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Abstract:
GOALS: To determine the cortical and subcortical brain
regions activated as subjects evaluated multi-modal feature p`airs
to see if they "bind" or combine to elicit an object. METHODS:
fMRI, in 6 normal adults viewing visually presented stimulus pairs:
one a word, and the other a line drawing (e.g., picture of a light
bulb and the word "shade", to activate the internal representation
"lamp"). One-half of these stimulus pairs did bind to elicit an
object; the other half did not. A control task required evaluating
stimulus pairs consisting of one of the elicited objects (from the
first experiment) and one of the features, to decide if they were
semantically related. RESULTS: For picture/words that bind to
elicit an object, signal change was detected in the ventral
temporo-occipital regions, SMA, caudate nuclei, and the dorsal
thalami bilaterally as well as the left primary somatomotor cortex.
For the control task, no signal changes were seen in the
somatomotor region and minimal signal change in the thalamus.
CONCLUSION: The thalamus is essential in binding, and activates
when the two stimuli presented are from different visual modalities
(words and pictures). The observed somatomotor signal changes
suggest that multimodal semantic binding can result in activation
of regions subserving domains that encode characteristics not
explicitly presented in the input stimuli (e.g., somatomotor
properties of visually presented stimuli).
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