[CCoE Notice] PhD Dissertation Defense - Wu

[Khator, Suresh]

PhD Dissertation Announcement

Modulation of the N400 by semantic and knowledge violations during sleep
Weiwei Wu

Friday, November 18, 2011, 10:30 am, E321

Committee Chair: Bhavin R. Sheth

Though sentences we read or hear have meaning, it does not necessarily mean that they are true. So far some knowledge has been accumulated about the critical brain response and its relative time course to establish the meaning and truth of linguistic expressions during wake. Little is known about linguistic processing in the brain during sleep. The present study focuses on the brain's ability to detect context anomalies during sleep, including semantic violation and knowledge violation.

Seven native English speakers were recruited from the University of Houston and participated in the experiment. Sentence triplets were presented orally to subjects during NERM sleep. Nineteen channels of EEG signals were recorded from subjects and ERPs were obtained following the onset of stimuli. The result shows an N400 in response to both knowledge and semantic violations, indicating that the brain can retrieve world knowledge and validate the truth value of the incoming statements during NREM sleep. The brain network was evaluated as a whole and quantified through graph theoretic techniques and the result suggests that the network structure is not influenced by linguistic anomalies of the sentences.  The present study provides further evidence of sensory information processing during NREM sleep and examines the limit of the sleeping brain's ability to process ongoing information with a high level of cognitive content



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