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Marianne Dieterich - One of the best experts on this subject based on the ideXlab platform.

  • functional magnetic resonance imaging activations of cortical Eye fields during saccades smooth pursuit and optokinetic nystagmus
    Annals of the New York Academy of Sciences, 2009
    Co-Authors: Marianne Dieterich, Thomas Stephan, Stefanie Mullerschunk, S Bense, Klaus Seelos, T A Yousry
    Abstract:

    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 of the cortical network of Eye-movement control were found in the frontal, Parietal, and occipital cortex. While the activation pattern for OKN was not a combination of the patterns for saccades and smooth pursuit, the results suggest that cortical control of OKN occurs in a network parallel to that of saccades and smooth pursuit. Furthermore, a division of the FEF and the PEF into two parts was confirmed for the three ocular motor tasks, as well as a division within each of the three paradigms. MT+/V5 showed two partitions only for saccades, but not for smooth pursuit or OKN.

  • Direction-dependent visual cortex activation during horizontal optokinetic stimulation (fMRI study).
    Human brain mapping, 2006
    Co-Authors: Sandra Bense, B. Janusch, P. Schlindwein, T. Bauermann, Goran Vucurevic, Thomas Brandt, Peter Stoeter, Marianne Dieterich
    Abstract:

    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 compared with the control condition (stationary target) and with each other. Direction-dependent differences were not found in the cortical Eye fields, but an asymmetry of activation occurred in paramedian visual cortex areas, and there were stronger activations in the hemisphere contralateral to the slow OKN phase (pursuit). This can be explained by a shift of the mean Eye position of gaze (beating field) in the direction of the fast nystagmus phases of approximately 2.6 degrees, causing asymmetrical visual cortex stimulation. The absence of a significant difference in the activation pattern of the cortical Eye fields supports the view that the processing of Eye movements in both horizontal directions is mediated in the same cortical ocular motor areas. Furthermore, no hemispheric dominance for OKN processing was found in right-handed volunteers.

  • dominance for vestibular cortical function in the non dominant hemisphere
    Cerebral Cortex, 2003
    Co-Authors: Marianne Dieterich, Sandra Bense, S Lutz, A Drzezga, Thomas Stephan, P Bartenstein, Thomas Brandt
    Abstract:

    The aim of this (15)O-labelled H(2)O bolus positron emission tomography (PET) study was to analyse the hemispheric dominance of the vestibular cortical system. Therefore, the differential effects of caloric vestibular stimulation (right or left ear irrigation with warm water at 44 degrees C) on cortical and subcortical activation were studied in 12 right-handed and 12 left-handed healthy volunteers. Caloric irrigation induces a direction-specific sensation of rotation and nystagmus. Significant regional cerebral blood flow increases were found in a network within both hemispheres, including the superior frontal gyrus/sulcus, the precentral gyrus and the inferior Parietal lobule with the supramarginal gyrus. These areas correspond best to the cortical ocular motor centres, namely the prefrontal cortex, the frontal Eye field and the Parietal Eye field, known to be involved in the processing of caloric nystagmus. Furthermore, distinct temporo-Parietal activations could be separated in the posterior part of the insula with the adjacent superior temporal gyrus, the inferior Parietal lobule and precuneus. These areas fit best to the human homologues of multisensory vestibular cortex areas identified in the monkey and correspond to the parieto-insular vestibular cortex (PIVC), the visual temporal sylvian area (VTS) and areas 7 and 6. Further cortical activations were seen in the anterior insula, the inferior frontal gyrus and anterior cingulum. The subcortical activation pattern in the putamen, thalamus and midbrain is consistent with the organization of efferent ocular motor pathways. Cortical and subcortical activation of the described areas was bilateral during monaural stimulation, but predominant in the hemisphere ipsilateral to the stimulated ear and exhibited a significant right hemispheric dominance for vestibular and ocular motor structures in right-handed volunteers. Similarly, a significant left hemispheric dominance was found in the 12 left-handed volunteers. Thus, this PET study showed for the first time that cortical and subcortical activation by vestibular caloric stimulation depends (i) on the handedness of the subjects and (ii) on the side of the stimulated ear. Maximum activation was therefore found when the non-dominant hemisphere was ipsilateral to the stimulated ear, i.e. in the right hemisphere of right-handed subjects during caloric irrigation of the right ear and in the left hemisphere of left-handed subjects during caloric irrigation of the left ear. The localization of handedness and vestibular dominance in opposite hemispheres might conceivably indicate that the vestibular system and its hemispheric dominance, which matures earlier during ontogenesis, determine right- or left-handedness.

T A Yousry - One of the best experts on this subject based on the ideXlab platform.

  • functional magnetic resonance imaging activations of cortical Eye fields during saccades smooth pursuit and optokinetic nystagmus
    Annals of the New York Academy of Sciences, 2009
    Co-Authors: Marianne Dieterich, Thomas Stephan, Stefanie Mullerschunk, S Bense, Klaus Seelos, T A Yousry
    Abstract:

    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 of the cortical network of Eye-movement control were found in the frontal, Parietal, and occipital cortex. While the activation pattern for OKN was not a combination of the patterns for saccades and smooth pursuit, the results suggest that cortical control of OKN occurs in a network parallel to that of saccades and smooth pursuit. Furthermore, a division of the FEF and the PEF into two parts was confirmed for the three ocular motor tasks, as well as a division within each of the three paradigms. MT+/V5 showed two partitions only for saccades, but not for smooth pursuit or OKN.

