Resting-state brainwaves altered in schizophrenia

By Eleanor McDermid, Senior medwireNews Reporter

Patients with schizophrenia have increased resting-state gamma-band connectivity in a distinct region of the brain, and the increases correlate with clinical symptoms, research shows.

This is contrary to studies of task-based brain activity, in which schizophrenia patients had reduced connectivity, “suggesting that resting-state studies might reveal new aspects in the pathophysiology of schizophrenia”, say lead study author Christina Andreou (University Medical Center Hamburg-Eppendorf, Germany) and colleagues.

The team recorded resting-state brain activity, using electroencephalography (with eyes closed), in 22 patients with first-episode schizophrenia, most of whom were taking antipsychotic medication.

“The increase of gamma-band connectivity was not unspecific, but rather involved a distinct and strongly lateralized network”, Andreou et al write in Schizophrenia Bulletin.

Relative to 22 mentally healthy age- and gender-matched controls, the patients had increased gamma-band connectivity across a network of 82 connections between 33 regions. Most of the 33 regions were in the left hemisphere, with just nine in the right.

The regions accounting for most of the connections included the left angular gyrus, with 15 connections; the left rolandic operculum, with 12; the left medial orbitofrontal cortex, with 11 connections; and the left inferior temporal gyrus, with nine. The pars triangularis of the inferior frontal gyrus, the orbital part of the superior frontal gyrus and postcentral and precentral gyrus – all on the left side – had eight connections each. These areas accounted for about half of the total number of connections.

The network included areas involved in language and memory, which have been linked to auditory hallucinations and disorganisation symptoms, especially speech, in patients with schizophrenia. This suggests a “link between aberrant gamma-band connectivity at rest and core clinical symptoms of schizophrenia”, say the researchers.

However, this putative link is “not a straightforward one”, they report. Although positive and disorganisation symptoms were significantly associated with gamma-band connectivity, connectivity was lower in patients with more severe symptoms, despite being increased in the patient group overall.

But the researchers note that gamma-band connectivity has been linked to suppression of inappropriate memory formation, suggesting that increased connectivity “might represent a successful adaptation” in the brains of schizophrenia patients.

Alternatively, it could be a primary abnormality, reflecting “the formation of aberrant associations among the involved brain areas”, they suggest. These alternative explanations would result in divergent changes in connectivity during clinical recovery, which longitudinal studies could address.

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