chapter 4 sensation nd perception

What does RiCH BAG stand for then after G what does it go to

-rods (and) photoreceptor (light into neural signal)

-cones photoreceptor

-horizontal cells (modifier 1) help with lateral inhibition contrast

-bipolar cells (bridge) carry from photoreceptors

-amacrine cells (modifier 2) modify connection bipolar and gang

-Ganglion cells (out to the optic nerve made up of ganglion cells) lateral inhibition occurs here

very back of retina

Retina

The layer of tissue at the back of the eye that contains photoreceptors (rods and cones) and begins processing visual information.

light stop sign reaches retina- turned into neural signal

Optic Nerve

A bundle of ganglion cell axons that carries visual information from each eye toward the brain.

Information detected by your right and left retinas travels through their respective optic nerves.

Optic Chiasm

The location where some optic nerve fibers cross to the opposite side of the brain.

• Nasal retinal fibers cross

• Temporal retinal fibers stay on the same side

temporal (-) nasal (-) temporal

This causes information from the left visual field → right hemisphere and right visual field → left hemisphere.

what part of receptor fields correlate with optic chasm

Receptive field = the specific area of the visual field where light affects the firing of a particular neuron.

For example, a particular ganglion cell doesn't respond to everything you see. It responds to light falling on a specific small area of the retina, which corresponds to a particular location in your visual field.

Imagine you're staring straight ahead:

LEFT visual field | RIGHT visual field

Because the eye's optics reverse the image:

• Information from your LEFT visual field lands on the right side of each retina.

• Information from your RIGHT visual field lands on the left side of each retina.

Here's the important part: your brain wants information about the same side of visual space to end up together.

At the optic chiasm, some ganglion-cell axons cross to accomplish this.

LEFT visual field
→ activates retinal receptive fields in both eyes
→ information is combined and sent to the RIGHT hemisphere

RIGHT visual field
→ activates retinal receptive fields in both eyes
→ information is combined and sent to the LEFT hemisphere

Each retina has a:

• Nasal half = side closer to your nose CROSS

• Temporal half = side closer to your temples DONT CROSS

LGN — Lateral Geniculate Nucleus

A structure in the thalamus that receives visual information and helps process/regulate the flow of visual information before sending it to the visual cortex.

LGN receives info from cortex larger (likely feedback) as well as retina smaller

—idea of center surround receptor fields

visual relay/processing station in the thalamus thalamus also very involved in sensory integration

V1 — Primary Visual Cortex

he first major cortical area that receives visual information. It is located in the occipital lobe.

V1 = Primary visual cortex = Primary visual receiving area = Striate cortex another name

begins processing features like orientation edges and location

Extrastriate Cortex

Visual areas beyond V1 that perform further processing of visual information.

pathways after the v1 and estraiete cortex

higher level processing occurs here in

temporal

parietal pathway

ventrall-temporal- what- perception. temporal lobe

dorsal-parietal- how/where - action pathway. parietal lobe

After early visual processing, the ventral pathway can help you recognize that you're looking at a mug, while the dorsal pathway helps guide your hand to reach for the mug.

Ventral Visual Pathway

Ventral = Temporal = What = Perception pathway

Helps us perceive and identify objects — essentially answering:

“What am I looking at?”

TASK PERCEPTION

Dorsal Visual Pathway

Dorsal = Parietal = How = Action pathway

“where pathway,” Milner & Goodale argued that “how/action pathway” is more accurate.

Uses visual information to guide actions and interactions with objects.

TASK ACTION

what does ventral and dorsal pathway help with visual and continuous function

ventral or what pathway help identifies an object itself perception like example identifying a mug and the dorsal pathway helps you identify how like how or helps guide your hand to mug

temporal lobe impaired

impairment in object discrimination task (what is it) occipital tasks

parietal lobe impairment

impair performance on landmark discrimination tasks (where/ how pathway)

Object Discrimination Problem same as /explain

temporal lobe impaired

Researchers used ablation (removing/damaging part of the brain).

When the temporal lobe was ablated, subjects had difficulty with an object discrimination task.

important recognizes the why for object perception and identification.

Landmark Discrimination Problem same as /explain

parietal lobe impairment

When researchers ablated the parietal lobe, subjects had difficulty with a landmark discrimination task.

For example, they might need to choose the food well that is closest to a landmark.

They struggled to use the landmark's spatial relationship to guide their response.

or true tasks themselves such throwing ball

provided evidence that the dorsal/parietal pathway processes visual information important for spatially guided action.

what was card issue what was damaged

D.F. had damage to the ventral (perception) pathway.

• Match the slot angle ❌: She couldn’t consciously tell which way the slot was tilted.

• Put the card in the slot ✅: Her dorsal (action) pathway could still guide her hand correctly.

Key idea: She couldn’t accurately perceive the orientation, but she could act on it.

Ablation

intentionally removing or destroying a specific area of the brain in research to determine what function that area performs.

Researchers look at what ability becomes impaired after that brain area is damaged.

ethical generally conducted with nonhuman animals

what is the contralateral representation of vision

Contralateral = opposite side.

Each hemisphere of the brain primarily processes information from the opposite side of the visual field.

• 👀 Left visual field → Right hemisphere

• 👀 Right visual field → Left hemisphere

At the optic chiasm, the fibers from the nasal half of each retina cross, while fibers from the temporal half stay on the same side.

Example

🍎 ← LEFT visual field | 👁 fixation | RIGHT visual field → 🥎

The apple on your left is processed primarily by your right visual cortex.

