During a manic episode, the brain enters a state of widespread dysregulation: dopamine signaling ramps up in reward-processing areas, the prefrontal cortex loses its ability to restrain emotional circuits, and the amygdala fires more intensely than normal. These aren’t isolated glitches. They’re interconnected shifts in brain chemistry, circuit activity, and even cellular energy production that together produce the euphoria, impulsivity, sleeplessness, and grandiosity that define mania. Understanding what’s actually happening inside the skull during these episodes helps explain why mania feels so compelling to the person experiencing it and why it can be so damaging.
Dopamine and the Reward System Go Into Overdrive
The most established neurochemical explanation for mania centers on dopamine, the neurotransmitter most closely tied to motivation, pleasure, and reward-seeking. Imaging and pharmacological studies converge on a picture of what researchers call “hyperdopaminergia” during mania: elevated availability of certain dopamine receptors in the striatum (a deep brain region involved in reward and movement) and a hyperactive reward-processing network.1PubMed Central. The dopamine hypothesis of bipolar affective disorder: the state of the art and implications for treatment This surge in dopamine activity helps explain why people in a manic state often feel unstoppable, chase risky rewards, and experience a sense of brilliance or invincibility. The brain’s reward system is essentially telling them that everything they do is working.
A more recent imaging study adds a revealing wrinkle. People experiencing active mania showed roughly a 22–24% reduction in dopamine transporter density in the striatum compared to healthy volunteers.2PubMed Central. A Positron Emission Tomography Study of Dopamine Transporter Density in Patients With Bipolar Disorder With Current Mania and Those With Recently Remitted Mania Dopamine transporters are the proteins that vacuum up dopamine after it’s been released, clearing it from the synapse. With fewer of these transporters operating, dopamine lingers longer in the gap between neurons, amplifying every reward signal. The same study found that the more severe someone’s manic symptoms were, the lower their transporter levels tended to be in the right striatum. Once mania remitted, transporter levels crept back toward normal, suggesting this isn’t a permanent feature of the brain but something that shifts with the mood state itself.
When the Brakes Fail
Dopamine is only part of the story. A manic episode also involves a breakdown in the circuit that connects the prefrontal cortex to the amygdala, the brain’s emotional alarm system. Normally, the prefrontal cortex acts as a regulator. It evaluates incoming emotional signals from the amygdala and tamps them down when they’re excessive. In mania, that regulatory function weakens substantially.
Functional brain imaging shows that people in a manic state have reduced activity in the ventrolateral prefrontal cortex and the orbitofrontal cortex, regions responsible for impulse control and emotional regulation. At the same time, the amygdala becomes significantly more active, particularly on the left side.3PubMed. Increased amygdala activation during mania: a functional magnetic resonance imaging study Think of it as an accelerator stuck to the floor while the brake pedal goes soft. Another imaging study specifically examined this dynamic during an emotion-labeling task and found that manic patients had significantly reduced prefrontal regulation of the amygdala response.4PubMed Central. Evidence for deficient modulation of amygdala response by prefrontal cortex in bipolar mania Without that top-down control, emotions run unfiltered, which contributes to the irritability, rage, and emotional volatility that can accompany the euphoria.
A review synthesizing multiple imaging studies confirmed this lateralized pattern as a consistent finding: reduced activity in the right ventral prefrontal cortex and increased activity in the left amygdala, left anterior cingulate cortex, and left basal ganglia.5Translational Psychiatry. Functional neuroanatomy of mania The fact that the disruption has a consistent left-right pattern across studies suggests mania isn’t just random neural chaos. It’s a specific circuit malfunction that reliably produces a specific set of symptoms.
Other Neurotransmitters Shift Too
Dopamine dominates the conversation about mania, but the brain’s other chemical messengers are also thrown off balance. GABA, the brain’s main inhibitory neurotransmitter (the one responsible for calming neural activity down), shows reduced uptake during manic episodes. Meanwhile, glutamate, the brain’s main excitatory neurotransmitter, shows increased uptake. One study using platelet measurements found that glutamate uptake correlated with the severity of manic symptoms: the higher the mania rating, the greater the glutamate activity.6PubMed. Platelet uptake of GABA and glutamate in patients with bipolar disorder The overall picture is a brain tipping toward excitation and away from inhibition, which tracks with the subjective experience of racing thoughts, pressured speech, and the inability to slow down.
