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Abstract:
Abstract: We examined whether attentional mechanisms that
appear to operate across modalities are restricted to the
processing of perceptual information. We present data from two
individuals with parietal lobe damage who exhibit tactile
extinction and also show tactile/visual and tactile/auditory
extinction - a marked difficulty in detecting a contralesional
touch when simultaneously presented with a visual or auditory
stimulus. We describe three findings. (1) While neither subject is
impaired in detecting a contralesional tactile stimulus alone, both
exhibit difficulty when a touch is presented simultaneous with
another tactile, visual or auditory stimulus. (2) Tactile
extinction does not occur when the competing visual or auditory
stimulus is either a spoken or written word that subjects must read
or categorize. (3) Tactile extinction does occur with spoken or
written words when subjects are asked merely to report whether a
stimulus was presented. For example, there is pronounced tactile
extinction when a subject is asked to detect the presence of a word
flashed on the screen (simultaneous with a touch) but not when he
is asked to read the same word. These results indicate that the
cross-modal competition underlying tactile extinction is limited to
the context of perceptual monitoring and does not occur in the
course of multi-modal processing more generally. We propose that
there are distinct attentional systems dedicated to perceptual
monitoring vs. meaning (or language) based processing.
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