John L Bradshaw

University of Vic, Vic, Catalonia, Spain

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Publications (382)1564.14 Total impact

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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].
    Journal of Traumatic Stress 01/2015; · 2.72 Impact Factor
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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.
    Journal of Traumatic Stress 01/2015; · 2.72 Impact Factor
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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.
    Neurobiology of Aging 11/2014; 36(3). DOI:10.1016/j.neurobiolaging.2014.11.012 · 4.85 Impact Factor
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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.
    Research in Autism Spectrum Disorders 09/2014; 8(9):1008–1015. DOI:10.1016/j.rasd.2014.05.004 · 2.96 Impact Factor
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    ABSTRACT: 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.
    Cognitive and behavioral neurology: official journal of the Society for Behavioral and Cognitive Neurology 09/2014; 27(3):139-47. DOI:10.1097/WNN.0000000000000036 · 1.14 Impact Factor
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    Addiction 07/2014; 109(7):1139-40. DOI:10.1111/add.12584 · 4.60 Impact Factor
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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.
    Psychiatry Research 05/2014; 218(3). DOI:10.1016/j.psychres.2014.04.037 · 2.68 Impact Factor
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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.
    Neurobiology of aging 03/2014; DOI:10.1016/j.neurobiolaging.2014.03.018 · 4.85 Impact Factor
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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.
    Genes Brain and Behavior 02/2014; DOI:10.1111/gbb.12122 · 3.51 Impact Factor
  • 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.
    Psychonomic science 02/2014; 13(2):69-70. DOI:10.3758/BF03342414
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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.
    Journal of Clinical and Experimental Neuropsychology 01/2014; DOI:10.1080/13803395.2013.873773 · 2.16 Impact Factor
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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.
    Addiction 01/2014; 109(7). DOI:10.1111/add.12494 · 4.60 Impact Factor
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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.
    Brain and Cognition 01/2014; 85C:201-208. DOI:10.1016/j.bandc.2013.12.006 · 2.68 Impact Factor
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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.
    American Journal of Medical Genetics Part B Neuropsychiatric Genetics 01/2014; 165(1). DOI:10.1002/ajmg.b.32203 · 3.27 Impact Factor
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    ABSTRACT: Alcohol dependence, a chronic relapsing disorder, is characterized by an impaired ability to regulate compulsive urges to consume alcohol. Very few empirical studies have examined the presence of these executive deficits, how they relate to craving, and the enduring nature of these deficits during abstinence. As such, the current study aimed to characterize these cognitive deficits within a sample of 24 alcohol-dependent participants post-detoxification and 23 non-alcohol-dependent participants. Participants were administered the Sustained Attention to Response Task to measure response inhibition and sustained attention and the Random Number Generation Task to examine executive deficits. Correlations between cognitive performance and clinical measures of alcohol dependence were examined. As predicted, the alcohol-dependent group exhibited poorer performance across the domains of response inhibition, executive function, and attentional control. Cognitive performance was related to clinical measures of craving and years of alcohol consumption, whereas the duration of abstinence was not associated with improved cognitive performance. These findings highlight the need for therapeutic strategies to target these enduring neurocognitive deficits in improving the treatment of alcohol dependence.
    Archives of Clinical Neuropsychology 12/2013; DOI:10.1093/arclin/act090 · 1.92 Impact Factor
