Wounds of the Visual Pathway: Part Ii: The Striate Cortex

Spalding, J. M. K.

doi:10.1136/jnnp.15.3.169

Cited by 103 publications

(34 citation statements)

References 8 publications

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“…However, as the incision progresses more posteriorly, the anterior bundle begins to be transected, leading to a risk of causing superior temporal homonymous quadrantanopia. 12,38,39,44 As the incision approaches the LGB (minimum of 22.4 mm), the fibers devoted to the central part of the retina are also put at risk. The sublenticular part also contains the inferior thalamic peduncle including the auditory radiations, temporal corticopontine fiber bundle, and parietooccipital projections.…”

Section: 2448mentioning

confidence: 99%

Microsurgical anatomy of the inferior limiting insular sulcus and the temporal stem

Ribas

Yağmurlu

Wen

et al. 2015

JNS

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T he temporal stem is a widely used term, but is still a controversial concept. Definitions of the stem range from its being as small as the fiber bundles passing between the limen insula and the anterior end of the temporal horn, to its being as large as including all the fibers passing beneath the length of the inferior limiting insular sulcus (ILS). 13,42,45,46 The transsylvian approach to the medial temporal lobe is commonly directed through or adjacent to the ILS and temporal stem, where opening of the temporal horn and exposure of the amygdala and the hippocampus are key steps. Unfortunately, the temporal lobe is the site of important brain functions, and complications involving visual and language deficits are not rare. 12,34,38 In this study, based on the larger definition of the stem, the location of each white matter pathway between the ILS and temporal horn was described, with special attention to their relation to the limen insula. The meeting point of the ILS with the limen insula can be identified during surgery and used as a landmark to estimate the position of each set of fibers beneath the ILS. MethodsFourteen adult cadaveric cerebral hemispheres were examined using ×3 to ×40 magnification. The specimens were fixed with formalin and preserved in a 70% alcohol abbreviatioNs DTI = diffusion tensor imaging; ILS = inferior limiting insular sulcus; LGB = lateral geniculate body; TLP = temporal limen point. obJect The purpose of this study was to describe the location of each white matter pathway in the area between the inferior limiting insular sulcus (ILS) and temporal horn that may be crossed in approaches through the temporal stem to the medial temporal lobe. Methods The fiber tracts in 14 adult cadaveric cerebral hemispheres were examined using the Klingler technique. The fiber dissections were completed in a stepwise manner, identifying each white matter pathway in different planes and describing its position in relation to the anterior end of the ILS. results The short-association fibers from the extreme capsule, which continue toward the operculae, are the most superficial subcortical layer deep to the ILS. The external capsule fibers are found deeper at an intermediate layer and are formed by the uncinate fasciculus, inferior frontooccipital fasciculus, and claustrocortical fibers in a sequential anteroposterior disposition. The anterior commissure forms the next deeper layer, and the optic radiations in the sublenticular part of the internal capsule represent the deepest layer. The uncinate fasciculus is found deep to the anterior third of the ILS, whereas the inferior frontooccipital fasciculus and optic radiations are found superficial and deep, respectively, at the posterior two-thirds of this length. coNclusioNs The authors' findings suggest that in the transsylvian approach, a 6-mm incision beginning just posterior to the limen insula through the ILS will cross the uncinate fasciculus but not the inferior frontooccipital fasciculus or optic radiations, but that longer incisions carry a...

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Section: 2448mentioning

confidence: 99%

Microsurgical anatomy of the inferior limiting insular sulcus and the temporal stem

Ribas

Yağmurlu

Wen

et al. 2015

JNS

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“…The visual cortex is ideal for testing new neuroimaging techniques because its structure and function have been comprehensively mapped with invasive anatomical and electrical studies in mammals (37)(38)(39) and in humans (40)(41)(42). Visual cortex activations were used extensively in early evaluations of PET and fMRI as functional brain mapping tools (43)(44)(45)(46).…”

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confidence: 99%

Retinotopic mapping of adult human visual cortex with high-density diffuse optical tomography

