Research Interests

Research in my laboratories involves projects spanning three fascinating areas:

1. Psychoneuroimmunology (PNI)
• PNI is the study of the interactions between the central nervous system (CNS) and the immune system. Early work has shown that the CNS exerts considerable control over immune function, and these controls have significant contributions to the ability of an individual to survive disease and recover from injury. However, more recently it has been demonstrated that the immune system has powerful effects on cognition, affect and behaviour, and not only serves to signal the CNS that injury or infection has occurred, but also triggers self-care behaviours and motivates recuperation and rest. Moreover, glial cells - the major non-neuronal cell type in the CNS - release inflammatory molecules that are important in the development of major neuropathologies and cognitive and affective disorders.
2. Neurobiology of pain
• Pain is an intrinsically interesting topic to study. From a clinical point of view, pain is an incredibly distressing and disabling aspect of disease and injury that is both widespread and poorly addressed. From a neuroscientific point of view, pain is an amazing model to study as the relationships between noxious stimulus, protective behavioural responses and neural activity are so clear. And it is fascinating from a Psychological perspective as the experience of pain involves sensory-discriminative, emotional-motivational and cognitive aspects. That is, pain tells you where something hurts, it is accompanied by unpleasantness and motivates protective and recuperational behavioviours, and it demands attention and cognitive resources.
3. Animal cognition
• The study of the cognitive abilities of non-human animals is important for many reasons. All animals require basic cognitive functions to solve similar survival problems: How to find food and to learn which food is safe to consume, how to avoid danger, to learn and remember the extent of territory and to navigate through the environment, to remember other animals and learn their social standing, to learn the consequences of their behaviour, to learn predictive relationships between events, and to learn to discriminate between different experiences or to generalise from one item in a category to another item. Studying how different animals solve these problems can reveal something of the breadth and generality of solutions to cognitive problems, can reveal the function of cognitive abilities (e.g., by studying cognitive changes in species that adapt to particular problems), and can reveal fine differences in cognitive abilities that may not be apparent by simply studying one species (i.e., humans). Moreover, from a practical standpoint, valid animal models of cognition are important tools in studying the neurobiology of memory, attention, discrimination, executive function, motivation and learning.

My previous research interests focused on the role of proinflammatory cytokines in modulating the analgesic and motivational effects of opioid drugs. However, since coming to The University of Sydney I have changed my research direction. Research in my laboratory focuses on how disease impairs cognitive function in rodent models of memory, motivation and executive function. Here is an overview of some recent projects which have not yet made it to publication:

1. Cognitive dysfunctions in pain
• Persistent inflammatory pain reduces contextual fear conditioning in the rat With Linda Watkins, Steve Maier and Jerry Rudy at the University of Colorado. Status: Manuscript in preparation.
• Spinal and supra spinal interleukin-1 mediates pain-induced impairment in contextual fear conditioning With Linda Watkins, Steve Maier and Jerry Rudy at the University of Colorado. Status: Manuscript in preparation.
• Acute pain produces working memory deficits in the rat With Olivia Garnett, Honours student in the School of Psychology, the University of Sydney. Status: Manuscript in preparation.
• Acute pain increases generalization of conditioned fear in the rat: A role for NMDA receptor mediated processes in the spinal cord. With Alex Davis, Honours Student in the School of Psychology, the University of Sydney. Status: Work is continuing.
2. Long-term and persistent cognitive dysfunctions caused by chemotherapy and cancer
• The chemotherapy agent oxaliplatin produces persistent cognitive impairments in the rat With Joanna Fardell, PhD Candidate in the School of Psychology, the University of Sydney, and Janette Vardy, Medical Oncologist at the Sydney Cancer Centre. Status: Manuscript in preparation.
• The chemotherapy agent Methotrexate produces persistent cognitive impairments in the rat With Joanna Fardell, PhD Candidate in the School of Psychology, the University of Sydney, and Janette Vardy, Medical Oncologist at the Sydney Cancer Centre. Status: Manuscript in preparation.
• Oxaliplatin causes long-term relational learning problems in the rat. With Melissa Sharpe, Honours student and Joanna Fardell, PhD Candidate in the School of Psychology, the University of Sydney, and Janette Vardy, Medical Oncologist at the Sydney Cancer Centre. Status: Manuscript in preparation.
• Methotrexate produces working memory and behavioural inhibition impairments in the rat With Warren Logge, Honours student, and Joanna Fardell, PhD Candidate in the School of Psychology, the University of Sydney, and Janette Vardy, Medical Oncologist at the Sydney Cancer Centre. Status: Work is continuing.
3. Complex spatial cognition in the rat
• Motivational differences in response and place learning in the rat: Place learning is sensitive to reinforcer devaluation but response learning is not. Status: Manuscript in preparation
• Free operant procedure for studying spatial cognition in the rat. Status: Work is continuing.

Publications

2004

1. Johnston, I. N., Wieseler-Frank, J., Milligan,E. D., Frank, M. G., Zapata, V., Campisi, J., Langer, S., Martin, D.,Green, P., Fleshner, M., Leinwand, L., Maier, S. F. & Watkins, L. W.(2004) Immune interactions in morphine analgesia: A role forproinflammatory cytokines and fractalkine in analgesic tolerance and subsequent hyperalgesia and allodynia. Journal of Neuroscience, 24, 7353-7365.
2. Johnston, I. N. & Westbrook, R. F. (In press). Inhibition of morphine analgesia by LPS: Role of opioid and NMDA receptors and spinal microglia. BehaviouralBrain Research.
3. Johnston, I. N. & Westbrook, R. F. (2004). Inhibition of morphine analgesia by lithium: Role of peripheral and central opioid receptors. BehaviouralBrain Research,151(1-2), 151-8.

2003

4. Johnston, I. N. & Westbrook, R. F. (2003). Acute and conditionedillness reduces morphine analgesia. Behavioural Brain Research, 142, 89-97.

2000

5. McNally,G. P., Johnston, I. N. & Westbrook, R. F. (2000). A peripheral, intracerebral or intrathecaladministration of an opioid receptor antagonist blocks illness-inducedhyperalgesia in rats. Behavioral Neuroscience, 114, 1183-1190.