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Related Concept Videos

Vision01:24

Vision

Vision is the result of light being detected and transduced into neural signals by the retina of the eye. This information is then further analyzed and interpreted by the brain. First, light enters the front of the eye and is focused by the cornea and lens onto the retina—a thin sheet of neural tissue lining the back of the eye. Because of refraction through the convex lens of the eye, images are projected onto the retina upside-down and reversed.
Osmoregulation in Fishes02:32

Osmoregulation in Fishes

When cells are placed in a hypotonic (low-salt) fluid, they can swell and burst. Meanwhile, cells in a hypertonic solution—with a higher salt concentration—can shrivel and die. How do fish cells avoid these gruesome fates in hypotonic freshwater or hypertonic seawater environments?
Motor and Sensory Areas of the Cortex01:14

Motor and Sensory Areas of the Cortex

The cerebral cortex, the brain's outermost layer, is pivotal in processing complex cognitive tasks, emotions, and various sensory inputs and executing voluntary motor activities. This intricate structure is divided into three primary functional areas: the motor areas, sensory areas, and association areas.
Motor Areas
The motor areas located in the frontal lobe are central to controlling voluntary movements. This region is further subdivided into the primary motor cortex and the premotor cortex.
Anatomy of the Eyeball01:20

Anatomy of the Eyeball

The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
Photoreceptors and Visual Pathways01:22

Photoreceptors and Visual Pathways

At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
Visual System01:26

Visual System

Light enters the eye through the cornea, a transparent, dome-shaped surface covering the surface of the eyeball that helps to direct and focus incoming light. This light is then channeled toward the pupil, an adjustable opening whose size is controlled by the iris. The iris, a pigmented muscle, regulates the amount of light entering the eye by contracting or dilating the pupil, thereby ensuring optimal light levels for clear vision.
Once through the pupil, the light passes through the lens, a...

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Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography
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Visual pathways in elasmobranchs: organization and phylogenetic implications.

R G Northcutt1

  • 1Neurobiology Unit, Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093-0201.

The Journal of Experimental Zoology. Supplement : Published Under Auspices of the American Society of Zoologists and the Division of Comparative Physiology and Biochemistry
|January 1, 1990
PubMed
Summary
This summary is machine-generated.

Elasmobranch fishes have more visual processing centers than previously thought, with complex bilateral retinal projections. Their thalamic organization is now understood to be similar to other vertebrates, refuting earlier primitive views.

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Area of Science:

  • Neuroscience
  • Comparative Anatomy
  • Ichthyology

Background:

  • Previous studies suggested elasmobranchs have fewer visual nuclei than other vertebrates.
  • Early research claimed a simpler, more primitive visual thalamus organization in elasmobranchs.

Purpose of the Study:

  • To re-evaluate the number and organization of primary retino-recipient nuclei in elasmobranchs.
  • To investigate the thalamic organization and telencephalic projections in elasmobranch visual systems.

Main Methods:

  • Utilized sensitive tracing methods to identify visual pathways.
  • Examined retinal projections and thalamic nuclei in elasmobranch species.

Main Results:

  • Identified ten primary retinofugal targets plus the optic tectum in most elasmobranchs.
  • Found evidence of bilateral retinal projections to these nuclei.
  • Refuted claims of a single thalamic nucleus; identified anterior and dorsal posterior thalamic nuclei with specific inputs and outputs.
  • Demonstrated similar thalamic organization to other gnathostomes.

Conclusions:

  • Elasmobranch visual systems are more complex than previously believed.
  • The thalamic organization of elasmobranchs is comparable to other vertebrates, not primitive.
  • Updated understanding of elasmobranch visual neuroanatomy.