RESEARCH
visualizing extracts
synapses
eurobiologist Kristen thick—and creates images of them with an elec-
Harris recently joined the tron microscope. virtual brain
Center for Learning and She and her colleagues then meticulously Understanding how a person makes
Memory (CLM), and she measure and outline the various parts of neu- a sandwich is key to comprehending
brings with her a pioneer- rons cross-sectioned in each slice. Some of the how the brain functions. Computer
ing technique to study structures are as small as 10 to 20 nanometers. scientist Dana Ballard and psychologist Mary Hay-
how neurons change and Finally, with the help of a computer, the images hoe are decrypting the distinct sets of instructions,
how the changes relate to learning and memory. are stacked atop one another like cards in a deck or “micro operations,” that the brain executes when
Harris has a special interest in the structure to create a complete 3-D reconstruction of spe- performing simple tasks, like walking on a sidewalk.
and function of protrusions on neurons called cifi c sets of synapses, dendrites and axons. Ballard tracks subjects’ eye and hand movements as
dendritic spines. The spines receive chemical “It’s like piecing a puzzle back together,” says they follow researchers’ instructions in virtual environ-
signals passing from the axon of one neuron to Harris. “Only you can get lost in this puzzle ments. He compares the data to computer programs
the dendrites of another. These places of connec- and it takes both biological knowledge about he’s written to simulate thinking processes in humans.
tion between neurons, called synapses, change how the structures relate to one another, and His ultimate goal is to lay the groundwork for a com-
as the brain learns and remembers. patience to understand and reconstruct what prehensive psychological model of the human brain.
Some of Harris’s research involves studying one is looking at.”
images of dendrites to learn how the spines grow Before arriving at the CLM in Fall 2006, Harris tangled turbulence
and diminish in response to stimuli. She looks directed laboratories at the Medical College of Anyone who’s been on an airplane
at the brains of rats of varied ages to understand Georgia, Boston University, and Harvard Medical knows what it’s like to experience tur-
how long-term potentiation, a cellular model of School. She was drawn to the CLM, Department bulence. But for the fi rst time, scientists
learning, changes as organisms mature. of Neurobiology and Institute for Neuroscience know how it looks—and it’s pretty wild. Doctoral stu-
One of the most important discoveries by the chance to collaborate with the universi- dent Jori Ruppert-Felsot and physicist Harry Swin-
from the Harris lab is that rapid changes in the ty’s cutting-edge faculty and by the opportunity ney collected data on water that they rapidly pumped
structure of synapses are accompanied by local to do research with the next generation of neuro- into and out of a rotating two-foot high cylindrical tank,
changes in the ability of dendrites to manufac- scientists. simulating the effects of the earth’s rotation on atmo-
ture new proteins. These changes occur within “I want to interact with the larger student spheric and oceanic turbulence. A team from Massa-
minutes of being stimulated, much more rapidly population,” Harris says, “and to help advance a chusetts Institute of Technology analyzed the data and
than previously held theories of several hours. terrifi c degree program in neuroscience.” created a complex image of turbulent fl ow. Knowing
To see these changes, Harris slices portions patrick brendel the underlying skeleton of turbulence is integral to
of the rat brain, usually from the hippocampus, understanding how natural phenomena like hurricanes
into very thin sections—about 40 nanometers Learn more at: synapse-web.org form, Swinney said.
the need for speed
Gone are the days when computer
processors become faster as they are
scaled to smaller sizes. The computer
axon
industry is trying to eke out more speed by adding
GE: JC FIALA and KM HARRIS
more processors to single chips. But what’s really
needed is a revolution in chip architecture, say com-
ssTEM IMA dendrite
puter scientists Doug Burger and Stephen Keckler.
Together they developed a new kind of microproces-
sor called TRIPS, which processes blocks of instructions
all at once, rather than conventional chips that process
A 3-D reconstruction of a dendrite and its spines created by serial section transmission electron miscroscopy one instruction at a time. They believe the chip will
(ssTEM), a technique pioneered by Kristen Harris. Synapses, the connection points between the axon of one achieve supercomputer speeds by 2012 and if adopted
neuron with the dendrites of another, occur at these spines. by industry would accelerate industrial, scientifi c and
personal computing.
focus on science
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