Journal of neuroscience methods
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The ability to detect and sort overlapping spike waveforms in extracellular recordings is key to studies of neural coding at high spatial and temporal resolution. Most spike-sorting algorithms are based on initial spike detection (e.g. by a voltage threshold) and subsequent waveform classification. Much effort has been devoted to the clustering step, despite the fact that conservative spike detection is notoriously difficult in low signal-to-noise conditions and often entails many spike misses. ⋯ They unify the advantages of independent component analysis (ICA) and overlap-search algorithms because they blindly perform source separation even in cases where several neurons are recorded on a single electrode. We apply HMMs to artificially generated data and to extracellular signals recorded with glass electrodes. We show that in comparison with state-of-art spike-sorting algorithms, HMM-based spike sorting exhibits a comparable number of false positive spike classifications but many fewer spike misses.
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J. Neurosci. Methods · Sep 2008
Localization of neurosurgically implanted electrodes via photograph-MRI-radiograph coregistration.
Intracranial electroencephalography (iEEG) is clinically indicated for medically refractory epilepsy and is a promising approach for developing neural prosthetics. These recordings also provide valuable data for cognitive neuroscience research. Accurate localization of iEEG electrodes is essential for evaluating specific brain regions underlying the electrodes that indicate normal or pathological activity, as well as for relating research findings to neuroimaging and lesion studies. ⋯ As the technique does not require any calibration between the different image modalities, it can be applied to existing image databases. The final result is a set of electrode positions on the patient's rendered MRI yielding locations relative to sulcal and gyral landmarks on individual anatomy, as well as MNI coordinates. We demonstrate the results of our method in eight epilepsy patients implanted with electrode grids spanning the left hemisphere.
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J. Neurosci. Methods · Sep 2008
Using the CatWalk method to assess weight-bearing and pain behaviour in walking rats with ankle joint monoarthritis induced by carrageenan: effects of morphine and rofecoxib.
The CatWalk automated quantitative gait analysis technique has been validated as a method to quantify behaviour in rodent models of neuropathic and arthritic pain. Its suitability for pharmacological testing of pain relief has been questioned, however, based on findings using paw soft tissue plantar inflammation as stimulus. In this study, we investigated the effectiveness of morphine and rofecoxib in reducing pain behaviour in monoarthritic rats. ⋯ The monoarthritic rat showed a reduced print area, weight load and duration of stance for the injected paw at all times tested, and a significant loss of interlimb coordination at 3 and 5h after injection. Both morphine (3.75 and 15 micromol/kg s.c.) and rofecoxib (7.5 and 30 micromol/kg p.o.) reduced the effects of carrageenan. In conclusion, behavioural effects interpreted as reflecting movement-related pain in monoarthritic rats and pharmacological treatment of the monoarthritis can objectively and efficiently be quantified in detail by the CatWalk method.
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J. Neurosci. Methods · Sep 2008
Blocking pterygopalatine arterial blood flow decreases infarct volume variability in a mouse model of intraluminal suture middle cerebral artery occlusion.
The mouse model of intraluminal suture middle cerebral artery occlusion (MCAO) is still associated with several issues, such as variability of infarction volume and survival. Thus, the method is far from standardization. The effect of blood flow in the pterygopalatine artery (PPA) in the mouse MCAO model remains obscure. ⋯ Although mean infarct volume did not obviously differ between the MCAO-U and other two groups, infarct volumes varied significantly more within the MCAO-U, than in the other two groups (p<0.05). We concluded that collateral circulation from the PPA to the brain significantly influences the MCAO model, and cannot be ignored. An approximately consistent mouse MCAO model can be generated using commercially available silicone-coated sutures while blocking PPA blood flow during occlusion.