Exam 2 Flashcards
Finish cards by Monday, Study Tuesday, Review Wednesday
What is one of the first sensory systems studied in cognitive neuroscience?
Vision
Why is vision significant in neuroscience?
Many landmark discoveries were made through studying vision
What general principles does the visual system illustrate?
It applies to other sensory systems.
What are the three main topics covered in the lecture?
Computational challenges of vision.
How vision addresses these challenges.
Depth perception as a specific example.
Why is vision complex despite feeling effortless?
It is an extremely complex computational problem
How has the brain evolved to handle vision?
It has devoted massive resources over evolution.
Why is vision more complex than intellectual tasks like chess?
Unlike intellectual tasks like chess, which we associate with intelligence, vision is more computationally complex.
How does AI compare to human vision?
AI has improved but still struggles with visual processing.
What was an AI limitation in the 1990s regarding chess?
AI could play chess but could not visually recognize the board-a human had to input the board state.
Are computing differences difficult?
The human brain processes sensory input effortlessly, but the underlying computations are extremely difficult.
What does the brain have to do?
The brain must infer objects, textures, colors, spatial layout, and 3D geometry from a 2D retinal image.
How much of the primate brain is dedicated to vision?
~55% of the primate brain is specialized for vision.
The visual cortex is one of the largest specialized areas in the brain.
Monkeys have most of their brain dedicated to vision.
What is the inverse problem in vision?
The light reaching the retina is ambiguous, and many different real-world objects could create the same image
The light reaching the retina is ambiguous—many different real-world objects could create the same visual input.
The brain must work backward to infer the most likely structure of the world.
How does the brain solve the inverse problem?-
It infers the most likely structure of the world.
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What is an example of an inverse problem?
A 3D object can project multiple possible 2D images onto the retina.
The brain must choose one interpretation based on available cues.
Visual illusions demonstrate how the brain constructs rather than directly perceives reality.
What do visual illusions demonstrate?
The brain constructs rather than directly perceives reality.
Does perception equal reality?
- No, the brain constructs the most plausible interpretation
What are some examples of visual illusions?
The spiral illusion appears to spiral inward, but it is actually a series of circles.
The table illusion: Two tables look like different shapes, but they are identical in 2D.
The Monster Illusion: Two identical monsters appear different sizes due to depth cues.
What is change blindness?
The brain prioritizes central visual information and ignores peripheral change
What is selective attention in vision?
- Large visual changes can be missed if not focused on.
Example: A video where a character unexpectedly changes, but many viewers don’t notice.
Is color perception a direct reflection of wavelength?
not just a direct reflection of wavelength.
What is color constancy
Example: “The Dress” illusion (blue/black vs. white/gold) → Differences in light interpretation change color perception.
What is the primary challenge of depth perception?
The retina receives a 2D image, but we perceive a 3D world.
Depth perception relies on cues and assumptions made by the brain.
What are monocular depth cues?
Occlusion (Interposition): If one object blocks another, the blocked object is perceived as farther away.
Linear Perspective: Parallel lines converge in the distance.
Texture Gradient: Repeating patterns become smaller and more compressed with depth.
Relative Size: If two objects are the same size, the one that appears smaller is farther away.
Shadows & Shading: Shadows provide depth cues about object positioning
What are binocular depth cues?
Binocular Disparity: The slight difference between the images in each eye provides depth information.
What is convergence?
Convergence: The amount the eyes turn inward helps estimate how close an object is.
What is motion Parallax?
Closer objects move faster across the retina than distant objects when moving.
Example: Looking out a car window—near objects blur by, but distant mountains move slowly.
The Brain’s Assumptions in Vision ?
Prefers simpler explanations over complex ones (Gestalt principles).
Ignores highly improbable interpretations of visual input.
Example: The hollow-face illusion—a concave mask appears convex because of strong expectations about faces.
What is the hollow-face illusion?
A concave mask appears convex due to strong expectations about faces.
What are Gestalt principles of perception?
Figure-Ground: We distinguish objects from backgrounds.
Similarity & Proximity: We group objects that are similar or close together.
Continuity: We perceive smooth, continuous patterns rather than abrupt changes.
