Page Tools

 

Scientific Report


Scientific Report

Download the Scientific Report [7.5 MB]

View the entry for
Terrence J. Sejnowski

 

Terrence J. Sejnowski

Terrence J. Sejnowski

Professor and Laboratory Head
Computational Neurobiology Laboratory

"My goal is to discover the principles linking brain mechanisms and behavior. My laboratory uses both experimental and modeling techniques to study the biophysical properties of neurons and synapses, the sites at which neurons connect with each other, as well as the population dynamics of large networks of neurons."

A piece of cerebral cortex the size of a large grain of sand may contain 5 billion interlocked synapses of different shapes and sizes that are at the detection limit of light microscopes. This microscopic intricacy presents a major challenge to researchers trying to gain a fundamental understanding of the brain and other biological structures that exhibit such diversity and complexity at the subcellular level.

Sejnowski and his team use computer simulations to explore the subcellular architecture and physiology of neurons and synapses. They developed a computer program, known as MCell, that takes into account not just the shapes and sizes of synapses but also the locations of their molecular components and the timing of their interactions. For example, to relay signals between neurons, the presynaptic terminal at chemical synapses releases several thousand neurotransmitter molecules in packets called quanta. These molecules diffuse over to the postsynaptic membrane, where they bind to receptors, activate ion channels, and generate an electrical signal in the postsynaptic cell. MCell uses Monte Carlo techniques from physics to model the diffusion of the molecules and their chemical interactions.

At the chick ciliary ganglion, which connects nerve fibers originating in the brain with the neurons that control the size of the pupil, the presence of docked vesicles outside traditional synaptic junctions in electron micrographs suggested that neurotransmitter molecules may be released from vesicles at extrasynaptic sites. In collaboration with Darwin Berg and Mark Ellisman at UC San Diego, Sejnowski's team simulated the release of single quanta in a 3-D model based on a reconstruction from high-resolution serial electron microscopic tomography. The amplitude distribution of the simulated synaptic activity was consistent with experimental recordings only when extrasynaptic transmission was included in the model. This surprising prediction was subsequently confirmed experimentally by Peter Sargent at UC San Francisco, who is also collaborating on this project. Many types of extrasynaptic receptors are also found on neurons in the brain, which raises the possibility that neurons may communicate through sites outside the classically defined synaptic release zones.

Lab Photo

Left to rght:
Sitting: Mary Ellen Perry, Terrence Sejnowski, Philip Low, Sheri Leone Standing: Antonio Pinto-Duarte, Chris Uebelher, Collins Assisi, Suhita Nadkarni, Samat Moldakarimov, Tom Bartol, Jason McInerney, Tanya Baker, Maxim Bazhenov, Dejan Vucinic, Jorge Aldana, Max Bonjean, Jay Coggan, Ping Wang, John Jacobson, Jiucang Hao, Jed Wing, Chris Hiestand, Peter Werner, and Lee Campbell

Print version -
Terrence J. Sejnowski

Home > Faculty & Research > Faculty > Terrence J. Sejnowski

Faculty

Terrence J. Sejnowski

Terrence J. Sejnowski

Professor and Laboratory Head
Computational Neurobiology Laboratory

Terrence J. Sejnowski, professor and head of the Computational Neurobiology Laboratory, is a pioneer in the field of computational neuroscience.

Among other things, Sejnowski is interested in the hippocampus, believed to play a major role in learning and memory; and the cerebral cortex, which holds our knowledge of the world and how to interact with it. In his lab, Sejnowski's team uses sophisticated electrical and chemical monitoring techniques to measure changes that occur in the connections among nerve cells in the hippocampus during a simple form of learning. They use the results of these studies to instruct large-scale computers to mimic how these nerve cells work. By studying how the resulting computer simulations can perform operations that resemble the activities of the hippocampus, Sejnowski hopes to gain new knowledge of how the human brain is capable of learning and storing memories. This knowledge ultimately may provide medical specialists with critical clues to combating Alzheimer's disease and other disorders that rob people of the critical ability to remember faces, names, places and events.

Education

Awards and Honors

Selected Publications

Links

Salk News Releases