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Abstract:
This pilot study measured performance on a lateralized
lexical decision task in adults with ADHD (n=13) and controls
(n=13). Bilateral presentations were used to maximize independent
hemispheric processing. This procedure first addresses hemispheric
differences in word recognition. Subjects must decide whether the
target stimulus is a word or nonword in either the left or right
visual field. Next, the paradigm is used to ask how much
interhemispheric interaction can occur. Specifically, we looked for
lexicality priming between targets and distracters as a form of
implicit cognitive interhemispheric transfer. Targets and
distractors consist of English words and orthographically regular
nonwords. In control subjects this task showed a robust right
visual field (RVF) advantage, signaling left hemisphere (LH)
superiority. A lexicality priming effect was also found in controls
such that words and nonwords were processed more accurately when
paired with like distracters (i.e.. word with word and nonword with
nonword) indicating the presence of interhemipsheric transfer. ADHD
subjects demonstrated equal performance to controls in the left
hemisphere but showed performance deficits in the right hemisphere,
specific for word decisions and especially for low frequency words.
ADHD subjects also showed no lexicality priming effect indicating a
loss of normal interhemispheric transfer. These results suggest a
right hemisphere deficit in word recognition and impaired
interhemispheric communication in adults with ADHD.
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