Files in this item
Linking actions to outcomes : the role of the posterior pedunculopontine tegmental nucleus in instrumental learning
Item metadata
dc.contributor.advisor | Winn, Philip | |
dc.contributor.author | MacLaren, Duncan A. A. | |
dc.coverage.spatial | 265 | en_US |
dc.date.accessioned | 2012-10-16T15:07:01Z | |
dc.date.available | 2012-10-16T15:07:01Z | |
dc.date.issued | 2012-11-01 | |
dc.identifier.uri | http://hdl.handle.net/10023/3183 | |
dc.description.abstract | Located in the mesopontine tegmentum, the pedunculopontine tegmental nucleus (PPTg) is comprised principally of glutamatergic, cholinergic and GABAergic neurons. In addition to being fully integrated into basal ganglia, PPTg projects to thalamus and motor output sites in the brainstem. Previous studies have shown a range of behavioural changes after PPTg manipulation. Prominent amongst these is an apparent deficit in the ability to learn the consequences of actions. PPTg is divisible into a posterior component (pPPTg) in receipt of rapid polymodal sensory input and projecting into VTA/SNc dopamine neurons and an anterior component (aPPTg) in receipt of basal ganglia outflow and projecting into SNc and lower brainstem structures. The research described here assesses the role of the pPPTg in instrumental learning. Using a contingency degradation paradigm, it was shown that inactivation of the pPPTg (by muscimol microinfusion) specifically blocked the updating of associations between actions and outcomes, without the affecting the ability to re-execute previously learned instrumental actions. Selective bilateral destruction of pPPTg cholinergic neurons (with the fusion toxin diphtheria toxin – urotensin II [Dtx-UII]) resulted in >90% loss of pPPTg cholinergic neurons. These lesions produced no detectable changes on any measured aspect of an instrumental learning task consisting of various fixed and variable ratio schedules of reinforcement and extinction. Subsequent experiments found that the same selective cholinergic pPPTg lesions also produced no changes in the locomotor response to nicotine or rate of nicotine sensitisation. These results are the first to demonstrate a brainstem role in action-outcome learning. Results support the view that PPTg performs a ‘first pass’ analysis on incoming sensory data and interfaces salient aspects of this with appropriate basal ganglia and brainstem circuitry, with glutamatergic pPPTg projections sending an essential signal and cholinergic projections performing as part of a wider modulatory system. | en_US |
dc.language.iso | en | en_US |
dc.publisher | University of St Andrews | |
dc.subject | Pedunculopontine | en_US |
dc.subject | Learning | en_US |
dc.subject | Action-outcome | en_US |
dc.subject | Cholinergic | en_US |
dc.subject | Dtx-UII | en_US |
dc.subject | Basal ganglia | en_US |
dc.subject.lcc | QP408.L2 | |
dc.subject.lcsh | Operant conditioning--Physiological aspects | en_US |
dc.subject.lcsh | Learning--Physiological aspects | en_US |
dc.subject.lcsh | Pons Varolii--Physiology | en_US |
dc.subject.lcsh | Pons Varolii--Effect of chemicals on | en_US |
dc.title | Linking actions to outcomes : the role of the posterior pedunculopontine tegmental nucleus in instrumental learning | en_US |
dc.type | Thesis | en_US |
dc.contributor.sponsor | Wellcome Trust | en_US |
dc.contributor.sponsor | University of St Andrews. School of Psychology | en_US |
dc.type.qualificationlevel | Doctoral | en_US |
dc.type.qualificationname | PhD Doctor of Philosophy | en_US |
dc.publisher.institution | The University of St Andrews | en_US |
This item appears in the following Collection(s)
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.