Venue: Centre Broca
Dr. Laura Bradfield
Senior Research Fellow
Head of the Brain and Behaviour Lab
School of Life Sciences, UTS, Sydney, Australia
Invited by Shauna Parkes (INCIA)
Title
Behavioural and Brain Mechanisms of Sustained Contingency Degradation
Abstract
Preclinical models of treatments for substance use disorder have typically involved extinction, during which once-rewarded cues or actions are no longer paired with reward. One problem with extinction, however, is that extinguished responding tends to spontaneously recover over time. We therefore tested whether contingency degradation might be effective in producing a reduction in responding that does not spontaneously recover. In Experiment 1, rats were trained to press a left lever for pellets and a right lever for a sucrose solution, or the opposite arrangement, counterbalanced. Following training, although both levers continued to earn their respective outcomes, one of outcomes was also delivered when no lever press had occurred. This degraded the contingency between that lever and its outcome, because rats selectively reduced responding on that lever. When given a 10 min test in which both levers were extended and no outcomes delivered, rats responded in accordance with the degradation contingencies (i.e. NonDegraded > Degraded) regardless of whether they were tested 1 day or 2 weeks after degradation, suggesting that degradation does not spontaneously recover. In Experiment 2, we investigated whether chemogenetically inhibiting glutamatergic neurons in the lateral OFC impaired degradation learning using this paradigm. Animals injected with the control virus (mCitrine+DCZ group) learned degradation, whereas animals for whom the lateral OFC was inhibited prior to degradation training (hM4Di+DCZ group) did not (i.e. nondegraded = degraded), and this pattern of results was retained at both immediate and delayed tests. A third experiment will determine whether this sustained impairment in extinction will persist when the lateral OFC is chemogenetically silenced during test. Together, these experiments suggest that the behavioural and brain mechanisms of contingency degradation and extinction are distinct, and that degradation is more effective in producing a lasting behavioural change.
Biography
Dr Laura Bradfield is a Senior Research Fellow and head of the Brain and Behaviour Lab in the School of Life Sciences at UTS. She joined UTS as a Research Fellow in 2018 after undertaking her PhD and postgraduate studies at UNSW Sydney. Laura’s primary areas of interest include investigating the behavioural and brain mechanisms of compulsive disorders, the glial mechanisms of goal-directed decision-making, and contextual modulation of goal-directed action. Her work is currently funded by two NHMRC Ideas Grants, and she has previously been awarded an ARC Discovery Project as well as two NHMRC project grants. In total Laura’s research has attracted approximately $3.5 million. Laura has published 30+ journal articles and three book chapters, including first author articles in the influential journals Neuron and Nature Neuroscience. She is a Reviewing Editor at eLife, eNeuro and Frontiers in Behavioural Neuroscience, and an Associate Editor at the Journal of Neuroscience. Laura has spoken widely about her research at conferences and events in Australia and overseas. In 2022, she won the UTS Faculty of Science’s “Supervisor of the Year” award, and she is also passionate about increasing diversity in science and improving conditions within the scientific community for underrepresented individuals.