Vision

What is sensitivity?

The ability to detect the presence of light or a stimulus

What is visual acuity?

The ability to see fine details, contours, and patterns clearly

What is light?

A form of electromagnetic radiation

What are the two ways to describe light?

wave when traveling and photon when absorbed

How does the brain receive what you perceive?

as patterns of action potentials

Do sensory receptor cells recieve specific types of stimulus?

yes

When a sensory receptor detects stimulus, does it create an action potential or a graded potential?

graded potential

where does transduction occur?

sensory receptor cell

is perception bottom-up or top-down processing

both

the initial detection of stimuli through the body’s sensory organs

sensation

What is responsible for detecting and transmitting info about a stimulus?

sensory receptor ells

interpretation and organization of sensory information

perception

What does perception lead to?

conscious experiences of our environment and the world we interact with

What is wavelength?

The distance between two consecutive wave peaks.

What happens to wavelength when frequency decreases?

Wavelength increases

What is the visible light wavelength range?

400–700 nanometers.

What is the retina?

Light-sensitive tissue at the back of the eye

Name of the central retinal depression

fovea

What is the fovea responsible for?

sharpest central vision, color details and highest visual acuity

What is accommodation?

Changing the shape of the lens to focus on objects at different distances.

What happens to the lens when viewing distant objects?

It becomes flatter as zonule fiber tension increases.

What happens to the lens when viewing nearby objects?

It becomes rounder as the ciliary muscle contracts.

Why is the image on the retina inverted?

The cornea and lens bend light, projecting an inverted image.

What is myopia?

Nearsightedness; distant objects are difficult to focus on

What causes myopia?

An eyeball that is too long or a lens that is too curved.

Where does light focus in an eye with myopia?

In front of the retina

Farsightedness, nearby objects are difficult to focus on

hyperopia

What causes hyperopia?

An eyeball that is too short or a lens that is too flat.

What are the two main functions of the retina?

Transduction :converting light into electrical activity
Transmission: sending information through the optic nerve

What are the five major types of retinal cells?

Photoreceptors, bipolar cells, ganglion cells, horizontal cells, and amacrine cells

What are the five prominent retinal layers

Outer nuclear, inner nuclear, ganglion cell, outer plexiform, and inner plexiform layers

What is the basic pathway of visual information through the retina?

Photoreceptors - Bipolar cells - Retinal ganglion cells - LGN - Brain

What forms the optic nerve?

axons of retinal ganglion cells.

What are rods responsible for?

Detecting brightness and supporting vision in dim light.

Do rods detect color?

No

What are the two types of photoreceptor cells?

rods and cones

Where are rods mainly located?

peripheral retina

What is rhodopsin?

photopigment found in rod receptors

How sensitive are rods to light?

They can respond to a single photon.

What are cones responsible for?

Color vision and seeing fine details

Where are cones concentrated?

fovea

Why do cones provide high visual acuity?

specialized for detecting fine details and are concentrated in the fovea

How many types of cone photopigments are there?

Three, sensitive to long, medium, and short wavelengths.

What do photoreceptors respond to?

light

Do cones or rods need more light to function?

Cones need more light than rods.

What specialized molecules are in photoreceptor cells?

photopigment molecules

What is scotopic vision?

Vision under dim-light conditions, mainly supported by rods.

What is phototopic vision?

Vision under bright-light conditions, mainly supported by cones

What happens when a photon strikes a photopigment?

photopigment changes shape, triggering a cascade that changes the photoreceptor's membrane voltage

Which photoreceptors are more numerous: rods or cones?

Rods.

What is the relationship between sensitivity and acuity with rods and cones?

Rods mainly support sensitivity, cones mainly support visual acuity.

What is the optic disc?

The location where ganglion cell axons leave the eye to form the optic nerve

Why is the optic disc called the blind spot?

It has no photoreceptors, so it cannot detect light

Why don't we normally notice our blind spot?

our brain fills in the rest and the other eye helps

The central region of the retina.

macula

Where is the fovea located?

At the center of the macula.

What is age-related macular degeneration?

Progressive degeneration of the central retinal region, including the macula and fovea

Which type of vision is affected by macular degeneration?

Central vision

A gene-based progressive degeneration of rod photoreceptors.

retinitis pigmentosa

Which type of vision is affected by retinitis pigmentosa?

Peripheral vision.

What is tunnel vision?

loss of peripheral vision that leaves a narrower central field of vision.

Where do retinal ganglion cell axons project?

To the lateral geniculate nucleus (LGN) of the thalamus.

Where do LGN axons project?

To the primary visual cortex (V1).

Approximately what percentage of ganglion cell axons project to the LGN

Approximately 90%.

What is V1?

The primary visual cortex

What is another name for V1?

striate cortex

Where does information from the left visual field go?

right hemisphere

Where does information from the right visual field go?

left hemisphere

Is visual information divided by eye or by visual field?

by visual field

What is a retinotopic map?

point-by-point representation of the retinal surface in another visual structure

What is topographical mapping?

ordered projection of a sensory surface onto the central nervous system.

How are neurons organized in V1?

spatially organized according to visual information from the retina.

What is cortical magnification?

The disproportionate amount of cortical space devoted to certain parts of the sensory field.

Why does the fovea receive a large amount of cortical representation?

important for detailed, high-acuity vision

How much of the retinal area does the fovea occupy compared with its cortical representation?

0.01% of retinal area but 8–10% of the cortical retinotopic map.

What happens to visual processing after the early visual areas?

splits into two streams: the ventral and dorsal pathways

What is the ventral stream also known as?

“what” pathway

Where does the ventral stream travel?

From the occipital lobe to the temporal lobe

What is the main function of the ventral stream?

Identifying form, identity and object recognition

What is the dorsal stream also known as?

The “where/how” pathway

Where does the dorsal stream travel?

occipital lobe to parietal lobe

What is the main function of the dorsal stream?

Processing an object's location and guiding actions toward it.

What types of actions does the dorsal stream help with?

Reaching and grasping

What does double dissociation mean?

Two different brain areas are associated with different functions

What did the double dissociation in the monkey study demonstrate?

Temporal cortex damage impaired object discrimination
parietal cortex damage impaired spatial discrimination

Which pathway is most involved in the object discrimination task?

The ventral pathway

Which pathway is most involved in the landmark discrimination task?

The dorsal pathway