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Results for “spatial localization”

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At least 235 records · Page 13Linked to original sources
PubMedDate not supplied

[Accuracy of the spatial localization of the sources of brain bioelectrical activity in a model homogeneous unrestricted environment].

The possibility is considered of use of the model of homogeneous unlimited medium (HUM) for localization of sources of brain bioelectrical activity at recording of electric potentials on its surface. It is shown that when the recording electrodes are arranged in accordance with 10-20 system, the source localization error does not exceed 10% of the head radius practically in any position of the source. A significant dependence is revealed of the source localization error on the concrete electrodes system used in experiment. It demands careful treatment of the available general recommendations on correction of the position of the source found by HUM model without consideration of the concrete arrangement of recording electrodes.

Brain↗
PubMed1987

Recession vs marginal myotomy surgery for strabismus: effects on spatial localization.

Palisade endings (PEs) are found at the musculotendinous junction in eye muscles and this is the site of much strabismus surgery. To assess the role of PEs in supplying proprioceptive information about eye position, we compared the effects of marginal myotomy and recession surgeries on tests of eye-hand coordination (open-loop pointing responses) taken before and after surgery in two groups of children having medial rectus weakening procedures for the first time. The results indicate that the myotomy is more proprioceptively "de-afferenting" than the recession, and we assume this is due to the greater disruption of PEs in this procedure.

Child↗
PubMed1984

[Spatial localization of proliferating and dying cells in the developing hippocampus in the mouse].

Mapping on arrangement of mitoses (M) and pyknoses (P) has been performed in the mouse developing hippocamp. Analysis on the M arrangement confirms the data known on the hippocampal germinative zones and time of their reduction in the mouse ontogenesis. Previously unknown germinative zone of Ammon's horn has been revealed--the suprafimbrial zone that exists since the 16th day of embryogenesis up to the 7th postnatal day. Analysis on the P arrangement demonstrates that they appear in the hippocampal germinative zones during the perinatal periods. Localization of the P corresponding to that of the M agree with the data on "mitotic" death of the germinative and glial cells in the developing brain.

Age Factors↗
PubMedDate not supplied

[Spatial localization of sources of slow EEG activity by the equivalent dipole method].

Coordinates and moments of equivalent sources of various kinds of slow activity--local, generalized and synchronous (delta- or theta-ranges) -- were estimated on a computer on the basis of a model of single equivalent dipole, by the method of the coordinates descent. Investigation of local delta-activity caused by a volume process in the brain shows that its localization coincides with the peripheral zone of the tumour. Localization of the delta-focus enables to indicate its position not only on the surface, but in the depth of the brain as well. The dipole localization method helps to specify the concept of "secondary" slow waves and to differentiate slow activity of total brain-, brain-stem and local nature.

Bone Neoplasms↗
PubMed1993

CT and SPECT image registration and fusion for spatial localization of metastatic processes using radiolabeled monoclonals.

The fusion of computed tomography (CT) and single-photon emission computerized tomography (SPECT) antibody images can enhance the information provided by either single modality by providing precise anatomical-functional correlation. Functional abnormalities seen on low resolution SPECT antibody images can be precisely located with specific anatomic structures seen in high resolution CT images. External fiducials located on each image modality aid in the automated registration, alignment and matching of CT and SPECT antibody images. The potential benefits of multimodal fusion include (A) the discrimination of more subtle activity peaks using anatomic organ segmentation, (B) temporal discrimination of recurrent disease, (C) assessment of residual activity post-surgery and (D) automated localization of significant focal activity. In addition, the correlation of function with anatomy may be used to establish the physiologic status of ambiguously identified objects in the anatomic image.

Aged↗
PubMedDate not supplied

Multimodal basis for egocentric spatial localization and orientation.

The perceptual and sensorimotor mechanisms that guide our abilities at localizing and orienting in space integrate sensory information from vision and from a "body-referenced mechanism" that itself makes use of extraretinal signals regarding eye position relative to the head and head orientation relative to the body and to gravity. The experiments and theoretical treatment center on two perceptual dimensions: the visual perception of elevation and of orientation within the frontoparallel plane. Several experiments measuring localization in the horizontal plane are also treated. The experiments involve measurements of the physical elevation of visually perceived eye level (VPEL, a norm for perceived elevation), measurements of the physical orientation within the frontoparallel plane corresponding to visually perceived vertical (VPV), and measurements of the direction within a horizontal plane perceived as straight ahead (VPSA). VPEL and VPV are each significantly and systematically influenced by both the pitch and the roll of visual fields, and it is these influences that provide the basis for experimentally isolating the contributions of vision from those of the body-referenced mechanism. The VPEL discrimination is nearly invariant with variation in head and eye orientation. The possibility that influences from vision and from the body-referenced mechanism combine linearly is well supported. The visual influences on VPEL and VPV are controlled by the action of individual lines, and the same pitched-from-vertical lines (from pitched planes) or oblique lines within erect planes influence both discriminations. The Great Circle Model (GCM) accounts for the influences of individual lines, and contains rules for the influence of combinations of lines on both VPEL and VPV. GCM is interpreted by a 3-dimensional vector treatment in "egocentric orientation space."

Eye↗