S Bense - One of the best experts on this subject based on the ideXlab platform.

  • functional magnetic resonance imaging activations of cortical Eye fields during saccades smooth pursuit and optokinetic nystagmus
    Annals of the New York Academy of Sciences, 2009
    Co-Authors: Marianne Dieterich, Thomas Stephan, Stefanie Mullerschunk, S Bense, Klaus Seelos, T A Yousry
    Abstract:

    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 of the cortical network of Eye-movement control were found in the frontal, Parietal, and occipital cortex. While the activation pattern for OKN was not a combination of the patterns for saccades and smooth pursuit, the results suggest that cortical control of OKN occurs in a network parallel to that of saccades and smooth pursuit. Furthermore, a division of the FEF and the PEF into two parts was confirmed for the three ocular motor tasks, as well as a division within each of the three paradigms. MT+/V5 showed two partitions only for saccades, but not for smooth pursuit or OKN.

Rene M Muri - One of the best experts on this subject based on the ideXlab platform.

  • Eye movement control by the cerebral cortex
    Current Opinion in Neurology, 2004
    Co-Authors: C Pierrotdeseilligny, Dan Milea, Rene M Muri
    Abstract:

    Purpose of review This review focuses on Eye movement control by the cerebral cortex, mainly in humans. Data have emerged based on the important contribution of recent techniques such as transcranial magnetic stimulation and functional magnetic resonance imaging, which provide complementary results to those of the classical lesion and electrical stimulation studies. Recent findings The location of the human frontal Eye field and its role in pursuit Eye movement control were recently detailed. Cumulative evidence for the role of the dorsolateral prefrontal cortex in unwanted reflexive saccade inhibition, short-term spatial memory and prediction suggests that this area controls decisional processes governing ocular motor behaviour. The organization of spatial memory in the dorsolateral prefrontal cortex (short-term), the parahippocampal cortex (medium-term) and the hippocampal formation (long-term) is also reviewed with the results of recent transcranial magnetic stimulation studies. The relatively complicated anatomy of the posterior Parietal cortex in humans is briefly described followed by some additional results concerning the location of the Parietal Eye field - within the posterior half of the intraParietal sulcus - and its role in visuo-spatial integration and attention. The other areas involved in spatial attention are also examined in the light of several recent contributing reports. Lastly, there are also new functional magnetic resonance imaging findings concerning the posterior cingulate cortex, which appears to be mainly involved in the control of externally guided Eye movements and attentional mechanisms. Summary Many new findings on the organization of saccades and pursuit Eye movements at the cortical level have recently been reported. Furthermore, Eye movements are increasingly used as a tool to elucidate relatively complex neuropsychological processes such as attention, spatial memory, motivation and decisional processes, and a considerable number of reports dealing with these questions have been observed.

Akihisa Terakita - One of the best experts on this subject based on the ideXlab platform.

  • expression of uv sensitive parapinopsin in the iguana Parietal Eyes and its implication in uv sensitivity in vertebrate pineal related organs
    PLOS ONE, 2012
    Co-Authors: Seiji Wada, Emi Kawanoyamashita, Mitsumasa Koyanagi, Akihisa Terakita
    Abstract:

    The pineal-related organs of lower vertebrates have the ability to discriminate different wavelengths of light. This wavelength discrimination is achieved through antagonistic light responses to UV or blue and visible light. Previously, we demonstrated that parapinopsin underlies the UV reception in the lamprey pineal organ and identified parapinopsin genes in teleosts and frogs of which the pineal-related organs were reported to discriminate light. In this study, we report the first identification of parapinopsin in the reptile lineage and show its expression in the Parietal Eye of the green iguana. Spectroscopic analysis revealed that iguana parapinopsin is a UV-sensitive pigment, similar to lamprey parapinopsin. Interestingly, immunohistochemical analyses using antibodies specific to parapinopsin and parietopsin, a Parietal Eye green-sensitive pigment, revealed that parapinopsin and parietopsin are colocalized in the outer segments of the Parietal Eye photoreceptor cells in iguanas. These results strongly suggest that parapinopsin underlies the wavelength discrimination involving UV reception in the iguana Parietal Eye. The current findings support the idea that parapinopsin is a common photopigment underlying the UV-sensitivity in wavelength discrimination of the pineal-related organs found from lampreys to reptiles.

  • Parietal Eye phototransduction components and their potential evolutionary implications
    Science, 2006
    Co-Authors: Dong Gen Luo, Akihisa Terakita, Yoshinori Shichida, Hsi Wen Liao, Manija A Kazmi, Thomas P Sakmar, Kingwai Yau
    Abstract:

    The Parietal-Eye photoreceptor is unique because it has two antagonistic light signaling pathways in the same cell—a hyperpolarizing pathway maximally sensitive to blue light and a depolarizing pathway maximally sensitive to green light. Here, we report the molecular components of these two pathways. We found two opsins in the same cell: the blue-sensitive pinopsin and a previously unidentified green-sensitive opsin, which we name parietopsin. Signaling components included gustducin-α and Gαo, but not rod or cone transducin-α. Single-cell recordings demonstrated that Go mediates the depolarizing response. Gustducin-α resembles transducin-α functionally and likely mediates the hyperpolarizing response. The parietopsin-Go signaling pair provides clues about how rod and cone phototransduction might have evolved.