Visual Processing

Accommodation

The process by which the eye's lens changes shape to focus on near or distant objects, allowing for clear vision at varying distances.

Anterior chamber

The fluid-filled space in the front part of the eye, located between the cornea and the iris, which helps maintain intraocular pressure and provides nutrients to the eye.

Astigmatism

A common refractive error caused by an irregularly shaped cornea or lens, leading to blurred or distorted vision.

Cataracts

a clouding of the eye's lens that affects vision, often associated with aging and resulting in blurred or dimmed sight.

Center-surround receptive field

A type of neural arrangement in the retina where the response of a neuron is influenced by the light intensity in its center and surrounding areas, crucial for visual contrast detection.

Ciliary muscles

Muscles in the eye that control the shape of the lens, allowing for focusing on objects at varying distances.

Cones

Photoreceptor cells in the retina responsible for color vision and function best in bright light conditions.

Convergence

The process by which multiple neurons synapse onto a single neuron, enhancing sensitivity to stimuli and contributing to visual processing.

Dark adaptation

The process by which the eyes adjust to low light conditions, increasing sensitivity to dim light as photopigments regenerate in the rods.

Duplex theory of vision

A theory that explains how both rods and cones contribute to vision, with rods being more sensitive in low light and cones providing color vision in brighter conditions.

Edge detection

the process of distinguishing where one object ends and the next begins, making edges as clear as possible

Electromagnetic energy

is the form of energy that travels in waves and encompasses visible light, which is crucial for visual perception.

Electromagnetic spectrum

The range of all types of electromagnetic radiation, including visible light, ultraviolet light, and infrared radiation, each with different wavelengths.

Field of view

The extent of the observable world seen at any given moment, typically measured in degrees.

Fovea

A small depression in the retina where visual acuity is highest, allowing for sharp direct vision.

Frequency

The number of occurrences of a repeating event per unit of time, often used to describe waves, including light and sound.

Heterochromia

A condition where an individual has differently colored eyes or variations in color within the same eye.

Hyperopia

A common vision condition also known as farsightedness, where distant objects may be seen more clearly than close ones due to a shorter than normal eyeball or a cornea that is too flat.

Hyperpolarization

The process in which the membrane potential of a cell becomes more negative than its resting potential, often resulting from the influx of chloride ions or the efflux of potassium ions.

Intensity

The brightness or strength of a stimulus, particularly in relation to visual perception.

Iris

The colored part of the eye that surrounds the pupil and regulates the amount of light entering the eye by adjusting the size of the pupil.

Lateral inhibition

A neural mechanism in which the activity of one neuron inhibits the activity of neighboring neurons, enhancing the contrast in visual perception.

Lens

A transparent structure in the eye that helps to focus light onto the retina by changing its shape.

Light adaptation

The process by which the eye adjusts to changes in light levels, allowing for improved vision in bright or dim environments.

Macula

The central area of the retina responsible for high acuity vision and color perception.

Macular degeneration

A medical condition that leads to the deterioration of the macula, causing loss of central vision and affecting the ability to see fine details.

Myopia

A common vision condition where distant objects appear blurry while close objects can be seen clearly, often caused by an elongated eyeball or excessive curvature of the cornea.

Near point

The closest point at which the eye can focus on an object clearly without strain.

Neurotransmitter

A chemical substance that transmits signals across a synapse from one neuron to another, playing a crucial role in communication within the nervous system.

Off-center receptive fields

are regions in the retina that respond to light in a way that enhances contrast and helps in detecting edges and motion.

On-center receptive fields

are regions in the retina that respond to light in a way that increases firing rates when light is present in the center and decreases when light is in the surrounding area, aiding in visual perception.

Opsin

A light-sensitive protein found in photoreceptor cells of the retina, crucial for converting light into electrical signals, enabling vision.

Optic disc

The point in the retina where the optic nerve fibers exit, creating a blind spot as it lacks photoreceptors.

Photon

A particle of light that carries energy and is fundamental in the process of vision, as it triggers phototransduction in photoreceptor cells.

Photopic vision

Vision under well-lit conditions, primarily involving cone cells in the retina.

Photopigment

a molecule that absorbs light and by doing so releases an electric potential by altering the voltage in the cell

Posterior chamber

The fluid-filled space in the eye located behind the iris and in front of the lens, which helps maintain intraocular pressure and provides nutrients to the eye.

Presbyopia

A common age-related condition that affects near vision due to the loss of elasticity in the lens of the eye, making it difficult to focus on close objects.

Pupil

The adjustable opening in the center of the iris that regulates the amount of light entering the eye.

Pupillary reflex

The automatic response of the pupil to constrict or dilate in reaction to changes in light intensity, helping to protect the retina and improve vision.

Purkinje shift

The phenomenon where the peak sensitivity of the human eye shifts toward shorter wavelengths in low light conditions, affecting color perception.

Receptive field

Area in the visual world that a specific neuron responds to

Retina

The light-sensitive layer at the back of the eye that converts light into neural signals for processing by the brain.

Retina image

A representation of the visual information captured by the retina, including the arrangement of photoreceptors and neural connections.

Retinal

Derived from vitamin A that is a part of a photopigment.

Retinitis pigmentosa

A genetic disorder that causes progressive degeneration of the retina, leading to vision loss.

Rods

Photoreceptor cells in the retina responsible for vision in low light conditions.

Sclera

The white outer layer of the eyeball, providing structure and protection to the eye.

Scotopic vision

Vision under low light conditions, primarily mediated by rod cells in the retina.

Wavelength

The distance between successive peaks of a wave, which determines the color of light in the visible spectrum.

Zonule fibers

Connective tissue strands that attach the ciliary body to the lens, helping to hold the lens in place and allowing for changes in its shape during accommodation.

Horizontal cells

Make lateral connections among receptors and bipolar cells

Amacrine cells

Laterally connect among bipolar and ganglion cells

Hyperacuity

Resolution of details of 10 or less of vernier gratings

Cortical magnification factor

Gives millimetres of cortex per degree of visual angle, as a unction of retinal eccentricity

Chromatic aberration

Different wavelengths focus at different points

Spherical aberration

Light rays focus at different points depending on how far from the centre they pass through a lens

Diffraction

Light waves bend around obstacles in their path or through a slit I affects different wavelengths to different extent

Radiance

Radiant power from a light source

Illuminance

Amount of light falling on a surface

Luminance

Amount of light reflected from a surface

Reflectance

Proportion of light reflected from a surface

Brightness

Perceptual impression of intensity of light source; psychological counterpart to radiance

Lightness

Perceptual impression of surface greyness; psychological counterpart to reflectance

Retinal locus

Threshold lower in the periphery

Simultaneous contrast

Central squares appear different shades

Contrast sensitivity function

Describes ability of a system to preserve contrast and spatial frequency information after it has been encoded

Cornea

Clear surface in front of pupil

Transduction

Converting light energy to neural signals