[18F]-FEOBV

Progressive age-related cognitive deficits occurring in both AD and DS have been connected to the degeneration of several neuronal populations, but mechanisms are not fully elucidated. The most consistent neuronal losses throughout the progression of AD are seen in cholinergic neurons where these losses negatively affect cognition, particularly in attention, learning, and memory formation. Evidence of reduced cholinergic integrity in DS is largely limited to animal models and post-mortem human data. The investigators propose to use molecular, functional, and structural biomarkers to assess the cholinergic integrity in adults with DS. The investigators anticipate using the data gathered in this pilot study to inform future study designs to determine AD risk stratification in DS by identifying individuals who show an accelerated decline in cholinergic integrity that correlates with cognitive and neurobehavioral changes. Also, our cholinergic biomarkers may identify whether individuals with DS are likely to respond to pro-cholinergic interventions, including the novel cholinergic modulators that are being developed to enhance cholinergic-sensitive cognitive functioning. The investigators anticipate using the data gathered here to inform future treatment studies in TRC-DS and beyond where novel cholinergic treatments may offer opportunities for early intervention in DS and be complementary to disease-modifying approaches such as anti-amyloid treatments.

Apathy is a neurocognitive syndrome characterized by reduced goal-directed behaviors, contributing to decreased patient and caregiver quality of life. Apathy pathophysiology involves disruption of cortico-striato-thalamo-cortical loops, modulated by several neurotransmitter systems including dopamine and acetylcholine, thus complexifying pharmacological management. Post-stroke apathy (PSA) can provide a proper in vivo model to study the underlying neurochemical substrates of apathy as a syndrome. The present project aims to provide a better characterization of the cholinergic and dopaminergic functioning in apathy as a syndrome.
In order to precise the respective alterations of these two systems, investigators will use a positron emission tomography (PET) molecular imaging of dopaminergic (with [18F]-FDOPA, a marker of the decarboxylating enzyme of dopamine) and - for the first time in apathetic patients - cholinergic (with [18F]-FEOBV, a marker of the vesicular acetylcholine transporter) transmissions in 15 apathetic and 15 unapathetic patients 3 months after stroke, without overlapping depression. This dual imaging study may provide help in guiding therapeutic management of PSA. The functional network analysis allowed by functional MRI is crucial to complement regional neurotransmitter deficits observed with PET. Altogether, a multimodal approach in apathy, combining PET and MRI, can allow identifying which circuits of the cortico-striato-thalamo-cortical loops are disrupted and how these circuits are modulated by other neurotransmitters.