Abstract
AbstractThe Papez circuit comprises several interconnected brain areas important for spatial navigation and orientation. An early symptom of dementia is disorientation, suggesting that brain regions responsible for providing a sense of direction are adversely affected. We examinedpost-mortemhuman tissue from cases with no cognitive impairment, mild cognitive impairment, and Alzheimer’s disease. A key part of the Papez circuit, the anterodorsal thalamic nucleus (ADn), contained a high density of misfolded pathological Tau (pTau) at all disease stages, including in control cases. Moreover, pTau preferentially accumulated in calretinin-expressing neurons. At the subcellular level, we detected pTau filaments in ADn cell bodies, dendrites, and in specialized presynaptic terminals. Large vesicular-glutamate-transporter-2-containing terminals from the lateral mammillary nucleus, rather than corticothalamic terminals, preferentially contained pTau, suggesting that Tau crosses specific synapses within the Papez circuit. As the ADn contains a high density of head direction cells, pTau may degrade the processing of orientation signals, explaining why people become disorientated years-to-decades before memory deficits emerge.
Publisher
Cold Spring Harbor Laboratory