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A circuit analysis of habituation in Caenorhabditis elegans Wicks, Stephen Robert
Abstract
The tap withdrawal response of the nematode Caenorhabditis elegans supports several forms of behavioural plasticity, including habituation (Rankin, Beck, & Chiba, 1990). The relative simplicity of this organism, both in terms of its nervous system and its genetic tractability, suggest that it would be a fruitful model system within which to investigate the neural and molecular substrates of learning. This report examines the production of the tap withdrawal response and the plasticity exhibited by that response at the cellular/circuit level. The neural circuit that mediates the tap response was identified through a program of single-cell laser microsurgery. Further behavioural analyses determined some of the functional properties of the tap withdrawal circuit neurons, both in the production of the tap withdrawal response and in the generation of the plasticity that that response expresses. First, this work demonstrated that the response was not unitary, but rather was composed of two competing reflexive behaviours: forward locomotion in response to posterior mechanosensory input and backward locomotion in response to anterior mechanosensory input. An animal's response to given stimulus was determined by the relative degree to which each of these reflexes were recruited. Second, it was demonstrated that each constituent reflex habituated in the absence of the other, and that habituation of the intact response was a summation of these two processes. Third, a dynamic network simulation of the circuit was used to predict the sign or polarity of the synapses that constitute the circuit. Fourth, it was demonstrated that at least two independent interstimulus interval-dependent processes were recruited during habituation: One that affects habituation kinetics and one that affects recovery from habituation. Finally, an analysis of the effects of tap withdrawal response habituation on other non-mechanosensory withdrawal behaviours was used, in conjunction with ablation studies, to identify potential loci of change within the circuit that might underlie habituation. The implications both of the functional properties of tap withdrawal circuit elements during habituation and the restriction of potential sites of change are discussed.
Item Metadata
Title |
A circuit analysis of habituation in Caenorhabditis elegans
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1996
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Description |
The tap withdrawal response of the nematode Caenorhabditis elegans supports several
forms of behavioural plasticity, including habituation (Rankin, Beck, & Chiba, 1990). The relative
simplicity of this organism, both in terms of its nervous system and its genetic tractability,
suggest that it would be a fruitful model system within which to investigate the neural and
molecular substrates of learning. This report examines the production of the tap withdrawal
response and the plasticity exhibited by that response at the cellular/circuit level. The neural
circuit that mediates the tap response was identified through a program of single-cell laser
microsurgery. Further behavioural analyses determined some of the functional properties of the
tap withdrawal circuit neurons, both in the production of the tap withdrawal response and in the
generation of the plasticity that that response expresses. First, this work demonstrated that the
response was not unitary, but rather was composed of two competing reflexive behaviours:
forward locomotion in response to posterior mechanosensory input and backward locomotion in
response to anterior mechanosensory input. An animal's response to given stimulus was
determined by the relative degree to which each of these reflexes were recruited. Second, it was
demonstrated that each constituent reflex habituated in the absence of the other, and that
habituation of the intact response was a summation of these two processes. Third, a dynamic
network simulation of the circuit was used to predict the sign or polarity of the synapses that
constitute the circuit. Fourth, it was demonstrated that at least two independent interstimulus
interval-dependent processes were recruited during habituation: One that affects habituation
kinetics and one that affects recovery from habituation. Finally, an analysis of the effects of tap
withdrawal response habituation on other non-mechanosensory withdrawal behaviours was used,
in conjunction with ablation studies, to identify potential loci of change within the circuit that might underlie habituation. The implications both of the functional properties of tap withdrawal
circuit elements during habituation and the restriction of potential sites of change are discussed.
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Extent |
10570028 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-03-17
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0087897
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1996-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.