CGS Lecture 13

Rods and cones in the eye turn…

photons into neurochemical reactions

Rods

Photoreceptor cells in the eye that are responsible for vision at low light levels

How do rods operate?

Mixes all colors in the wavelength to tell you there’s a certain amount of light out there

What are rods sensitive to? (2)

Most sensitive to green light, high light sensitivity (sensitive even to the smallest amount of light)

Rods are too sensitive to operating during… because….

Sunlight because their not contributing since they’re all responding at max/as fast as they can fire

What is the 1 type of rod?

“Black and white” vision

Cones

Photoreceptor cells in the eye that are responsible for color vision and high spatial acuity

What are cone sensitive to?

Are differentially sensitive to wavelengths, low light sensitivity (needs a lot of light to operate)

What are the 3 types of cones?

• long wavelength cone, red

• medium wavelength cone, green

• short wavelength cone, blue

Cones are not useful at… because…

Night because you can’t see color in low light

Are there more rods or cones?

Rods

Binocular vision

Seeing 2 pictures of the same thing with your 2 eyes

Stereopsis

Taking 2 pictures of the same thing from a slightly different perspective

Ganglion cells

Neurons that transmit information from the retina to the brain via the optic nerve. Axons of the ganglion cells form the optic nerve.

What is the purpose of ganglion cells?

To pool all the information and send it to the brain, output

What are the 2 parallel processing streams (visual systems)?

Magnocellular and parvocellular streams (both ganglion cells)

Magnocellular stream (big ganglion cells) and what lobe it goes to

Cellular stream responsible for processing strong contrast between light and dark and spatial orientation (“where” vision). Goes to the parietal lobe

Magnocellular cells like when (2) and respond well to (1)

things are moving across the retina, there is a strong contrast between light and dark, and respond well to signals changing in depth

Parvocellular system (small ganglion cells) and what lobe it goes to

Cellular system responsible for color perception and object recognition (“what” vision). Goes to the temporal lobe

Parvocellular cells like when (3)

things are in a certain form (like when a line is oriented in a certain way for them to respond), color (some cells only respond to specific colors in light), and signals are changing in depth

Temporal lobe is where… (3)

Languages, concepts, and autobiographical memory is

Where is the sensory motor cortex?

Parietal lobe

The dorsal stream is known as the _____ pathway

"where" pathway

The ventral stream is known as the _____ pathway

“what” pathway

Surface perception

The 3D representation of scenes that allows the visual system to parse objects and recognize/identify them.

Scene perception

The process of joining multiple objects together to generate a layout of a scene.

What are 4 performance factors that can affect perception?

knowledge and experience (how much you know about the subject matter), principles of perceptual organization (grouping things together accurately), attention (registering things), and expectations (knowing what you are looking for)

Gestalt psychology was pioneered by who?

Max Wertheimer

Gestalt psychology

The whole is greater than the sum of it’s parts

Cue Approach

The idea that cues for depth perception are still available in a 2D image.

What are the 2 types of cues?

Monocular and Pictorial

Monocular cue

Visual cues that help people perceive depth using only one eye

Pictorial cue

Features that add depth and distance to an image

Occlusion (monocular cue)

An illusion where one object appears to hide or block another object.

Atmospheric Perspective (monocular cue)

Contours that are further away in an image are blurred

Linear Perspective (monocular cue)

The brain's ability to discern between different angles found in architectural structures.

Size and Distance approach (monocular cue)

The perception that objects farther away appear larger, even if they have the same size as closer objects.