I completed an undergraduate degree in Psychology, and a PhD in neuroscience at UNSW, before spending 8 years as a postdoctoral research at USyd and UNSW. During this time I received several NHMRC project grants, and published high impact papers in journals such as Neuron, Current Biology, and Journal of Neuroscience.
I now head the decision-making neuroscience research group at the Centre for Neuroscience and Regenerative Medicine. Together, we investigate in the behavioural and brain mechanisms of compulsive disorders, the contextual modulation of decision-making, as well as decision-making in dementia.
I am passionate about improving the future of science by training and mentoring a diverse set of scientists, and ensuring individuals are treated fairly and equally. Science benefits from diversity.
Review editor and eNeuro
Associate editor at Journal of Neuroscience
Peer review mentor at Journal of Neuroscience
Review editor at Frontiers in behavioural neuroscience
Member of Society for Neuroscience
Member of Women in Learning
Can supervise: YES
The neural circuitry of decision-making
The context of decision-making
Decision-making deficits in neurodegenerative disorders, primarily Alzheimer's disease
Decision-making deficits in compulsve neuropsychiatric disorders
This chapter discusses the considerable research that has identified distinct functional circuits linking frontal cortex with the basal ganglia in the control of goal-directed and habitual actions. OCD is characterized by hyperactivity in a circuit involving some of these regions. Recent accounts of the interaction of goal-directed actions and habits suggest that these control processes interact hierarchically, so one alternative to current theories is that OCD reflects a dysfunction in this interactive process resulting in dysregulated action selection, whether that selection is driven by the outcome itself or by cues predicting the outcome. Importantly, it appears that both sources of action selection depend on the OFC—outcome based retrieval on the medial OFC and cue-related retrieval on the lateral OFC. From this perspective, therefore, hyperactivity of the OFC could produce both elevated outcome retrieval and increased responsiveness to outcomes-related cues, resulting in dysregulated action selection and compulsive action initiation as a consequence.
Bradfield, LA & Hart, G 2020, 'Rodent medial and lateral orbitofrontal cortices represent unique components of cognitive maps of task space', NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS, vol. 108, pp. 287-294.View/Download from: Publisher's site
Abstract Rats use spatiotemporal features of the environment to navigate to a goal, but whether representations of 'action space' are necessary for non-navigational goal-directed actions is unknown. We addressed this question by assessing goal-directed action control across contexts and under hippocampal inactivation and found that such actions do indeed rely on a representation of action space but only immediately after initial acquisition. One Sentence Summary Goal-directed actions depend on a hippocampal representation of action space immediately after initial encoding but not after a delay.
Jean-Richard-dit-Bressel, P, Ma, C, Bradfield, LA, Killcross, S & McNally, GP 2019, 'Punishment insensitivity emerges from impaired contingency detection, not aversion insensitivity or reward dominance', ELIFE, vol. 8.View/Download from: Publisher's site
Bradfield, LA, Hart, G & Balleine, BW 2018, 'Inferring action-dependent outcome representations depends on anterior but not posterior medial orbitofrontal cortex.', Neurobiology of learning and memory, vol. 155, pp. 463-473.View/Download from: Publisher's site
Although studies examining orbitofrontal cortex (OFC) often treat it as though it were functionally homogeneous, recent evidence has questioned this assumption. Not only are the various subregions of OFC (lateral, ventral, and medial) hetereogeneous, but there is further evidence of heterogeneity within those subregions. For example, several studies in both humans and monkeys have revealed a functional subdivision along the anterior-posterior gradient of the medial OFC (mOFC). Given our previous findings suggesting that, in rats, the mOFC is responsible for inferring the likelihood of unobservable action outcomes (Bradfield, Dezfouli, van Holstein, Chieng, & Balleine, 2015), and given the anterior nature of the placements of our prior manipulations, we decided to assess whether the rat mOFC also differs in connection and function along its anteroposterior axis. We first used retrograde tracing to compare the density of efferents from mOFC to several structures known to contribute to goal-directed action: the mediodorsal thalamus, basolateral amygdala, posterior dorsomedial striatum, nucleus accumbens core and ventral tegmental area. We then compared the functional effects of anterior versus posterior mOFC excitotoxic lesions on tests of Pavlovian-instrumental transfer, instrumental outcome devaluation and outcome-specific reinstatement. We found evidence that the anterior mOFC had greater connectivity with the accumbens core and greater functional involvement in goal-directed action than the posterior mOFC. Consistent with previous findings across species, therefore, these results suggest that the anterior and posterior mOFC of the rat are indeed functionally distinct, and that it is the anterior mOFC that is particularly critical for inferring unobservable action outcomes.
