David C. Lyon, Ph.D.
Visiting Scientist, Salk Institute for
Biological Studies
Assistant Professor
University of California, Irvine
Department of Anatomy & Neurobiology
364 Med Surge II, Irvine CA 92697
Salk: (858) 453-4100 x1064
UCI: (949) 824-0447, Fax: (949) 824-8549
E-mail: lyon@salk.edu
or dclyon@uci.edu
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Assistant Professor |
2006-present, |
|
Postdoctoral Fellow |
2004-2006, Salk Institute, Ed
Callaway, Advisor |
|
Postdoctoral Fellow |
2002-2004, Massachusetts
Institute of Technology, Mriganka Sur, Advisor |
|
Postdoctoral Associate |
2001-2002, |
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Ph.D. Psychology |
1995-2001, |
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M.A.* Psychology |
1993-1995, |
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B.A. Psychology |
1992, |
Awards/Fellowships
- 2003 Krieg Cortical
Scholar Award, Cajal Club
- 2002-2005 National
Research Service Award, National Eye Institute
- 1997-2000 Vanderbilt
Vision Training Grant, National Eye Institute
- 1995-1996 Graduate
Student Fellowship,
- 1994-1995 State of
Research
In collaboration with researchers at the Salk
Institute, I use molecular and genetic tools to trace neuronal circuits in
sensory cortex and thalamus of mammals. Our custom made viruses are applied
extracellularly, infect only those neurons with the appropriate
receptor (Red in the figures below) then transport only a single synapse
from the host cell (resulting in GFP expression).
At the Salk Institute, I used the CVS strain of rabies virus to trace disynaptic subcortical inputs to extrastriate visual cortex in primates. This neurotropic virus will transport indefinitely across synapses until infecting all cells, but if timed properly can be used as an effective multisynaptic tracer. Three day survival time allows for most disypatic connections to be traced.
With this protocol we were able to show that the
superior colliculus (SC) is connected disynaptically to the direction selective
visual area MT (Lyon, Nassi and Callaway, VSS
ABSTRACT, 2005, Poster PDF right click and save as).
In addition, we have injected several cortical areas to demostrate
that this disynaptic pathway is exclusive to higher order dorsal stream visual
areas (Lyon, Nassi, Callaway, 2005, SFN ABSTRACT). This pathway from SC to dorsal
stream visual areas may represent a fast circuit involved in directing eye
movements, a key feature shared by the superior colliculus and dorsal stream.
In addtion, as
illustrated below, we have shown that magno and parvo
cells of the lateral geniculate nucleus (LGN) project disynaptically to
cortical area MT (Nassi, Lyon and Callaway, 2006,
Neuron, see
press release). This disynaptic pathway is likely to
travel through large Meynert cells in layer 6 of V1, as these cells project
directly to MT and are in a position to receive geniculate input from
both magno and parvo cells (see diagram on the right). This unexpected early
integration of the parvo pathway into a motion
processing system typically considered to be dominated by the magno pathway is
likely to provide MT with a more complete range of temporal, spatial and
chromatic cues than the magno pathway alone.
............ ........... 
Pattern of excitatory (black
dots) and inhibitory (white dots, only shown within 400 um) neurons providing
inputs to an orientation pinwheel in Cat V1. Outer circle represents 250 um
from injection of CTB, inner circle. Local inhibitory neurons were identified
with anti-GABA immunofluorescence (Modified from Mariņo et al., 2005, Nature Neuroscience).
My research at MIT blended neuronanatomical
tracing and immunohistochemistry with optical imaging and single unit
recordings. We used these techniques to explore mechanisms of orientation
selectivity in striate cortex (V1) mediated by local and long range intrinsic
horizontal connections in cats (Mariņo et al., 2005, Nature
Neuroscience, see
press release).
Ongoing projects begun at MIT include the study
of the affects of attention and context on orientation selectivity by
presenting "center-surround" gratings to alert monkeys and recording
responses of V1 neurons (Lyon et al., 2004, VSS Abstract; Sharma et al., 2003, SFN
Abstract). We are also exploring the effects of sequence order and
abrupt transitions in luminance on the adaptation of V1 neurons in awake monkeys (Lyon et al., 2004, SFN Abstract).
Research interests stemming from my graduate
work with Jon Kaas at Vanderbilt University focus on the organization of the
visual system in highly visual mammals including primates, tree shrews, cats
and ferrets. I use neuroanatomical tracing techniques -the reconstruction of
connection patterns of extrastriate visual cortex following multiple injections
of fluorescent tracers in cortical and subcortical visual structures, such as
the superior colliculus- to compare the resulting connection patterns with
cytochrome and myeloarchitecture.
Organization
of
Optical imaging techniques are also used to
evaluate existing models of extrastriate cortex organization.
Intrinsic signal optical
imaging of the representation of the vertical and horizontal meridians of Owl
Monkey V2 and V3.From Lyon et al., 2002, PNAS.
Other research efforts have been directed
towards describing several architectonic subdivisions of the pulvinar nucleus, a
structure providing a secondary visual pathway from the retina (directly and
via the superior colliculus) to most of extrastriate cortex.
Architectonic subdivsions and Pseudo 3D rendering of the shape and extent
of three pulvinar subdivisions in the tree shrew. From Lyon, Jain and Kaas,.
2003a, J Comp Neurol.
Other interests are in the plasticity of
extrastriate visual cortex following large scale ablations of striate cortex
(see Collins et al., 2003, J Neurosci).
And the organization and plasticity of the
somatosensory system in primates (see Jain et al., 2001, SFN Abstract), tree
shrews, and very small mammals such as insectivores (Catania et al., 1999, J
Comp Neurol).
