New insights into brain disruptions in schizophrenia

People with schizophrenia can find it difficult to perceive and think about the world in the same way as those without the disorder; symptoms are wide-ranging, and include hallucinations, delusions, and/or disorganised speech. And, while much research has tried to get to the bottom of what causes these symptoms, the exact changes that lead to the development of schizophrenia are still being explored. 

Some studies have found differences in the brains of people with schizophrenia in what's known as the 'primary sensorimotor-to-association axis'. In those without schizophrenia, these connections allow information from regions of the cortex that separately handle visual signals, sounds, touch, and body movements to be properly integrated. Researchers have suggested that disruptions to this aspect of brain organisation might help to explain some of the symptoms of schizophrenia, including delusions. However, a new paper in Biological Psychiatry: CNNI suggests that disruption to another set of connections might also be involved. 

In their study, Alexander Holmes at Monash University, Australia, and colleagues analysed two sets of fMRI scans. One set consisted of brain scans from 114 patients with early psychosis and 48 healthy control participants. The other set consisted of scans of 50 patients with established schizophrenia plus 121 controls. 

After analysis, the team didn't find evidence of any abnormalities in this primary sensorimotor-to-association axis in the brains of people with schizophrenia — a finding that took them by surprise. This might be explained by differences in the severity of schizophrenia symptoms among patients in their group, compared with those in earlier studies, they suggest. 

However, they did find that, compared with healthy participants and those in the early stages of psychosis, people with long-standing schizophrenia showed a key difference in what's known as the 'secondary visual-to-sensorimotor axis'. 

In a healthy person, this enables the brain to use visual signals about what the body is doing to guide precise physical movements. The fact that this disruption was found only for those diagnosed with schizophrenia, but not for those with early psychosis, suggests that it emerges as the illness progresses. The researchers also found that these atypicalities were linked to higher clinical scores on specific aspects of schizophrenia, including delusions. 

More work is certainly needed to better understand why these changes develop, and what they mean for the perceptions and thoughts of people with schizophrenia. But the team believes that, in future, targeting these changes may open up a new route to treatments for this disorder, which remains notoriously difficult to treat. 

Read the paper in full: https://doi.org/10.1016/j.bpsc.2023.08.008