John L Bradshaw

Deakin University, Geelong, Victoria, Australia

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Publications (402)1679.18 Total impact

  • E. Klimkeit · N. Rinehart · T. May · J. Bradshaw
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    ABSTRACT: Abstract Attention-deficit/hyperactivity disorder (ADHD), depression, Tourette's syndrome (TS), obsessive–compulsive disorder (OCD), schizophrenia, and autism spectrum disorders (ASDs) are neurodevelopmental disorders thought to involve frontostriatal brain regions. This article outlines how each of these conditions is characterized in terms of gender ratios, prevalence rates, age of onset, and clinical presentation, as well as neuropsychological functioning and treatment. Also discussed are genetic factors and the different brain areas implicated from available neuroimaging data.
    No preview · Chapter · Dec 2015
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    ABSTRACT: While Major Depressive Disorder (MDD) is primarily characterized by mood disturbances, impaired attentional control is increasingly identified as a critical feature of depression. Deep transcranial magnetic stimulation (deepTMS), a noninvasive neuromodulatory technique, can modulate neural activity and induce neuroplasticity changes in brain regions recruited by attentional processes. This study examined whether acute and long-term high-frequency repetitive deepTMS to the dorsolateral prefrontal cortex (DLPFC) can attenuate attentional deficits associated with MDD. Twenty-one MDD patients and 26 matched control subjects (CS) were administered the Beck Depression Inventory and the Sustained Attention to Response Task (SART) at baseline. MDD patients were readministered the SART and depressive assessments following a single session (í µí±› = 21) and after 4 weeks (í µí±› = 13) of high-frequency (20 Hz) repetitive deepTMS applied to the DLPFC. To control for the practice effect, CS (í µí±› = 26) were readministered the SART a further two times. The MDD group exhibited deficits in sustained attention and cognitive inhibition. Both acute and long-term high-frequency repetitive frontal deepTMS ameliorated sustained attention deficits in the MDD group. Improvement after acute deepTMS was related to attentional recovery after long-term deepTMS. Longer-term improvement in sustained attention was not related to antidepressant effects of deepTMS treatment.
    Full-text · Article · Oct 2015 · Neural Plasticity
  • B A Gargaro · T May · B J Tonge · D M Sheppard · J L Bradshaw · N J Rinehart
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    ABSTRACT: Objective: Cognitive flexibility or attentional set-shifting capacity has long been considered a core area of executive dysfunction for individuals with autism. Whether these difficulties are due to higher-level attentional difficulties associated with comorbid ADHD remains unclear. Method: The current study compared the performance of 48 participants with autism, ADHD, autism-ADHD, and a comparison group (N = 12 per group) on a set-shifting task, which included a local-global paradigm. Results: Results of this study revealed that participants with attentional difficulties (autism + ADHD and ADHD alone) exhibited a significant shifting cost (difference between maintaining and shifting attention). Conclusion: Attentional difficulties associated with ADHD may be associated with an enhanced attentional shifting cost. Implications of these results were discussed in relation to screening for ADHD symptoms in studies of individuals with autism which seek to determine the neuropsychological profile of this condition.
    No preview · Article · Sep 2015 · Journal of Attention Disorders
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    ABSTRACT: Preclinical studies suggest that cortical alterations within the prefrontal cortex (PFC) are critical to the pathophysiology of alcohol dependence. Combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) allows direct assessment of cortical excitability and inhibition within the PFC of human subjects. We report the first application of TMS-EEG to measure these indices within the PFC of alcohol-dependent (ALD) patients post-detoxification. Cortical inhibition was assessed in 12 ALD patients and 14 healthy controls through single and paired-pulse TMS paradigms. Long-interval cortical inhibition indexed cortical inhibition in the PFC. In the motor cortex (MC), short- interval intracortical inhibition and cortical silent period determined inhibition, while intracortical facilitation measured facilitation, resting and active motor threshold indexed cortical excitability. ALD patients demonstrated altered cortical inhibition across the bilateral frontal cortices relative to controls. There was evidence of altered cortical excitability in ALD patients; however, no significant differences in MC inhibition. Our study provides first direct evidence of reduced cortical inhibition in the PFC of ALD patients post-detoxification. Altered cortical excitability in the MC may reflect hyper-excitability within the cortex associated with chronic alcohol consumption. These findings provide initial neurophysiological evidence of disrupted cortical excitability within the PFC of ALD patients.