Lyon DC (in press) The evolution of visual cortex and visual systems. In: The Evolution of the Nervous System in Mammals. Eds, LA Krubitzer and JH Kaas. Elsevier, London.
Nassi* JJ, Lyon* DC, Callaway EM (2006) The parvocellular LGN provides a robust disynaptic input to the visual motion area MT. Neuron. 50:319-327. PDF Full Text *Co-First Authors
Collins CE,
Mariņo J, Schummers J, Lyon DC, Schwabe L, Beck O, Wiesing P, Obermayer K, Sur M (2005) Invariant computations in local
cortical networks with balanced excitation and inhibition. Nature
Neuroscience. 8:194-201. PDF Full Text Cited In
Faculty 1000
Lyon DC, Jain N and Kaas JH (2003a) The visual
pulvinar in tree shrews I. Multiple subdivisions revealed through acetylcholinesterase and Cat-301 chemoarchitecture.
Journal of Comparative Neurology. 467(4):593-606. PDF Full Text
Lyon DC, Jain N and Kaas JH (2003b) The visual
pulvinar in tree shrews II. Projections of four nuclei to areas of visual
cortex. Journal of Comparative Neurology. 467(4):607-627. PDF
Full Text
Collins CE,
Lyon DC, Xu X, Casagrande V, Stephansic
J, Shima D and Kaas JH (2002) Optical imaging reveals
retinotopic organization of dorsal V3 in New World owl monkeys. Proceedings
of the National Academy of Sciences, USA. 99(24):15735-15472. PDF Full Text
Qi H-X, Lyon DC and Kaas JH (2002) Topography, connections
and architecture of the parietal ventral somatosensory area in marmosets. Journal
of Comparative Neurology. 443(2):168-182. PDF Full Text
Lyon DC and Kaas JH (2002) Connectional evidence
for dorsal and ventral V3, and other extrastriate areas in the prosimian
primate, Galago garnetti. Brain, Behavior and Evolution.
59(3):114-129. PDF
Full Text
Lyon DC and Kaas JH (2002) Evidence from V1
connections for both dorsal and ventral subdivisions of V3 in three species of
New World monkeys. Journal of Comparative Neurology.
449(3):281-297. PDF
Full Text
Lyon DC and Kaas JH (2002) Evidence for a
modified V3 with dorsal and ventral halves in macaque monkeys. Neuron.
33(3):453-461. PDF
Full Text
Kaas JH and Lyon DC (2001) Visual cortex
organization in primates: Theories of V3 and adjoining visual areas. Progress
in Brain Research. 134:285-295. PDF Full Text
Lyon DC and Kaas JH (2001) Connectional and
architectonic evidence for dorsal and ventral V3, and area DM in marmoset
monkeys. Journal of Neuroscience. 21(1):249-261. PDF Full Text
Catania KC, Lyon DC, Mock OB and Kaas JH (1999)
Cortical organization in shrews: Evidence from five species. Journal of
Comparative Neurology. 410(1):55-72. PDF Full Text
Lyon DC, Jain N and Kaas JH (1998) Cortical
connections of striate and extrastriate visual areas in tree shrews. Journal
of Comparative Neurology. 401(1):109-128. PDF Full Text
Selected Abstracts
Wickersham I, Lyon DC, Barnard RJO, Mori T, Finke S, Conzelmann KK, Young JAT, Callaway EM (2006) Transcomplemented transsynaptic tracing: a new tool for precision mapping of neural circuits. Cold Spring Harbor, Neuronal Circuits: From Structure to Function.
Lyon DC, Nassi JJ, Callaway EM (2005) Primate dorsal stream visual areas receive disynaptic
inputs from the superior colliculus. Society For Neuroscience. 31. Abstract
Lyon DC, Nassi JJ, Callaway EM (2005) Disynaptic connections from the superior colliculus to cortical area MT revealed through transynaptic labeling with rabies virus.Vision Sciences Society, 5. Poster PDF right click and save as.
Lyon DC, Schummers J, Sharma J, Sur M (2004)
Effects of stimulus sequence and abrupt transitions in luminance on V1 neurons
in awake monkey. Society for Neuroscience. 30. Abstract
Lyon DC, Sharma J, Schummers J, Sur M (2004) Non
Linear Modulation of Contextual Influences by Attention in Awake Monkey V1.
Vision Sciences Society, 4. Abstract
Lyon DC, Schummers J, Marino J, Sur M (2003)
Anatomical distribution of inhibitory and excitatory inputs to pinwheel centers
and orientation domains in Cats. Society for Neuroscience.
Sharma J, Lyon DC, Sur M (2003) Influence of
attention on center-surround interactions in alert monkey V1. Society for
Neuroscience.
Lyon DC and Kaas JH (2002) Retinotopic
organization of the connections of primate visual cortex with the pulvinar
nucleus. Federation of European Neuroscience Societies, 3. Paris, France.
Jain N, Qi HX, Collins
CE, Lyon DC and Kaas JH (2001) Reorganization of somatosensory cortical area 3b
following early postnatal dorsal column lesions in macaque monkeys. Society for
Neuroscience. 27.
Invited Talks
- Vanderbilt University, Department of Psychology, October, 2006
- University of Chicago, Department of Neurobiology, Pharmacology, and Physiology, February 2006
- University of California, Irvine, Department of Anatomy
and Neurobiology, January 2006
- Harvard
Medical School, Department of Neurobiology, October 2001
Links
Ed Callaway Lab, Salk Institute
Ken Catania, Biological
Sciences, Vanderbilt University
Emily Grossman, Department of
Cognitive Sciences, UC Irvine
Jon
Kaas, Department of Psychology, Vanderbilt
Vision Research Center
Mriganka Sur Lab, Department of Brain and Cognitive Sciences, Picower Center for Learning and Memory,MIT