Edward W Wlotko | PubMed Health

PubMed2006

Multiple effects of sentential constraint on word processing.

Behavioral and electrophysiological studies have uncovered different patterns of constraint effects on the processing of words in sentences. Whereas response time measures have indicated a reduced scope of facilitation from strongly constraining contexts, event-related brain potential (ERP) measures have instead revealed enhanced facilitation for semantically related endings in such sentences. Given this disparity, and the concomitant possibility of functionally separable stages of context effects, the current study jointly examined expectancy (cloze probability) and constraint effects on the ERP response to words. Expected and unexpected (but plausible) words completed strongly and weakly constraining sentences; unexpected items were matched for contextual fit across the two levels of constraint and were semantically unrelated to the most expected endings. N400 amplitudes were graded by expectancy but unaffected by constraint and seemed to index the benefit of contextual information. However, a later effect, in the form of increased frontal positivity from 500 to 900 ms post-stimulus-onset, indicated a possible cost associated with the processing of unexpected words in strongly constraining contexts.

Adult↗

PubMed2005

Word learning and individual differences in word learning reflected in event-related potentials.

Adults learned the meanings of rare words (e.g., gloaming) and then made meaning judgments on pairs of words. The 1st word was a trained rare word, an untrained rare word, or an untrained familiar word. Event-related potentials distinguished trained rare words from both untrained rare and familiar words, first at 140 ms and again at 400-600 ms after onset of the 1st word. These results may point to an episodic memory effect. The 2nd word produced an N400 that distinguished trained and familiar word pairs that were related in meaning from unrelated word pairs. Skilled comprehenders learned more words than less skilled comprehenders and showed a stronger episodic memory effect at 400-600 ms on the 1st word and a stronger N400 effect on the 2nd word. These results suggest that superior word learning among skilled comprehenders may arise from a stronger episodic trace that includes orthographic and meaning information and illustrate, how an episodic theory of word identification can explain reading skill.

Evoked Potentials↗