    Full-text · Article · Aug 2015 · The World Journal of Biological Psychiatry
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    ABSTRACT: Although the experience of vicarious sensations when observing another in pain have been described postamputation, the underlying mechanisms are unknown. We investigated whether vicarious sensations are related to posttraumatic stress disorder (PTSD) symptoms and chronic pain. In Study 1, 236 amputees completed questionnaires about phantom limb phenomena and vicarious sensations to both innocuous and painful sensory experiences of others. There was a 10.2% incidence of vicarious sensations, which was significantly more prevalent in amputees reporting PTSD-like experiences, particularly increased arousal and reexperiencing the event that led to amputation (φ = .16). In Study 2, 63 amputees completed the Empathy for Pain Scale and PTSD Checklist-Civilian Version. Cluster analyses revealed 3 groups: 1 group did not experience vicarious pain or PTSD symptoms, and 2 groups were vicarious pain responders, but only 1 had increased PTSD symptoms. Only the latter group showed increased chronic pain severity compared with the nonresponder group (p = .025) with a moderate effect size (r = .35). The findings from both studies implicated an overlap, but also divergence, between PTSD symptoms and vicarious pain reactivity postamputation. Maladaptive mechanisms implicated in severe chronic pain and physical reactivity posttrauma may increase the incidence of vicarious reactivity to the pain of others. Copyright © 2015 International Society for Traumatic Stress Studies.
    No preview · Article · Aug 2015 · Journal of Traumatic Stress
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    ABSTRACT: To determine the extent and nature of driving self-regulation in drivers with Parkinson disease (PD) and factors associated with self-regulatory practices. Although people with PD have consistently been shown to have driving impairments, few studies have examined self-regulatory driving practices and their relationship to driving performance. We used a self-report driving questionnaire to examine driving self-regulation in 37 drivers with PD and 37 healthy age-matched controls. We also analyzed factors associated with self-regulatory practices, primarily demographic, disease-related, psychological, and simulated driving performance variables. The drivers with PD reported significantly higher rates of self-perceived decline in their driving ability (P=0.008) and driving significantly shorter distances per week (P=0.004) than controls. Unfamiliar situations (P=0.009), in-car distractions (P<0.001), low visibility conditions (P=0.004), and long journeys (P=0.003) were particularly challenging for the drivers with PD, and their pattern of driving avoidance mirrored these difficulties. The use of self-regulatory strategies among drivers with PD was associated with female sex (rho=0.42, P=0.009) and perceived decline in driving ability (rho=-0.55, P<0.001), but not with age or objective measures of disease severity, cognition, or simulated driving performance. Drivers with PD reported driving less overall and restricting their driving to avoid particularly difficult circumstances. Further research is warranted on effective use of self-regulation strategies to improve driving performance in people with PD.
    No preview · Article · Jun 2015 · Cognitive and behavioral neurology: official journal of the Society for Behavioral and Cognitive Neurology
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    ABSTRACT: Although the experience of vicarious sensations when observing another in pain have been described post-amputation, the underlying mechanisms are unknown. We investigated whether vicarious sensations are related to post-traumatic stress disorder (PTSD) symptoms and chronic pain. In study one, 236 amputees completed questionnaires about phantom limb phenomena and vicarious experiences (i.e., vicarious sensations to both innocuous and painful sensory experiences of others). There was a 10.2% incidence of vicarious sensations, which was significantly more prevalent in amputees reporting PTSD-like experiences, particularly increased arousal and ‘re-experiencing’ the event that led to amputation (phi = .16). In study two, 63 amputees completed the Empathy for Pain Scale and PTSD Checklist-Civilian Version. Cluster analyses revealed three groups. One group did not experience vicarious pain or PTSD symptoms, and two groups were vicarious pain responders, but only one had increased PTSD symptoms. Only the latter group showed increased chronic pain severity compared with the non-responder group (p = .025, r = .35). The findings from both studies implicate an overlap, but also divergence, between PTSD symptoms and vicarious pain reactivity post-amputation. Maladaptive mechanisms implicated in severe chronic pain and physical reactivity post-trauma may increase the incidence of vicarious reactivity to the pain of others. Post-traumatic stress disorder symptoms associated with painful and non-painful vicarious reactivity following amputation. Available from: https://www.researchgate.net/publication/275653108_Post-traumatic_stress_disorder_symptoms_associated_with_painful_and_non-painful_vicarious_reactivity_following_amputation [accessed May 1, 2015].
