Neuroscience letters
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Neuroscience letters · Apr 2008
Short-term modulation of the ipsilateral primary sensory cortex by nociceptive interference revealed by SEPs.
We studied the modulation of the topographic arrangement of the human ipsilateral primary somatosensory cortex following interference of nociceptive stimuli by means of dipole source analysis. Multichannel somatosensory evoked potentials were obtained by electrical stimulation of digits 1 and 5 of the left hand before, during and after the application of pain to digits 2-4 of the right hand. The primary cortical response of the SEP (N20) was obtained for dipole localization of the representation of the primary sensory cortex receiving input from digits 1 to 5. ⋯ Our results provide further evidence for the presence of a quickly adapting interaction between primary somatosensory areas of both hemispheres following an interference of nociceptive stimulation in SEPs. This modifying process is probably mediated by interhemispheric and intercortical connections leading to hyperexcitability of the primary sensory cortex contralateral to that receiving nociceptive input. Spatial attention does not seem to have an impact on this kind of short-term intercortical plasticity.
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Neuroscience letters · Apr 2008
Comparative StudyGray matter differences between pediatric obsessive-compulsive disorder patients and high-risk siblings: a preliminary voxel-based morphometry study.
Neuroimaging studies have identified alterations in frontostriatal circuitry in obsessive-compulsive disorder (OCD). Voxel-based morphometry (VBM) allows for the assessment of differences in gray matter density across the whole brain. VBM has not previously been used to examine regional gray matter density in pediatric OCD patients and the siblings of pediatric OCD patients. ⋯ VBM analysis revealed significantly lower gray matter density in OCD patients compared to healthy in the left ACC and bilateral medial superior frontal gyrus (SFG). Furthermore, a small volume correction was used to identify a significantly greater gray matter density in the right putamen in OCD patients as compared to unaffected siblings of OCD patients. These findings in patients, siblings, and healthy controls, although preliminary, suggest the presence of gray matter structural differences between affected subjects and healthy controls as well as between affected subjects and individuals at risk for OCD.
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Neuroscience letters · Apr 2008
Primary motor cortex activation by transcranial direct current stimulation in the human brain.
Transcranial direct current stimulation (tDCS) can modulate motor cortex excitability in the human brain. We attempted to demonstrate the cortical stimulation effect of tDCS on the primary motor cortex (M1) using functional MRI (fMRI). An fMRI study was performed for 11 right-handed healthy subjects at 1.5 T. ⋯ In addition, there were activations on the left supplementary motor cortex and the right posterior parietal cortex. We demonstrated that tDCS has a direct stimulation effect on the underlying cortex. It seems that tDCS is a useful modality for stimulating a target cortical region.
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Neuroscience letters · Apr 2008
Time course of auditory masker effects: tapping the locus of audiovisual integration?
In a focused attention paradigm, saccadic reaction time (SRT) to a visual target tends to be shorter when an auditory accessory stimulus is presented in close temporal and spatial proximity. Observed SRT reductions typically diminish as spatial disparity between the stimuli increases. Here a visual target LED (500 ms duration) was presented above or below the fixation point and a simultaneously presented auditory accessory (2 ms duration) could appear at the same or the opposite vertical position. ⋯ It is therefore conceivable that the relatively high-energetic masker causes a broad excitatory response of SC neurons. During this state, the spatial audio-visual information from multisensory association areas is fed back and merged with the spatially unspecific excitation pattern induced by the masker. Assuming that a certain threshold of activation has to be achieved in order to generate a saccade in the correct direction, the blurred joint output of noise and spatial audio-visual information needs more time to reach this threshold prolonging SRT to an audio-visual object.
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Neuroscience letters · Apr 2008
TNF-alpha differentially modulates ion channels of nociceptive neurons.
Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine involved in the development and maintenance of inflammatory and neuropathic pain conditions. The mechanisms by which TNF-alpha elicits pain behavior are still incompletely understood. Numerous studies suggest that TNF-alpha sensitizes primary afferent neurons. ⋯ D.), and voltage-activated sodium channels currents were increased by +5.62+/-4.27%, by TNF-alpha. In addition, TNF-alpha induced a significant increase in IV ramps at a potential of +20 mV, which did not exist when the experiments were conducted in a potassium-free solution, indicating that this effect is mainly the result of a change in potassium conductance. These different actions of TNF-alpha might help to explain how it sensitizes primary afferent neurons after nerve injury and thus facilitates pain.