Doeltgen S.H.,University of Canterbury |
Doeltgen S.H.,Van der Veer Institute for Parkinsons and Brain Research |
Dalrymple-Alford J.,University of Canterbury |
Dalrymple-Alford J.,Van der Veer Institute for Parkinsons and Brain Research |
And 3 more authors.
Neurorehabilitation and Neural Repair | Year: 2010
Background. Neuromuscular electrical stimulation (NMES) of the muscles underlying the pharynx and faucial pillars affects the excitability of corticobulbar projections in a frequency- and duration-specific manner. The anterior hyomandibular (submental) muscles are primary targets for the clinical application of NMES to improve disordered swallowing, but the optimal NMES parameters for this application are unknown. Objective. To determine the influence of NMES parameters on the excitability of corticobulbar projections to the submental musculature. Methods. Transcranial magnetic stimulation (TMS) was used in event-related protocols, triggered by either volitional contraction of the submental muscles or pharyngeal swallowing, to assess corticobulbar excitability prior to, immediately following, and 30, 60, and 90 minutes post-NMES in 25 healthy volunteers. In the first 2 experiments, 4 stimulus frequencies (5, 20, 40, and 80 Hz) and 3 NMES dosages, manipulated through stimulus train durations or number of repetitions, were evaluated. The optimal excitatory NMES triggered by volitional swallowing (event-related NMES) was then replicated in a new sample and contrasted with non-event-related NMES (either discrete events or continuously for 1 hour). Results. It was found that 80Hz NMES increased motor-evoked potential (MEP) amplitude at 30 minutes and 60 minutes poststimulation only after 60 repetitions of 4-s event-related NMES trains. Non-event-related and continuous NMES did not affect MEP amplitudes. No changes in MEP onset latencies were observed. Conclusions. Changes in corticobulbar excitability induced by NMES of the submental muscle group are frequency and dose dependent and only occur after NMES triggered by volitional swallowing. Underlying neural mechanisms are discussed. © 2010 The Author(s).
Van Stockum S.,Van der Veer Institute for Parkinsons and Brain Research |
Van Stockum S.,University of Otago |
MacAskill M.R.,Van der Veer Institute for Parkinsons and Brain Research |
MacAskill M.R.,University of Otago |
And 3 more authors.
Journal of Clinical Neuroscience | Year: 2012
Reflexive saccades (fast eye movements) and voluntary saccades activate overlapping parts of the oculomotor system. It is assumed that striatal dopamine depletion in Parkinson's disease (PD) only affects the voluntary saccadic system and that the often-reported facilitation of the reflexive saccadic system in PD is secondary to impairment of the voluntary saccadic system. If this assumption is correct, facilitation of reflexive saccades should co-occur with impaired performance of voluntary saccades in patients with PD. We measured reflexive and voluntary saccades in a group of patients with PD (both "on" and "off" medication) and a matching group of control subjects. Interestingly, performance measures showed strong positive correlations across reflexive and voluntary saccades in the PD group. Our results suggest that facilitation of reflexive saccades does not co-occur with impairment of voluntary saccades and that PD may affect the parts of the oculomotor system which are common to reflexive and voluntary saccade generation. © 2011 Elsevier Ltd. All rights reserved.
Melzer T.R.,Van der Veer Institute for Parkinsons and Brain Research |
Melzer T.R.,University of Otago |
Watts R.,Van der Veer Institute for Parkinsons and Brain Research |
Watts R.,University of Canterbury |
And 13 more authors.
Journal of Neurology, Neurosurgery and Psychiatry | Year: 2012
Objective: Mild cognitive impairment and dementia are common non-motor features of Parkinson's disease (PD). The aim of this study was to characterise grey matter changes associated with clearly defined stages of cognitive impairment in PD using structural MRI. Methods: 96 PD subjects were classified using detailed cognitive testing as PD with normal cognition (PD-N, n=57), PD with mild cognitive impairment (PD-MCI, n=23) or PD with dementia (PD-D, n=16); 34 controls matched for mean age and sex ratio also participated. Grey matter volume differences were evaluated using voxel based morphometry of grey matter segments derived from T1 weighted 3 T MRI, and multiple linear regression assessed the relationship between cognitive and motor impairments and grey matter concentration. Results: Compared with controls, no grey matter differences were found in PD-N. PD-MCI showed limited grey matter atrophy in the temporal, parietal and frontal cortex as well as the bilateral caudal hippocampus, amygdala and right putamen. PD-D subjects exhibited far more extensive atrophy in regions involved in PD-MCI but also had reduced grey matter volume in other large areas of the temporal lobe (including the parahippocampi), the intracalcarine and lingual gyri, posterior cingulate gyrus, frontal regions and bilateral caudate. Grey matter loss in PD correlated with global cognitive score but not motor impairment in most of these regions. Interpretation: Marked grey matter atrophy occurs in PD with dementia but far less extensive changes are evident in PD-MCI. Some grey matter atrophy precedes the development of dementia but may be accelerated once frank dementia begins.