    No preview · Article · Jan 2015 · Journal of Traumatic Stress
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    ABSTRACT: Although the experience of vicarious sensations when observing another in pain have been described post-amputation, the underlying mechanisms are unknown. We investigated whether vicarious sensations are related to post-traumatic stress disorder (PTSD) symptoms and chronic pain. In study one, 236 amputees completed questionnaires about phantom limb phenomena and vicarious experiences (i.e., vicarious sensations to both innocuous and painful sensory experiences of others). There was a 10.2% incidence of vicarious sensations, which was significantly more prevalent in amputees reporting PTSD-like experiences, particularly increased arousal and ‘re-experiencing’ the event that led to amputation (phi = .16). In study two, 63 amputees completed the Empathy for Pain Scale and PTSD Checklist-Civilian Version. Cluster analyses revealed three groups. One group did not experience vicarious pain or PTSD symptoms, and two groups were vicarious pain responders, but only one had increased PTSD symptoms. Only the latter group showed increased chronic pain severity compared with the non-responder group (p = .025, r = .35). The findings from both studies implicate an overlap, but also divergence, between PTSD symptoms and vicarious pain reactivity post-amputation. Maladaptive mechanisms implicated in severe chronic pain and physical reactivity post-trauma may increase the incidence of vicarious reactivity to the pain of others.
    No preview · Article · Jan 2015 · Journal of Traumatic Stress
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    ABSTRACT: Recent studies in young adult females with the fragile X mental retardation 1 (FMR1) gene premutation (PM) have shown subtle but significant impairments in executive control and postural stability. Less is known about the influence of age and FMR1 gene expression on executive control and postural stability in females with the PM. Here, we examined the attentional demands of reactive stepping using a well-validated measure of choice stepping reaction time under dual-task interference. We explored the interrelationships between step initiation times during a concurrent verbal fluency task and specific impairments in executive control previously reported in females with the PM. Our results showed increased dual-task interference on step initiation times and variability in female PM compared with control subjects. In addition, we observed greater choice stepping reaction time dual-task costs above the breakpoint of 81 CGG repeats relative to below this CGG range. Dual-task interference on both reaction time and movement time were significantly predicted by low working memory capacity in female PM carriers. Importantly, we revealed that FMR1 messenger RNA level is the most significant predictor accounting for dual-task stepping variability in both reaction time and movement time in PM females. These findings for the first time provide evidence linking elevated FMR1 messenger RNA levels that have been previously associated with FMR1 RNA toxicity and deficits in cerebellar motor and cognitive networks in a subgroup of at-risk PM women. Copyright © 2014 Elsevier Inc. All rights reserved.
    Full-text · Article · Nov 2014 · Neurobiology of Aging
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    ABSTRACT: This study aimed to (1) determine preliminary validity of the Developmental Behaviour Checklist-Hyperactivity Index (DBC-HI) as a screening measure of combined-type ADHD in autism and ADHD, and (2) compare emotional-behavioural disturbance using the DBC in autism, ADHD and autism + ADHD. Forty-nine age- and PIQ-matched young people [6–18 years; 12 autism, 13 ADHD, 12 autism + ADHD, 12 typically developing] were recruited. Parents completed the Conners-Revised Rating Scale and DBC. The DBC-HI displayed strong internal consistency and good external validity, reliably measuring combined-type ADHD. The DBC-HI distinguished autism from autism + ADHD with fair sensitivity and specificity. Individuals with autism + ADHD exhibited a more severe profile of emotional-behavioural disturbance than autism or ADHD alone. The DBC may be a useful ‘all-in-one’ screening tool to (1) identify comorbidity and (2) determine the severity of emotional-behavioural disturbance in autism and/or ADHD.