This excitatory tilt connects back to the circuit problems described above. When the prefrontal cortex is underperforming while subcortical emotional regions are overheating, reduced GABA and increased glutamate make that imbalance worse. The brain’s chemical environment and its circuit behavior reinforce each other.
Reward Anticipation Stays Elevated Even Between Episodes
One of the more striking findings in mania research is that reward-system hyperactivity isn’t confined to active episodes. When people with bipolar disorder are in a stable, non-symptomatic state and asked to anticipate a monetary reward in a brain scanner, they still show greater activity in the ventral striatum and orbitofrontal cortex compared to people without the disorder.7PubMed Central. Waiting to win: elevated striatal and orbitofrontal cortical activity during reward anticipation in euthymic bipolar disorder adults The heightened response appeared during the anticipation phase of the reward, not the outcome itself, suggesting the brain is primed to overvalue what might happen rather than what actually does.
This matters because it suggests the brain’s reward circuitry in bipolar disorder isn’t just disrupted during mania and normal the rest of the time. It appears to be wired differently at baseline, creating a vulnerability. During a manic episode, additional factors like dopamine surges and sleep deprivation push this already-sensitive system past a tipping point. A separate study found increased activity in the left dorsal anterior cingulate and the head of the caudate during manic states, both regions involved in motivation and goal-directed behavior.8PubMed. Increased anterior cingulate and caudate activity in bipolar mania The result is someone who feels intensely driven toward goals but whose judgment about those goals is compromised.
The Brain’s Resting Networks Get Disrupted
When you’re not focused on anything in particular, your brain defaults to a set of interconnected regions called the default mode network. This network handles self-reflection, daydreaming, and thinking about the future. In bipolar disorder, the connectivity within this network is altered. A resting-state brain imaging study found that people with bipolar disorder showed decreased connectivity between default mode network regions and the medial prefrontal cortex, along with increased connectivity with the left putamen and insula.9PubMed Central. Disrupted default mode network connectivity in bipolar disorder: a resting-state fMRI study
In practical terms, this means the brain’s “idle mode” is wired differently, pulling in regions associated with emotion and motor drive while weakening connections to areas involved in self-monitoring. This might contribute to the grandiosity and distorted self-perception common in mania. The person’s resting brain activity is already biased toward action and emotion rather than calm self-reflection.
Sleep Loss and the Circadian Clock
Sleep disruption is one of the most reliable warning signs that a manic episode is approaching, and there’s growing evidence that it isn’t just a symptom of mania but a contributor to it. People with bipolar disorder often experience an advanced sleep phase during manic episodes, meaning their internal clock shifts earlier.10Clinical Psychopharmacology and Neuroscience. Bipolar Disorder, Circadian Rhythm and Clock Genes They sleep less and less, sometimes going days without rest, and each night of lost sleep seems to ratchet the mania higher.
Animal research helps explain why. In mice, sleep deprivation alone can produce mania-like behavior and trigger changes in gene expression related to circadian rhythms and inflammation in the prefrontal cortex. Mice carrying a mutation in the Clock gene, a core component of the biological clock, also display mania-like behavior, reduced neural activity, and loss of microglia (the brain’s immune cells).11PubMed. Behavioral, cellular, and molecular changes in two animal models of bipolar disorder mania: sleep deprivation-induced mice and Clock-mutant mice Both sleep deprivation and Clock mutation led to significant changes in inflammatory pathways, suggesting that the circadian system and the brain’s immune environment are tightly linked. When the clock breaks, inflammation rises, and the prefrontal cortex starts functioning differently.
