Image of neuron provided by: Dr. Daniel Johnston.
“Our work strongly supports the idea that
learning involves changes in dendrites.”
Dan Johnston
involves changes in dendrites.” comes as no surprise to Johnston, who says that the fundamental
In a recent article published in Nature Neuroscience, Johnston mechanisms of learning and memory overlap in almost all areas of
showed that a kind of membrane channel, called an h-channel, neuroscience. “You start talking about schizophrenia, age-
increased in dendrites of rat hippocampal cells when they were related memory problems, or mental health disorders,” he says,
exposed to a simulated learning task. He and his colleagues electri- “and you start talking about the basic mechanisms of learning and
cally stimulated neurons in a pattern that mimics the electrical memory: synaptic transmission and the plasticity and circuitry of
pulses that occur during learning. They found that the neurons’ neurons.”
dendrites produced more h-channels and rapidly produced pro- Epicenter for Learning and Memory
teins used to build more h-channels. To better understand the basic mechanisms of learning and mem-
h-channels may keep neurons from over-firing when informa- ory, Johnston is bringing together top minds from diverse fields
tion is pouring into them from many synapses, says Johnston. A at the college’s new Center for Learning and Memory (CLM). Sci-
neuron’s dendrites serve as a kind of information switchboard, and entists from chemistry and psychology to medicine and computer
a single hippocampal neuron can be connected to thousands of science will find a home at the CLM, which promises to be at the
other neurons through synapses on its dendrites. epicenter of new discoveries in learning and memory.
During learning, Johnston says the production of new h-chan- The CLM will provide a wealth of research opportunities for
nels in dendrites could help a neuron stay in normal firing range. undergraduate and graduate students, eventually housing a total
“h-channel plasticity might keep the cell within an operating win- of twelve research faculty in the recently completed Neural and
dow in which it can continue to learn,” he says. Molecular Science building.
In a separate study published in Neuron, Johnston found that Already joining the CLM is Dr. Helmut Koester, an innovator
rats with low numbers of h-channels in their dendrites experi- in the development of high-speed optical imaging of neurons, a
enced epileptic seizures. “We found that a decrease in h-channels method that allows him to view activity around a single synapse.
allowed cells to be hyper-excited,” he explains. “When there are Dr. Rick Aldrich, a renowned neuroscientist who studies the
no h-channels, the cells fire more and this leads to epilepsy.” It’s molecular mechanisms of ion channel function, will be joining the
not clear yet what mechanisms cause h-channels to decrease in CLM and the Department of Neurobiology from Stanford Univer-
dendrites, but Johnston and his colleagues did find that changes in sity in Spring 2006.
other channels can be acquired through some injury to the brain, “This is going to be an exciting place for doing neuroscience,”
a process they reported in Science that they labeled “acquired Johnston says. ✥
channelopathy.”
The relationship between disease and learning and memory To learn more about Johnston’s work and the CLM, visit clm.utexas.edu
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