Investigation of the Processing of Noun and Verb Words with fMRI in Patients with Schizophrenia.

Abstract

Action naming is reported to be more damaged in patients with schizophrenia than object naming. Aim of this study is to understand the cortical mechanism underlying the negative symptoms seen in patients with schizophrenia such as inactivity, restricted behavioral repertoire, by using functional MRI (fMRI) to determine whether the action origin words have a different representation in the brain regions of patients with schizophrenia and healthy individuals. Our hypothesis is that restriction in the repertoire of movement and behavior and the failure of words of "action" than words of "object" are interrelated through the same cortical mechanisms. If this hypothesis is correct, the reason for not taking action in patients with schizophrenia may be improper definition of the action (verb). fMRI study was conducted with 12 patients with schizophrenia and 12 healthy individuals. fMRI recording was performed after applying positive and negative syndrome (PANSS) scale, Calgary depression scale, hand preference scale to the participants. During the sessions, "lexical decision task" is applied by showing a total of 240 words (120 words - 60 verbs (words of action) and 60 nouns (words of object) - and 120 non-words) to the subjects. In fMRI findings, in the group main effect, which can also be expressed as the difference of the noun and verb words in the group of schizophrenia from the noun and verb words in the healthy control group, the activation of the anterior prefrontal cortex is found to be lower in patients with schizophrenia than in healthy individuals. When the brain areas which show the difference in verb words in schizophrenia group from both noun words in schizophrenia group and noun and verb words in healthy individuals are examined, inferior frontal gyrus pars triangularis (BA45) showed more activation in patients with schizophrenia than healthy individuals, but again for the same task, inferior frontal gyrus pars opercularis (BA44) and left primary sensory area showed less activation in patients with schizophrenia than healthy individuals. There is no difference between patients with schizophrenia and healthy volunteers in terms of correctly identified words and reaction time. Considering the lack of difference between the groups in terms of number of correctly identified words and reaction time, and BA 44's role in recognition and imitation of action and being a part of the mirror neuron system, the significant inverse correlation between PANSS negative score and BA40 can be seen as an effort to compensate for BA44 inadequate activity through BA40.