Kyoto University. Japan: Scientists from Kyoto University's Institute for Integrated
Cell-Material Sciences (iCeMS) in Japan have developed an advanced
imaging system to identify cells responsible for storing memory within a
tiny worm. Their study, published in the journal Proceedings of the National Academy of Sciences,
not only offers a new way to identify molecular substrates of memory
but may also one day lead to understanding how memory loss occurs in
humans.
The human brain is estimated to contain approximately 100 billion
cells that form trillions of connections and make up a highly complex
network involved in memory. To simplify the investigation of the cells
directly responsible for storing memory itself, the researchers turned
to a highly defined and simple worm model, called Caenorhabditis elegans, which measures one millimeter in length and has only 302 neurons.
"Worms respond to stress from vibrations by moving backwards and
escaping in a process called 'mechanosensing,'" explained Assist Prof
Takuma Sugi, who led the study, "however, over time they get
desensitized to this stimulus through memory acquisition, or learned
habituation."
Because only a few types of brain cells, known as neurons, in the
worms are responsible for this process, it is possible to determine each
cell's responsibility. But to measure the worms' movements rapidly and
accurately, the scientists built a state-of-the-art integrated imaging
system -- involving four charge-coupled device cameras, a laser,
mirrors, and an automated mechanical stimulation device -- to
simultaneously capture the movement of 9 Petri dishes containing the
genetically modified worms that emitted a green light upon laser
stimulation.
"In the end, we identified two neurons, AVA and AVD interneurons that
relay signals, to be responsible for the learned habituation," said
Sugi.
Since the genome of worms is 40% identical to a human's, the
scientists are hoping that the new imaging system and the interneurons
they discovered may further our understanding of how memory is stored in
humans.
"It is possible that these results can be applied for therapies
involving memory disorders and reducing stress in the future," said
Sugi.