Biomarkers of the Locus Coeruleus Nucleus: Links With Early Tau Pathology, Cognition and Alzheimer's Disease Risk

Condition(s) studied

Investigational drug(s) / intervention(s)

a positon emission tomography (PET) exam: TEP exam using tau-specific tracer ( Flortaucipir, unique dose 360 MBq)

MRI Contrast: Data acquisition will include different sequences (anatomical MRI, resting fMRI). The MRI sequences performed will be anatomical imaging (i.e. T1 imaging, FLAIR), a diffusion sequence, a neuromelanin-sensitive sequence and functional imaging at rest (i.e. "the resting state", which allows the functional connectivity within the so-called "default" network to be assessed).

oculometry assessment: Pupillometry and oculometry will be conducted using an EyeBrain medical device (class IIa). Several cognitive tasks will be submitted to the participant, during which the same measurements will be taken. Different stimuli will be presented on the computer screen (visual scenes, text, geometric shapes) during the eye tracking measurement, and an instruction (cognitive task, such as semantic categorization, free exploration of the gaze, reading, saccade execution) will be associated with each type of stimulus. The successive stimuli will be spaced more than 7 secondes apart in order to allow the pupillary response to the first stimulus to be recorded and then to return to the basal diameter before presentation of the next stimulus.

cognitive exams: Cognitive measures will be acquired during an evaluation session through 6 interactive cognitive exercises. These exercises are developed using tools offered by Covirtua Healthcare.

Study summary

Alzheimer's disease (AD) is characterized by a long-lasting silent phase. Among initial events, emergence of tau pathology in locus coeruleus (LC) brainstem nucleus, well before the one observed in medial temporal cortex, is highly relevant. LC integrity and function can be assessed in vivo with MRI and pupil measures. The current research proposes to evaluate these LC markers in an aged healthy cohort (n=100, with half APOE4 positive) and to relate these markers with cerebral tau pathology, AD risk and cognitive function.

Eligibility

Primary outcome measure(s)

• diagnostic capabilities of Locus Coeruleus biomarkers for a positive PET-Tau exam — 24 monnths
  The diagnostic capabilities (sensitivity, specificity and AUC) of each of the elements of oculometry (pupillary response, number, latency and amplitude of ocular saccades), functional MRI (LC-hippocampus and LC-prefrontal cortex) and structural MRI (LC intensity) for a positive PET-Tau examination

Trial sites (1)

More University Hospital, Toulouse trials in France

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