Erin Munro

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