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Abstract:
Many studies indicate that hemineglect patients process some
of the stimuli that they fail to acknowledge. However, the
cognitive level of such treatments remain controversial. Here we
show that neglected numerals (in arabic or verbal notations) are
processed for quantity. We engaged patients in a number comparison
task. Patients had to categorize a foveally presented target as
smaller or larger than a fixed reference, and we measured their
reaction times. Unbeknownst to them, some targets were preceded by
a brief numerical prime in their extinguished field. We show that
the numerical magnitude of the prime had a significant effect on
reaction times. Patients were faster when the target and the prime
fell on the same side of the reference than in the opposite case.
Furthermore, there was no interaction between this quantity priming
effect and the notations of the stimuli. This supports the idea
that the prime had indeed been semantically processed. In a series
of additional tests we show that patients had no awareness of the
prime, and were unable to report its presence. We thus demonstrate
a sharp distinction between the semantic processing of stimuli and
their availability for conscious report.
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