Characteristics of Brain Activation during Semantic Processing in Schizophrenia

Kim, Jae Jin; Seok, Jeong Ho; Kwon, Jun Soo; Lee, Dong Soo; Lee, Myung Chul

Abstract

OBJECTIVES
Investigators reported that schizophrenies have deficits in semantic processing. However, it is unclear which brain area is associated with semantic processing dysfunction in schizophrenia. This study was designed to explore the activated brain areas associated with semantic processing in schizophrenic patients compared with controls.
METHODS
Twelve patients with schizophrenia and twelve healthy controls were studied under two different visual task conditions. Subjects were required to respond to a specific semantic category in a specific figure among word-figure stimuli during the first task, and to respond to a specific figure among figure-only stimuli during the second task. Brain activation during each task was measured using [15O]H2O PET. Activated brain areas were analyzed by subtraction methods using SPM99 in each group.
RESULTS
In healthy control group, the left superior temporal gyrus, left premotor area and left cerebellum were activated during semantic processing along with activation of the left inferior temporal gyrus which is a main semantic processing area. But activation of the main semantic processing area in patient group was more posteriorly than controls. In contrast with control group, lateralized activation pattern to the left and cerebellar activation were not observed in patient group.
CONCLUSION
Our results suggest that patient's deficit in elaboration due to early semantic processing, decreased efficacy due to the loss of lateralization and decreased modulatory ability due to the loss of cerebellar activation may be involved in the characteristics of brain activation patterns in schizophrenia. This distorted semantic processing in schizophrenia may play a role as one of the basic determinants in thought disorder.