An Energy Crisis at the Cellular Level
Deeper inside the cell, mania appears to involve problems with mitochondria, the structures that generate energy for neurons. Evidence links bipolar disorder to abnormal mitochondrial shape, impaired energy production, disrupted calcium handling, and an imbalance in proteins that control whether a cell lives or dies.12PubMed Central. Mitochondrial dysfunction as a critical event in the pathophysiology of bipolar disorder The brain is the body’s most energy-hungry organ, consuming roughly a fifth of total calories, so even modest mitochondrial dysfunction has outsized effects on neural function. Reduced energy production could impair the prefrontal cortex’s ability to maintain the demanding work of impulse control and emotional regulation, contributing to the circuit failures that characterize mania.
There’s also a molecular signal that drops during acute mood episodes: brain-derived neurotrophic factor (BDNF), a protein that supports the survival and growth of neurons. Circulating BDNF levels are low during mania, depression, and mixed states, and this drop is associated with higher levels of inflammatory markers and lower mitochondrial DNA copy numbers.13Elsevier ScienceDirect / Journal of Affective Disorders Reports. Circulating levels of brain-derived neurotrophic factor (BDNF) in patients with bipolar disorders may be influenced by mitochondrial dysfunction, inflammation, and history of childhood trauma Low BDNF may make the brain less resilient to the stresses of repeated episodes, setting the stage for cumulative damage over time.
Does Mania Physically Change the Brain?
One of the most concerning findings in bipolar disorder research is that manic episodes appear to leave a structural footprint. A longitudinal imaging study followed people with bipolar disorder over time and found that those who experienced manic episodes between scans showed significant decreases in frontal cortical volume, specifically in the dorsolateral prefrontal and inferior frontal cortex. Those who did not experience mania during the same period showed no such changes.14PubMed. Manic episodes are related to changes in frontal cortex: a longitudinal neuroimaging study of bipolar disorder 1 This strongly suggests that the volume loss isn’t just a preexisting feature of bipolar disorder but something that mania itself accelerates.
A narrative review of structural studies confirmed this pattern: manic episodes have been related to accelerated decreases in cortical volume and thickness, with the most consistent findings in prefrontal brain areas.15PubMed Central. Mania-related effects on structural brain changes in bipolar disorder – a narrative review of the evidence Interestingly, people scanned after their very first manic episode don’t yet show significant gray matter differences compared to healthy individuals, suggesting the structural damage accumulates with repeated episodes rather than appearing all at once.16PubMed Central. Preservation of Gray Matter Volume in Early Stage of Bipolar Disorder: A Case for Early Intervention This is a strong argument for early and aggressive treatment. Every manic episode you prevent may be protecting the very brain regions you need for future emotional regulation.
Epigenetic Fingerprints of Acute Mania
Mania doesn’t just alter neurotransmitters and circuits. It appears to change how genes are read. A study comparing people hospitalized for acute mania with unaffected controls found that a specific gene involved in cortisol production (CYP11A1) was less methylated during mania, meaning it was more actively expressed. Six months after the episode resolved, methylation levels showed a trend toward normalization.17PubMed Central. Association of DNA Methylation with Acute Mania and Inflammatory Markers The same study found that inflammatory markers, including C-reactive protein and interleukin-1 receptor antagonist, were significantly associated with DNA methylation levels in manic patients but not in controls.
This means the manic state is accompanied by a measurable shift in gene regulation tied to both the stress response and inflammation. The fact that these changes partially reverse after recovery is somewhat reassuring, but the connection between mania, inflammation, and epigenetic modification raises questions about what cumulative effects repeated episodes might have on gene expression over a lifetime.
How Treatments Target These Brain Changes
Knowing what goes wrong during mania helps explain why certain medications work. Lithium, the oldest mood stabilizer, acts on multiple systems simultaneously. One of its key targets is an enzyme called GSK-3, which plays roles in cell survival, energy metabolism, and neural plasticity. By inhibiting GSK-3, lithium promotes the accumulation of a signaling molecule that drives cell proliferation and survival.18PubMed Central. Lithium’s role in neural plasticity and its implications for mood disorders Lithium also increases levels of protective proteins like BDNF and reduces cell death processes.19PubMed. Potential mechanisms of action of lithium in bipolar disorder. Current understanding Given the evidence that manic episodes erode prefrontal cortex volume over time, a drug that supports neural survival and growth may be doing more than just controlling the current episode. It may be limiting the structural damage that each episode inflicts.
