Enhanced left frontal involvement during novel metaphor comprehension in schizophrenia

The neural basis involved in novel metaphor comprehension in schizophrenia is relatively unknown. Fourteen people with schizophrenia and fourteen controls were scanned while they silently read novel metaphors, conventional metaphors, literal expressions, and meaningless word-pairs. People with schizophrenia showed reduced comprehension of both novel and conventional metaphors. Furthermore, while controls showed enhanced brain activation in right inferior frontal gyrus (IFG) for novel metaphors versus meaningless word-pairs, people with schizophrenia showed an over-activation of left IFG and middle frontal gyrus (MFG). Direct comparison between the groups revealed greater activation in left precuneus for both novel metaphors and literal expressions vs. baseline for individuals with schizophrenia. Direct comparison for novel metaphors vs. literal expressions also revealed increased activation for individuals with schizophrenia in left MFG. These results suggest that the inefficient processing of novel metaphors in schizophrenia involves compensatory recruitment of additional brain regions that include the left MFG and left precuneus.