Synapse Loss in Schizophrenia May Start in Left Frontal

Imagine a neighborhood of the brain quietly collapsing, not all at once but along a pattern written into its chemistry and wiring. That is the picture emerging from a new PET imaging study that traces where synapses—those tiny bridges that let neurons talk—are most depleted in people with schizophrenia.

Researchers scanned 122 adults, including 29 diagnosed with schizophrenia, using a tracer that binds to a protein marking synaptic density. This is one of the largest in vivo looks at synapses in the disorder and it reveals more than a diffuse loss: the damage clusters. Frontal and temporal regions showed the largest deficits, particularly structures tied to memory and emotion. And the shrinkage was not symmetrical. The left hemisphere stood out, showing a much greater drop in synaptic density than the right.

Why the left side? The study points to molecular identity. Regions that normally carry abundant receptors for serotonin, GABA, and glutamate—the chemical systems that balance excitation and inhibition and shape perception and mood—were the ones most affected. In other words, a brain region’s receptor landscape seems to predict its vulnerability to losing synapses.

That observation matters because it helps explain a stubborn clinical puzzle: schizophrenia tends to hit some circuits harder than others. Language, planning, and certain cognitive skills are often left-lateralized. If the left hemisphere harbors networks rich in those neurotransmitter receptors, it could explain why those abilities are commonly disrupted.

To test how these losses might unfold across the brain, the team ran computational models that simulate the spread of synaptic decline along structural connections. The simulations nominate a locus in the left frontal lobe as a plausible starting point, with abnormalities rippling outward through anatomically connected areas over time.

Synaptic loss in schizophrenia appears to follow the brain's molecular and wiring map.

The work, which includes contributions from a Rutgers investigator and appears in Molecular Psychiatry, stops short of proving cause and effect. The scans capture a single snapshot. We do not yet know when synaptic reductions first arise, whether they accelerate, or how medications and illness course alter the pattern. Longitudinal imaging will be essential to answer those questions.

Still, the study reframes how researchers think about brain injury in schizophrenia: not as random erosion but as a patterned vulnerability tied to receptor profiles and connectivity. That shift opens a different avenue for intervention—one that aims to protect or rebuild synapses in the regions most at risk. The next step is to follow people over time and test whether early treatment can close the breach before it spreads.