Research
I study networks of axons electrically coupled by gap
junctions, or the axonal plexus (as illustrated above). There is evidence for
an axonal plexus among pyramidal cells in the neocortex, hippocampus, and
cerebellum. These systems are an example of an excitable system connected
together in a random graph. They are related to models of the heart, pancreas,
and other electrically coupled excitable media that can exhibit heterogeneity.
My research on these systems involves: computational neuroscience, dynamical
systems, graph theory, cellular automata, and scientific programming. My
specific goals are to describe the dynamics of these networks in the normal
brain and in epilepsy.
In my dissertation, I showed that the axonal plexus
exhibits 3 different behaviors, depending on the somatic voltage and gap
junction conductance:
- Noisy
non-oscillatory activity,
- re-entrant
activity (or topological spiral waves),
or
- externally-driven
oscillations (or topological target
patterns).
Re-entrant activity and externally-driven oscillations are
two different kinds of very fast oscillation
(> 80 Hz), seen when cells are depolarized in the brain. I have movies depicting each behavior. For more information, see
my poster, talk,
or paper on The Axonal Plexus. All code is available on ModelDB. There is also an article about my doctoral
research in the Alma Matters Plus Archives for the Tufts University GSAS.
As a postodoc at BU, I created a realistic model of the
neocortical axonal plexus. This model shows that:
- Neocortical
pyramidal cells can send postsynaptic signals by adjusting their somatic
voltage.
- Pyramidal
cells can form cell assemblies by depolarizing together.
- If
enough cells depolarize together, then they will exhibit very fast
oscillations.
- There
is a chance that small groups of axons will exhibit very fast oscillations
regardless of cell polarization in normal neocortex.
- Lesions
and axonal sprouting promote groups of cells that oscillate at VFO
frequencies regardless of cell polarization. This may lead to epilepsy by
kindling postsynaptic cells.
For more information, see my poster
presented at CNS*2010 or talk.
Publications
Erin Munro and Nancy Kopell. Neocortical pyramidal cells can send
signals to post-synaptic cells without firing: a model of the axonal plexus. Submitted.
Erin Munro and Christoph
Börgers. Mechanisms of very fast oscillations in networks of axons
coupled by gap junctions. J. Comput. Neurosci. 2010, 28(3):539-55
Erin Munro. The axonal plexus: a
description of the behavior of a network of neurons connected by gap junctions. Ph.D. dissertation, Mathematics, Tufts University, 2008
Erin Munro and Christoph Börgers. The axonal plexus: a description of the behavior of a network of neurons connected by gap junctions. BMC Neuroscience 2007, 8 (Suppl 2):P47
Posters
A Model of Very Fast
Oscillations in a Realistic Cortical Axonal Plexus
The Axonal Plexus: A description
of the behavior of a network of axons connected by gap junctions
Electrically Coupled
Integrate-and-Fire Neurons
Talks
A realistic
neocortical axonal plexus model has implications for neocortical
processing and temporal lobe epilepsy
The Axonal Plexus:
A description of the behavior of a network of axons connected by gap junctions
Other links of interest