Closure: Our brain fills in missing gaps to form complete objects.
What are the key takeaways from vision processing?
- Vision is computationally challenging but efficiently solved by the brain.
How do perceptual illusions inform us about vision?
They reveal how the brain processes information using assumptions.
Does the brain prioritize visual information?
- It leads to attention limits like change blindness.
What factors shape visual perception?
Experience, context, and assumptions.
What was the first domain of study on cognitive neuroscience?
Vision/”Sensory processing in general to start a new vision for the first sensory systems. Landmark findings” Visual system
What are parallels?
Other sensory remains.
What is the computational challenge?
The computational challenges that vision overcomes just how difficult those computational challenges are.
What are the three main points of the first lecture?
Computational challenges on vision, vision is an inferential process, and Depth perception as an illustrative example.
How is vision complex?
It is effortless where you open your eyes and you see what things are in the world, see environment an extremely complex environment.
From where did eyesight come from?
Eyesight came through natural selection over the course of evolution
Can chess machines see in the 90s
In the 90s, they needed someone to see the chess pieces in order to move them at their designated place. First CRT. And input it onto the board. Or move them at their designated location.
- Is vision challenging?
Computers can’t do it, but the brain can! - 55% of the primary cortex is specialized for vision, 11% touch, and 3% audition.
- How do you take a highway that lands on some sensory receptors?
Uh, in the case of the beta vision in the camera.
Computers are not great at what?
Processing visual information effectively compared to the human brain
How do we take light and compute from it?
analyzing what objects, alarms, textures, colors, spatial layout, and geometry exist in the environment.
How do we know that vision is important
By noticing how much cortical real estate is devoted to vision (~55% of neurons).
- Why is vision a constructive process?
he brain always makes guesses because there are multiple possible interpretations for visual input.
- What did President Reagan say about perception?
e need to construct a representation of the world. It is not necessarily critical, but making the best guess about what is out there in the world causes something to happen.”
What we see is what is out in the world - true or false?
False. Our perception is the best guess based on the sensory data received.
- What do visual illusions show?
at what we perceive is not necessarily an accurate representation of the world.
- How does depth trick your brain?
The brain uses multiple cues to infer depth, object geometry, and layout. Example: The size illusion where two identical tables appear different due to inferred depth.
- What do we do when we see?
We take sensory information and construct a representation of the world.
- What is another thing that is not obvious in visual perception?
The brain has a limited capacity for visual information and must selectively attend to some aspects (Change Blindness).
- What is the Fraser spiral?
A well-known optical illusion demonstrating how visual perception can be deceived.
- Even though we have a panoramic view, what is really happening?
We devote significant resources to central focus areas while paying less attention to peripheral details. This can cause us to miss major changes (Change Blindness).
Eventhought we have a panoramic view of the world in front of us, What’s really happening is that we’re sort of we’re devoting a lot of resources to the theme and officially on the miniseries unit, and we’re are really devoting much fewer resources to things that are in our periphery. ( simple: THings that we are not attentive to, Cambridge,lead us to those things that can lead us to miss seemingly really striking changes in place to not pay specific attention to it. )
Do we have control of perception?
No, perception is influenced by the brain’s focus on changing stimuli while static stimuli may fade away (Troxler’s fading).
- What is an example that demonstrates vision is not a faithful record?
Troxler’s fading, where surrounding colors fill in, and we perceive everything as moving.
- How does Troxler’s fading work?
When we fixate on a point, the surrounding colors blend into the background, making static objects seem to disappear.
- How does the brain adapt to color?
The brain continuously adapts to the colors being perceived at the moment, affecting how future colors appear.
- What happens when you fixate on a color for an extended period?
The brain adapts, and perception of color shifts over time, influencing future visual experiences.
- What is an inverse problem in vision?
Light reflects off objects in the world and lands on the retina, but multiple real-world configurations could create the same sensory data.
- What is the Necker cube?
A visual illusion that demonstrates multiple interpretations of the same visual data.
- Why is the Necker cube an example of an inverse problem?
The cube has multiple valid interpretations, and the brain must choose one based on ambiguous sensory data.
- Do all visions have multiple interpretations?
