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Abstract
Our previous work showed a semantic bias in interpreting ambiguous words in schizophrenia,
with disproportionate misinterpretation of subordinate meanings (toast at a wedding).
We proposed pre-selection in schizophrenia of dominant-meaning networks at points
of lexical ambiguity, thereby misleading thought. This selection bias may be due to
semantic memory hyper-priming causing strong associates to dominate cognition. Alternately,
later verbal memory maintenance failure may cause weaker associates to fade more quickly
than stronger associates from memory due to less initial activation. To further examine
this semantic bias, patients and controls were presented short 4 word long sentences
(The toast was buttered). The second word was a homograph or unambiguous noun. The
last word disambiguated homographs (dominant or subordinate meaning) or was congruent
or incongruent with unambiguous nouns. Previously, we showed increasingly larger N400
from unambiguous associates to dominate associates to subordinate associates to unambiguous
non-associates in controls. Pre-selection of dominant meanings predicts that schizophrenia
patients would show small N400 to dominant associates and as large N400 to subordinate
associates as to incongruous endings. Here, controls again showed graded N400 amplitudes.
Patients with schizophrenia showed small N400 to congruent and dominant endings and
large N400 to subordinate and incongruous endings. These data suggest early pre-selection
of dominant associates in schizophrenia. This effect is unlikely solely due to verbal
memory maintenance failure, as patients were able to detect incongruity, albeit with
a smaller N400 effect, and displayed generally larger N400 to all stimuli. These results
suggest alterations in semantic memory associative networks coupled with verbal working
memory maintenance decay in schizophrenia.
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