Hart, G, Bradfield, LA & Balleine, BW 2018, 'Prefrontal Corticostriatal Disconnection Blocks the Acquisition of Goal-Directed Action.', The Journal of neuroscience : the official journal of the Society for Neuroscience, vol. 38, no. 5, pp. 1311-1322.View/Download from: Publisher's site
The acquisition of goal-directed action requires encoding of the association between an action and its specific consequences or outcome. At a neural level, this encoding has been hypothesized to involve a prefrontal corticostriatal circuit involving the projection from the prelimbic cortex (PL) to the posterior dorsomedial striatum (pDMS); however, no direct evidence for this claim has been reported. In a series of experiments, we performed functional disconnection of this pathway using targeted lesions of the anterior corpus callosum to disrupt contralateral corticostriatal projections with asymmetrical lesions of the PL and/or pDMS to block plasticity in this circuit in rats. We first demonstrated that unilaterally blocking the PL input to the pDMS prevented the phosphorylation of extracellular signal-related kinase/mitogen activated protein kinase (pERK/pMAPK) induced by instrumental training. Next, we used a full bilateral disconnection of the PL from the pDMS and assessed goal-directed action using an outcome-devaluation test. Importantly, we found evidence that rats maintaining an ipsilateral and/or contralateral connection between the PL and the pDMS were able to acquire goal-directed actions. In contrast, bilateral PL-pDMS disconnection abolished the acquisition of goal-directed actions. Finally, we used a temporary pharmacological disconnection to disrupt PL inputs to the pDMS by infusing the NMDA antagonist dl-2-amino-5-phosphonopentanoic acid into the pDMS during instrumental training and found that this manipulation also disrupted goal-directed learning. These results establish that, in rats, the acquisition of new goal-directed actions depends on a prefrontal-corticostriatal circuit involving a connection between the PL and the pDMS.SIGNIFICANCE STATEMENT It has been hypothesized that the prelimbic cortex (PL) and posterior dorsomedial striatum (pDMS) in rodents interact in a corticostriatal circuit to mediate goal-directed learning. However, no dire...
Hart, G, Bradfield, LA, Fok, SY, Chieng, B & Balleine, BW 2018, 'The Bilateral Prefronto-striatal Pathway Is Necessary for Learning New Goal-Directed Actions.', Current biology : CB, vol. 28, no. 14, pp. 2218-2229.e7.View/Download from: Publisher's site
The acquisition of new goal-directed actions requires the encoding of action-outcome associations. At a neural level, this encoding has been hypothesized to involve a prefronto-striatal circuit extending between the prelimbic cortex (PL) and the posterior dorsomedial striatum (pDMS); however, no research identifying this pathway with any precision has been reported. We started by mapping the prelimbic input to the dorsal and ventral striatum using a combination of retrograde and anterograde tracing with CLARITY and established that PL-pDMS projections share some overlap with projections to the nucleus accumbens core (NAc) in rats. We then tested whether each of these pathways were functionally required for goal-directed learning; we used a pathway-specific dual-virus chemogenetic approach to selectively silence pDMS-projecting or NAc-projecting PL neurons during instrumental training and tested rats for goal-directed action. We found that silencing PL-pDMS projections abolished goal-directed learning, whereas silencing PL-NAc projections left goal-directed learning intact. Finally, we used a three-virus approach to silence bilateral and contralateral pDMS-projecting PL neurons and again blocked goal-directed learning. These results establish that the acquisition of new goal-directed actions depends on the bilateral PL-pDMS pathway driven by intratelencephalic cortical neurons.
Bradfield, LA & Balleine, BW 2017, 'Thalamic Control of Dorsomedial Striatum Regulates Internal State to Guide Goal-Directed Action Selection.', The Journal of neuroscience : the official journal of the Society for Neuroscience, vol. 37, no. 13, pp. 3721-3733.View/Download from: Publisher's site
We (Bradfield et al., 2013) have demonstrated previously that parafascicular thalamic nucleus (PF)-controlled neurons in the posterior dorsomedial striatum (pDMS) are critical for interlacing new and existing action-outcome contingencies to control goal-directed action. Based on these findings, it was suggested that animals with a dysfunctional PF-pDMS pathway might suffer a deficit in creating or retrieving internal contexts or "states" on which such information could become conditional. To assess this hypothesis more directly, rats were given a disconnection treatment using contralateral cytotoxic lesions of the PF and pDMS (Group CONTRA) or ipsilateral control lesions (Group IPSI) and trained to press a right and left lever for sucrose and pellet outcomes, after which these contingencies were reversed. The rats were then given an outcome devaluation test (all experiments) and a test of outcome-specific reinstatement (Experiments 1 and 3). We found that devaluation performance was intact for both groups after training of initial contingencies, but impaired for Group CONTRA after reversal. However, performance was restored by additional reversal training. Furthermore, when tested a second time after reversal training, rats in both groups demonstrated responding in accordance with the original contingencies, providing direct evidence of modulation of action selection by state. Finally, we found that external context could substitute for internal state and so could rescue responding in Group CONTRA, but only in the reinstatement test. Together, these findings suggest that animals use internal state information to guide action selection and that this information is modulated by the PF-pDMS pathway.SIGNIFICANCE STATEMENT Individuals with Parkinson's disease dementia often suffer a characteristic deficit in "cognitive flexibility." It has been suggested that neurodegeneration in the pathway between the centromedian/parafascicular thalalmic nucleus (PF) and striatum m...
