Tim Stilson
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February 2004 |
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| 15 | 16 | 17 Chapter Meeting | 18 | 19 | 20 | 21 |
| 22 | 23 | 24 Chapter Meeting | 25 | 26 | 27 | 28 |
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Speaker: Stephanie Hoogendoorn
Title: "Computational Modeling of the Thalamus in the Rat
Whisker Barrel Sensory System"
Where: 704 Thackeray
Time: 3:00 PM (Tuesday)
Refreshments will be served immediately afterward in 705.
Abstract: Computational Modeling of Synaptic Dynamics underlying the temporal responses of
thalamic barreloid neurons to periodic whisker deflections.
Previous experimental studies suggest that frequency-dependent properties of thalamic barreloid
neurons to periodic whisker deflections reflect the effects of synaptic depression, low-threshold
calcium T-current, and local inhibition of neurons in the ventral posterior medial nucleus (VPM) by
the thalamic reticular nucleus (nRt). We incorporate synaptic depression and T-current (Sohall,
Huguenard 1998) into a quadratic integrate-and-fire model in order to simulate a network of VPM
and nRt neurons. Input consists of spike trains obtained previously from VPM-projecting neurons
in brainstem nucleus principalis (PrV). Stimuli consisted of periodic sinusoidal or pulsatilewhisker
deflections over the frequency range 1-40 Hz. Model neurons, like their biological counterparts,
display adaptation, with responses of both VPM and nRt being larger during the first vs subsequent
cycles. Also, simulated and real nRT cells display more sustained and less temporally distinct
discharges over each deflection cycle. Analysis of model neurons indicate that synaptic depression
of the PrV to VPM pathway can account for decremented VPM and nRt responses to later cycles
in the stimulus train. We also find that T-current enhanced nRt spiking, and hence synaptic
inhibition. T-current has a greater effect at lower frequencies in both VPM and nRt, and further,
the effect is more pronounced for (high velocity) pulsatile deflections than for (lower velocity)
sinusoidal movements. T-current acts by prolonging and temporally smoothing nRT responses.
Prolonged nRT firing can also be produced by simulating long-lasting synapses at VPM to nRt
connections. Together, PrV-VPm synaptic depression and low-pass nRT characteristics enhance
the temporal modulation of VPm responses by temporally focusing activity evoked by whisker
movement while suppressing spiking during inter-deflection periods. (grant number NIMH 61372.)
24th -- Chapter Meeting
Speaker: Glen Whitehead
Title: "Graph Theory Applied to Chemistry"
Where: 704 Thackeray
Time: 3:00 PM (Tuesday)
Abstract: In this presentation, two applications of
graph theory to chemistry are discussed. The
first application is boiling point models of alkanes. The second
application is melting point models
of a special class of alkanes.
Burch, Wakefield and Whitehead developed boiling point models for alkane
isomers containing up
to and including 12 carbon atoms. These models are based on the
following indices: molecular
weight, number of carbon atoms, Hosoya index, Wiener number, Wiener Path
numbers, methyl index
and ethyl index. Nonlinear regression techniques were used to
determine coefficients and exponents
of indices in our models.
Burch and Whitehead developed melting point models for a special class of
alkanes. This class
contains alkanes having 10 to 20 carbon atoms and only one methyl group.
This class of alkanes
are of special interest to petroleum engineers interested in manufacturing
synthetic diesel fuel.
These models are based on the following indices: number of carbon atoms,
Wiener Path numbers,
mean Wiener index, and the methyl locant index. Nonlinear regression
techniques were used to
determine coefficients and exponents of the indices in our model.