What is the locus coeruleus, and should I care?

Until relatively recently, conventional MRIs have not imaged a structure in the brain stem called the locus coeruleus (LC).  You can see it in this image.  The LC is about 15mm long by 1-3mm, and appears to play an important role in the formation of memories.  So, not surprisingly, atrophy of the LC is being correlated with neurodegenerative diseases and dementia, notably Alzheimer's disease and dementia with Lewy bodies.

This week's issue of ALZForum carried an interesting article discussing what we know about the LC.  It discussed recent developments in imaging techniques and recent investigations, including those finding the LC is one of the first regions of the brain to accumulate the nasty tau proteins that characterize Alzheimer's disease.  It also discussed the results of cognitive tests and MRIs of healthy young people, older people with healthy LC, and older people with atrophied LC.   Who do you think did best and worst in these tests?

What does the LC do?  It generates the the neurotransmitter norepinephrine used in neurological processes.  Neurons in one part of the LC project toward the hippocampus, and another part projects toward the cerebellum and spinal cord.  Through the release of norepinephrine, LC neurons modulate attention, learning, and memory by manipulating synaptic activity. This is important for network plasticity.

So what good is knowing this?  One thing is the prospect of finding another biomarker for Alzheimer's disease and dementia with Lewy bodies.  The hope is that this can further refine our diagnostic ability, which is important in research on neurodegenerative disease.  If you are testing a new drug treatment candidate, you want maximum confidence that you know what disease or diseases is afflicting the test subject and causing their cognitive decline.