Luna Ortiz, Carlos Ricardo (2018) Modelling and Analysis of Drosophila Early Visual System A Systems Engineering Approach. PhD thesis, University of Sheffield.
Abstract
Over the past century or so Drosophila has been established as an ideal model organism to
study, among other things, neural computation and in particular sensory processing. In this
respect there are many features that make Drosophila an ideal model organism, especially
the fact that it offers a vast amount of genetic and experimental tools for manipulating
and interrogating neural circuits. Whilst comprehensive models of sensory processing in
Drosophila are not yet available, considerable progress has been made in recent years in
modelling the early stages of sensory processing. When it comes to visual processing,
accurate empirical and biophysical models of the R1-R6 photoreceptors were developed
and used to characterize nonlinear processing at photoreceptor level and to demonstrate that
R1-R6 photoreceptors encode phase congruency.
A limitation of the latest photoreceptor models is that these do not account explicitly for
the modulation of photoreceptor responses by the network of interneurones hosted in the
lamina. As a consequence, these models cannot describe in a unifying way the photoreceptor
response in the absence of the feedback from the downstream neurons and thus cannot be
used to elucidate the role of interneurones in photoreceptor adaptation.
In this thesis, electrophysiological photoreceptor recordings acquired in-vivo from wild-
type and histamine defficient mutant fruit flies are used to develop and validate new com-
prehensive models of R1-R6 photoreceptors, which not only predict the response of these
photoreceptors in wild-type and mutant fruit flies, over the entire environmental range of
light intensities but also characterize explicitly the contribution of lamina neurons to photore-
ceptor adaptation. As a consequence, the new models provide suitable building blocks for
assembling a complete model of the retina which takes into account the true connectivity
between photoreceptors and downstream interneurones.
A recent study has demonstrated that R1-R6 photoreceptors employ nonlinear processing
to selectively encode and enhance temporal phase congruency. It has been suggested that
this processing strategy achieves an optimal trade-off between the two competing goals of
minimizing distortion in decoding behaviourally relevant stimuli features and minimizing
the information rate, which ultimately enables more efficient downstream processing of
spatio-temporal visual stimuli for edge and motion detection.Using rigorous information theoretic tools, this thesis derives and analyzes the rate-distortion characteristics associated with the linear and nonlinear transformations performed
by photoreceptors on a stimulus generated by a signal source with a well defined distribution.
Metadata
Supervisors: | Coca, Daniel |
---|---|
Awarding institution: | University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Automatic Control and Systems Engineering (Sheffield) |
Identification Number/EthosID: | uk.bl.ethos.736576 |
Depositing User: | Carlos Ricardo Luna Ortiz |
Date Deposited: | 13 Mar 2018 14:22 |
Last Modified: | 25 Sep 2019 20:03 |
Open Archives Initiative ID (OAI ID): | oai:etheses.whiterose.ac.uk:19574 |
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