Search results for "RESONANCE"
showing 10 items of 6625 documents
Role of Octreoscan and Correlation with MR Imaging in Graves' Ophthalmopathy
1995
Since the identification of somatostatin receptors on lymphocytes, orbital infiltration with mononuclear cells in Graves' ophthalmopathy has provided a rationale for receptor imaging with the radiolabeled somatostatin analog Octreotide. In 40 patients with Graves' ophthalmopathy and 10 controls, 110 MBq indium-Octreotide were administered i.v., and scans were performed at 4 and 24 h after injection. An uptake ratio between the orbits and the brain was determined. In 20 ophthalmophathy patients, magnetic resonance imaging (MRI) of the orbits was performed and the T2 relaxation time was measured within the rectus muscles. Compared to controls (4 h Octreotide uptake: median 6.0 counts/pixel/MB…
Effects of valence and arousal on implicit approach/ avoidance tendencies: A fMRI study.
2018
To date, it is still a matter of debate, whether valence or valence and arousal interactively foster implicit approach and avoidance tendencies, and which neural circuitries underlie these effects. To address these questions, we investigated the effects of valence and arousal on implicit approach/avoidance tendencies during fMRI in healthy volunteers (N=46). The implicit approach of positive social scenes was associated with shorter response preparation times and increased activation of the lingual, parahippocampal and fusiform gyri. Valence and arousal did not influence reaction times interactively, but we observed increased activation of prefrontal, motor, temporal, middle cingulate and p…
Asymmetric modulation of human visual cortex activity during 10 degrees lateral gaze (fMRI study).
2005
We used BOLD fMRI to study the differential effects of the direction of gaze on the visual and the ocular motor systems. Fixation of a target straight ahead was compared to fixation of a target 10 degrees to the right and 10 degrees to the left from gaze straight ahead, and to eyes open in complete darkness in thirteen healthy volunteers. While retinotopic coordinates remained the same in all fixation conditions, the fixation target shifted with respect to a head-centered frame of reference. During lateral fixation, deactivations in higher-order visual areas (one ventral cluster in the lingual and fusiform gyri and one dorsal cluster in the postero-superior cuneus) and, as a trend, activati…
Eye closure in darkness animates sensory systems.
2003
Single subject and group analyses (n = 12) showed that the eyes-open and eyes-closed states in complete darkness considerably and consistently differ in the patterns of associated brain activation in fMRI. During nonchanging external stimulation, ocular motor and attentional systems were activated when the eyes were open; the visual, somatosensory, vestibular, and auditory systems were activated when the eyes were closed. These data suggest that there are two different states of mental activity: with the eyes closed, an "interoceptive" state characterized by imagination and multisensory activity and with the eyes open, an "exteroceptive" state characterized by attention and ocular motor act…
Direction‐dependent visual cortex activation during horizontal optokinetic stimulation (fMRI study)
2005
Looking at a moving pattern induces optokinetic nystagmus (OKN) and activates an assembly of cortical areas in the visual cortex, including lateral occipitotemporal (motion‐sensitive area MT/V5) and adjacent occipitoparietal areas as well as ocular motor areas such as the prefrontal cortex, frontal, supplementary, and parietal eye fields. The aim of this functional MRI (fMRI) study was to investigate (1) whether stimulus direction‐dependent effects can be found, especially in the cortical eye fields, and (2) whether there is a hemispheric dominance of ocular motor areas. In a group of 15 healthy subjects, OKN in rightward and leftward directions was visually elicited and statistically compa…
Functional Magnetic Resonance Imaging Activations of Cortical Eye Fields during Saccades, Smooth Pursuit, and Optokinetic Nystagmus
2009
Saccades, smooth pursuit, and optokinetic nystagmus (OKN) are three basic eye movements in our ocular motor repertoire that enable us to explore the visual field. These eye movements are cortically controlled in different cortical eye fields, including the frontal eye fields (FEF) and parietal eye fields (PEF), as well as the motion-sensitive visual area MT+/V5. It is not known if this cortical control is organized in parallel cortico-cortical networks or in adjacent subregions of one system. Nor do we know where the specific eye fields are exactly located. Functional magnetic resonance imaging (fMRI) was used to investigate these open questions about the FEF, PEF, and MT+/V5. Activations o…
Brainstem evoked potentials and magnetic resonance imaging abnormalities in differential diagnosis of intracranial hypotension.
2019
Summary Objective To compare brainstem acoustic evoked potentials (BAEP) and magnetic resonance imaging (MRI) in the differential diagnosis of intracranial hypotension (IH), Chiari malformation (CM) and sensorineural hearing loss (SNHL). Methods BAEP were recorded in 18 IH, 18 CM, 20 SNHL patients and 52 controls. MRI were acquired in all IH and CM patients. Results Abnormal BAEP were observed in 94% of IH patients, in 33% of CM and 70% of SNHL patients. After recovery from IH, BAEP abnormalities disappeared. Internal auditory canal (IAC) MRI abnormalities were described in 88% of IH patients. MRI signs of IH were observed in 33–78% in IH patients, but the most frequent MRI sign was 8th ner…
Inhibitory interhemispheric visuovisual interaction in motion perception.
2003
Findings of an earlier functional magnetic resonance imaging (fMRI) study that coherent motion stimulation of the right or left visual hemifield exhibited negative signal changes (deactivations) in the primary visual cortex and the lateral geniculate nucleus contralateral to the stimulated hemisphere were evaluated to determine the functional significance of this contralateral inhibition of the visual system. Fourteen subjects participated in a psychophysical study on the perception of single object motion (0.4 degrees /s) in one visual hemifield with or without concurrent coherent motion stimulation of the contralateral hemifield. Mean detection times for horizontal object motion (0.5 +/- …
fMRI signal increases and decreases in cortical areas during small-field optokinetic stimulation and central fixation
2001
Small-field optokinetic nystagmus (OKN) was performed in seven healthy volunteers in order to analyze the activation and deactivation patterns of visual motion, ocular motor, and multisensory vestibular cortex areas by means of fMRI during coherent visual motion stimulation. BOLD signal decreases (deactivations) were found in the first and second long insular gyri and retroinsular areas (the human homologue of the parietoinsular vestibular cortex and the visual posterior sylvian area in the monkey) of both hemispheres, extending into the transverse temporal gyrus and inferior-anterior parts of the superior temporal gyrus (BA 22), and the precentral gyri at two separate sites (BA 4 and 6). F…
Evidence for cortical visual substitution of chronic bilateral vestibular failure (an fMRI study).
2007
Bilateral vestibular failure (BVF) is a rare disorder of the labyrinth or the eighth cranial nerve which has various aetiologies. BVF patients suffer from unsteadiness of gait combined with blurred vision due to oscillopsia. Functional MRI (fMRI) in healthy subjects has shown that stimulation of the visual system induces an activation of the visual cortex and ocular motor areas bilaterally as well as simultaneous deactivations of multisensory vestibular cortex areas. Our question was whether the chronic absence of bilateral vestibular input (BVF) causes a plastic cortical reorganization of the above-described visual-vestibular interaction. We used fMRI to measure the differential effects of…