Sensation and Perception - Pagano Unit 2

Visual pathways

How information travels from the eye

Optic nerves

Formed from axons of retinal ganglia, cross at optic chiasm

Optic chasm

Location where optic nerves cross over each other - half of each nerve's fibers go to each side of the cortex

Optic chiasm - predators vs prey

Prey have complete crossover, predators have partial crossover

Importance of optic chiasm

allows visual cortex to receive the full visual field from each eye

What happens with a left optic nerve injury?

No left eye vision, still binocular

What is the effect of a tumor at the optic chiasm?

Left eye lost left world, right eye lost right world

What is the result of a left optic aneurysm?

Lost left eye's right visual field

What occurs with a loss of the optic tract?

Loss of the opposing visual field

How to amend a lost optic tract

Incisions on inner thigh, then shrink aneurysm through superglue in the nervous system

What % of visual fibers go to the LGN?

90

Blindsight

Blind people perceiving motion with no conscious awareness

Number of layers of the LGN

6 discrete - Especially the first two

Results of single-cell recording in the LGN

All LGN cells have circular fields

A map of the world is in each layer of the LGN

Each eye sends information to segregated layers

Spatial organization is maintained on

the retina and the LGN

Segregated layers in the LGN

Layers correspond to one eye only

6 unique copies of the world for each LGN

Layers 1 and 2 LGN correspond to what pathway

The dorsal pathway - Cortex, then occipital / parietal lobe

Layers 3-6 LGN correspond with what pathway

The ventral pathway - Cortex, then temporal lobe

The dorsal pathway does

Touch, motor control, responses to identified things, binocular vision, dim vision, the "How" pathway

The ventral pathway does

Colors, identifying objects and faces - the "What" pathway

Types of cells in each pathway

Dorsal: Huge cells, from rods, larger receptive fields

Ventral: Smaller cells, from cones, finer details and color

Color opponency

the idea that color vision is based on two pairs of opponents; red vs. green and blue vs. yellow

Types of chromatic channels

R/G and B/Y - Only one color can fire at a time - One color's firing inhibits the other through receptive field structures

Opponent neurons

Excitatory responses to one color, inhibitory responses to other colors

R/G Example

Red (+/-) Center, Green (-/+) Surround

~Red light will excite in the center and inhibit the surround, green light vice versa

Psychophysics experiments for opponent neurons

Showing people a range of colors and seeing what proportion people use the terms for color

Negative afterimages

experiences of one color after the removal of another - comes from the opponency process

Retinotropic maps

Cortical mapping of the information from the retina

-Spatially organized cortex

Cortical magnification

Enhancement of information from the foveal area - 80% of cortex for 10% of visual field

Circular cortical cells

Have a circular receptive field, most simple cells

Simple cells of the cortex

Receives info from the circular cells

Each cell responds only to specific bar orientations

Bar-shaped receptive fields or edge-shaped fields

Tuning curves of the cortex

Orientation-specific response spectra

Complex cells

Correct orientation, motion, and location

-Preferred directions matter over location

End-stopped cells

Moving specific lengths / widths / angles

Motion illusions can be

secondary qualities -> perceptions from brain wiring

Cortex organization

Thin sheet of neurons organized into 1x1x2mm hyper columns

Perpendicular probing of the cortex

Cells with the same orientation and overlapping receptive fields

Oblique penetration of cortex

Rows of columns with progressions of orientations and overlapping fields

Oblique penetration the other way

Progression of receptive fields and ocular dominance columns

Hypercolumns

Cubes of cortex -> all orientations, locations, and both visual fields

Binocular cells

Random, rare, where 3D info is combined

-Can be complex cells and beyond

-Two receptive fields

Binocular cells only fire when

hit simultaneously at a specific 3D location

-Leads to distance perception

Binocular cells are found within ______% of people and (are / are not) developed over time

85-90%, are

How much cortical power is innate?

Some possibly but difficult question to answer when cortical functions are secondary qualities

Cells found within the ventral cortex

Single cells look for shapes, shapes and colors, etc

Similar structure to hyper columns

Columns always represent the same shape

The grandmother cell

A hypothesized type of neuron that responds only to a very specific stimulus, such as a person's grandmother.