The ball on your right is processed primarily by your left visual cortex.

opposites!! central vision is by singular eye same hemisphere

Feature Detectors

Feature detectors are neurons in the visual system that respond best to specific features of a visual stimulus, such as an edge's orientation, movement, or length.

example one neuron respond to vertical line barely respond to horizontal line

simple complex hypercomplex

Simple Cells

Neurons that respond best to an edge or bar with a specific orientation at a specific location in their receptive field.

Example: A simple cell might fire strongly when:

👉 | appears in one particular location

but not when the same | is somewhere else.

Specific orientation + location

📍 Specific spot

Complex Cells

Respond best to a particular orientation, especially when that edge/bar is moving across the receptive field.

Unlike simple cells, they are less dependent on the exact location of the stimulus within their receptive field.

xample: A complex cell might respond strongly to a vertical line:

| → → →

moving across its receptive field.

Orientation + movement

Hypercomplex Cells

Respond to specific orientations but are also sensitive to features such as the length, corners, or ends of a stimulus.

They're often called end-stopped cells.

Example: A hypercomplex cell may respond strongly to:

——

but respond less when the line becomes:

———————

because it prefers a particular line length/end position.

Orientation + length/endpoints

can be moving must refer to end point in some specificity

What is selective adaptation?

happens when you repeatedly or continuously view a specific stimulus, causing the neurons that respond to that feature to become less responsive.

ou stare at vertical lines ||||| for a long time.

• Your vertical-orientation feature detectors repeatedly fire.

• They become adapted and respond less strongly.

• Afterward, your perception of orientation can be temporarily altered.

Selective Rearing

Selective rearing means raising an organism in an environment where it is exposed to only certain types of sensory stimuli.

The goal is to see how early experience affects the development of the brain and perception.

Example: Raising an animal where it primarily sees vertical lines and has little/no experience with horizontal lines.

Selective rearing = control what the organism experiences while developing.

🐱 Blakemore & Cooper Kitten Experiment

Method

Kittens were raised during early development in environments containing primarily:

• Vertical stripes OR

• Horizontal stripes

So one group had very little visual experience with horizontal orientations, while the other had very little experience with vertical orientations.

Results of Blakemore kitten experiment

Vertical-reared kittens:
→ responded normally to vertical features
→ had difficulty perceiving/responding to horizontal features

Horizontal-reared kittens:
→ responded normally to horizontal features
→ had difficulty perceiving/responding to vertical features

Their visual-cortex neurons also showed fewer neurons responding to the orientations they had not experienced.

implications

experience during early development affects the development of feature detectors in the visual cortex.

some factors of perception are not innate and visual expeericne helps determine how neurons become tuned to features

Not necessarily forever, but the effects were long-lasting

• then later exposed to a normal environment, some visual abilities could improve, but the early deprivation could leave persistent deficits.

So for your class, the main takeaway is:

Early visual experience can produce lasting changes in the development of the visual cortex.

Retinotopic Organization

Retinotopic organization means that the spatial layout of the visual field/retina is preserved in the brain.

Basically, areas that are next to each other on the retina are generally processed by neurons located near each other in the visual cortex.

Cortical Magnification

means that more visual cortex is devoted to processing information from the fovea than information from the peripheral retina

Fovea = small area of retina with lots of cones → highest visual acuity

Even though the fovea is physically small, it gets a disproportionately LARGE amount of V1 devoted to processing its information.

Example

When you're reading:

WORD

You look directly at the word → image falls on your fovea → a large amount of visual cortex processes that detailed information.

magnifying every single word other words in peripheral

What is a double dissociation?

A double dissociation occurs when damage to brain area A disrupts function A but not function B, while damage to brain area B disrupts function B but not function A.

This provides strong evidence that the two functions depend on different brain systems.

idea temporal/ parietal lobe

one damaged other will work still

this supports the existence of two visual pathways:

Temporal → Ventral → What → Perception

Parietal → Dorsal → How/Action

Inferotemporal Cortex (IT Cortex)

The inferotemporal cortex is an area in the temporal lobe involved in the perception and recognition of complex objects.

Charles Gross found neurons in the inferotemporal cortex that responded especially strongly to complex stimuli, such as:

• Hands

• Faces

• Objects

👉 Inferotemporal cortex = complex OBJECT perception

Fusiform Face Area (FFA)

The fusiform face area is a region in the ventral temporal cortex that responds especially strongly to faces.

Example: Looking at your friend's face produces strong activation in the FFA and contributes to processing the face.

However, remember the Greeble study from your slides: after people became experts at recognizing Greebles, Greebles produced increased FFA activation.

Dr. P — The Man Who Mistook His Wife for a Hat

big concept is that Dr. P could see visual features, but had difficulty recognizing what he was seeing.

Visual agnosia = difficulty recognizing or identifying objects through vision, despite being able to see them.

He could see individual features, but struggled to combine/interpret them into meaningful objects.

major symptoms

-Difficulty recognizing faces

(ecognized people using nonvisual information)

-Focused on individual visual features

(describe shape/featyres without correctly identifying object)

-Had difficulty recognizing objects based on their overall visual appearance.

Famously mistook his wife's head for his hat.

🧠 What brain region was likely affected?

Temporal lobe, particularly areas of the inferotemporal cortex involved in complex-object recognition.

here could also be involvement of face-processing regions associated with the fusiform face area (FFA) given his severe difficulty recognizing faces.

what pathway-ventral-temporal -perception

what is exactly was damaged

infernotemporal cortex