The striatum is the brain region most directly tied to the dopamine hypothesis of schizophrenia. It is the major target of every antipsychotic medication ever marketed, the site where decades of PET imaging have documented elevated dopamine synthesis, and the structure most responsible for the assignment of salience — the brain's signal that something is worth paying attention to. When salience attribution goes wrong, ordinary events feel charged with meaning, and the seeds of delusion and hallucination begin to grow.
The striatum in schizophrenia shows elevated presynaptic dopamine synthesis and release capacity, especially in the associative striatum, with PET findings present in untreated patients and in those at clinical high risk for psychosis.
What the striatum does
The striatum is the major input nucleus of the basal ganglia. It includes the caudate, putamen, and ventral striatum (which contains the nucleus accumbens). It receives massive inputs from cortex, thalamus, and midbrain dopamine neurons, and projects out to other basal ganglia structures that ultimately influence motor, cognitive, and motivational systems. Functionally it is divided into:
- Sensorimotor striatum (mostly putamen) — habit learning, motor control
- Associative striatum (mostly caudate, plus dorsal putamen) — cognitive control, action selection, reinforcement learning
- Limbic/ventral striatum (nucleus accumbens) — reward, motivation, salience
The PET evidence
Positron emission tomography (PET) using radiotracers like 18F-DOPA allows researchers to measure dopamine synthesis capacity in living people. A 2012 meta-analysis by Howes and colleagues in Archives of General Psychiatry aggregated PET studies of schizophrenia and found a large, robust elevation of striatal dopamine synthesis in patients (effect size around 0.8). Crucially, this finding holds in untreated patients and in unaffected individuals at clinical high risk who later transition to psychosis, suggesting it precedes the full disorder rather than being caused by treatment.
Subsequent subdivision-specific work, particularly by the Howes lab, has localised the elevation primarily to the associative striatum (caudate and dorsal putamen), not to the limbic striatum as older theories assumed. This was a significant refinement of the dopamine hypothesis.
Aberrant salience
The salience hypothesis, articulated by Shitij Kapur in American Journal of Psychiatry (2003), proposes that elevated striatal dopamine causes ordinary stimuli — a stranger's glance, a song lyric, a passing thought — to be attributed inappropriate salience. The brain experiences them as meaningful and important, and the conscious mind constructs explanations. Those explanations become delusions. Hallucinations may emerge from similar misattribution of internal sensory signals as externally meaningful.
This framework helps explain why antipsychotics work. By blocking D2 receptors, they reduce the inappropriate salience attached to stimuli, gradually allowing the delusions and hallucinations to lose their grip. They do not erase memories of the experience or change long-standing beliefs directly; they reduce the reinforcement that keeps salience pathology in motion.
Origins of the dopamine elevation
Why is striatal dopamine elevated? Current thinking points upstream, to the hippocampus and prefrontal cortex. Anthony Grace's animal work suggests that hippocampal hyperactivity drives an increase in spontaneously active dopamine neurons in the ventral tegmental area, which in turn raises striatal dopamine release capacity. Reduced prefrontal regulation of dopamine neurons may also contribute. The striatum is, in this view, the downstream stage where upstream circuit dysfunction becomes psychotic.
For more on the upstream story, see our pieces on the hippocampus and prefrontal cortex.
Antipsychotic action and the striatum
Every approved antipsychotic medication for schizophrenia, from chlorpromazine in the 1950s to xanomeline-trospium (Cobenfy) in 2024, ultimately reduces striatal dopamine signalling — directly through D2 blockade or partial agonism, or indirectly through other receptor systems. The relationship between D2 receptor occupancy in the striatum and clinical response is one of the most robust dose-response relationships in all of psychiatry: roughly 60–80% striatal D2 occupancy corresponds to therapeutic effect, with side effects like extrapyramidal symptoms emerging at higher occupancies.
Cobenfy is interesting here because it works upstream of dopamine — by activating muscarinic acetylcholine receptors that modulate dopamine release — rather than blocking D2 directly. The clinical effect, however, still flows through the striatum.
Treatment-resistant schizophrenia and the striatum
Around 20–30% of people with schizophrenia have a poor response to standard antipsychotics. PET studies suggest that many of these patients have normal striatal dopamine synthesis. This is one of the cleanest biological explanations for treatment resistance — if dopamine is not elevated, blocking dopamine cannot help. Clozapine, the only medication with a strong evidence base for treatment-resistant cases, works through a more complex mechanism that may include effects beyond D2 blockade.
Volume changes
Structural changes in the striatum are smaller than in the hippocampus or PFC, but real. Volume can increase modestly with chronic D2 blockade — a medication effect, not an illness effect. Drug-naive first-episode patients show smaller volumes than would be expected, with subsequent enlargement on treatment.
What the striatum story does not explain
The striatal dopamine model is the strongest single biological account of positive symptoms — but it does not explain negative or cognitive symptoms well. It also does not address the developmental origins of the disorder. The striatum is the stage on which positive symptoms play out; the script is written in the hippocampus, the PFC, the thalamus, and the brain's developmental history.
"Elevated dopamine" in schizophrenia refers to specific aspects of dopamine signalling in specific brain regions, measured under research conditions. It does not mean people with schizophrenia are "high on dopamine" in any general sense, and it does not justify lifestyle interventions like dopamine fasts (which have no scientific basis).
The bottom line
The striatum is where the dopamine hypothesis lives. Decades of PET imaging show elevated presynaptic dopamine, particularly in the associative striatum, and this finding is the strongest biological account of positive psychotic symptoms. Antipsychotic medications work by reducing striatal dopamine signalling, and the relationship between striatal occupancy and clinical effect is one of the most reliable in psychiatry. Understanding the striatum is essential for understanding why current treatments work for some people and not others — and why the next generation of treatments will probably need to look beyond it.
This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.