Dr Simon Fisher

Dr Simon Fisher

Postdoctoral Fellow

School of Biomedical Sciences and Pharmacy

Career Summary


An early interest in trying to figure out human behaviour led Simon to study Psychology and Information Systems. After some time in the corporate world, and lots of traveling, Simon returned to academia to pursue Behavioural and Systems Neuroscience.
"I wanted to get back to long-held interests of how the brain, this highly complex fleshy organ we all carry around, drives behaviour."
Simon explains that a foundational aspect of his thinking is the relationship between the microscopic world of the brain and the complex behaviour that we all perform and observe in others.
"It's amazingly interesting how changes in protein expression in particular cells, and how chemicals in the brain interact with these cells, can lead to overt changes in behaviour and underlie neuropsychiatric disorders."
"There's a certain beauty in this scaling from low level physical, relatively blind and chaotic processes, all the way up to the purposeful and complex repertoire of human behaviour."
How the brain learns with plasticity
It has long been proposed that the brain learns by changing the strength of connections between pathways, a process known as synaptic plasticity. The basic roots of this idea go back to thinking by the eminent psychologist William James and others in the late nineteenth century, and it was most famously formalised by Donald Hebb in the mid twentieth century. Modern neuroscience tools have allowed researchers to investigate synaptic plasticity in great detail.
In his PhD with John Reynolds at Otago University in New Zealand, Simon defined how a mechanism of synaptic plasticity could bind representations of actions and outcomes to enable basic learning in a brain area called the striatum.
"The striatum is a central hub for signals related to learning. They all come in there - information related to movements of the limbs, sensory information about the outcome, and of course reward-related signals - giving information on if this thing in the world is important or useful to learn."
"A nice example is learning to turn on a light switch: you reach out and eventually will move the switch down, during which the related motor signals will be sent to the striatum. This action causes an outcome - the light comes on - which evokes sensory signals in the brain that are also sent to the striatum. Because you've achieved a goal there's also likely to be reward-related signals from dopamine neurons that project to the striatum. So we have all of these signals arriving, at particular time points. I showed how through plasticity mechanisms the action and outcome signals can be associated so that in the future you'll repeat that same action to achieve the goal of turning on the light."
This work has broad implications for our fundamental understanding of how the brain works, and provides the basis for treatment research on neurological conditions in which learning and movement is impaired, for example Parkinson's disease.
Applying these plastic changes
After his PhD Simon started a post-doc position with Prof. Bernard Balleine at UNSW during which he looked in greater detail, with more advanced techniques, at the signals that enter the striatum to support learning.
He found that "plasticity of signals from the medial prefrontal cortex to a particular part of the striatum, the dorsomedial area (DMS), are critical to learning associations between actions and their outcomes in the world. Also that a region of the amygdala - involved in processing the salience of events in the world - plays an integral role in this learning."
The findings resolved important questions in the field about which pathways in particular are important for learning action-outcome associations, and how the different regions 'talk' to each other. Simon says that we now have "a much more complete picture of how the system works, so we have a better foundation for investigating what goes wrong in disorders involving maladaptive learning and decision making."
How learning mechanisms can go wrong in disorders
In 2018, as part of a joint NHMRC grant between Prof. Chris Dayas and Prof. Balleine (UNSW), Simon transitioned to the University of Newcastle to look at how changes in these learning pathways can be impaired in mental health conditions, such as obsessive-compulsive disorder (OCD), schizophrenia, and addiction.
"Normal and efficient action selection depends on flexible interactions between two systems in the brain" Simon states. "One governs more deliberated, goal-directed action control, and is mediated by the dorsomedial striatum, while the other governs more automatic or habitual action control, and is mediated by the dorsolateral striatum."
"When fluid interactions between these two systems goes awry, disordered decision making, including compulsive behaviours and pathological habits, can develop."
Simon is now using cutting-edge neuroscience tools, such as pathway-specific genetic manipulations and miniaturised microscopes, to investigate changes in this circuity that leads to the development of compulsive behaviour.
"The big questions I have now circle back around to my very early interests - for example, how do changes in the basic machinery of learning circuits lead to the complex expression of disordered behaviour, and can we manipulate the circuits back to normality?"
Luckily for Simon, many functions of the brain are poorly understood at present, so there is a lot of scope for investigations and more great discoveries.


  • Doctor of Philosophy, University of Otago - New Zealand


  • behaviour
  • learning
  • neuroscience
  • synaptic plasticity

Fields of Research

Code Description Percentage
170101 Biological Psychology (Neuropsychology, Psychopharmacology, Physiological Psychology) 50
060805 Animal Neurobiology 25
110999 Neurosciences not elsewhere classified 25

Professional Experience

UON Appointment

Title Organisation / Department
Postdoctoral Fellow University of Newcastle
School of Biomedical Sciences and Pharmacy


Code Course Role Duration
HUBS3403 Neuroscience
Faculty of Health and Medicine, University of Newcastle

The purpose of this course is to build on students’ prior learning in the biomedical science sub-discipline of Neuroscience. Lecturers with research interests in various areas of neuroscience will use their expertise to help students increase their understanding of the anatomical, molecular and physiological features of the nervous system through exposure to lectures and laboratory classes.

Taught: Synaptic plasticity

Lecturer 19/03/2019 - 29/03/2019
PHAR3103 Mental and Neurological Health
Faculty of Health and Medicine, University of Newcastle

Presents the pathophysiology of altered health states and their management including both pharmacological and non-pharmacological interventions.

Taught: Introduction to CNS 1-3

Lecturer 25/02/2019 - 4/03/2019


For publications that are currently unpublished or in-press, details are shown in italics.

Journal article (3 outputs)

Year Citation Altmetrics Link
2017 Fisher SD, Robertson PB, Black MJ, Redgrave P, Sagar MA, Abraham WC, Reynolds JNJ, 'Reinforcement determines the timing dependence of corticostriatal synaptic plasticity in vivo', Nature Communications, 8 (2017)
DOI 10.1038/s41467-017-00394-x
Fisher SD, Reynolds JNJ, 'The intralaminar thalamusâ an expressway linking visual stimuli to circuits determining agency and action selection', Frontiers in Behavioral Neuroscience, 8
DOI 10.3389/fnbeh.2014.00115
Fisher SD, Gray JP, Black MJ, Davies JR, Bednark JG, Redgrave P, et al., 'A behavioral task for investigating action discovery, selection and switching: comparison between types of reinforcer', Frontiers in Behavioral Neuroscience, 8
DOI 10.3389/fnbeh.2014.00398

Thesis / Dissertation (1 outputs)

Year Citation Altmetrics Link
2016 Fisher S, Action discovery in the basal ganglia through reinforcement of spike timing-dependent plasticity, University of Otago (2016)

Research Supervision

Number of supervisions


Current Supervision

Commenced Level of Study Research Title Program Supervisor Type
2019 PhD Investigating the Role of Striatal D1 and D2 Medium Spiny Neurons in the Transition to Compulsive Drug Seeking Behaviour PhD (Anatomy), Faculty of Health and Medicine, The University of Newcastle Co-Supervisor

Dr Simon Fisher


Postdoctoral Fellow
School of Biomedical Sciences and Pharmacy
Faculty of Health and Medicine

Contact Details

Email simon.fisher@newcastle.edu.au
Phone (02) 4921 5618


Room MS306C/D