Journal of neuroscience methods
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J. Neurosci. Methods · Mar 2012
Application of triphasic pulses with adjustable phase amplitude ratio (PAR) for cochlear ECAP recording: I. amplitude growth functions.
This study describes the use of triphasic electrical stimulation pulses with an adjustable phase amplitude ratio (PAR) for the reduction of electrical stimulus artifacts. It is hypothesized that the setting of a certain PAR can facilitate a nearly artifact-free recording of electrically evoked compound action potentials (ECAP) in the cochlea. Artifact reduction with triphasic pulses using single epochs is expected to prevent latency or polarity effects, which are seen in standard forward masking or alternating polarity strategies. ⋯ However, recording of ECAP with triphasic pulses showed drawbacks: additional artifacts depending on stimulation and/or recording parameters are introduced, the ratio between the additional artifact and improved detectability of neural responses is dependent on PAR, and response thresholds obtained with triphasic pulses--although similar in shape--are in most cases substantially higher compared to thresholds measured with the Miller method. Higher thresholds most probably occur because the triphasic pulse patterns seem to less effectively stimulate neural structures compared to biphasic pulses since measured response thresholds are higher. For certain electrode groups threshold profiles obtained with triphasic pulses were found to be similar compared to stimulation with biphasic pulses.
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J. Neurosci. Methods · Mar 2012
A fully implanted programmable stimulator based on wireless communication for epidural spinal cord stimulation in rats.
Clinical research indicates that the epidural spinal cord stimulation (ESCS) has shown potential in promoting locomotor recovery in patients with incomplete spinal cord injury (ISCI). This paper presents the development of a fully implantable voltage-regulated stimulator with bi-directional wireless communication for investigating underlying neural mechanisms of ESCS facilitating motor function improvement. The stimulation system consists of a computer, an external controller, an implantable pulse generator (IPG), a magnet, the extension leads and a stimulation electrode. ⋯ The encapsulated IPG measures 33mm×24mm×8mm, with a total mass of ∼12.6g. Feasibility experiments are conducted in three Sprague-Dawley rats to validate the function of the stimulator, and to investigate the relationship between lumbar-sacral ESCS and hindlimb electromyography (EMG) responses. The results show that the stimulation system provides an effective tool for investigation of ESCS application in motor function recovery in small animals.
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J. Neurosci. Methods · Feb 2012
Three-dimensional alteration of microvasculature in a rat model of traumatic spinal cord injury.
Acute spinal cord injury (SCI) always leads to severe destruction of the microvascular networks. To investigate the three-dimensional (3D) alterations of microvasculature following SCI, we utilized an established rat SCI model. Based on the hypothesis that the spinal cord would undergo reorganization and postinjury modification of the vascular networks after SCI, we reconstructed the normal and injured angioarchitecture using micro-CT images of silicone rubber microsphere-perfused specimens. ⋯ The method used here has the potential to improve our understanding of changes in the spatial architecture of vascular networks after SCI compared to the conventional histomorphology techniques. In summary, we developed a new methodology to analyze neurovascular pathology based on 3D vascular network patterns and features in an experimental rat SCI model. This technique could be used as a complementary tool to investigate the efficacy and side effects of therapeutic drugs or rehabilitation regimens.
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J. Neurosci. Methods · Feb 2012
Validation of an air-puff passive-avoidance paradigm for assessment of aversive learning and memory in rat models of chronic pain.
Chronic pain is associated with cognitive deficits. Considerable overlap in brain regions involved in pain and aversion suggests that aversive learning and memory may be affected during chronic pain. Passive-avoidance paradigms traditionally use foot-shock to induce context-conditioned avoidance and may be unsuitable for use in animal models of chronic pain, which are commonly associated with hypersensitivity of the hind-paws. ⋯ However, there was no difference in the response between either model and its respective control group. Thus, air-puff can be used as an alternative to foot-shock to induce a passive-avoidance response. The data generated using this model suggest that aversive learning and memory remain intact in the rat spinal nerve ligation and complete Freund's adjuvant models of chronic neuropathic and inflammatory pain, respectively.
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J. Neurosci. Methods · Jan 2012
An implantable triple-function device for local drug delivery, cerebrospinal fluid removal and EEG recording in the cranial subdural/subarachnoid space of primates.
Transmeningeal pharmacotherapy for cerebral cortical disorders requires drug delivery through the subdural/subarachnoid space, ideally with a feedback controlled mechanism. We have developed a device suitable for this function. The first novel component of the apparatus is a silicone rubber strip equipped with (a) fluid-exchange ports for both drug delivery and local cerebrospinal fluid (CSF) removal, and (b) EEG recording electrode contacts. ⋯ The entire apparatus was implanted in 5 macaque monkeys, with the subdural strip positioned over the frontal cortex and the minipump assembly secured to the cranium under a protective cap. The system was successfully tested for up to 8 months for (1) transmeningeal drug delivery using acetylcholine (ACh) and muscimol as test compounds, (2) RF-transmission of neocortical EEG data to assess the efficacy of drug delivery, and (3) local CSF removal for subsequent diagnostic analyses. The device can be used for (a) monitoring neocortical electrophysiology and neurochemistry in freely behaving nonhuman primates for more than 6 months, (b) determining the neurobiological impact of subdural/subarachnoid drug delivery interfaces, (c) obtaining novel neuropharmacological data on the effects of central nervous system (CNS) drugs, and (d) performing translational studies to develop subdural pharmacotherapy devices.