Yes, all visual experiences can have multiple interpretations that are nearly identical to reality.
What is an inverse problem?
Start with the effect and work backwards to identify how it came about.
How does the inverse problem apply to vision?
Start with a pattern of light on the retina and work backwards to determine the real-world structure that caused it.
What is the major challenge of the inverse problem in vision?
Many possible configurations of the world can produce the same retinal image.
What does the brain do when faced with multiple possible solutions to an inverse problem?
It makes the best guess based on available cues.
- What is an example of an inverse problem involving distance and size?
Identical objects can appear different in size depending on their perceived depth.
How do we know something is smaller or larger?
Based on displacement; larger objects farther away can appear smaller.
- What are some components of inverse problems in vision?
Reflectance, illumination, and color (e.g., “The Dress” illusion).
- What is the dice problem?
To dice appearing different colors are actually the same.
- How does the visual system solve inverse problems?
It makes assumptions and uses them to construct the most likely interpretation of reality.
- What is unconscious inference in vision?
The brain perceives objects and events that are most likely given the sensory data received.
- What explanation does the brain prefer?
The simplest explanation (principle of simplicity).
- What is the coincidence avoidance principle?
The brain avoids interpretations that require improbable coincidences.
- What does vision assume about objects?
That they are simple and regular whenever possible.
- What assumptions does vision make about lighting?
That it is uniform and shadows are smooth.
- How does vision perceive faces?
The brain assumes faces are convex even when they are concave.
- What is the major challenge of vision?
The inverse problem of identifying real-world properties from light on the retina.
- What is the challenge of perceiving a 3D world from a 2D retina?
Many different 3D configurations could create the same 2D image.
- What are cues that support depth perception?
Oculomotor cues, binocular disparity, dynamic cues, pictorial cues.
What are oculomotor cues?
Strain on the lens used to infer distance.
- What is convergence in vision?
The relative angle between the eyes as they turn inward to focus on close objects.
What is binocular disparity?
The difference between the images in each eye, which changes with depth.
What is motion parallax
Objects closer to us move faster across our field of view than distant objects when we move.
What are pictorial depth cuues?
Occlusion, shadows, linear perspective, relative height, texture gradient, known size.
- What is occlusion?
When one object blocks another, the blocked object appears farther awa
What is texture gradient?
Patterns become smaller and more compressed with increasing depth
. What is known size?
The brain uses prior knowledge of an object’s size to infer its distance.
What is constraint satisfaction in depth perception?
The brain integrates multiple cues to create a cohesive depth interpretation.
What is Troxler’s fading?
A visual phenomenon where stationary objects in the peripheral vision fade and disappear when one fixes their gaze on a central point.
What is color perception?
The brain’s interpretation of different wavelengths of light, influenced by context, lighting conditions, and prior knowledge.
What is in envision?
Start with a pattern of light on the retina, and
work backwards to identify the configuration of the
world that caused it
Inverse problems with many possible solutions, solution, what this means?
Inverse problems with many possible solutions
Solution
What this means
* Any image could represent many possible realities
* Make assumptions, use those assumptions to make inferences
* Vision is an inferential, constructive process
* You see what is most likely to be there, given the assumptions
that your visual system makes.
3. Inverse
problems
Unconscious inference:
We perceive the objects and
events that are most likely, given a pattern of inputs to the retina.
This happens automatically in vision, without conscious effort.
Coincidence avoidance
principle:
Vision avoids
interpretations that require
low-probability coincidences
Principle of simplicit
Vision assumes that objects and
events are as simple and regular as possible
What happens on the retina?
Retina is a 2D sheet
* Light from the 3D world
is projected onto the 2D
retina
* Challenge: scenes with
very different 3D
properties could
produce the same
pattern of light on the
2D retina
What are the cues that are involve in depth perception?
Oculomotor cues
* Binocular disparity
* Dynamic cues
* Pictorial cues
What is Accomedation
Degree of strain on lens
* Monocular cue
Convergence?
Relative angle between eyes
* Binocular cue
Binocular disparity
Each eye receives a slightly
different projection of the world.
This difference is known as
binocular disparity.
