Search results for " Movement"
showing 10 items of 1376 documents
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…
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…
Competition between clonal plasma cells and normal cells for potentially overlapping bone marrow niches is associated with a progressively altered ce…
2011
Disappearance of normal bone marrow (BM) plasma cells (PC) predicts malignant transformation of monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM) into symptomatic multiple myeloma (MM). The homing, behavior and survival of normal PC, but also CD34 hematopoietic stem cells (HSC), B-cell precursors, and clonal PC largely depends on their interaction with stromal cell-derived factor-1 (SDF-1) expressing, potentially overlapping BM stromal cell niches. Here, we investigate the distribution, phenotypic characteristics and competitive migration capacity of these cell populations in patients with MGUS, SMM and MM vs healthy adults (HA) aged 60 years. Our result…
Nonlinear analysis of sleep EEG data in schizophrenia: calculation of the principal Lyapunov exponent
1995
The generating mechanism of the electroencephalogram (EEG) points to the hypothesis that EEG signals derive from a nonlinear dynamic system. Hence, the unpredictability of the EEG might be considered as a phenomenon exhibiting its chaotic character. The essential property of chaotic dynamics is the so-called sensitive dependence on initial conditions. This property can be quantified by calculating the system's first positive Lyapunov exponent, L1. We calculated L1 for sleep EEG segments of 13 schizophrenic patients and 13 control subjects that corresponded to sleep stages I, II, III, IV and REM (rapid eye movement), as defined by Rechtschaffen and Kales, for the lead positions Cz and Pz. Du…
Blockade of nicotinic and muscarinic receptors facilitates spontaneous migration of human peripheral granulocytes: failure in cystic fibrosis.
2012
Circulating leucocytes express muscarinic (m) and nicotinic (n) receptors and synthesize acetylcholine (ACh) regulating various cell functions. Leucocytes from patients with cystic fibrosis contain less ACh; therefore it was tested whether the regulation of cellular functions like migration differed from healthy volunteers.Peripheral blood (10-20 ml) was used, leucocytes were isolated by Ficoll® gradient and the commercial MIGRATEST® combined with flow cytometric analysis was applied (pore size 3 μm).In the absence of test substances 4900±1800 (n=10) leucocytes migrated within a time period of 2 h. In the presence of tubocurarine (TC, 30 μM) the cell number increased to 7500±2700 [n=10] cor…
ERP and EOG responses elicited by deviant tones when presented with and without standard tones to reading subjects
2002
Event-related potentials (ERPs) and horizontal electro-oculograms (HEOGs) were recorded in 11 subjects to infrequently presented spatially deviant tones (oddball-deviants) embedded in a series of frequently presented standard tones and also to these deviant tones when presented without the standard tones (alone-deviants). Subjects were instructed to read a self-selected book during the stimulus presentation. The mismatch negativity (MMN), a component of the ERP, was elicited by the oddball-deviants, whereas ERPs to the alone-deviants were characterized by a prominent N1. In an additional counting condition (subjects counting the oddball-deviants), the MMN to the oddball-deviants was followe…
Performance characteristics of Parkour practitioners: Who are the traceurs?
2015
International audience; Parkour is a modern physical activity that consists of using the environment, mostly urban, as a playground of obstacles. The aims of this study were (i) to investigate age, anthropometric and training characteristics of Parkour practitioners, called ‘traceurs’ and (ii) to assess jump performances and muscular characteristics of traceurs, compared to those of gymnasts and power athletes. The mean age of the population of traceurs studied (n = 130) was 19.4 ± 4.3 years, women represented 12.4% of the total field and mean training volume was 8.1 ± 0.5 hours/week. Vertical and long jump performances were analysed on smaller samples of participants (four groups, n = 15 p…
From spatial acoustic changes to attentive behavioral responses within 200 ms in humans
1999
Human event-related potentials (ERPs) and electro-oculograms (EOGs) were recorded in 14 subjects presented with spatially deviant tones in a series of standard tones. In separate sessions, they were instructed to read a book, to count the deviant tones, and to respond to the deviant tones by shifting the eyes towards them from the standard tone source. When reading a book, the mismatch negativity (MMN) of ERP, reflecting pre-attentive detection of acoustic changes, was elicited to the deviant tones at approximately 105-180 ms. No deviance related EOGs were observed in the reading or counting conditions. When the subjects responded behaviorally to the deviant tones, EOGs revealed that the ey…