Increased cortical thinning in schizophrenia patients

By Mark Cowen

Patients with schizophrenia show greater cortical thinning in selected subregions of both the frontal and temporal lobes over a 2-year period than mentally healthy individuals, study results show.

However, these structural changes were not associated with neuropsychologic measures or clinical symptoms, the researchers note.

Derin Cobia (Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA) and colleagues say that the "maintenance of neuropsychological performance and clinical stability in the face of changing neuroanatomical structure suggests the involvement of alternative compensatory mechanisms."

The team studied 20 patients with schizophrenia, aged 17‑65 years, and 20 age- and gender-matched mentally healthy individuals (controls) without a history of substance abuse (moderate or severe) or dependence (any type) during the past 6 months.

All of the participants underwent magnetic resonance imaging at baseline and after 2 years to assess changes in cortical thickness.

Patients with schizophrenia were also assessed for cognitive functioning at both time points using a neuropsychologic test battery, and for clinical symptoms using the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms.

The researchers found that schizophrenia patients showed significantly greater cortical thinning than controls over the study period, particularly in the middle frontal gyrus, the superior temporal gyrus, and the middle temporal gyrus.

Furthermore, these changes in thickness were significantly associated with longitudinal cortical volume loss, but were unrelated to changes in surface area.

The team explains that both frontal and temporal lobes have previously been implicated in a number of cognitive processes that are affected in schizophrenia patients, including attention, language, working memory, and various aspects of executive functioning, as well as in the expression of different clinical symptoms.

However, in the current study, neuropsychologic performance and psychopathology severity remained stable in the schizophrenia patients over the 2-year period, despite progressive loss in cortical structure.

"Overall it appears that ongoing abnormalities in the cerebral cortex continue after initial onset of schizophrenia, particularly the lateral aspects of frontal and temporal regions, and do not relate to neuropsychological or clinical measures over time," Cobia and team conclude.

They suggest that "the recruitment of additional structures and circuits may… occur to sustain performance, while the structural integrity of primary regions declines."

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