The effects of locus coeruleus stimulation on the BOLD global signal in TgF344‐AD rats

Functional connectivity of the brain as measured by the blood oxygen level dependent (BOLD) signal in fMRI is altered during Alzheimer’s disease (AD) progression. Common practice during preprocessing of fMRI data is removal of the global signal, defined as the averaged brain signal, by regression, removing major sources of noise while risking loss of neural activity. The locus coeruleus (LC), one of the first brain regions to accumulate hyperphosphorylated tau, contributes to brainwide neuromodulatory regulation. Therefore, we combined optogenetics and fMRI to study how LC activity affects the global signal in the TgF344‐AD rat model of AD, which overexpresses mutant human amyloid precursor protein and presenilin‐1.