    No preview · Article · Sep 2014 · Research in Autism Spectrum Disorders
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    ABSTRACT: Objective: We sought to quantify subtle changes in motor control in multiple sclerosis (MS) using a Fitts law reciprocal aiming task presented on a computer touchscreen. Background: Upper-limb motor control is impaired in MS. However, many commonly used motor assessments do not detect subtle changes in motor function or differentiate between aspects of movement such as planning and online control. Fitts law states that movement time varies as a function of task difficulty, with smaller targets and greater distances making the task more difficult. Methods: We gave a Fitts aiming task to 22 patients with MS and 22 matched controls. We manipulated movement difficulty by changing the targets’ size and distance apart. Results: The patients spent a significantly longer time than the controls stationary in each target before starting the next movement, and had a lower peak velocity, suggesting deficits in movement planning. The patients also spent longer in the deceleration phase of each movement, indicating deficits in the online control of movement. Conclusions: The computerized Fitts task allows quick, easy, and sensitive measurement of subtle aspects of movement. This task should be useful in clinical and research settings for assessing MS motor symptoms, disease progression, and treatment efficacy.
    Full-text · Article · Sep 2014 · Cognitive and behavioral neurology: official journal of the Society for Behavioral and Cognitive Neurology
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    Full-text · Article · Jul 2014 · Addiction
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    ABSTRACT: This study aimed to compare the gait of children with ADHD - Combined Type (ADHD-CT) to typically developing (TD) children. Children with ADHD-CT (n=14; mean age 10 years 4 months) and a TD group (n=13; mean age 10 years 9 months) walked at self-selected slow, preferred and fast speed on an electronic walkway system. Participants completed a total of 15 walking trials; 5 trials per walking condition. Groups were matched on age, intellectual functioning, height and weight. In the preferred walking condition, there was no difference in spatio-temporal gait variables between the ADHD-CT and TD control groups. At self-selected fast speed, children with ADHD-CT were faster and walked with a higher cadence. The subtle alterations in gait pattern that may reflect a timing deficit is consistent with previous ADHD motor studies. In addition, this study extends previous studies in characterising the unique gait profile of non-medicated children with ADHD-CT where a diagnosis of autism spectrum disorder has been ruled out.
    No preview · Article · May 2014 · Psychiatry Research
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    ABSTRACT: Recent studies report a higher risk of dementia and motor symptoms in females with the fragile X mental retardation 1 premutation (PM-carriers) than has hitherto been appreciated. Here, we use dual-task gait paradigms to identify potential markers of cognitive and motor decline in female PM-carriers. Spatiotemporal gait characteristics and variability of gait were assessed during single- and dual-task conditions in 28 female PM-carriers (mean age 41.32 ± 8.03 years) and 31 female controls with normal fragile X mental retardation 1 alleles (mean age 41.61 ± 8.30 years). Despite comparable gait characteristics at baseline, gait performance was significantly poorer for PM-carriers when performing concurrent working memory tasks (counting backwards by 3's or 7's) when compared with controls. Correlational analyses showed that low working memory capacity was significantly associated with dual-task interference for the gait domains of pace (speed, step length) and variability (step time, swing time) in PM-carriers. Multiple regression analyses further showed that the interaction between age and CGG repeat length was strongly predictive of gait variability during dual-task performance. These findings indicate for the first time that vulnerability in specific domains of gait control may act as sensitive surrogate markers of future decline in female PM-carriers.
