form of a mental number
line (MNL). Here we show that the MNL modulates the representation of visual and
haptic space both in healthy individuals and right-brain-damaged patients, both
with and without left unilateral spatial neglect (USN). Participants were asked
to estimate the midpoint of visually or haptically explored rods while listening
to task-irrelevant stimuli: a small digit ("2"), a large digit ("8"), or a
non-numerical auditory stimulus ("blah"). In a control silent condition, the
bisection error of USN patients was biased rightwards (namely, the marker of USN)
only in the visual modality. Regardless of the direction of the bisection error
committed in silent trials, listening to the small digit shifted the perceived
midline leftwards, and listening to the large digit shifted the perceived midline
rightwards, compared to a control condition in which a neutral syllable ("blah")
was presented. The shift induced by listening to numbers occurred independently
of the modality of response (i.e., both in vision and haptics), and in every
group of participants. Interestingly, the effect of auditory numbers processing
on space estimation was overall larger for haptically than for visually explored
space in all participants. In conclusion, the present data show that listening to
irrelevant numbers affects space perception also in patients with left USN,
indicating that the spatial representation and attention processes disrupted by
USN are not involved in these numerical magnitude-spatial effects.
CI - Copyright A(c) 2012 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS