Mr Philip Dean
Research Officer
Qualifications: MSc Neuroscience (Edinburgh), BSc Biochemistry & Genetics (Sheffield)
Email: p.dean@surrey.ac.uk
Phone: Work: 01483 68 2877
Room no: 01 AC 04
Office hours
9.00am to 5.30pm
Further information
Research Interests
I work within the Brain and Behaviour Group, and am interested in a wide variety of clinical neuroscience and neuropsychology topics, as well as the application of neural imaging techniques (fMRI, DTI, MRS and EEG) in understanding the biological basis of behaviour.
My current interest is in brain injury, particularly mild traumatic brain injury (mTBI) and stroke. My two most recent studies concern:
- A behavioural intervention in chronic upper-limb hemiparesis after stroke. Looking at motor activity before and after intervention on the lesioned and intact hemispheres.
- Behavioural and biological changes present in chronic mTBI and their relation to post-concussion syndrome (PCS).
Publications
Journal articles
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(2013) 'Long-term effects of mild traumatic brain injury on cognitive performance'. Frontiers Research Foundation Frontiers in Human Neuroscience, 7 Article number 30 , pp. 1-11.Full text is available at: http://epubs.surrey.ac.uk/755159/
Abstract
Although a proportion of individuals report chronic cognitive difficulties after mild traumatic brain injury (mTBI), results from behavioral testing have been inconsistent. In fact, the variability inherent to the mTBI population may be masking subtle cognitive deficits. We hypothesized that this variability could be reduced by accounting for post-concussion syndrome (PCS) in the sample. Thirty-six participants with mTBI (>1 year post-injury) and 36 non-head injured controls performed information processing speed (Paced Visual Serial Addition Task, PVSAT) and working memory (n-Back) tasks. Both groups were split by PCS diagnosis (4 groups, all n = 18), with categorization of controls based on symptom report. Participants with mTBI and persistent PCS had significantly greater error rates on both the n-Back and PVSAT, at every difficulty level except 0-Back (used as a test of performance validity). There was no difference between any of the other groups. Therefore, a cognitive deficit can be observed in mTBI participants, even 1 year after injury. Correlations between cognitive performance and symptoms were only observed for mTBI participants, with worse performance correlating with lower sleep quality, in addition to a medium effect size association (falling short of statistical significance) with higher PCS symptoms, post-traumatic stress disorder (PTSD), and anxiety. These results suggest that the reduction in cognitive performance is not due to greater symptom report itself, but is associated to some extent with the initial injury. Furthermore, the results validate the utility of our participant grouping, and demonstrate its potential to reduce the variability observed in previous studies.
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(2012) 'Post-concussion syndrome: Prevalence after mild traumatic brain injury in comparison with a sample without head injury.'. Informa Health Care Brain Injury, England: 26 (1), pp. 14-26.Full text is available at: http://epubs.surrey.ac.uk/327557/
Abstract
Primary objective: To compare the prevalence of persistent post-concussion syndrome (PCS; >1 year post-injury) in participants with mild traumatic brain injury (mTBI) and those without head injury. Research design: A cross-sectional sample of 119 participants with mTBI and 246 without previous head injury. Methods: Online questionnaires collected data about post-concussion symptoms, cognitive failures, anxiety, depression, sleep behaviour and post-traumatic stress disorder. Variability within the sample was addressed by splitting by PCS diagnosis to create four groups: mTBI + PCS, mTBI-PCS, Control + PCS and Control-PCS. PCS was diagnosed using ICD-10 criteria in all groups, with controls not requiring previous head injury. Main outcomes and results: PCS was present to a similar extent in participants with no head injury (34%) compared to those with mTBI (31%). Only report of headaches, which could be caused by expectation bias, distinguished between mTBI + PCS and Control + PCS groups. In addition, significantly higher cognitive problems were observed in participants with mTBI compared with the control group. Conclusions: Persistent PCS, as currently defined, is not specific to mTBI. These data suggest that somatic and cognitive symptoms are most likely to be able to distinguish PCS after mTBI from that present in the general population. Further research is necessary into these factors in order to create more specific PCS diagnostic criteria.
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(2012) 'Motor Planning in Chronic Upper-Limb Hemiparesis: Evidence from Movement-Related Potentials.'. Public Library of Science PLoS One, 7 (10)Full text is available at: http://epubs.surrey.ac.uk/729883/
Abstract
Background Chronic hemiplegia is a common long-term consequence of stroke, and subsequent motor recovery is often incomplete. Neurophysiological studies have focused on motor execution deficits in relatively high functioning patients. Much less is known about the influence exerted by processes related to motor preparation, particularly in patients with poor motor recovery. Methodology/Principal Findings The current study investigates motor preparation using a modified response-priming experiment in a large sample of patients (n = 50) with moderate-to-severe chronic hemiparesis. The behavioural results revealed that hemiparetic patients had an increased response-priming effect compared to controls, but that their response times were markedly slower for both hands. Patients also demonstrated significantly enhanced midline late contingent negative variation (CNV) during paretic hand preparation, despite the absence of overall group differences when compared to controls. Furthermore, increased amplitude of the midline CNV correlated with a greater response-priming effect. We propose that these changes might reflect greater anticipated effort to respond in patients, and consequently that advance cueing of motor responses may be of benefit in these individuals. We further observed significantly reduced CNV amplitudes over the lesioned hemisphere in hemiparetic patients compared to controls during non-paretic hand preparation, preparation of both hands and no hand preparation. Two potential explanations for these CNV reductions are discussed: alterations in anticipatory attention or state changes in motor processing, for example an imbalance in inter-hemispheric inhibition. Conclusions/Significance Overall, this study provides evidence that movement preparation could play a crucial role in hemiparetic motor deficits, and that advance motor cueing may be of benefit in future therapeutic interventions. In addition, it demonstrates the importance of monitoring both the non-paretic and paretic hand after stroke and during therapeutic intervention.
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(2010) 'Task complexity differentially affects executed and imagined movement preparation: evidence from movement-related potentials.'. Public Library of Science PLoS ONE, 5 (2)Full text is available at: http://epubs.surrey.ac.uk/713997/
Abstract
Background The neural simulation theory predicts similarity for the neural mechanisms subserving overt (motor execution) and covert (movement imagination) actions. Here we tested this prediction for movement preparation, a key characteristic of motor cognition. Methodology/Principal Findings High-density electroencephalogram (EEG) was recorded during covert and overt actions. Movement preparation was studied with a motor priming paradigm, which varied task complexity and amount of advance information. Participants performed simple or complex sequential finger movements either overtly or covertly. Advance information was either fully predictive or partially predictive. Stimulus-locked event-related potential (ERP) data showed the typical pattern of foreperiod activation for overt and covert movements. The foreperiod contingent negative variation (CNV) differed between simple and complex movements only in the execution task. ERP topographies differed between execution and imagination only when advance information was fully predictive. Conclusions/Significance Results suggest a differential contribution of the movement preparation network to action imagination and execution. Overt and covert actions seem to involve similar though not identical mechanisms, where overt actions engage a more fine-grained modulation of covert preparatory states.
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(2009) 'On the equivalence of executed and imagined movements: evidence from lateralized motor and nonmotor potentials.'. Hum Brain Mapp, United States: 30 (10), pp. 3275-3286.doi: 10.1002/hbm.20748
- . (2008) 'Neural correlates of movement preparation in healthy ageing'. European Journal of Neuroscience, 27 (1), pp. 254-260.
- . (2006) 'EEG dipole analysis of motor-priming foreperiod activity reveals separate sources for motor and spatial attention components.'. Clin Neurophysiol, Netherlands: 117 (12), pp. 2675-2683.
- . (2003) 'Accuracy and Precision of Binocular 3-D Motion Perception'. Journal of Experimental Psychology: Human Perception and Performance, 29 (5), pp. 869-881.
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(2003) 'Perception of binocular 3-D motion: Visual direction is more important than binocular disparity'. Journal of Vision, 3 (9)doi: 10.1167/3.9.95
Conference papers
- . (2012) 'The relationship between structural changes in mTBI and persistent PCS: DTI and cortical thickness analysis'. Edinburgh: Ninth World Congress On Brain Injury
- . (2012) 'Long-term effects of mild traumatic brain injury on cognitive performance'. BRAIN INJURY, 26 (4-5), pp. 395-396.
- . (2011) 'Response time slowing by glucose dependent on strength of stimulus response association: investigations with the flanker task'. Majorca: International Conference On Cognitive Neuroscience
- . (2010) 'An electrophysiological investigation of glucose effects in the Flanker task'. University of Warwick, UK: Warwick Workshop on Motor Priming and Cognitive Control
- . (2009) 'Food for Thought: An electrophysiological investigation of glucose administration effects on movement preparation and execution'. Berlin: Society for Psychophysiological Research Annual Meeting
- . (2006) 'Seperating spatial attention and motor-related lateralized ERP components in an S1-S2 motor priming paradigm'. Florence: Human Brain Mapping
- . (2006) 'Ageing in Motor Control: Behavioural and ERP correlates of Motor Priming in the Elderly.'. British Neuroscience Association Annual Meeting
- . (2005) 'Movement preparation and execution following a no-response pre-cue: A pilot study using behavioural and EEG data.'. Psychology Postgraduate Affairs Group Meeting
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(2003) 'Perceived direction of binocular 3-D motion when tracking a moving object'. Journal of Vision, 3 (9)doi: 10.1167/3.9.859
Book chapters
- . (2008) 'Preparing the unlikely event - when no-response priming activates the motor system'. in Columbus F (ed.) Biological Psychology: New Research Hauppange, New York : Nova Science Publishers
Posters
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(2010) Using 3T Magnetic Resonance Spectroscopy to Assess The Long Term Effects of Mild Traumatic Brain Injury.. Joint Annual Meeting ISMRM-ESMRMB. 1-7 May, 2010. Stockholm, Sweden.Full text is available at: http://epubs.surrey.ac.uk/244012/
Abstract
The present study explores the link between brain metabolites, PCS symptoms and cognitive ability in participants who have experienced an mTBI. Lactate has been previously been shown to be elevated in acute mTBI (Son, Park et al. 2000), however, 2 month post-incidence lactate levels had returned to normal. The present study suggests that PCS symptoms as well as metabolite abnormalities may persist. More specifically the data provides initial evidence for a link between the elevation of lactate and with severity of long-term PCS following mTBI. Poster presented in Session: Other Spectroscopy Methodology Proceedings of the International Society for Magnetic Resonance in Medicine, 18 (2010); p. 937. ISSN 1545-4428. Available at: http://www.ismrm.org/meetings-workshops/2010-annual-meeting-3/
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(2010) Post-Concussion Syndrome without head injury? A Survey Study (Poster 0588).. Eight World Congress On Brain Injury. Washington, DC on March 10-14, 2010Full text is available at: http://epubs.surrey.ac.uk/244011/
Abstract
Objectives According to ICD-10 or DSM-IV criteria Post-Concussion Syndrome (PCS) requires a prior mild traumatic brain injury (mTBI). However, PCS symptoms are non-specific and can also affect non-mTBI populations. Symptoms further overlap with other diagnoses, such as depression. Consequently, the degree to which PCS is specific to or caused by mTBI is still debated. With the present study we aim to investigate the nature of PCS in greater detail by looking whether PCS is specific to mTBI, and the extent to which these symptoms and related factors (depression, anxiety, daytime sleepiness and cognitive failures) exist in the non-mTBI population. Method An online survey was sent to University staff and students. Included in this survey were the Rivermead Post Concussion Questionnaire (RPQ), Cognitive Failures Questionnaire (CFQ), Hospital Anxiety and Depression Scale (HADS), Epworth Sleepiness Scale (ESS), along with demographic questions and those related to the mTBI sustained. PCS was diagnosed as 3 or more symptoms within DSM-IV criteria. Results The survey created a database of 375 entries, 127 for mTBI and 248 controls (no history of mTBI). Within these groups the proportion of individuals experiencing PCS symptoms was not statistically different (39% for mTBI, 32% for control; Chi squared p=0.2), and there was no group difference for the RPQ, HADS or ESS. However, respondents with a history of mTBI showed significantly higher CFQ scores (p<0.001) than controls. In contrast, when split by PCS diagnosis, those with PCS revealed significantly greater scores for all questionnaires (p<0.001). When split into subgroups (mTBI+PCS, mTBI-PCS, Control+PCS, Control-PCS), a similar pattern was observed. The two groups with PCS both had greater scores for the RPQ, CFQ and HADS than both groups without PCS (p<0.005). There was only one difference when comparing the two groups with mTBI to those without (CFQ: mTBI+PCS greater than Control+PCS (p<0.05)). The ESS score for Control+PCS was greater when compared to both groups without PCS (mTBI-PCS (p<0.01); Control-PCS (p<0.005)). Conclusions The study suggests that PCS is equally common in a self-selected sample of persons with and without brain injury. Data on depression, anxiety, cognitive failures and daytime sleepiness scores show no increase in those with mTBI, but are significantly higher in those with PCS. Analysis of the four subgroups revealed no interaction between mTBI and PCS. This suggests that
- . (2009) Advance movement preparation in hemiparetic patients: Electrophysiological indices.. Society for Psychophysiological Research Annual Meeting
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(2008) Advance movement preparation in hemiparetic patients: validity effects seen in a response priming task with the affected arm.. Seventh World Congress On Brain Injury, 9-12 April, 2008.Lisbon, Portugal.Full text is available at: http://epubs.surrey.ac.uk/244010/
Abstract
Poster presented at the Seventh World Congress On Brain Injury, 9-12 April, 2008.Lisbon, Portugal. Organised by The International Brain Injury Association. www.internationalbrain.org
Departmental Duties
I manage the Electroencephalography (EEG) laboratories (room 04AC04), helping design, run and analyse experiments for any staff and PhD students wishing to use this technique. We use a 64-channel QuickAmp with EasyCap and electrically shielded Ag/AgCl ring electrodes, and a 32-channel BrainAmp MR Plus which can be used in combination with TMS and MRI. The lab also contains tDCS and actigraphy devices, a behavioural testing room, and a bank of computers for analysis or general office use.
I also work with functional Magnetic Resonance Imaging (fMRI), MRS and DTI using the CUBIC facilities at Royal Holloway University.
Software
As part of our research, we use certain specific software:
EEG
Brain Vision Analyser
Brain Vision Recorder
fMRI, DTI & VBM
MRS
Behavioural Experiments
General