Dalrymple-Alford J.C.,Van der Veer Institute for Parkinsons and Brain Research |
Dalrymple-Alford J.C.,University of Canterbury |
Dalrymple-Alford J.C.,University of Otago |
Livingston L.,Van der Veer Institute for Parkinsons and Brain Research |
And 13 more authors.
Movement Disorders | Year: 2011
There is growing interest in identifying Parkinson's disease (PD) patients with mild cognitive impairment (PD-MCI), but widely disparate criteria have been used. We assessed 143 PD patients and 50 matched controls on 20 measures across 4 cognitive domains (executive function, attention and working memory, learning and memory, visuoperception). Twenty-four patients met criteria for dementia (PD-D); nondementia patients were classified as either with normal cognition or MCI for 12 neuropsychological criteria. We compared the influence of these criteria on the distribution of global cognitive performance in the resulting PD-MCI groups relative to the control and PD-D groups. Different criteria produced substantial variation in the proportion of PD-MCI cases identified. Fourteen percent PD-MCI was found when using 2 scores in 1 domain at 2 standard deviations (SD) below normative scores, with no controls identified as MCI, through to 89% PD-MCI with 1 score in 1 domain at 1 SD below normative scores, when 70% of controls were identified as MCI. The balance of cases with impaired cognition but not those with generally intact cognition was better served by using criteria that required 2 specific deficit scores or deficits across 2 domains. As comparisons with external normative data may have greater applicability across centers, we suggest that 2 scores at -1.5 SD within any single domain (30% PD-MCI) or 1 score at -1.5 SD in each of 2 domains (37% PD-MCI) provide suitable criteria to minimize the inclusion of cognitively well patients. Clinical dementia rating did not improve the relative identification of cognitively impaired and unimpaired nondementia PD patients. © 2011 Movement Disorder Society.
Pritchard V.E.,University of Canterbury |
Pritchard V.E.,Van der Veer Institute for Parkinsons and Brain Research |
Woodward L.J.,University of Canterbury |
Woodward L.J.,Van der Veer Institute for Parkinsons and Brain Research
Psychological Assessment | Year: 2011
Executive functions (EF) necessary for purposeful goal-directed activities undergo rapid change and development during the preschool years. However, of the few psychometrically valid measures of EF suitable for use with preschoolers, information on task sensitivity and predictive validity is scant. The neurodevelopmental correlates of early executive difficulties are also largely unknown. In this study, the discriminant and predictive validity of the recently developed Shape School task (Espy, Bull, Martin, & Stroup, 2006) was examined with data from a regional sample of 209 preschool children at age 4 years. A 2-tiered measurement approach was used, with task completion examined in addition to efficiency. Children's performance was also examined in relation to functioning in a range of neurodevelopmental domains. The Shape School task showed some usefulness in capturing expected differences between at-risk and typically developing children. Performance loaded heavily on language and global cognitive abilities. However, several other factors were also implicated, including attention, motor skills, and ocular control. In addition, task completion and efficiency scores appeared to reflect different aspects of performance, and their associations with neurodevelopmental function and later academic achievement on the Woodcock-Johnson Tests of Achievement at age 6 years also differed. Implications for the application of the Shape School task are discussed. © 2011 American Psychological Association.
Norrie J.,Massey University |
Heitger M.,University of Otago |
Heitger M.,Van der Veer Institute for Parkinsons and Brain Research |
Leathem J.,Massey University |
And 5 more authors.
Brain Injury | Year: 2010
Primary objective: To examine fatigue prevalence, severity, predictors and co-variates over 6 months post-mild traumatic brain injury (MTBI). Research design: Longitudinal prospective study including 263 adults with MTBI. Procedures: Participants completed the Fatigue Severity Scale (FSS), Rivermead Post-concussion Symptoms Questionnaire (RPSQ), Hospital Anxiety and Depression Scale (HADS) and the Short Form 36 Health Survey-Version 2 (SF-36v2). Complete data were available for 159 participants. Key measures; prevalence - RPSQ Item 6: severity - FSS. The effect of time on fatigue prevalence and severity was examined using ANOVA. Multiple regression analysis identified statistically significant covariates. Main outcomes and results: Post-MTBI fatigue prevalence was 68%, 38% and 34% at 1 week, 3 and 6 months, respectively. There was a strong effect for time over the first 3 months and moderate-to-high correlations between fatigue prevalence and severity. Early fatigue strongly predicted later fatigue; depression, but not anxiety was a predictor. Fatigue was seen as laziness by family or friends in 30% of cases. Conclusions: Post-MTBI fatigue is a persistent post-concussion symptom, exacerbated by depression but not anxiety. It diminishes in the first 3 months and then becomes relatively stable, suggesting the optimum intervention placement is at 3 months or more post-MTBI. © 2010 Informa UK Ltd. All rights reserved.
Leow L.P.,Van der Veer Institute for Parkinsons and Brain Research |
Leow L.P.,Tan Tock Seng Hospital |
Beckert L.,Christchurch Public Hospital |
Beckert L.,University of Otago |
And 4 more authors.
