casemed.case.edu
Neuroscientists discover new cell type
that may help brain maintain memories of smells
May open new approach to
understanding memory impairments in Alzheimer’s disease
discovered a new cell
type in the part of the brain that processes our sense of smell. This new cell
type, the Blanes cell, is a member of a group of
previously unstudied brain cells described by the Spanish neuroanatomist
Blanes (pronounced blon – es) in the late 1800s. Blanes
cells have unusual properties that may help the brain maintain memories of
smells and also open a new approach to understanding the basis of memory
impairments in Alzheimer’s disease. Their paper will appear in the March 16
issue of the journal Neuron.
It was surprising to the researchers that
no one had studied these cells before, given the references to them in
important scientific papers going back for more than 100 years.
“This is a well-studied part of the brain,”
said Ben W. Strowbridge, Ph.D., associate professor
of neuroscience at Case and the senior author. “These are large cells that
weren’t really hiding.”
The perception of a smell begins when
odor molecules in the air interact with one of the millions of specialized
olfactory sensory neurons in the nose. These sensory neurons then send signals
to a brain region called the olfactory bulb, where the work of recognizing the
odor begins. One of the puzzling aspects of olfaction is how our perception of an
odor can evolve over multiple sniffs. Because of their unique ability to
maintain their activity between sniffs, Blanes cells
may provide the missing link needed to answer this critical question.
Alhtough there are
relatively few Blanes cells in the brain, they appear
to play a critical role in shaping the output of the olfactory system. The Case
researchers found that the influence of Blanes cells
on the output signals leaving the olfactory bulb is magnified hundreds of times
by the specific pattern of connections they make with other cell types. One of
the surprising results from their study was the discovery that Blanes cells selectively choose to talk with another cell
type in the olfactory bulb, the granule cell. It is this specific pattern of
connections that explains how Blanes cells can have
such a disproportionately large impact in the olfactory system.
Discovering how one brain cell talks with
another brain cell remains one of the most important but technically
challenging questions in neuroscience. The Case researchers faced two
significant hurdles in trying to answer this question in the olfactory system.
The first was the shear numbers of potential partner neurons each Blanes cell might have. The other hurdle relates to
difficulty in visualizing the incredibly thin connection between the Blanes cell and its target neurons.
Todd Pressler,
a doctoral candidate student in Strowbridge’s lab and
the lead author on the study, took advantage of a new type of imaging method
called multiphoton microscopy to overcome these
hurdles and to discover that Blanes cells talk to
granule cells.
“The multiphoton
microscope allowed me to identify the axon and then follow it for long
distances without damaging the Blanes cell,” Pressler said. “Once I could follow the axon as it coursed
through the brain, it was relatively easy to see where it ended and where I
should look for potential target cells. Because I knew where to look, this part
of the project was shortened from potentially years to just a matter of weeks.”
The multiphoton
microscope used in this study was built by Strowbridge
specifically for these types of experiments and was funded by grants from the
Mt. Sinai Health Care Foundation and the National Institutes of Health.
Strowbridge and Pressler highlighted two sets of experiments they hope to
pursue in the near future. The first relates to the possible connection between
the sense of smell and Alzheimer’s disease. The Case investigators found that
the biological machinery that helps the olfactory brain to remember smells is
identical to the machinery that enables other types of memories in the cortical
brain region most susceptible to damage in this debilitating disease.
“By understanding the biological process
that allow us to store memories in the olfactory brain, we might find a novel
window into pathological changes that affect memory in people with Alzheimer’s
disease,” said Strowbridge.
In addition to leveraging the olfactory
system to better understand Alzheimer’s disease, Pressler
is excited about the prospect of unraveling the patterns of synaptic
connections made by the other five named but as yet unstudied brain cells in
the olfactory bulb.
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