Color perception cells

Orientations like a rainbow - PBGYOR when viewed obliquely

Landmark discrimination test

Looking for the incentive closest to the object - impacted with the parietal lobe

Object discrimination test

Looking for the incentive under the object with specific characteristics - Impacted with the temporal lobe

The location and object discrimination tests indicate

The dorsal and ventral pathways are separate

Matching tasks

Tilting a card to match the slot

Posting tasks

Quickly inserting a card to match the slot

D.F.'s results from matching and posting

She could not match the card yet perfectly post it -> indicates she had no identification abilities but could respond to locations

Results of Pagano's distance experiments

Conscious identification perceptions are worse than unconscious motor reactions

-Verbal distance estimations were underestimates of the arm's extension to hit a target

Verbal reports and the impacts on perception

If participants believed the targets were closer, they would report closer distances even if the targets were the same day after day

-Seen with Pagano's experiment where the distances were the same both days but participants were told different ranges

Reaching for a phone in the dark

Intermediate light - Can't see the phone (no cones) but if you remember where it was, you are likely to accurately reach for it (rods)

Where does naming occur in the brain?

Deep in the temporal lobe after identification

Consequences of loss of action guidance

You have to consciously force yourself to take actions

Consequences of loss of motion perception

Motion blindness -> only seeing static frames

Consequences of loss of object naming

Can use objects but not name from memory

Why are faces so recognizable?

The brain hates randomness and are always looking for patterns

Fusiform face area

Perceptual segregation

Grouping parts into objects, separating them from others, and identifying them

Psychology started in the year

1890

Structuralism

1890-1910

Discover basic elements of mental experience

Discover laws for combination into complex mental experiences

Structuralism is an _______ field

atomistic - focus on basic blocks

Structuralism used what method to learn about the world

Introspection at the most basic levels

Results of structuralism

Failed as a field - Unscientific

Replaced with behaviorism in US, Gestalt in Europe

Gestalt psychology

1910-1930

Wholistic - Perception is about seeing configurations of the whole, not parts first

Examples of wholistic thought

Melodies - the configuration of sounds matters more than the actual sounds

Apparent movement - The ball is not actually moving but the order of the flashes make the illusion

Law of pragnanz

Simplicity and good figure

Stimuli will always be interpreted in the simplest and most ordered way

Law of proximity

elements close to one another tend to be perceived as a unit

Law of similarity

objects that are similar tend to be grouped together

Law of good continuation

lines tend to be seen as following the smoothest path

Law of illusory contours

empty space is filled in to form more simple groups

-Creates depth and activates cells stimulated by the illusory shape

"Whiter than White"

Follows illusory contours -> the space in the illusions are brighter

Neon color spreading

Illusory presentations of color from colored border segments

Common fate

the tendency to perceive objects that are moving together as belonging together

Camouflage history

Originally - People wore contrast to intimidate

Modern - Weapon evolution led to camouflage mattering more

Impacts of camouflage on Gestalt

Defeats the concept of pragnanz

Dazzle camo

Using bright contrast to make figure-ground ineffective

-WWI: Decreased likelihood of tornado strikes

Affects headings and speeds

Can be colorful

Impacts of gestalt psych

First to propose psychology followed nature and was a science

Enrichment relies on involuntary laws of nature

Object recognition

detecting and identifying objects using representations

The average computer vision system's error rate dropped from ____% to _____% in recent years

16%, 2%

inverse projection problem

an image on the retina can be caused by an infinite number of objects because of DM

viewpoint invariance

the ability to recognize an object seen from different viewpoints

Two factors prohibiting computer object recognition

Hidden objects and viewpoint variance

contralateral fibers

fibers that cross over hemispheres

selective adaptation

repeated exposure to a stimulus results in decreased firing rates and intensities of firing

contrast threshold

the smallest amount of contrast required to detect a pattern

selective rearing

A procedure in which animals are reared in special environments. An example of selective rearing is the experiment in which kittens were reared in an environment of vertical stripes to determine the effect on orientation selectivity of cortical neurons.

experience-dependent plasticity

the process through which neural connections are created and reorganized throughout life as a function of an individual's experiences

ablation

the removal of a body part or the destruction of its function

-used in the monkey experiments

Object perception requires

contrast sensitivity

Contrast sensitivity

the ability to detect differences in light and dark areas in a visual pattern

Acuity vs contrast sensitivity Example

Reading street signs vs keeping your car on the road

Pilot error

Example of poor design

-Identical gauges and levers can lead to mistakes

Operator error

Chernobyl - A million dials across a room without labels makes it impossible to see if something is wrong

Configurational displays

Use pragnanz to design effective displays

-Abnormal activity represented through abnormal shapes and colors

Good displays serve what function

Alert of what the problem is and how to fix it

Boeing plane dip problem

System in airplanes that lowered the nose when too upwards malfunctioned, where the nose dipped too low

Button to fix the problem had no alerts or indicators, so 500 people died

-Nothing on display indicated an issue

Oconee Power plant

Had the same original design as Three Mile but they caught the problem and rebuilt it before something was too late