Kurucu H, Colom-Cadena M, Davies C, et al. - Loss of inhibitory neurons and synapses in Alzheimer disease (AD) may contribute to disrupted excitatory/inhibitory balance and cognitive impairment.

• Researchers analyzed post-mortem human brain tissue (n = 5 control, 10 AD cases) from the inferior or middle temporal gyrus and primary visual cortex.

• Different cortical layers have different inhibitory neuron densities.

• Layer 4 in both brain regions had the highest inhibitory neuron density, with the visual cortex having a higher inhibitory neuron density than the temporal cortex.

• In all 6 cortical layers, the inhibitory neuron density was significantly lower in AD patients than in controls.

• Plaque-associated loss of inhibitory synapses and accumulation of Aβ in a small subset of inhibitory presynaptic terminals is seen by high-resolution array tomography imaging, with the highest concentration near amyloid plaques.