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Educating the blind brain: a panorama of neural bases of vision and of training programs in organic neurovisual deficits.

Coubard OA, Urbanski M, Bourlon C, Gaumet M - Front Integr Neurosci (2014)

Bottom Line: The visual system involves five main routes originating in the retinas but varying in their destination within the brain: the occipital cortex, but also the superior colliculus (SC), the pretectum, the supra-chiasmatic nucleus, the nucleus of the optic tract and terminal dorsal, medial and lateral nuclei.Organic neurovisual deficits may occur at any level of this circuitry from the optic nerve to subcortical and cortical destinations, resulting in low or high-level visual deficits.Given the extent of its neural bases in the brain, vision in its motor and perceptual aspects is also a useful tool to assess and modulate central nervous system (CNS) in general.

View Article: PubMed Central - PubMed

Affiliation: The Neuropsychological Laboratory, CNS-Fed Paris, France ; Laboratoire Psychologie de la Perception, UMR 8242 CNRS-Université Paris Descartes Paris, France.

ABSTRACT
Vision is a complex function, which is achieved by movements of the eyes to properly foveate targets at any location in 3D space and to continuously refresh neural information in the different visual pathways. The visual system involves five main routes originating in the retinas but varying in their destination within the brain: the occipital cortex, but also the superior colliculus (SC), the pretectum, the supra-chiasmatic nucleus, the nucleus of the optic tract and terminal dorsal, medial and lateral nuclei. Visual pathway architecture obeys systematization in sagittal and transversal planes so that visual information from left/right and upper/lower hemi-retinas, corresponding respectively to right/left and lower/upper visual fields, is processed ipsilaterally and ipsialtitudinally to hemi-retinas in left/right hemispheres and upper/lower fibers. Organic neurovisual deficits may occur at any level of this circuitry from the optic nerve to subcortical and cortical destinations, resulting in low or high-level visual deficits. In this didactic review article, we provide a panorama of the neural bases of eye movements and visual systems, and of related neurovisual deficits. Additionally, we briefly review the different schools of rehabilitation of organic neurovisual deficits, and show that whatever the emphasis is put on action or perception, benefits may be observed at both motor and perceptual levels. Given the extent of its neural bases in the brain, vision in its motor and perceptual aspects is also a useful tool to assess and modulate central nervous system (CNS) in general.

No MeSH data available.


Related in: MedlinePlus

(A) The human eye and its visual axis. The fovea (1° to 2° of visual angle) contains high density of cones but no rod. Cone concentration decreases with increasing distance to the fovea and stabilizes for the rest of the retina. Rod concentration reaches its maximum at 20° of retinal eccentricity than decreases until the peripheral limit of the retina. (B) The two eyes move in direction thanks to a step (saccade) or smooth (pursuit) movement to foveate a target in eccentricity (to the left, to the right, up, down, or in any oblique direction). (C) The two eyes move in depth thanks to a step or smooth (vergence) movement to foveate a target in distance (at close or at far). (A) Adapted from Bagot (1999, p. 128, Figure 35) (© O.A. Coubard, with permission); (B,C) From O.A. Coubard.
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Figure 1: (A) The human eye and its visual axis. The fovea (1° to 2° of visual angle) contains high density of cones but no rod. Cone concentration decreases with increasing distance to the fovea and stabilizes for the rest of the retina. Rod concentration reaches its maximum at 20° of retinal eccentricity than decreases until the peripheral limit of the retina. (B) The two eyes move in direction thanks to a step (saccade) or smooth (pursuit) movement to foveate a target in eccentricity (to the left, to the right, up, down, or in any oblique direction). (C) The two eyes move in depth thanks to a step or smooth (vergence) movement to foveate a target in distance (at close or at far). (A) Adapted from Bagot (1999, p. 128, Figure 35) (© O.A. Coubard, with permission); (B,C) From O.A. Coubard.

Mentions: “In the beginning was the act” (Von Goethe, 1808–1832/2014). In line with von Goethe, we point out in this review that vision is first and foremost action. The reason why the eyes move is twofold. First they move as direct consequence of retina morphophysiology (see Figure 1A). Only the fovea containing a high density of cones allows humans to perceive visual stimuli with high acuity, while the rest of the retina containing less cones but high density of rods perceives blur. For that reason, the eyes have to move to foveate visual stimuli in eccentricity or in depth. Second the eyes move as visual perception is impossible as soon as movement is absent, which has been demonstrated different ways since the seminal work by Yarbus (1967). Indeed when fixational eye movements are suppressed and the visual stimulus stabilized on the retina, perception just vanishes in a few seconds. This is due to the fact that one function of fixational eye movements, among other functions, is to continuously refresh neural activity in visual pathways (for a review see Martinez-Conde et al., 2013).