* The degree of binocular
disparity changes with depth,
and thus it can be used as a cue
for calculating depth
Pictorial cues
Occlusion
T-junctions imply occlusion and are cues for depth ranking but not depth
measurement (they give us the order of items in depth but not precise
depth estimates)
Linear perspective
arallel lines must converge in the distance, and we can use the distance
between parallel lines as a cue for depth
Relative height to horizon
We perceive objects nearer to
the horizon as more distant
Texture gradient
Assuming a textured pattern
is uniform, the pattern will
become gradually smaller as
depth increases
Known size
If a known object has a “canonical
size,” we can estimate its depth
because we know how far away it
would it would have to be to result
in its observed size on the retina
However, this is often overruled by
other cues
Cavanagh (2006)
“Top-down” knowledge
Constraint satisfaction
Putting it all together
* Cues arise from depth differences in the 3D world
* Each cue in a local region gives rise to a set of possible
interpretations
* Each possibility constrains the depth assignments of
edges and surfaces around the cue
* Final interpretation is what is most compatible with all
cues
Cavanagh (2006)
An Overview of the Visual Pathway
There is energy in the world in the form of light.
- What is the basic function of the visual system?
To detect light and process visual information to infer objects and their locations in the world.
What are the major components of the visual system?
The retina, thalamus (lateral geniculate nucleus), and visual cortex (V1 and higher-level areas).
What is the role of the retina in vision?
It contains photoreceptors that transduce light energy into neural signals.
- What are the two types of photoreceptors in the retina?
Rods and cones.
What is the function of rods?
Rods are highly sensitive to light and are used for night vision and peripheral vision.
- What is the function of cones?
Cones detect color and are responsible for high-resolution vision in bright conditions.
Where are cones most concentrated in the retina?
In the fovea, the central part of the retina.
- Where are rods most concentrated in the retina?
In the peripheral regions of the retina.
- What is the fovea?
A small, central region of the retina with a high concentration of cones for sharp central vision.
What is the optic disc
The area where the optic nerve exits the eye; it lacks photoreceptors, creating a blind spot.
What is the lateral geniculate nucleus (LGN)?
A relay center in the thalamus that processes and transmits visual information to the cortex.
What is the function of the primary visual cortex (V1)?
It processes basic visual features like orientation, edges, and movement.
. What is light?
A form of electromagnetic radiation that travels in straight lines and can be reflected, refracted, or absorbed.
How does a pinhole camera work
It restricts light to a small aperture, ensuring that each point on the film receives light from a single direction, creating a clear image.
- What is the function of the cornea?
It is the main focusing structure of the eye, bending incoming light to direct it toward the retina.
- What is the function of the lens?
It fine-tunes focus by changing shape through accommodation.
- How does the lens change shape for focusing?
The ciliary muscles adjust its curvature to focus on near or far objects.
What is refraction?
The bending of light as it passes from one medium to another.
Why does a pencil appear bent when placed in water?
Because light is refracted at the boundary between water and air.
What are the two main focusing structures of the eye?
The cornea and the lens.
What is the phototransduction process
he conversion of light into neural signals by photoreceptors.
- What are retinal ganglion cells?
eurons in the retina that receive input from photoreceptors and send signals to the brain.
What is a receptive field?
The specific region of the visual field that a neuron responds to.
How do receptive fields vary between the fovea and periphery?
Foveal receptive fields are small and detailed, while peripheral receptive fields are larger and less detailed.
What is the difference between on-center and off-center receptive fields?
On-center cells respond to light in the center and darkness in the surround; off-center cells respond to the opposite pattern.
. What does the blind spot demonstrate about perception?
The brain fills in missing information from the optic disc, making the blind spot unnoticeable
- What is contrast sensitivity?
The ability of the visual system to detect differences in luminance.
- How do retinal ganglion cells detect contrast?
hrough center-surround organization, enhancing edge detection.
What is lateral inhibition
A process in which neighboring neurons inhibit each other to enhance contrast and sharpen edges.
What is color perception?
he ability to distinguish different wavelengths of light.
What are the three types of cone cells?
Short-wavelength (blue), medium-wavelength (green), and long-wavelength (red) cones.