Antipsychotic medications, frequently used to treat acute mania, work more directly on the dopamine and circuit problems. They block dopamine receptors, which counters the hyperdopaminergic state, and they tend to dampen limbic overactivity while allowing prefrontal function to recover.20JEB Medical Sci. An Overview of Antipsychotics: Mechanisms of Action The combination of a mood stabilizer for long-term neuroprotection and an antipsychotic for acute symptom control reflects the multilayered nature of the brain disruption in mania: you need to cool the immediate fire and also repair the smoke damage.
Mixed States and How They Differ
Not everyone’s mania looks like textbook euphoria. Mixed states, in which features of mania and depression occur simultaneously, involve a somewhat different neurochemical picture. Research suggests that mixed episodes arise from disturbances in the balance between catecholamine and acetylcholine neurotransmission, compounded by genetic susceptibility in circadian and dopamine pathways.21PubMed Central. Mixed States in Bipolar Disorder: Etiology, Pathogenesis and Treatment If pure mania is the accelerator jammed down, a mixed state is like having the accelerator and the brake pressed at the same time. The result is agitation, racing thoughts combined with despair, and a particularly high risk of impulsive self-harm. Mixed states are often harder to treat precisely because the brain chemistry doesn’t fit neatly into the “too much dopamine” framework that works reasonably well for classic mania.
When Mania Begins in Childhood
Pediatric bipolar disorder with psychotic features shows structural connectivity disruptions that are more widespread than what’s typically seen in adults with straightforward mania. A study of children and adolescents with bipolar disorder and psychosis found that roughly 71 structural connections in the brain were significantly altered compared to healthy controls, with a mix of both increased and decreased connectivity strength.22Nature / Scientific Reports. Disrupted brain structural connectivity in Pediatric Bipolar Disorder with psychosis The efficiency of connections in the orbitofrontal cortex correlated with cognitive test scores, while negative psychotic symptoms correlated with connectivity in nearby but distinct orbitofrontal regions. This suggests that in young brains still undergoing development, the disruptions from bipolar disorder may have broader reach and more direct cognitive consequences than in adults whose neural architecture is already established.
The Body Beyond the Brain
Mania’s effects aren’t purely neurological. The gut-brain axis, the bidirectional communication system between intestinal bacteria and the central nervous system, appears to be involved in bipolar disorder’s pathology. Research has found that the composition of gut microbiota differs in people with bipolar disorder, and these differences may influence mood and energy fluctuations through immune and metabolic signaling pathways.23PubMed Central. Gut microbial clues to bipolar disorder: State-of-the-art review of current findings and future directions This is still early-stage research, and no one is prescribing probiotics for mania. But it fits with the broader picture that keeps emerging: mania isn’t just a problem of too much dopamine or too little prefrontal control. It involves the immune system, cellular energy production, gene regulation, the circadian clock, and now potentially the gut. The brain during a manic episode is a system under stress from multiple directions at once, and the more of those directions researchers investigate, the more interconnected they turn out to be.
There’s even a speculative evolutionary angle. One hypothesis proposes that genes conferring vulnerability to bipolar disorder may have been adaptive in ancestral environments with extreme seasonal variation, where the capacity for intense energy expenditure during long summer days and withdrawal during harsh winters could have been beneficial.24PubMed. Evolutionary origin of bipolar disorder-revised: EOBD-R The hypothesis notes that bipolar disorder has the epidemiological profile of an adaptation, correlates with a cold-adapted body build, and involves moods that respond to light and season. It remains speculative, but it offers a thought-provoking frame for why such a disruptive condition persists at relatively stable rates in human populations.