Semantic processing disturbance in patients with schizophrenia: a meta-analysis of the N400 component.
BACKGROUND
Theoretically semantic processing can be separated into early automatic semantic activation and late contextualization. Semantic processing deficits have been suggested in patients with schizophrenia, however it is not clear which stage of semantic processing is impaired. We attempted to clarify this issue by conducting a meta-analysis of the N400 component.


METHODS
Twenty-one studies met the inclusion criteria for the meta-analysis procedure. The Comprehensive Meta-Analysis software package was used to compute pooled effect sizes and homogeneity.


RESULTS
Studies favoring early automatic activation produced a significant effect size of -0.41 for the N400 effect. Studies favoring late contextualization generated a significant effect size of -0.36 for the N400 effect, a significant effect size of -0.52 for N400 for congruent/related target words, and a significant effect size of 0.82 for the N400 peak latency.


CONCLUSIONS
These findings suggest the automatic spreading activation process in patients with schizophrenia is very similar for closely related concepts and weakly or remotely related concepts, while late contextualization may be associated with impairments in processing semantically congruent context accompanied by slow processing speed.
Neuropsychology and Applied Cognitive Neuroscience Laboratory, Institute of Psychology, Chinese Academy of Sciences, Beijing, China.
Kui
K
Wang
Eric F C
EF
Cheung
Qi-yong
QY
Gong
Raymond C K
RC
Chan
D014150:Antipsychotic Agents / Q000627:therapeutic use; D016022:Case-Control Studies; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D011930:Reaction Time / Q000502:physiology; D012044:Regression Analysis; D012559:Schizophrenia / Q000188:drug therapy / Q000503:physiopathology*; D012660:Semantics
D014150:Antipsychotic Agents