What is the trichromatic theory of color vision?
The idea that color perception results from the combination of signals from the three cone types.
What is the opponent-process theory of color vision
The idea that color perception is based on opposing pairs (red-green, blue-yellow, black-white).
What is color blindness?
A condition caused by the absence or dysfunction of certain cone types
What is the role of the LGN in visual processing?
It segregates and relays visual signals from the retina to the cortex.
How does the brain reconstruct depth?
Using binocular disparity, motion parallax, and pictorial cues
What is motion parallax?
A depth cue where closer objects move faster across the retina than distant objects.
What are pictorial depth cues?
Monocular cues such as occlusion, perspective, and texture gradients that provide depth information.
How does the visual system detect motion?
By integrating temporal changes in visual stimul
How does the brain compensate for eye movements?
By using predictive signals and saccadic suppression to stabilize vision.
What is the function of higher-order visual areas
They process complex features such as object identity and spatial relationships.
What is visual adaptation?
he process by which photoreceptors adjust their sensitivity to different lighting conditions.
What is the relationship between the retina and the brain?
The retina acts as an initial processor of visual information before transmitting signals to the brain.
What happens if the retina is damaged?
It can result in vision loss, as photoreceptors cannot regenerate.
What are retinal implants?
Devices that aim to restore vision by stimulating the retina with electrical signals.
What is the primary difference between rods and cones?
Rods function in low light and detect contrast, while cones function in bright light and detect color.
Why do cones provide higher visual acuity than rods?
They have a one-to-one connection with ganglion cells, allowing finer detail detection.
How do photoreceptors contribute to night vision?
Rods become more sensitive in darkness, allowing vision in low-light conditions.
- What is the role of the optic nerve?
It transmits visual signals from the retina to the brain.
How does the brain process visual information beyond V1?
Through specialized pathways that identify objects (ventral stream) and locate them in space (dorsal stream).
How does the brain infer what objects exist in the world?
The brain receives light energy detected by specialized cells and uses this information to reconstruct objects and their locations.
What is the role of photoreceptors in vision
Photoreceptors are specialized neurons in the retina that convert light energy into neural signals, initiating the process of vision.
Q: How does visual information travel from the retina to the brain?
Signals from the retina are transmitted through the optic nerve to the thalamus, specifically the lateral geniculate nucleus (LGN), and then relayed to the primary visual cortex (V1) for processing.
What is the role of cortical circuitry in vision?
The brain has dedicated cortical circuits for processing visual information, occupying a large portion of the brain to solve complex visual problems such as object recognition and spatial awareness.
Where is the process of the overview of the visual pathway?
It goes from the retina to the thalamus.
What is the further processing in dorsal / ventral pathways?
Where and the what know the terms.
What is light?
It just a form of electromagnetic radiation
What is light?
Light is a form of electromagnetic radiation, specifically a frequency band within the electromagnetic spectrum. It is the range of frequencies that human photoreceptors are sensitive to, distinguishing it from other forms of electromagnetic radiation like radio waves and microwaves.
What are the Optic: properties of light?
Wavelength, 400- 700 Nm Light is an electromagnetic wave. Light is travels in a straight line
How does a camera capture light, and how does this relate to vision?
A camera captures light by allowing it to pass through a lens and focus onto a photosensitive surface. Similarly, the eye focuses light onto the retina using the cornea and lens, ensuring that incoming light is properly organized to form a clear image.
Q: Why does light scattering cause blurring in an imaging system?
When light scatters in all directions from objects, it can overlap on a photosensitive surface, creating a blurred or washed-out image. The eye and cameras use apertures or lenses to limit incoming angles of light, preventing this blurring effect and creating sharper images.
What is aperture?
And so they just all blend together and all the information just blends together. And so there’s a trick you can use to solve this,
which is you restrict the light that’s coming in to only be from a limited range of angles or in more within a minute range of things.
You’re called aperture.(since they mix it, and like a camera get all lights will get a flash).
What are Pinhole Cameras?
Restrict incoming light so that waves can only come from one direction per point
what the problem with this? What happens when the pinhole gets smaller or larger. Nautilus have this mechanism. Low resolution, get small hole hight resolution.