Bradfield, LA, Dezfouli, A, van Holstein, M, Chieng, B & Balleine, BW 2015, 'Medial Orbitofrontal Cortex Mediates Outcome Retrieval in Partially Observable Task Situations', NEURON, vol. 88, no. 6, pp. 1268-1280.View/Download from: Publisher's site
Parkes, SL, Bradfield, LA & Balleine, BW 2015, 'Interaction of Insular Cortex and Ventral Striatum Mediates the Effect of Incentive Memory on Choice Between Goal-Directed Actions', JOURNAL OF NEUROSCIENCE, vol. 35, no. 16, pp. 6464-6471.View/Download from: Publisher's site
Bradfield, LA & Balleine, BW 2013, 'Hierarchical and Binary Associations Compete for Behavioral Control During Instrumental Biconditional Discrimination', JOURNAL OF EXPERIMENTAL PSYCHOLOGY-ANIMAL BEHAVIORAL PROCESSES, vol. 39, no. 1, pp. 2-13.View/Download from: Publisher's site
Bradfield, LA, Bertran-Gonzalez, J, Chieng, B & Balleine, BW 2013, 'The Thalamostriatal Pathway and Cholinergic Control of Goal-Directed Action: Interlacing New with Existing Learning in the Striatum', NEURON, vol. 79, no. 1, pp. 153-166.View/Download from: Publisher's site
Bradfield, LA, Hart, G & Balleine, BW 2013, 'The role of the anterior, mediodorsal, and parafascicular thalamus in instrumental conditioning', Frontiers in Systems Neuroscience, vol. 7, no. OCT.View/Download from: Publisher's site
The traditional animal model of instrumental behavior has focused almost exclusively on structures within the cortico-striatal network and ignored the contributions of various thalamic nuclei despite large and specific connections with each of these structures. One possible reason for this is that the thalamus has been conventionally viewed as a mediator of general processes, such as attention, arousal and movement, that are not easily separated from more cognitive aspects of instrumental behavior. Recent research has, however, begun to separate these roles. Here we review the role of three thalamic nuclei in instrumental conditioning: the anterior thalamic nuclei (ANT), the mediodorsal (MD), and parafascicular thalamic nuclei (PF). Early research suggested that ANT might regulate aspects of instrumental behavior but, on review, we suggest that the types of tasks used in these studies were more likely to recruit Pavlovian processes. Indeed lesions of ANT have been found to have no effect on performance in instrumental free-operant tasks. By contrast the mediodorsal thalamus (MD) has been found to play a specific and important role in the acquisition of goal-directed action. We propose this role is related to its connections with prelimbic cortex (PL) and present new data that directly implicates this circuit in the acquisition of goal-directed actions. Finally we review evidence suggesting the PF, although not critical for the acquisition or performance of instrumental actions, plays a specific role in regulating action flexibility. © 2013 Bradfield, Hart and Balleine.
Bradfield, LA & McNally, GP 2010, 'The role of nucleus accumbens shell in learning about neutral versus excitatory stimuli during Pavlovian fear conditioning', LEARNING & MEMORY, vol. 17, no. 7, pp. 337-343.View/Download from: Publisher's site
Bradfield, LA & Balleine, BW 2017, 'The learning and motivational processes controlling goal-directed action and their neural bases' in Decision Neuroscience: An Integrative Perspective, pp. 71-80.View/Download from: Publisher's site
© 2017 Elsevier Inc. All rights reserved. Research has made considerable progress in describing the learning and motivational processes controlling goal-directed action and their related neural circuitry. Broadly this circuitry spans various regions within the corticostriatal-thalamic loop, within which specific structures mediate differentiable aspects of goal-directed learning and performance. These aspects include the acquisition of action-outcome contingencies, the encoding and retrieval or incentive value, the matching of that value to specific outcome representations, and finally the integration of this information for action selection. Information from each of the structures that mediate these processes converges on the striatum, with the posterior dorsomedial striatum in particular hypothesized to represent the neural locus of goal-directed action. Here we discuss evidence from rodent studies regarding the neural circuits mediating each of these individual processes before considering how they are integrated within the striatum for successful goal-directed action selection.