The Effect of Astrocyte-Mediated Extrasynaptic Glutamate Currents on the Dynamics and Firing of Hippocampus-like Neuronal Networks.
Abstract: Neurons are
the classic engines of sensory processing and cognition in the brain, though they
represent only one of two dierent general types of cell. Until recently, the rest,
called glia, were thought to play only a supportive, custodial role to neurons. Yet for
the past ten to fteen years, investigations have indicated that astrocytes, a type of
glia, may play a much more active ... read morerole in the processing of information than previously
assumed. Studies have reported that astrocytes can respond to and release
neurotransmitter onto neurons similar to the way traditional synapses function.
Interestingly, these studies have also shown that astrocytes can release
neurotransmitter onto two to twelve neighboring neurons in near synchrony. Astrocytes
can also produce waves of calcium, potentially releasing glutamate onto neurons across
an extensively interconnected syncytium. Several labs have hypothesized that astrocytes
may be involved in the synchronization of neuronal activity in the hippocampus. The
specic aims of this study were to determine the extent to which single astrocytes and
waves of astrocytes could aect local and global network ring and rhythms in hippocampal
CA1- and CA3-like models. The results indicate that single SICs are too local and too
weak to synchronize networks of neurons, unless the network is hyperexcitable, and that
SICs are too weak to disrupt oscillations in networks, regardless of their domain size.
However, waves of astrocyte intracellular calcium increases that release glutamate are
capable of producing synchronous oscillations, including gamma oscillations, if SICs are
suciently strong. It was also found that astrocytes, in both waves and single SIC
events, can elevate the ring probability of local neurons in-phase with the network eld
Thesis (M.S.)--Tufts University, 2012.
Submitted to the Dept. of Biomedical Engineering.
Advisor: Christoph Borgers.
Committee: Mark Cronin-Golomb, and Jamie Maguire.
Keywords: Neurosciences, Mathematics, and Behavioral sciences.read less