What are lenses?
light from objects scatter in many directions, lenses gather the scattered light form a single point in the world and focus it on a single point on a light sensing surface.
What they do is they ban light such that light coming from multiple angles can be converged to the same point on the film or on the retina.
phenomenon called refraction of light, they cast like the single point in the world.
What is refraction?
Refraction is the bending of light as it passes from one medium to another, depending on the angle of entry. This occurs because light travels at different speeds in different materials, altering its direction when it moves between them.(Pencil exam)
What is refraction?
Because light travels at different speeds in different materials light can bend when crossing a boundary between materials. Refraction is proportional to the ration of the speeds in each material.(slows down and pulls)
What are the lease optic and eyeballs
Divergent= Spreed’s outward.
Convergent= Bends inward
What are lenses?
It’s the cornea and the lens. Both of these structures are lenses. Most of the focusing power is actually coming from the cornea.The lens is really doing sort of fine adjustment to the cornea fixed.We saw that the lens can actually be adjusted by the ciliary body to be more or less rounded like more or less here or parts.
And and that can be used to bring things in focus depending on where they are in depth.. It’s not on the basis of this idea that light needs to be captured by the lenses and focus on to the retina.
Retina
Can put electric to retina to gain function back,
Okay. So the retina is this 2D sheet on the back of the eyeball.
It has photosensitive cells that are detecting the light converted to.
There’s blood vessels all over the retina. So actually, interestingly, they cast a shadow on the retina.
So there’s there’s actually this constant shadow on the retina that we just don’t see.
IAnd it has to do with this principle that the visual system really cares about things that are stable and sort of discounts,
sorry, things that are changing at discounts, things that are really highly stable.
What is the optic disc, and why does it create a blind spot?
The optic disc is the area where the optic nerve exits the retina. Since there are no photoreceptors in this region, it creates a natural blind spot in our vision. The brain compensates for this by filling in the missing information based on surrounding visual cues.
Q: What is the difference between the fovea and the periphery?
The fovea is a small indentation in the retina that contains a high density of cones, making it responsible for sharp, detailed central vision. The periphery, in contrast, contains more rods and is specialized for detecting motion and seeing in low-light conditions.
Why can we see blood vessels?
Due to the reason that it is stationary
What does the human retina have?
Retina has receptors that react to light and convert it into neural signals. Whe are going to learn the following: These are the photoreceptors that the rods and the cones. Send information LGM and Adonis
What are Photoreceptors?
Rod and Cone, photoreceptors are in the bottom and everything is on top of it.
Where are cones most concerted?
In the fovea, rods are absent from the fovea, non receptors at all exist in the blind spot.
Rods concentrated in the periphery. Cone In are in the center rather than the periphery. axons from. ganglia are leaving the eye
What are photoreceptors
Where are rods found? Rods: night time, not in fovea (everywhere else except the blind spot) low resolution vision, no color (black and white), good for low light conditions, Cones daylight packed in fovea, good for high-resolution vision and for color. First 10 minutes they change relies rods to cones instead of
What are the Three cone types?
S=Short-wavelenght, M= Medium-wavelnght And L=Long-wavelenght
Blue, green, to red. Blue short and red to longer wavelength
Distribution on retina
Ration of S:M:L (B:G:R)=1:5:10
Dearth of. “blue’ receptors at the center of the fovea(middle of the image) No blue.
What causes blondes?
Retinal Color Blindness: Loss of L cones or M cones causes red-green color blindness1/20 males, 1/4000 females
Retina: Fovea and Periphery
Rods and force they specialize for hight resolution vision in the daylight sees clearly & in color
Those find in the periphery on dark night only the periphery sees in the black and white with poor resolution the fovea is blind
What are the convergence of cones and rods?
Fovea and periphery. Cones are a higher resoultion. Rods have to have a higher multiple mapping, low spatial resolution.
What are receptive fields?
Receptive field: The spatial area type of stumulus that a sensory responds. to. What location in the visual field does the neuron respond to? what kind of visual stimulus does it respond to? Can talk about where and what type of information it is. Measuring where and what type of visual frame it was. responding too the cat experiment.
