A Center for Behavioral Neuroscience (CBN) research
team led by Emory’s Xiaoping Hu and Georgia State’s
Don Edwards has developed a magnetic resonance imaging (MRI) technique
using manganese for identifying anatomical structures and neural
pathways in the crayfish brain.
The technique, which was adapted from an imaging technique used
on rodents, employs the paramagnetic element manganese to image
neural activity in living crayfish, whose brains measure only 3
millimeters wide. Initial tests of the technique have yielded detailed
anatomical images of the crayfish brain that have never before been
seen. Hu is professor of biomedical engineering and a Georgia Research
Alliance Eminent Scholar in Imaging at the School of Medicine. Edwards
is professor of biology at Georgia State.
“Prior to the development of this technology, it would take
weeks of histology to identify simple structures in the crayfish
brain,” said CBN post-doctoral fellow Jens Herberholz. “Now
we can generate these images in just a few hours.”
Neuroscientists have been studying crayfish, an invertebrate, for
more than 50 years. The simple neural network and well-defined social
hierarchies of the crayfish make the animals ideal models for behavioral
research, especially studies of aggression. In an initial encounter,
two crayfish typically will fight one another until dominant/subordinate
roles are established. These roles remain stable between the two
animals, but may change when they encounter other crayfish.
A signature behavior associated with crayfish aggression is the
tail flip. One type of tail flip indicates aggressiveness, while
others signify subordination and the intention to escape. In their
research, Edwards and Herberholz use conventional methods of electrophysiology
to determine the neural circuitry of the tail flip. However, this
technique can only delineate single neural pathways. With manganese-enhanced
MRI, the scientists hope to determine activation of multiple pathways
“Our goal is to use manganese as an activity marker for identifying
entire patterns of brain activation in dominant and subordinate
crayfish,” Herberholz said. “We also want to compare
changes that occur before and after an aggressive encounter.”
MRI technology, which was developed for imaging the human brain,
has rarely been used to study a brain of the crayfish’s small
size. To overcome the limitations of the technology, Hu and Herberholz
are working to improve the resolution of their small-animal MRI
scanner and develop a more sensitive coil customized to the crayfish’s
Manganese can be rapidly infused into the crayfish brain and is
well tolerated. For these reasons, Hu projected it will be possible
to conduct longitudinal studies of an individual crayfish using
MRI technology to assess changes that occur in its brain over an
Hu and Edwards said the development of manganese-enhanced MRI for
studying the crayfish could not have happened without the CBN. Hu
recalled an initial meeting last year when Edwards spoke of his
need to image the crayfish brain.
“I had never before worked with crayfish,” Hu said.
“Now we have a powerful new tool for studying the invertebrate
The CBN, a science and technology center funded by the National
Science Foundation with additional support from the Georgia Research
Alliance, is a consortium of eight universities in the Atlanta area.
CBN researchers study four aspects of behavioral neuroscience: fear,
aggression, affiliation and reproduction.