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    ABSTRACT: Atrophy of the dentate nucleus is one of the major neuropathological changes in Friedreich ataxia (FRDA). Neuroimaging studies demonstrated white matter (WM) degeneration in FRDA. In this study, we used advanced tractography techniques to quantitatively measure WM changes in the dentato-thalamic and dentato-rubral tracts, and correlated these changes with cognitive profiles of FRDA. We also analysed diffusivity changes of the thalamo-cortical tract to assess whether neurological degeneration of WM extends beyond the primary site of involvement in FRDA. Twelve genetically proven individuals with FRDA and 14 controls were recruited. Sixty directions diffusion tensor images were acquired. The WM bundles from the dentate nucleus were estimated using a constrained spherical deconvolution method and the diffusivity characteristics measured. The Simon task was used to assess cognitive profile of FRDA. The dentato-rubral, dentato-thalamic and thalamo-cortical tracts manifested significantly lower fractional anisotropy, higher mean diffusivity and increased radial diffusivity in FRDA compared with controls. There was no difference in axial diffusivity between the two groups. The mean and radial diffusivity of the dentato-rubral tract was positively correlated with choice reaction time, congruent reaction time, incongruent reaction time and Simon effect reaction time and negatively with the larger GAA repeat. Significant changes in diffusivity characteristics were observed in the dentato-thalamic and thalamo-cortical tracts, suggesting extensive WM degeneration and affected WM structures in FRDA. Correlation of WM changes in the dentato-rubral tract with the cognitive assessment suggested that this tract is an important contributor to cognitive disturbances in FRDA.
    The Cerebellum 10/2013; 13(2). DOI:10.1007/s12311-013-0525-4 · 2.86 Impact Factor
  • Clinical Neurophysiology 10/2013; 124(10):e69. DOI:10.1016/j.clinph.2013.04.090 · 2.98 Impact Factor
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    ABSTRACT: Recent investigations report a higher risk of motor symptoms in females with the FMR1 premutation (PM-carriers) than has hitherto been appreciated. Here we examined basic sensorimotor and postural control under different sensory and attentional dual-task demands. Physiological performance and postural sway measures from the Physiological Profile Assessment (Lord et al., 2003) were conducted in 28 female PM-carriers (mean age: 41.32±8.03) and 31 female controls with normal FMR1 alleles (mean age: 41.61±8.3). Multiple regression analyses was conducted to examine the moderating role of CGG-repeat length on the relation between age and postural sway under dual-task interference. In female PM-carriers, our results showed significantly poorer proprioceptive awareness, slower reaction time, and greater postural displacement when performing a concurrent verbal fluency task. Significantly, these findings showed age- and genetically-modulated changes in dual-task postural displacement in the medio-lateral direction in female PM-carriers. These findings highlight the sensitivity of postural control paradigms in identifying early cerebellar postural changes that may act as surrogate markers of future decline in female PM-carriers.
    Behavioural brain research 07/2013; 253. DOI:10.1016/j.bbr.2013.07.033 · 3.39 Impact Factor
  • John L. Bradshaw
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    ABSTRACT: In an auditory reaction time task, changes in pupillary dilation were monitored during conditions of high and low background illumination. The latter were found to determine pupillary baseline levels, while the amplitude of the dilation peak at response stayed at a constant value. Unfulfilled expectancy that a response signal would occur was found to induce a smaller expectancy peak, despite the absence of an associated motor response. It was confirmed that temporal uncertainty relating to the length of the warning foreperiod could partly determine the Ss’ RT performance.
    Psychonomic science 06/2013; 14(6):271-272. DOI:10.3758/BF03329118
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Publication Stats

10k Citations
1,564.14 Total Impact Points

Institutions

  • 2002–2014
    • University of Vic
      • Department of Psychology
      Vic, Catalonia, Spain
  • 1971–2014
    • Monash University (Australia)
      • • School of Psychology and Psychiatry
      • • Centre for Developmental Psychiatry and Psychology
      Melbourne, Victoria, Australia
  • 2013
    • Victoria University Sydney
      Sydney, New South Wales, Australia
  • 2008
    • University of Western Australia
      • School of Psychology
      Perth, Western Australia, Australia
  • 1983–2008
    • Monash University (Malaysia)
      Labuan, Labuan, Malaysia
  • 1994–2006
    • University of Melbourne
      • • Department of Paediatrics
      • • Graduate School of Humanities and Social Sciences
      • • Department of Psychiatry
      Melbourne, Victoria, Australia
  • 2004
    • University of Auckland
      • Department of Sport and Exercise Science
      Auckland, Auckland, New Zealand
  • 2001
    • Victoria University Melbourne
      Melbourne, Victoria, Australia
  • 1996
    • La Trobe University
      • Department of Physiotherapy
      Melbourne, Victoria, Australia
  • 1992
    • Clayton State University
      Georgia, United States