Always assuming the animal does not move and looks at the eye fixed. in front.
What is the rental. ganglion cells?
Contain photoreceptors in the setting, Location on space gets on a specific location on retina.
What is the retinal ganglion cells
Do not simply respond to the precess of light
Respond to. contrast of light and dark
On center-cells respond to light in center off center cells respond to dark in center.
Excitation. and. inhibition
Illumination, oon center, off- center
How does visual information travel from the retina to the brain?
A: Signals from the retina travel via the optic nerve to the lateral geniculate nucleus (LGN) in the thalamus, then to the primary visual cortex (V1).
What is the optic chiasm?
: The optic chiasm is the point where optic nerve fibers from each eye partially cross, ensuring that visual information from the right visual field is processed in the left hemisphere and vice versa.
: What is the primary visual cortex (V1) responsible for?
A: V1 is the first stage of cortical processing for vision, handling edge detection, spatial organization, and basic feature extraction.
What are receptive fields in the visual system
Receptive fields are specific areas in the visual field where stimuli will cause a neuron to respond, helping to detect shapes, edges, and orientations.
What is cortical magnification?
A: Cortical magnification refers to the larger amount of V1 dedicated to processing information from the fovea compared to the periphery.
What are photoreceptors, and what types exist?
Photoreceptors are specialized neurons in the retina that detect light. There are two types:
Rods: Sensitive to low light levels but do not detect color.
Cones: Detect color and provide high-resolution vision in bright light.
Q: What is the difference between the fovea and the periphery of the retina?
The fovea contains a high density of cones for detailed central vision, while the periphery contains more rods, which are better for detecting motion and low-light conditio
What is the lateral geniculate nucleus (LGN)?
A: The LGN, located in the thalamus, acts as a relay station that processes visual signals before sending them to the primary visual cortex.
What is the superior colliculus?
A midbrain structure involved in directing eye movements and visual attention, receiving some direct retinal input
What is the role of hierarchical processing in the visual system
: Visual information is processed in increasingly complex ways, from simple light detection in the retina to detailed object and face recognition in higher cortical areas.
What are simple and complex cells in V1?
imple cells: Respond to edges of a specific orientation at a specific location.
Complex cells: Respond to edges of a preferred orientation regardless of exact position.
What are orientation columns in V1?
: Groups of neurons in V1 that respond preferentially to edges of a specific orientation, organized in a systematic fashion.
What is the difference between the dorsal and ventral visual pathways?
Dorsal stream: Processes spatial location and motion (“where” pathway).
Ventral stream: Processes object identity and recognition (“what” pathway).
How does damage to the visual pathway affect perception?
Optic nerve damage: Leads to blindness in one eye.
Optic chiasm damage: Causes loss of peripheral vision in both eyes.
Damage to V1: Results in cortical blindness, where the eyes function but no conscious visual perception occurs.
Q: What is blindsight?
A phenomenon where individuals with damage to V1 can respond to visual stimuli without conscious awareness, due to alternative visual pathways like the superior colliculus
How does the brain compensate for the blind spot?
he brain fills in missing visual information using surrounding context and patterns.
What is visual field representation in the brain
he left visual field is processed in the right hemisphere, and the right visual field is processed in the left hemisphere due to optic nerve crossings at the optic chiasm.
at is the role of motion-sensitive neurons?
Neurons in the dorsal stream detect and process movement, essential for tracking moving objects and spatial navigation.
What are face-selective neurons?
Found in the fusiform face area (FFA), these neurons specialize in detecting and recognizing faces.
What is the retinotopic map?
A spatial organization of visual information in the brain that preserves the layout of the retina.
What are edge detectors in the visual system?
Neurons in V1 that detect contrast between light and dark areas, essential for identifying object boundaries.
What is the role of color processing in vision?
Color information is processed by cones in the retina and further analyzed in the visual cortex, primarily in V4.
How does the brain process depth perception?
Depth is determined using binocular disparity, motion parallax, and monocular depth cues to reconstruct a 3D representation of the environment.
What is the function of the parietal cortex in vision?
The parietal cortex integrates spatial and motion information, crucial for visually guided actions and attention control.
