Schizophrenia is a mental illness with symptoms that affect a person’s thoughts, feelings, and behaviors. Neuroimaging has revealed this condition is associated with changes in the brain’s structure, function, and connectivity. These alterations involve multiple brain regions and systems, contributing to the complex nature of the illness and providing insight into its biological underpinnings.
Brain Areas Commonly Affected in Schizophrenia
The prefrontal cortex, located at the front of the brain, is central to executive functions like decision-making, planning, social behavior, and attention. It acts as a high-level control center, integrating information from other brain regions to guide thoughts and actions.
Deep within the brain’s temporal lobes are the hippocampus and the amygdala. The hippocampus is responsible for forming and retrieving memories, while the nearby amygdala is a hub for processing emotions like fear and pleasure. The amygdala also helps in learning which situations to approach or avoid.
The thalamus, located near the center of the brain, functions like a switchboard by relaying sensory information such as sights and sounds to the cerebral cortex. It also plays a role in sleep, consciousness, and alertness. Because these regions are highly interconnected, disruptions in one area can affect an individual’s ability to think, feel, and interact with the world.
Physical Alterations in Brain Structure
A consistent finding in schizophrenia is a reduction in gray matter volume in specific areas. Gray matter, composed of neuronal cell bodies, is responsible for processing information. These reductions are often observed in the prefrontal and temporal lobes, which may relate to difficulties with executive function and auditory processing.
Research also points to alterations in the brain’s white matter, which consists of nerve fibers (axons) that form the brain’s communication network. In individuals with schizophrenia, studies show reduced white matter volume and compromised structural integrity. This can impair the efficient transmission of signals between brain regions.
Enlargement of the brain’s ventricles, the fluid-filled cavities inside the brain, is another common structural finding. Because the skull is a fixed space, larger ventricles often indicate a loss of surrounding brain tissue. Evidence suggests these structural differences may originate during early development, long before the first symptoms appear.
Changes in Brain Activity and Chemical Signaling
Individuals with schizophrenia also show differences in functional brain activity. A well-documented observation is hypofrontality, which describes reduced neural activity in the prefrontal cortex, particularly during tasks requiring planning and working memory. This underactivity is thought to contribute to some of the cognitive challenges associated with the illness.
Conversely, other brain areas may show overactivity. For instance, the thalamus can exhibit excessive connectivity with sensory areas of the brain. This hyperactivity may be related to the misinterpretation of internal thoughts as external stimuli, which is a potential basis for hallucinations.
Functional changes are linked to the brain’s chemical messaging systems. Schizophrenia is associated with imbalances in neurotransmitters, the chemicals brain cells use to communicate. The dopamine system has historically been a focus, with its dysregulation thought to contribute to symptoms. More recent research also points to the role of glutamate, the primary excitatory neurotransmitter.
Impaired Communication Between Brain Regions
The structural changes in white matter provide a physical basis for communication breakdowns in the brain. Schizophrenia is increasingly understood as a disorder of disrupted neural connectivity, where different brain regions struggle to communicate effectively. This impaired wiring can lead to a failure to integrate information properly, affecting everything from sensory perception to complex problem-solving.
A prominent example involves the circuits linking the thalamus and the prefrontal cortex. Research shows decreased functional connectivity between these regions, which can disrupt the flow of information for higher-level cognitive functions. These issues are also seen in individuals at high risk for the illness, suggesting a pre-existing vulnerability.
How Brain Changes Relate to Symptoms of Schizophrenia
Negative symptoms, including apathy, emotional flatness, and lack of motivation, are strongly associated with reduced activity and gray matter volume in the prefrontal cortex. This underactivity can impair the ability to initiate and sustain goal-directed behavior.
Positive symptoms, such as hallucinations and delusions, are thought to relate to dysfunction in circuits involving the temporal lobes, hippocampus, and thalamus. For example, abnormal activity in the auditory cortex could lead to hearing voices. Disrupted connectivity between the thalamus and cortex might also cause the misattribution of internal thoughts to an external source.
Cognitive impairments that affect memory, attention, and problem-solving are linked to widespread network dysfunction. For instance, difficulties with working memory are tied to prefrontal cortex inefficiency, while problems with long-term memory formation point to hippocampal abnormalities. This breakdown in communication leads to the cognitive deficits that are a core feature of the illness.