Bipolar disorder is a mental health condition defined by significant shifts in mood, energy, and activity levels. Emerging research using neuroimaging technology has identified structural differences in the grey matter of individuals with bipolar disorder compared to those without the condition. These findings suggest the disorder is associated with physical changes in the brain’s architecture. Ongoing research focuses on understanding these differences and how the condition’s mood episodes may be tied to observable changes in the brain.
The Brain’s Grey Matter
The brain’s grey matter is a component of the central nervous system, consisting of a high concentration of neuronal cell bodies, dendrites, and glial cells. This tissue processes information, handles sensory perception, and controls voluntary movement. Its dense collection of neurons allows it to manage memory, learning, and emotions, making it central to many aspects of human life.
To visualize this, think of the brain as a computer network where grey matter represents the processing units that execute commands. The white matter, the brain’s other tissue type, acts as the network cables transmitting signals between grey matter regions and to the rest of the body. This arrangement allows for the integration of thought, emotion, and action.
Grey Matter Alterations in Bipolar Disorder
Neuroimaging studies have revealed structural differences in the brains of individuals with bipolar disorder, primarily showing a reduction in grey matter volume and density in specific regions. These changes are concentrated in areas involved in emotional regulation and cognitive processing. The alterations appear to be progressive, with evidence suggesting that a higher frequency of mood episodes, particularly mania, is associated with greater grey matter loss over time.
One of the most frequently cited areas of change is the prefrontal cortex, which is responsible for executive functions like decision-making and social behavior. Another area is the hippocampus, which plays a large part in learning and the formation of new memories. Research has identified reduced hippocampal volume in people with the condition, particularly those who have experienced more manic episodes.
The amygdala, known as the brain’s emotional center for processing fear and threat, also shows structural changes. Alterations in the insula, a region involved in self-awareness and interpreting the body’s internal signals, are also commonly observed.
Functional Consequences of Grey Matter Changes
The structural changes in grey matter directly relate to the symptoms of bipolar disorder. Reduced volume in the prefrontal cortex, for instance, is linked to challenges with emotional regulation, impulsivity, and executive function. This can result in difficulties with planning, problem-solving, and controlling impulses.
Similarly, volume loss in the hippocampus helps explain reported memory deficits, such as trouble recalling past events or difficulty learning new information. Changes within the amygdala contribute to the intense emotional states and heightened anxiety that characterize mood episodes. An altered amygdala affects how a person responds to emotional stimuli, leading to the powerful mood swings of mania and depression.
Alterations in the insula cortex are connected to disruptions in self-awareness and the perception of bodily states. This can manifest as a disconnect from one’s own emotional or physical feelings, a symptom prominent during mood episodes.
The Impact of Treatment on Grey Matter
Research shows some medications for bipolar disorder have neuroprotective effects that counteract grey matter loss. Lithium, a mood stabilizer, is the most studied in this regard. Long-term lithium treatment can slow or prevent grey matter reduction and may be associated with an increase in its volume.
Patients taking lithium often have greater cortical grey matter volume compared to those who are not, particularly in the prefrontal cortex and hippocampus. The mechanism is thought to involve lithium’s ability to promote brain-derived neurotrophic factor (BDNF). BDNF is a protein that supports the survival and growth of neurons.
These findings underscore the importance of consistent treatment. The neuroprotective properties of lithium offer benefits beyond mood stabilization, especially when treatment is started early. This highlights how proactive care can mitigate some of the neurological impacts of bipolar disorder.