How do eye movements affect visual processing?
Eye movements, controlled by the superior colliculus and other brain structures, help direct visual attention and stabilize images on the retina.
You visual system is cross-wired
Right hands is represented in the left hemisphere of my brain, left hemisphere is the left hemisphere
Know the parts of the brain
Have apicture of the brain
Perceptive Fields V1
Looking for the firing rates
The brain pefers movement?
True or false?
V1? does what?
Retinitis map in Visual cortex. it becomes like a mirror
why is there cortical magnification?
The density of ganglion cells encoding visual information decreases form the center of the visual field to the periphery
Ganglion cells representing central vision provide finer grained info (higher resoulution)
V1 is oriented from what?
Record from a neuron from the. brain. Stimulate photoreceptors on the retina, determine which patterns of light causes the pattern.
What is the primary focus of the lecture?
The lecture focuses on computational theories of visual cortex organization, specifically the distinction between the “what” and “where” pathways.
Q: What are the two major processing streams in the visual cortex?A:
Ventral Stream (What Pathway): Processes object recognition, identity, and detailed visual properties.
Dorsal Stream (Where Pathway): Processes spatial location, motion, and visually guided actions.
What evidence supports the existence of the ventral and dorsal streams?
vidence includes lesion studies in both humans and animals, where damage to specific regions results in selective impairments in object recognition (ventral) or spatial processing (dorsal).
What experimental paradigm was used to study these pathways in monkeys?
: The Object Discrimination Task (ventral stream) and Landmark Location Task (dorsal stream) were used, demonstrating selective impairments when lesions were applied to the respective pathways
: What is double dissociation, and how does it relate to the ventral and dorsal streams?
Double dissociation occurs when two related cognitive functions are shown to be independently impaired by damage to different brain regions, supporting the specificity of the “what” and “where” pathways.
How do patients with ventral stream damage behave?
A: Patients struggle to recognize objects visually (visual agnosia) but can identify objects through other sensory modalities, such as touch.
How do patients with dorsal stream damage behave?
Patients struggle with spatial coordination and visually guided actions (optic ataxia) but can still recognize objects normally.
What is an example of a patient with ventral stream damage?
A: Patient DF, who had damage to the lateral occipital cortex (LOC) and exhibited severe visual agnosia but intact motor responses to objects.
What experiment demonstrated DF’s dissociation between perception and action?
The posting task, where DF could not match a card’s orientation to a slot but could accurately insert the card when asked to perform the action.
What are single-unit recordings, and what do they reveal about the ventral stream?
Single-unit recordings involve measuring the activity of individual neurons, showing that specific neurons in the inferior temporal cortex respond selectively to complex objects like hands and face
How do fMRI studies support the distinction between the two streams?
A: Functional imaging studies show distinct activation in the ventral stream during object identification tasks and in the dorsal stream during spatial tasks.
What is object constancy, and why is it computationally challenging?
Object constancy refers to the ability to recognize an object despite changes in viewpoint, lighting, or occlusion. It is difficult because retinal images vary drastically based on these conditions.
What are Gestalt principles, and how do they contribute to visual perception?
A: Gestalt principles are rules governing perceptual organization, including:
Proximity: Objects near each other are grouped together.
Similarity: Similar objects are perceived as belonging to the same group.
Closure: The mind fills in missing information to create complete objects.
Good Continuation: Elements following a similar direction are perceived as connected.
What is top-down processing in vision?
Top-down processing is when prior knowledge and expectations influence visual perception, helping to interpret ambiguous stimuli.
What is the Template Matching Theory of object recognition?
A theory suggesting that objects are recognized by comparing them to stored templates. However, this theory is limited because objects appear in many different variations and orientations.
What is the Recognition by Components (RBC) theory?
A: RBC theory proposes that objects are recognized by decomposing them into basic 3D shapes (geons) and identifying their spatial arrangement.
What are the limitations of Recognition by Components theory?
It does not explain object-specific details like texture or color, and it oversimplifies real-world object perception.
What and where ?
Double dissociation money
What were they effected?
Rv
Df
Can’t recognize the object but can grasp it.
