An analysis of olfactory cortical behavior and function using computer simulation techniques
This thesis presents the results of computer simulations of olfactory cortex designed to explore the role of biological mechanisms in the behavior and function of cerebral cortical networks. Chapter 1 provides the basic description of the model of piriform cortex including simulation methodology an...
| Summary: | This thesis presents the results of computer simulations of olfactory cortex designed to explore the role of biological mechanisms in the behavior and function of cerebral cortical networks.
Chapter 1 provides the basic description of the model of piriform cortex including simulation methodology and parameters. The results of network simulations which reproduce three characteristic macroscopic evoked cortical responses are described with the suggestion that the simulated temporal dynamics which underlie these responses may reflect the operation of a fundamental computational strategy used in the storage and retrieval of olfactory information.
Using both single cell and network simulations, chapter 2 looks in detail at the patterns of synaptic currents produced along the dendritic tree of single cells and compares simulated results with actual experimental measurements. This technique provides the means to identify the relative synaptic contributions and provides an important constraint on the selection of synaptic weight distribution parameters in the network model. The results identify the sources of synaptic inputs underlying characteristic macroscopic evoked events and thus provide additional insights into the results of chapter 1.
Using the basic model outlined in chapter 1, chapter 3 explores the effects of incorporating a mechanism for activity dependent modification of synaptic weights along selected interconnection pathways. This is done in the context of storage and retrieval of patterned inputs to the model intended to simulate the patterns of activity which represent actual olfactory input. The results indicate that the basic model which reproduces known physiological responses can also be made to store and retrieve patterned input indicating that the dynamics of the simulated cortex are compatible with a continuous mechanism of Hebbian synaptic plasticity.
In chapter 4 the structure of the basic piriform cortex model is modified slightly to reflect more neocortical-like features. The dynamics of this modified network are compared with experimental observations of coherent oscillatory behavior in primary visual cortex. These simulations indicate that the observed behavior are characteristic of the network architecture and do not necessarily represent the encoding of stimulus specific information.
Chapter 5 provides a general overview of the simulation system used to implement all of the simulations used in this research.
Appendix 1 examines the effects of critical parameter variations on simulated EEGs.
Appendices 2 and 3 contain the complete GENESIS scripts describing the network and single cell models used in this work.
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