Educating the blind brain: a panorama of neural bases of vision and of training programs in organic neurovisual deficits.

Coubard OA, Urbanski M, Bourlon C, Gaumet M - Front Integr Neurosci (2014)

(A) The human eye and its visual axis. The fovea (1° to 2° of visual angle) contains high density of cones but no rod. Cone concentration decreases with increasing distance to the fovea and stabilizes for the rest of the retina. Rod concentration reaches its maximum at 20° of retinal eccentricity than decreases until the peripheral limit of the retina. (B) The two eyes move in direction thanks to a step (saccade) or smooth (pursuit) movement to foveate a target in eccentricity (to the left, to the right, up, down, or in any oblique direction). (C) The two eyes move in depth thanks to a step or smooth (vergence) movement to foveate a target in distance (at close or at far). (A) Adapted from Bagot (1999, p. 128, Figure 35) (© O.A. Coubard, with permission); (B,C) From O.A. Coubard.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256986&req=5

Figure 1: (A) The human eye and its visual axis. The fovea (1° to 2° of visual angle) contains high density of cones but no rod. Cone concentration decreases with increasing distance to the fovea and stabilizes for the rest of the retina. Rod concentration reaches its maximum at 20° of retinal eccentricity than decreases until the peripheral limit of the retina. (B) The two eyes move in direction thanks to a step (saccade) or smooth (pursuit) movement to foveate a target in eccentricity (to the left, to the right, up, down, or in any oblique direction). (C) The two eyes move in depth thanks to a step or smooth (vergence) movement to foveate a target in distance (at close or at far). (A) Adapted from Bagot (1999, p. 128, Figure 35) (© O.A. Coubard, with permission); (B,C) From O.A. Coubard.
Mentions: “In the beginning was the act” (Von Goethe, 1808–1832/2014). In line with von Goethe, we point out in this review that vision is first and foremost action. The reason why the eyes move is twofold. First they move as direct consequence of retina morphophysiology (see Figure 1A). Only the fovea containing a high density of cones allows humans to perceive visual stimuli with high acuity, while the rest of the retina containing less cones but high density of rods perceives blur. For that reason, the eyes have to move to foveate visual stimuli in eccentricity or in depth. Second the eyes move as visual perception is impossible as soon as movement is absent, which has been demonstrated different ways since the seminal work by Yarbus (1967). Indeed when fixational eye movements are suppressed and the visual stimulus stabilized on the retina, perception just vanishes in a few seconds. This is due to the fact that one function of fixational eye movements, among other functions, is to continuously refresh neural activity in visual pathways (for a review see Martinez-Conde et al., 2013).

Bottom Line: The visual system involves five main routes originating in the retinas but varying in their destination within the brain: the occipital cortex, but also the superior colliculus (SC), the pretectum, the supra-chiasmatic nucleus, the nucleus of the optic tract and terminal dorsal, medial and lateral nuclei.Organic neurovisual deficits may occur at any level of this circuitry from the optic nerve to subcortical and cortical destinations, resulting in low or high-level visual deficits.Given the extent of its neural bases in the brain, vision in its motor and perceptual aspects is also a useful tool to assess and modulate central nervous system (CNS) in general.

View Article: PubMed Central - PubMed

Affiliation: The Neuropsychological Laboratory, CNS-Fed Paris, France ; Laboratoire Psychologie de la Perception, UMR 8242 CNRS-Université Paris Descartes Paris, France.

ABSTRACT
Vision is a complex function, which is achieved by movements of the eyes to properly foveate targets at any location in 3D space and to continuously refresh neural information in the different visual pathways. The visual system involves five main routes originating in the retinas but varying in their destination within the brain: the occipital cortex, but also the superior colliculus (SC), the pretectum, the supra-chiasmatic nucleus, the nucleus of the optic tract and terminal dorsal, medial and lateral nuclei. Visual pathway architecture obeys systematization in sagittal and transversal planes so that visual information from left/right and upper/lower hemi-retinas, corresponding respectively to right/left and lower/upper visual fields, is processed ipsilaterally and ipsialtitudinally to hemi-retinas in left/right hemispheres and upper/lower fibers. Organic neurovisual deficits may occur at any level of this circuitry from the optic nerve to subcortical and cortical destinations, resulting in low or high-level visual deficits. In this didactic review article, we provide a panorama of the neural bases of eye movements and visual systems, and of related neurovisual deficits. Additionally, we briefly review the different schools of rehabilitation of organic neurovisual deficits, and show that whatever the emphasis is put on action or perception, benefits may be observed at both motor and perceptual levels. Given the extent of its neural bases in the brain, vision in its motor and perceptual aspects is also a useful tool to assess and modulate central nervous system (CNS) in general.

No MeSH data available.


Related in: MedlinePlus