Vision: Principles of Visual Neuroscience

Comprehensive vocabulary flashcards covering the anatomy of the eye, retinal circuitry, phototransduction, and central visual processing pathways.

Vision

The transformational process of light into meaningful perceptions of the external world through a series of neural processes.

Visible Light Spectrum

The range of electromagnetic radiation wavelengths between $380$ and $750$ nanometers that humans can detect.

Pupil

The aperture for light entry into the eye, regulated by autonomic nerves; sympathetic nerves facilitate dilation, while parasympathetic nerves regulate constriction.

Sclera

The tough, white outer area of the eye composed of collagen that promotes structural integrity and provides attachment sites for extraocular muscles.

Iris

The structure containing melanin that determines eye color and facilitates light scatter through crypts and burrows.

Cornea

The transparent, avascular surface that refracts light to focus it onto the retina, providing about $70\%$ of the eye's refractive power.

Trigeminal Nerve

The nerve responsible for the high sensitivity of the cornea to abrasions or surface damage.

Retina

A neural sheet at the back of the eye containing photoreceptors and interneurons that transduce light into electrical signals.

Ciliary Body

A structure containing muscles that adjust the lens for visual accommodation and secretes aqueous humor to maintain intraocular pressure.

Optic Nerve

The structure containing retinal ganglion axons that convey visual information from the eye to the brain.

Nearsightedness

A condition resulting from too much refraction where the image focuses in front of the retinal surface.

Farsightedness

A condition resulting from too little refraction where the image focuses behind the retinal surface.

Visual Accommodation

The process by which ciliary muscles contract to make the lens more curved, increasing refractive power for close-up objects.

Vitreous Humor

The substance behind the eye that helps maintain consistent eye pressure as the cornea/lens flex and bend.

Nasal Retina

The region of the retina near the nose whose axons cross the optic chiasm to project contralaterally.

Temporal Retina

The outer region of the retina whose axons go up the same side of the optic tract ipsilaterally.

Photoreceptors

The class of neurons (rods and cones) located at the back of the retina that detect light.

Bipolar Cells

Excitatory cells in the internuclear layer that relay signals from photoreceptors to retinal ganglion cells.

Horizontal Cells

Retinal neurons that receive input from photoreceptors and mediate lateral interactions between photoreceptors and bipolar cells.

Amacrine Cells

Retinal neurons that receive input from bipolar cells and mediate lateral interactions with other bipolar and ganglion cells.

Direct Pathway

The flow of visual information from photoreceptor to bipolar cell to ganglion cell.

Phototransduction

The process by which light absorption causes hyperpolarization of photoreceptors and a reduction in neurotransmitter release.

Rods

Photoreceptors with long outer segments containing rhodopsin; they are over $1,000$ times more sensitive than cones and dominate in low light.

Cones

Tapered photoreceptors specialized for color vision and high acuity that function best in bright light conditions.

11-cis Retinal

The light-sensitive molecule bound to opsin; light converts it into all-trans retinal to trigger a signaling cascade.

Fovea

The central pit of the retina responsible for high acuity vision, characterized by a dense composition of cones and sparse bipolar/ganglion cells.

Photoreceptor Convergence

The arrangement where many rods synapse onto one bipolar cell, increasing sensitivity to light changes but losing spatial resolution.

Scotopic Vision

Vision dominated by rods in dim light conditions, characterized by poor spatial acuity and lack of color perception.

Photopic Vision

Vision dominated by cones in bright light conditions, offering the best color vision and visual acuity.

Photobleaching

The inactivation of photopigments in the membranous discs due to exposure to high levels of light.

Center-Surround Antagonism

A receptive field organization in bipolar and ganglion cells where light in the center has the opposite effect of light in the surround.

ON Bipolar Cells

Bipolar cells expressing inhibitory mGluR6 receptors that depolarize in response to light (decreased glutamate).

OFF Bipolar Cells

Bipolar cells expressing ionotropic AMPA receptors that hyperpolarize in response to light (decreased glutamate).

Lateral Geniculate Nucleus (LGN)

The thalamic relay center where retinal inputs are organized into distinct layers before being sent to the primary visual cortex.

P-cells (Parvocellular)

Ganglion cells projecting to LGN layers $3$ through $6$; they have small receptive fields and are color sensitive.

M-cells (Magnocellular)

Ganglion cells projecting to LGN layers $1$ and $2$; they have large receptive fields and are optimized for motion detection.

Primary Visual Cortex (V1)

The region in the occipital lobe where information from both eyes is integrated and specialized for architectural processing.

Ocular Dominance Columns

Striped regions in the visual cortex where neurons preferentially respond to input from one eye.

Dorsal Stream

The 'where/how' pathway running from V1 to the temporal regions (MT/MST), responsible for motion and spatial relationships.

Ventral Stream

The 'what' pathway running from V1 to V4 and the inferotemporal (IT) cortex, responsible for object recognition and color perception.

Achromatopsia

The loss of color vision resulting from damage to area V4 in the ventral stream.