Search results for "Sensory system"
showing 10 items of 1266 documents
Dipole Source Analysis of Laser-Evoked Subdural Potentials Recorded From Parasylvian Cortex in Humans
2003
The location of the human nociceptive area(s) near the Sylvian fissure is still controversial in spite of evidence from imaging and evoked potential studies that noxious heat stimuli activate somatosensory areas in that region. Some studies have suggested the secondary somatosensory cortex (SII) on the upper bank of the Sylvian fissure posterior to the central sulcus, others the anterior insula or parietal area 7b. In this study, we applied dipole source analysis techniques to laser-evoked potentials (LEPs) that were recorded from subdural grid electrodes in three patients. As a functional marker, auditory-evoked potentials (AEPs) with a generator on the opposite bank of the Sylvian fissur…
Impact of the line of sight on toric phakic intraocular lenses for hyperopia
2003
We present a hyperopic patient with a decentered line of sight in whom the residual refractive error after toric phakic intraocular lens (TP IOL) implantation was improved by displacement and individualized treatment. A 35-year-old woman presented with asthenopic complaints 2 months after bilateral TP IOL implantation and IOL rotation 4 weeks later. Examination revealed the line of sight to be nasally and inferiorly decentered in relation to the center of the pupil. A more nasal reenclavation of the TP IOL decreased the coma, and the uncorrected visual acuity was 20/20. We conclude that line of sight should be measured before TP IOL implantation, especially in hyperopic eyes.
Functional MRI of human primary somatosensory and motor cortex during median nerve stimulation.
1999
Abstract Objectives: Somatosensory evoked potential (SEP) studies suggested that some early cortical SEP components may be generated in the primary motor cortex (M1) rather than the primary somatosensory cortex (S1). Methods: We now used functional magnetic resonance imaging (fMRI) to study activation of S1 and M1 by electrical median nerve stimulation in healthy volunteers. Results: The hand areas of both S1 and M1 showed significant activation (correlation coefficients >0.45) in 7 of 9 subjects (activated volume S1>M1). For comparison, a sequential finger opposition task significantly activated S1 in 7 and M1 in all 9 subjects (activated volume M1>S1). Conclusions: These data show that th…
Changes of sensory conduction velocity and refractory periods with decreasing tissue temperature in man.
1977
Changes with temperature of maximum sensory nerve conduction velocity as well as absolute and relative refractory periods were tested in 14 human subjects. Corresponding to previously published findings maximum conduction velocity decreased with cooling following a Q10 of +1.4. The absolute and relative refractory periods were increased by cooling, the Q10 being -3.1 and -3.35 respectively. There was a tendency showing a more pronounced temperature effect at low temperatures. The Q10 and the steepness of the regressionline changed at the level of 26.9 degrees C, but were significant for the relative refractory period only.
Relation between fixation disparity and the asymmetry between convergent and divergent disparity step responses
2007
Abstract The neural network model of Patel et al. [Patel, S. S., Jiang, B. C., & Ogmen, H. (2001). Vergence dynamics predict fixation disparity. Neural Computation, 13 (7), 1495–1525] predicts that fixation disparity, the vergence error for a stationary fusion stimulus, is the result of asymmetrical dynamic properties of disparity vergence mechanisms: faster (slower) convergent than divergent responses give rise to an eso (exo) fixation disparity, i.e., over-convergence (under-convergence) in stationary fixation. This hypothesis was tested in the present study with an inter-individual approach: in 16 subjects we estimated the vergence step response to a 1 deg disparity stimulus with a subje…
Somatosensory evoked potentials in Arnold-Chiari malformation.
2002
Abstract Nearly all patients with repaired myelomeningoceles have an Arnold–Chiari (AC) malformation and about 20% of these patients develop clinical signs of brainstem dysfunction. The management of symptomatic AC malformation is still controversial and techniques are needed to provide an objective assessment of brainstem function. We recorded somatosensory evoked potentials (SEPs) in 52 patients aged between 8 months and 20 years (median 7.3 years) with AC malformation, to determine whether the SEPs discriminate patients with symptomatic AC malformation from those without symptoms. The subcortical far-field components P13, P14 and N18, which are generated within the brainstem, were record…
Monocular versus binocular pupillometry.
2004
Purpose To quantify differences between monocular and binocular pupil size measurement under scotopic and mesopic conditions. Setting Department of Ophthalmology, Johannes Gutenberg-University, and Department of Medical Biometry, Epidemiology and Informatics, University of Mainz, Mainz, Germany. Methods Computerized dynamic pupillometry (P2000 SA, Procyon Instruments Ltd.) was used at 3 illumination levels: scotopic at 0.03 lux, mesopic low at 0.82 lux, and mesopic high at 6.4 lux. One hundred forty eyes of 70 healthy volunteers without ocular pathology were examined. The subjects were divided into 2 groups. In the first group, the pupil diameter was measured binocularly first. In the secon…
Changes in colour discrimination during the menstrual cycle.
2006
A group of normal women of reproductive age were recruited to investigate colour discrimination during the various phases of the menstrual cycle. Colour vision was tested with the Farnsworth-Munsell 100-hue arrangement test, and the test was administered at 3 time points: the beginning of the cycle, ovulation, and the end of the cycle. We found that colour discrimination was better at ovulation than at the other 2 time points. It is possible that psychological as well as hormonal factors could contribute to improved colour vision performance at ovulation.
Main posterior watershed zone of the choroid
1989
The main posterior watershed zone of the choroid is located between the nasal edge of the optic disc and the fovea and represents the area situated between the territories supplied by the temporal and nasal posterior ciliary arteries. In the fluorescein angiographies of 800 normal subjects a watershed zone was not observed in 33.1% due to technical reasons and in 22.3% due to the simultaneous filling of the peripapillar and macular choriocapillaris. In the remaining 44.6% the watershed zone was well outlined: it was straddling the optic disc in about half of these cases and involved the temporal half of the optic disc and the close choroid in the other half. Very rarely the watershed zone i…
Instructions for External Focus of Attention Improved Taekwondo Kicking Performance Only Among Less Skilled Youth
2022
External focus of attention (EFA) studies among children have yielded more equivocal results than have those among adults. Some investigators have found an internal focus of attention (IFA) advantage in children and have explained their results by children’s generally lower skill levels, compared to adults. According to the constrained action hypothesis, children’s lower skill levels are not yet associated with over-learned automatic movement patterns, so their motor performance is not disrupted by IFA instructions. In this study, our objective was to examine a possible interaction effect between children’s skill levels and their exposure to either IFA or EFA instructions on motor performa…