Brain research
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Three spatio-temporal neurophysiological patterns involved in visual selective attention were identified from the human event-related potentials (ERPs) by a novel common spatial pattern (CSP) decomposition method and the standardized low resolution brain electromagnetic tomography (sLORETA). In the experiment, stimuli were rapidly presented randomly to the right or left visual fields while subjects attended to one visual field at a time (Clark, Hillyard, 1996. Spatial selective attention affects early extrastriate but not striate components of the visual evoked potential. ⋯ The temporal waveforms indicated that contralateral PFC and PPC were activated synchronously at about 150 ms after the stimulus onset, with early attention effects only occurring in PFC, and the PPC was activated earlier than that of PFC during 200-260 ms. The results imply that humans adopt different allocation strategies for resources in visual attention and un-attention situations. For attention case, visual cortex consumes the most resources and for non-attention situation, the ACC and PPC consume the most resources.
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Comparative Study
Toward a comparison of microelectrodes for acute and chronic recordings.
Several variations of microelectrode arrays are used to record and stimulate intracortical neuronal activity. Bypassing the immune response to maintain a stable recording interface remains a challenge. Companies and researchers are continuously altering the material compositions and geometries of the arrays in order to discover a combination that allows for a chronic and stable electrode-tissue interface. ⋯ Results suggest significant variability within and between microelectrode types with no clear superior array. Some applications for the microelectrode arrays are suggested based on data collected throughout the longitudinal study. Additionally, specific limitations of assaying biological phenomena and comparing fundamentally different microelectrode arrays in a highly variable system are discussed with suggestions on how to improve the reliability of observed results and steps needed to develop a more standardized microelectrode design.
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Activation of the trigeminovascular pain signalling system, including cerebral arteries, meninges, trigeminal ganglion, and brain stem, is involved in migraine. Furthermore, stimulation of cyclic nucleotide (cAMP and cGMP) production as well as inhibition of phosphodiesterases (PDEs) induces headache and migraine. In order to investigate the possible role of PDE in the pain pathway of migraine, expression of the most recently discovered PDE subtypes (9A, 10A and 11A) in cerebral arteries, dura mater, and trigeminal ganglion and nucleus was examined. ⋯ Immunohistochemistry revealed that PDE9A, PDE10A and PDE11A are localised in the cytosol of nerve cell bodies of the trigeminal ganglion. We here present, for the first time, the expression of PDE9A, PDE10A, and PDE11A in the trigeminovascular system. The functional implications are yet unknown, but their localisation indicates that they may have a role in the pain pathway of migraine as well as trigeminal neuralgia and trigeminal autonomic cephalalgias.
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Behavioral analysis commonly assesses cognitive deficits in rodents following traumatic brain injury (TBI). We examined rats that received sham, mild or moderate injury in the controlled cortical impact model of TBI. The rats were tested in a novel hierarchy of four behavioral tasks with increasing cognitive demand. ⋯ Moderately-injured animals were also impaired if tested 3 weeks after injury. One day after phase three, sham- and mildly-injured animals were tested on a phase four conflict active avoidance task with the shock zone shifted 180 degrees from its phase three location and mildly-injured animals were impaired. The speed in which the animals complete the four phases of testing as well as the ability to discriminate between differing injury severity suggests that this set of neurobehavioral tasks will be useful to understand cognitive deficits underlying TBI as well as a useful screening method for therapeutic drugs.
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Novel neurorehabilitative strategies are needed to improve motor outcomes following stroke. Based on the disynaptic excitatory projections of the dentatothalamocortical pathway to the motor cortex as well as to anterior and posterior cortical areas, we hypothesize that chronic electrical stimulation of the contralesional dentate (lateral cerebellar) nucleus output can enhance motor recovery after ischemia via augmentation of perilesional cortical excitability. Seventy-five Wistar rats were pre-trained in the Montoya staircase task and subsequently underwent left cerebral ischemia with the 3-vessel occlusion model. ⋯ There was no difference on the left (ipsilesional) side motor performance among the sham or stimulation groups, varying from 15.9+/-6.7 to 17.2+/-2.1 pellets. We conclude that contralesional chronic electrical stimulation of the lateral cerebellar nucleus at 20 pps but not at 10 or 50 pps improves motor recovery in rats following ischemic strokes. This effect is likely to be mediated by increased perilesional cortical excitability via chronic activation of the dentatothalamocortical pathway.