Synaptic density affects clinical severity via network dysfunction in syndromes associated with frontotemporal lobar...

Area of Science:

• Neuroscience
• Neurology
• Radiochemistry

Background:

• Frontotemporal lobar degeneration (FTLD) is characterized by extensive synaptic loss.
• Understanding the impact of synaptic loss on network function is crucial for developing therapeutic strategies.
• Previous studies have established synaptic loss in FTLD, but its network consequences require further investigation.

Purpose of the Study:

• To investigate the relationship between synaptic density, neurite dispersion, and network function in FTLD.
• To determine how these factors correlate with clinical severity in FTLD syndromes.

Main Methods:

• Recruited 55 participants with FTLD syndromes and 24 healthy controls.
• Measured synaptic density using [11C]UCB-J positron emission tomography (PET) targeting SV2A.
• Assessed neurite dispersion with diffusion magnetic resonance imaging (dMRI) and network function with resting-state functional MRI (rs-fMRI).

Main Results:

• Synaptic density and neurite dispersion were associated with reduced functional connectivity, independent of brain atrophy.
• Functional connectivity significantly moderated the relationship between synaptic density and clinical severity.
• These findings demonstrate a clear link between synaptic loss, altered network function, and behavioral outcomes in FTLD.

Conclusions:

• Synaptic loss is a key pathological feature in FTLD syndromes with significant implications for brain network function.
• Altered functional connectivity mediates the effect of synaptic loss on clinical presentation and behavior.
• This research underscores the importance of targeting synaptic integrity and network function in FTLD therapeutic development.