    Full-text · Article · Mar 2014 · Neurobiology of aging
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    ABSTRACT: This study examines implicit sequence learning impairments that may indicate at-risk cerebellar profiles proposed to underlie some aspects of subtle cognitive and affective dysfunctions found amongst female FMR1 premutation carriers (PM-carriers). A total of 34 female PM-carriers and 33 age- and intelligence-matched controls completed an implicit symbolically primed serial reaction time task (SRTT) previously shown to be sensitive to cerebellar involvement. Implicit learning scores indicated a preservation of learning in both groups; however, PM-carriers demonstrated poorer learning through significantly elevated response latencies overall and at each specific block within the symbolic SRTT. Group comparisons also revealed a core deficit in response inhibition, alongside elevated inattentive symptoms in female PM-carriers. Finally, strong and significant associations were observed between poor symbolic SRTT performance and executive, visuospatial and affective deficits in the PM-carrier group. These associations remained strong even after controlling motor speed, and were not observed in age- and IQ-matched participants. The findings implicate cerebellar non-motor networks subserving the implicit sequencing of responses in cognitive-affective phenotypes previously observed in female PM-carriers. We contend that symbolic SRTT performance may offer clinical utility in future pharmaceutical interventions in female PM-carriers.
    Full-text · Article · Feb 2014 · Genes Brain and Behavior
  • John L. Bradshaw
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    ABSTRACT: In a reaction-time task, an increase in stimulus uncertainty led to increased RT. This was achieved by varying the number of possible sensory modalities for the signal, changing the length or variability of a warning foreperiod, and concurrently presenting masking noise. At the highest levels of uncertainty, concurrently-monitored pupillary dilation showed an overall flattening of associated response peaks, together with a rise in baseline levels. There was also evidence of expectancy phenomena with nonoccurring, anticipated signals.
    No preview · Article · Feb 2014 · Psychonomic science
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    ABSTRACT: Impulsivity is considered a core feature of problem gambling; however, self-reported impulsivity and inhibitory control may reflect disparate constructs. We examined self-reported impulsivity and inhibitory control in 39 treatment-seeking problem gamblers and 41 matched controls using a range of self-report questionnaires and laboratory inhibitory control tasks. We also investigated differences between treatment-seeking problem gamblers who prefer strategic (e.g., sports betting) and nonstrategic (e.g., electronic gaming machines) gambling activities. Treatment-seeking problem gamblers demonstrated elevated self-reported impulsivity, more go errors on the Stop Signal Task, and a lower gap score on the Random Number Generation task than matched controls. However, overall we did not find strong evidence that treatment-seeking problem gamblers are more impulsive on laboratory inhibitory control measures. Furthermore, strategic and nonstrategic problem gamblers did not differ from their respective controls on either self-reported impulsivity questionnaires or laboratory inhibitory control measures. Contrary to expectations, our results suggest that inhibitory dyscontrol may not be a key component for some treatment-seeking problem gamblers.
    No preview · Article · Jan 2014 · Journal of Clinical and Experimental Neuropsychology
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    ABSTRACT: To analyse problem gamblers' decision making under conditions of risk and ambiguity, investigated underlying psychological factors associated with their choice behaviour and examine whether decision making differed in strategic (e.g., sports betting) and non-strategic (e.g., electronic gaming machine) problem gamblers. Cross-sectional study. Out-patient treatment centres and university testing facilities in Victoria, Australia. 39 problem gamblers and 41 age-, gender- and estimated-IQ-matched controls. Decision making tasks included the Iowa Gambling Task (IGT) and a Loss Aversion Task. The Prospect Valence Learning (PVL) model was used to provide an explanation of cognitive, motivational and response style factors involved in IGT performance. Overall, problem gamblers performed more poorly than controls on both the IGT (p = 0.04) and the Loss Aversion Task (p = 0.01), and their IGT decisions were associated with heightened attention to gains (p = 0.003) and less consistency (p = 0.002). Strategic problem gamblers did not differ from matched controls on either decision making task, but non-strategic problem gamblers performed worse on both the IGT (p = 0.006) and the Loss Aversion task (p = 0.02). Furthermore, we found differences in the PVL model parameters underlying strategic and non-strategic problem gamblers' choices on the IGT. Problem gamblers demonstrated poor decision making under conditions of risk and ambiguity. Strategic (e.g., sports betting, poker) and non-strategic (e.g., electronic gaming machines) problem gamblers differed in decision making and the underlying psychological processes associated with their decisions.
