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Abstract:
Abstract: In a recent masked-priming experiment, (Dehaene,
Naccache et al. 1998), subjects were exposed to a masked prime
number and were then presented with a visible target number (both
numbers in Arabic or Verbal notation) which they had to compare to
number 5. Chronometric and brain-imaging data (ERP/fMRI) revealed
that primes were processed up to a motor level, suggesting that a
whole visuo-semantico-motor stream could occur unconsciously. In
this previous work however, we weren't able to directly image the
semantic stage, leaving the door open to alternative non-semantic
interpretations (Neumann, Klotz 1994).Here, we report new analyses
of these experiments which directly demonstrate an unconscious
semantic activation. We found that RTs were significantly faster in
trials repeating the same numerical quantity, than in trials in
which different quantities were presented as primes and targets. At
the cerebral level, repetition priming often results in reduced
activation in task-related areas, a phenomenon called repetition
suppression (RS) (Wiggs, Martin 1998). Here, the only brain regions
showing RS were located in the left and right intraparietal sulci,
brain areas thought to encode the quantity meaning of numbers. In
those regions, RS was unaffected by notation change. These results
directly demonstrate an unconscious semantic priming effect in an
area known to be involved in number semantics.
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