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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. Source


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%). Source


Peiris M.T.R.,Van der Veer Institute for Parkinsons and Brain Research | Peiris M.T.R.,University of Canterbury | Davidson P.R.,Van der Veer Institute for Parkinsons and Brain Research | Davidson P.R.,University of Canterbury | And 5 more authors.
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%). © 2011 IOP Publishing Ltd. Source


Leow L.P.,Van der Veer Institute for Parkinsons and Brain Research | Beckert L.,Christchurch Respiratory Physiology Laboratory | Beckert L.,University of Otago | Anderson T.,Van der Veer Institute for Parkinsons and Brain Research | And 3 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. Source


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. Source

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