Schizophrenia is a complex neurodevelopmental condition influencing a person’s thoughts, feelings, and actions. Its origins are multifaceted, involving a combination of genetic and environmental factors. Over decades of research, scientists have used brain imaging to identify consistent structural differences in the brains of individuals with schizophrenia compared to those without the condition.
Enlarged Ventricles in the Brain
One of the most consistently reported findings in neuroimaging studies of schizophrenia is the enlargement of the lateral ventricles. Ventricles are a network of interconnected, fluid-filled cavities deep within the brain. Up to 80% of individuals with schizophrenia show some degree of ventricular enlargement.
The term “enlargement” can be misleading, as it does not mean the ventricles themselves are actively growing. Instead, the increased ventricular volume is a consequence of a reduction in the volume of surrounding brain tissue, specifically grey matter. As this adjacent tissue shrinks or is lost, the ventricles passively expand to fill the available space.
The enlargement is not always uniform, with research pointing to specific parts of the ventricular system, like the temporal horn, being more affected. This suggests the tissue loss driving the expansion is concentrated in specific brain regions. This process is a marker of focal shrinkage in areas linked to the disorder’s pathology.
Brain Regions with Reduced Volume
Neuroimaging studies have pinpointed several areas where grey matter reduction is most prominent. These changes are believed to begin before the onset of clinical symptoms and can continue as the disorder progresses.
Among the most affected areas are the temporal lobes. Within these lobes, structures such as the hippocampus and the amygdala show volume reduction. The hippocampus is involved in memory formation, while the amygdala is central to processing emotions. The superior temporal cortex, also part of the temporal lobe, is another area of shrinkage contributing to ventricular enlargement.
Reductions are also observed in the frontal lobes. Specifically, the prefrontal cortex, which governs executive functions like planning, decision-making, and social behavior, is smaller in volume.
The parietal lobes also exhibit grey matter loss, as they are hubs for integrating sensory information. The thalamus, a structure located deep within the brain adjacent to the ventricles, is another area where shrinkage contributes to the observed ventricular enlargement.
Linking Brain Structure to Schizophrenia Symptoms
These structural alterations are directly linked to the clinical symptoms of schizophrenia, as the reduction of grey matter in specific regions disrupts their normal functions.
Reduced volume in the temporal lobes, for instance, is associated with recognized symptoms. Alterations in the auditory cortex are thought to contribute to auditory hallucinations. Similarly, shrinkage of the hippocampus helps explain the memory deficits seen with the disorder.
Deficits in the frontal lobes, particularly the prefrontal cortex, are linked to “negative” symptoms like avolition (a severe lack of motivation), flattened affect, and reduced speech. Its reduced volume also correlates with disorganized thought, difficulty planning, and impaired decision-making.
The widespread grey matter reduction contributes to broad cognitive impairments affecting attention, processing speed, and problem-solving. The loss of tissue in the thalamus is also noteworthy, as this structure acts as a relay station for sensory and motor signals. Its impairment can disrupt how information is filtered and coordinated throughout the brain.
Other Neurological Differences
Beyond changes in grey matter volume and ventricular size, the brain in schizophrenia is marked by other neurological differences. These involve the brain’s internal communication network and its chemical signaling systems.
Research has revealed alterations in the brain’s white matter, which is composed of myelinated nerve fibers (axons) that transmit signals between different regions. Studies show reduced white matter integrity in individuals with schizophrenia, suggesting that connectivity between brain areas is compromised. This disruption can impair the coordinated brain activity needed for complex cognitive functions.
The brain’s chemical signaling systems, managed by neurotransmitters, are also affected. The dopamine hypothesis suggests that an excess of dopamine activity in certain pathways contributes to psychotic symptoms like hallucinations and delusions. Many antipsychotic medications work by blocking dopamine receptors. More recent research has expanded this view to include other neurotransmitters, such as glutamate.