    No preview · Article · Jan 2014 · Addiction
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    ABSTRACT: There is evidence which demonstrates that a subset of males with a premutation CGG repeat expansion (between 55 and 200 repeats) of the fragile X mental retardation 1 gene exhibit subtle deficits of executive function that progressively deteriorate with increasing age and CGG repeat length. However, it remains unclear whether similar deficits, which may indicate the onset of more severe degeneration, are evident in female PM-carriers. In the present study we explore whether female PM-carriers exhibit deficits of executive function which parallel those of male PM-carriers. Fourteen female fragile X premutation carriers without fragile X-associated tremor/ataxia syndrome and fourteen age, sex, and IQ matched controls underwent ocular motor and neuropsychological tests of select executive processes, specifically of response inhibition and working memory. Group comparisons revealed poorer inhibitory control for female premutation carriers on ocular motor tasks, in addition to demonstrating some difficulties in behaviour self-regulation, when compared to controls. A negative correlation between CGG repeat length and antisaccade error rates for premutation carriers was also found. Our preliminary findings indicate that impaired inhibitory control may represent a phenotype characteristic which may be a sensitive risk biomarker within this female fragile X premutation population.
    No preview · Article · Jan 2014 · Brain and Cognition
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    ABSTRACT: Fragile X Mental Retardation 1 (FMR1) premutation carriers (PM-carriers) have a defective trinucleotide expansion on the FMR1 gene that is associated with continuum of neuropsychological and mental disorders. Currently, little is known about the distinct subcomponents of executive function potentially impaired in female PM-carriers, and there have been no investigations into associations between executive function and incidences of mental disorders. A total of 35 female PM-carriers confirmed by Asuragen triple primed PCR DNA testing and 35 age- and intelligence-matched controls completed tests of executive function (i.e., response inhibition and working memory) and self-reported on social anxiety, depression, and ADHD predominantly inattentive (ADHD-PI) symptoms. Compared to controls, PM-carriers were significantly elevated on self-reported social anxiety and ADHD-PI symptoms. Irrespective of mental symptoms, female PM-carries performed significantly worse than controls on a response inhibition test, and further investigations revealed significant correlations between executive function performance and self-reported symptoms of anxiety, depression and ADHD-PI. Critically, among PM-carriers with good executive function performance, no women exceeded threshold markers for probable caseness of mental disorder. However, rates of probable caseness were elevated in those with average performance (response inhibition: social anxiety: 41.7%; depression: 20%; ADHD: 44.4%; working memory: social anxiety: 27.3%; depression: 9.1%; ADHD: 18.2%) and highly elevated for those with poor executive function performance (response inhibition: social anxiety: 58.3%; depression: 80%; ADHD: 55.6%; working memory: social anxiety: 100%; depression: 50%; ADHD: 83.3%). These data suggest that subtle executive dysfunction may be a useful neuropsychological indicator for a range of mental disorders previously reported in female PM-carriers. © 2013 Wiley Periodicals, Inc.
    Full-text · Article · Jan 2014 · American Journal of Medical Genetics Part B Neuropsychiatric Genetics

Publication Stats

13k Citations
1,679.18 Total Impact Points

Institutions

  • 2015
    • Deakin University
      Geelong, Victoria, Australia
  • 1971-2015
    • Monash University (Australia)
      • • School of Psychology and Psychiatry
      • • Centre for Developmental Psychiatry and Psychology
      Melbourne, Victoria, Australia
  • 2002-2014
    • University of Vic
      • Department of Psychology
      Vic, Catalonia, Spain
  • 1994-2008
    • Monash University (Malaysia)
      Labuan, Labuan, Malaysia
  • 1994-2006
    • University of Melbourne
      • Department of Psychiatry
      Melbourne, Victoria, Australia
  • 2005
    • The Royal Children's Hospital
      Melbourne, Victoria, Australia
  • 1996
    • La Trobe University
      • Department of Physiotherapy
      Melbourne, Victoria, Australia
    • University of Western Australia
      Perth City, Western Australia, Australia
  • 1992
    • Clayton State University
      Georgia, United States