Dysphagia | Year: 2012
The risk of aspiration pneumonia in Parkinson's disease (PD) may be increased by sensory loss in the laryngopharynx and a reduced cough reflex. This study investigated changes in chemo- and mechanosensation with age and in PD and documented cough thresholds and cortical influences over cough. Single-breath citric acid inhalation cough challenge and flexible nasendoscopy were performed in 32 participants with idiopathic PD (mean age = 68.5 years, range = 45.8-82.5) and 16 healthy young adults (8 males, mean age = 25.1 years, range = 21.3-32.4), and 16 healthy elders (8 males, mean age = 72.8 years, range = 61.5-84.7) as controls. Individuals with PD had reduced sensation at the base of the tongue compared to age- and gender-matched counterparts (p < 0.005). All groups demonstrated lower natural cough thresholds than suppressed cough thresholds. No differences in natural cough thresholds were found across groups. Young adults demonstrated greater ability to suppress cough compared to healthy elders (p = 0.021). Tongue-base mechanosensory impairment in PD may account for vallecular residue and complaints of globus sensation. However, decreased cough response was not found to be a characteristic of PD. This study provided evidence for voluntary control of cough and the lack of decline of chemosensitivity with age or disease. © 2011 Springer Science+Business Media, LLC.
Leow L.P.,Van der Veer Institute for Parkinsons and Brain Research |
Huckabee M.-L.,University of Canterbury |
Huckabee M.-L.,Van der Veer Institute for Parkinsons and Brain Research |
Anderson T.,Van der Veer Institute for Parkinsons and Brain Research |
And 2 more authors.
Dysphagia | Year: 2010
This prospective, cross-sectional study evaluated the impact of dysphagia on quality of life in healthy ageing and in subjects with Parkinson's disease (PD) using the Swallowing Quality of Life (SWAL-QOL) questionnaire. Sixteen healthy young adults (8 males, mean age = 25.1 years) and 16 healthy elders (8 males, mean age = 72.8 years) were recruited. Thirty-two subjects with idiopathic PD (mean age = 68.5 years) were recruited from a movement disorders clinic. The severity of PD was staged using the Hoehn and Yahr scale. Results revealed that elders experienced symptoms of dysphagia more frequently than young adults but the overall SWAL-QOL scores were not significantly different. Subjects with PD who experienced dysphagia reported greatly reduced QOL, and significant differences were found in all but one subsection of the SWAL-QOL. Disease progression detrimentally impacts QOL, with subjects in later-stage PD experiencing further reduction in the desire to eat, difficulty with food selection, and prolonged eating duration. These features, which increase with disease severity, are likely to impact negatively upon nutritional status, which is already under threat from PD-related dysphagia. © 2009 Springer Science+Business Media, LLC.
Peiris M.T.,Van der Veer Institute for Parkinsons and Brain Research
Journal of neural engineering | Year: 2011
A system capable of reliably detecting lapses in responsiveness ('lapses') has the potential to increase safety in many occupations. We have developed an approach for detecting the state of lapsing with second-scale temporal resolution using data from 15 subjects performing a one-dimensional (1D) visuomotor tracking task for two 1 h sessions while their electroencephalogram (EEG), facial video, and tracking performances were recorded. Lapses identified using a combination of facial video and tracking behaviour were used to train the classification models. Linear discriminant analysis was used to form detection models based on individual subject data and stacked generalization was utilized to combine the outputs of multiple classifiers to obtain the final prediction. The performance of detectors estimating the lapse/not-lapse state at 1 Hz based on power spectral features, approximate entropy, fractal dimension, and Lempel-Ziv complexity of the EEG was compared. Best lapse state estimation performance was achieved using the detector model created using power spectral features with an area under the curve from receiver operating characteristic analysis of 0.86 ± 0.03 (mean±SE) and an area under the precision-recall curve of 0.43 ± 0.09. A novel technique was developed to provide improved estimation of accuracy of detection of variable-duration events. Via this approach, we were able to show that the detection of lapse events from spectral power features was of moderate accuracy (sensitivity = 73.5%, selectivity = 25.5%).
Farr H.,University of Canterbury |
Farr H.,Van der Veer Institute for Parkinsons and Brain Research |
David T.,University of Canterbury
Journal of Theoretical Biology | Year: 2011
Functional hyperemia is an important metabolic autoregulation mechanism by which increased neuronal activity is matched by a rapid and regional increase in blood supply. This mechanism is facilitated by a process known as "neurovascular coupling"-the orchestrated communication system involving neurons, astrocytes and arterioles. Important steps in this process are the production of EETs in the astrocyte and the release of potassium, via two potassium channels (BK and KIR), into the perivascular space. We provide a model which successfully accounts for several observations seen in experiment. The model is capable of simulating the approximate 15% arteriolar dilation caused by a 60-s neuronal activation (modelled as a release of potassium and glutamate into the synaptic cleft). This model also successfully emulates the paradoxical experimental finding that vasoconstriction follows vasodilation when the astrocytic calcium concentration (or perivascular potassium concentration) is increased further. We suggest that the interaction of the changing smooth muscle cell membrane potential and the changing potassium-dependent resting potential of the KIR channel are responsible for this effect. Finally, we demonstrate that a well-controlled mechanism of potassium buffering is potentially important for successful neurovascular coupling. © 2011 Elsevier Ltd.