A structural magnetic resonance imaging studyof Orbitofrontal Cortex in Psychosis

ABSTRACT BACKGROUND: The orbitofrontal cortex (OFC) is the most inferior and ventral region of the prefrontal cortex that lies above the orbits. Through its connections with the amygdala, hyppocampus, thalamus, dorsolateral prefrontal cortex and superior temporal lobe, it is involved in several cognitive processes, such as sensory integration, reward mechanism, decision-making, mood regulation and impulse control. OFC dysfunction is implicated in cognitive, affective and social impairments similar to those present in schizophrenia. Although with some inconsistencies, there is evidence that OFC volumes are reduced in schizophrenia, and that they may be associated with psychopathology and altered cognition. However, it is still not clear whether OFC deficits are present before the onset of the disease or whether they occur with the progression of the illness. OBJECTIVES: The aims of the study were to measure the volumes of the OFC and its subregions, as traced on MRI scans, in a group of schizophrenia patients (SCZ), in a group of First Episode Psychosis patients (FEP), recruited in the context of the Psychosis Incident Cohort Outcome Study (PICOS), and a in group of healthy controls (HC) and to investigate the changes in OFC volumes over time in this cohort. METHODS: socio-demographical and clinical data were initially acquired from 26 SCZ patients, 16 FE patients and 21 HC subjects. The MRI sessions were conducted using a 1.5 T scanner and the images were analyzed using the BRAINS2 software. Subjects were scanned the second time after a mean follow up period of 3 years. The OFC and its medial and lateral subregions were traced and they were segmented for grey and white matter. RESULTS: In the cross sectional comparison, both the white and grey matter of the left lateral OFC was found to be increased in SCZ patients in respect to FEP patients and HC. In the longitudinal comparison the OFC grey matter volume of FEP patients had a greater decrease across time than those of chronic SCZ patients and HC. DISCUSSION: The left lateral OFC seems to be a brain region particularly affected by volume alteration in schizophrenia. The OFC grey matter reduction in FEP patients across time might confirm the assumption that brain volume is more affected by loss in the very first time of the illness.