Gordon M. Shepherd

Gordon Murray Shepherd (born 1933) is a neuroscientist who carries out basic experimental and theoretical research on how neurons are organized into microcircuits to carry out the functional operations of the nervous system. He is currently professor of neurobiology at the Yale School of Medicine.

Early work

His electrophysiological studies of the olfactory bulb in 1963 produced one of the first examples of a brain microcircuit. Building on this work he collaborated with Wilfrid Rall at NIH to construct the first computational models of brain neurons. This predicted dendrodendritic interactions in the olfactory bulb, subsequently confirmed by electronmicroscopy, hypothesized to mediate lateral inhibition of the sensory input. A collaboration in 1975, using new methods of brain imaging, revealed that odors are encoded by different spatial activity patterns in the olfactory glomeruli of the olfactory bulb. This showed that the neural basis of smell in virtually all vertebrates involves odor representation by glomerular activity patterns ("odor images") which are then processed by lateral inhibition mediated by the dendrodendritic circuits.

Shepherd's lab continued to use the olfactory bulb as a general model for the integrative actions of neuronal dendrites. This showed that dendrites contain multiple computational units; backpropagating action potentials in dendrites carry out specific functional operations; and dendritic spines can function as semi-independent input-output units. The lab also provided a basic circuit for olfactory cortex.^[1] New concepts to replace the classical "neuron doctrine" were suggested, and the term "microcircuit" for characterizing specific patterns of synaptic interactions in the nervous system.

Recent and current studies

Shepherd's odor imaging studies have been extended by use of high-field functional MRI (7 and 9 Tesla), work started with his longtime colleague Charles Greer and members of the Yale Imaging Center. The lab has used viral tracing methods to reveal widely dispersed clusters of granule cells which are hypothesized to be necessary for processing the distributed glomeruli activated by odor stimuli. These experimental data are being used to build computational models of the distributed mitral and granule cell circuits, to obtain insight into the nature of the processing that underlies smell perception.^[2] A new appreciation of the extensive but largely hidden "flavor system" in the human brain suggests a new field he has called "neurogastronomy",^[3] which has the potential to enhance understanding of the factors contributing to obesity and other eating disorders.

In their studies of the neural basis of cognition, his lab is analyzing the active properties of the apical dendrites of cortical pyramidal cells for insight into their relation to cortical processing. They are presently interested in how these dendritic properties may be affected in the earliest stages of cognitive decline in Alzheimer's disease.

His lab was among the original group that founded the field of neuroinformatics, with the first funding of the Human Brain Project in 1993. The home site is "SenseLab", which contains a suite of 7 databases supporting research on olfactory receptors, odor maps, neuronal and dendritic properties, and neuronal and microcircuit models. The group includes Perry Miller, founder of the Yale Center for Medical Informatics, and Michael Hines, founder of the widely used modeling program NEURON. They are currently a member of the Neuroscience Information Framework (NIF), a NIH initiative to build a comprehensive web-based portal to support neuroscience research.

Partial bibliography

• Shepherd, G.M. (1974). The Synaptic Organization of the Brain. New York: Oxford University Press.
• Shepherd, G.M. (1983). Neurobiology. New York: Oxford University Press.
• Shepherd, G.M. (1991). Foundations of the Neuron Doctrine. New York: Oxford University Press.
• Segev, I., Rinzel, J. and Shepherd, G.M. (Eds.). (1995). The Theoretical Foundation of Dendritic Function: Selected Papers of Wilfrid Rall. Cambridge, Mass.: MIT Press
• Shepherd, G.M. (2010). Creating Modern Neuroscience: The Revolutionary 1950s. New York: Oxford University Press
• Shepherd, G.M. and Grillner, S. (Eds.) (2010). Handbook of Brain Microcircuits. New York: Oxford University Press

Honors

• honorary degree, University of Copenhagen, 1999
• Honorary degree, University of Pavia, 2006.

References

1. Gordon M. Shepherd (2004). The Synaptic Organization of the Brain. Fifth Edition. Oxford University Press. ISBN 978-0-19-515956-1.
2. Migliore M, Shepherd GM; Dendritic action potentials connect distributed dendrodendritic circuits J Comp Neurosci 24(2):207-21. 2007 Nawroth JC, Greer CA
3. Gordon M. Shepherd (2011). Neurogastronomy: How the Brain Creates Flavor and Why It Matters. Columbia University Press. ISBN 978-0-231-15910-4.

External links

• Gordon Shepherd's lab web page at Yale.
• Gordon Shepherd's Neurobiology Department web page at Yale.
• SenseLab