Multi-electrode analysis of pattern generation and its adaptation to reward

Harris, Christopher (2012) Multi-electrode analysis of pattern generation and its adaptation to reward. Doctoral thesis (PhD), University of Sussex.

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Abstract

Much behaviour is controlled by neural circuits known as central pattern generators
(CPGs). The aim of the work presented in this thesis was to uncover general
mechanisms that modify the behavioural output of CPGs in ways that maximise
adaptive fitness. To achieve this aim it was necessary to monitor populations of
neurons associated with a CPG that responds to changes in sensory reward. I used
multi-electrode arrays (MEAs) to monitor neuronal populations in semi-intact
preparations of the snail Lymnaea stagnalis. Spike patterns associated with cycles of
the feeding CPG were readily recorded in the buccal, cerebral and pedal ganglia. A
sensory food stimulus accelerated the CPG and this acceleration was shown to depend
on dopamine. Single-trial conditioning on the MEA allowed fictive feeding to be
induced by a previously neutral taste stimulus. In addition to the activity of the feeding
CPG the MEA also revealed a second neuronal population that had not previously been
characterized. This population fires continuously in-between the cycles of the feeding
CPG but becomes quiescent for a variable period following each cycle. The duration of
this quiescent period often predicted the timing of the next activation of the CPG.
Stimulation of a nerve associated with food reward failed to activate the CPG during
the quiescent period, indicating that it reflects a ‘network refractory period’ (NRP) of
the kind previously observed in locomotor CPGs. The sucrose and dopamine stimuli
both significantly shortened the NRP. These results show that the MEA recording
method can identify distinct populations of neurons associated with adaptive feeding
behaviour, and suggest a general mechanism that allows a CPG to adapt its behavioural
output to maximise reward

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QP Physiology > QP0351 Neurophysiology and neuropsychology
Depositing User: Library Cataloguing
Date Deposited: 22 Jan 2013 13:14
Last Modified: 08 Sep 2015 13:45
URI: http://sro.sussex.ac.uk/id/eprint/43335

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