Zeff

White

Dehghani

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

327

420

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Functional neuroimaging is a vital element of neuroscience and cognitive research and, increasingly, is an important clinical tool. Diffuse optical imaging is an emerging, noninvasive technique with unique portability and hemodynamic contrast capabilities for mapping brain function in young subjects and subjects in enriched or clinical environments. We have developed a high-performance, high-density diffuse optical tomography (DOT) system that overcomes previous limitations and enables superior image quality. We show herein the utility of the DOT system by presenting functional hemodynamic maps of the adult human visual cortex. The functional brain images have a high contrast-to-noise ratio, allowing visualization of individual activations and highly repeatable mapping within and across subjects. With the improved spatial resolution and localization, we were able to image functional responses of 1.7 cm in extent and shifts of <1 cm. Cortical maps of angle and eccentricity in the visual field are consistent with retinotopic studies using functional MRI and positron-emission tomography. These results demonstrate that high-density DOT is a practical and powerful tool for mapping function in the human cortex. functional brain mapping ͉ near-infrared spectroscopy ͉ neuroimaging ͉ retinotopy F unctional mapping of the human brain is an important aspect of cognitive neuroscience that is used to study brain organization and development. Increasingly, functional neuroimaging is being used as a diagnostic and prognostic tool in the clinical setting. Its expanding application in the study of disease and development necessitates new, flexible functional neuroimaging tools. Many situations are not amenable to scanner logistics, such as subjects who are in the intensive care unit, who are performing complex tasks, or who might otherwise require sedation for imaging, such as infants and young children. Additionally, there are imaging situations in which the neurovascular coupling either is not mature, such as in neonates and very young infants (1-3), or is altered due to injury or illness (4, 5). Diffuse optical imaging (DOI) is a methodology uniquely suited to such tasks, because it is a mobile system that uses a small, flexible imaging cap (6, 7). DOI images hemodynamic contrasts similar to functional MRI (fMRI) with blood oxygen-level dependent (BOLD) signals (fMRI-BOLD); however, DOI can measure changes in oxygenated hemoglobin (⌬HbO 2 ), deoxygenated hemoglobin (⌬Hb R ), and total hemoglobin (⌬Hb T ), whereas the BOLD signal is mainly dependent on ⌬Hb R (8). The ability to simultaneously image these contrasts allows DOI to distinguish differences in their magnitude (3, 4, 9), timing (3, 10-12), and localization (13-15), forming a more complete picture of neurovascular function. In contrast to positron emission tomography (PET), which uses ionizing radiation, DOI uses safe, infrared light for imaging. Despite unique strengths, however, DOI as a standard tool for functional mapping has been limited by low spatial resolution...

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“…Other studies, however, have shown that when the size of the visual half field stimulated was reduced to 5 ~ , the response was clearly cross-lateral in normal subjects [3,4]. Such a finding would be expected, since it is known that when the size of the visual field stimulated is reduced below 8 ~ , the response is represented in the striate cortex posterior to the calcarine fissure [5]. The effect of changing the size of the checks of the reversing stimulus also appears to increase the contralateral spread of the major positive component [6].…”

Section: Introductionmentioning

confidence: 74%

The topographic distribution of the magnetic P100M to full- and half-field stimulation

1992

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Visual evoked magnetic responses were recorded to full-field and left and right half-field stimulation with three check sizes (70', 34' and 22') in five normal subjects. Recordings were made sequentially on a 20-position grid (4 x 5) based on the inion, by means of a single-channel direct current-Superconducting Quantum Interference Device second-order gradiometer. The topographic maps were consistent on the same subjects recorded 2 months apart. The half-field responses produced the strongest signals in the contralateral hemisphere and were consistent with the cruciform model of the calcarine fissure. Right half fields produced upper-left-quadrant outgoing fields and lower-left-quadrant ingoing fields, while the left half field produced the opposite response. The topographic maps also varied with check size, with the larger checks producing positive or negative maximum position more anteriorly than small checks. In addition, with large checks the full-field responses could be explained as the summation of the two half fields, whereas full-field responses to smaller checks were more unpredictable and may be due to sources located at the occipital pole or lateral surface. In addition, dipole sources were located as appropriate with the use of inverse problem solutions. Topographic data will be vital to the clinical use of the visual evoked field but, in addition, provides complementary information to visual evoked potentials, allowing detailed studies of the visual cortex.

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Wounds of the Visual Pathway: Part Ii: The Striate Cortex

Cited by 103 publications

References 8 publications

Microsurgical anatomy of the inferior limiting insular sulcus and the temporal stem

Microsurgical anatomy of the inferior limiting insular sulcus and the temporal stem

Retinotopic mapping of adult human visual cortex with high-density diffuse optical tomography

The topographic distribution of the magnetic P100M to full- and half-field stimulation

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