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How does information travel from the thalamus to primary visual cortex
The optic radiations
Primary visual cortex is also known as _______ and is located within the _________.
V1, Calcarine sulcus
The visual cortex is arranged _________, with adjacent lights flashing on the eye activating adjacent regions of primary visual cortex.
Retinotopically
In class, we stared in the center of a faint blue ring. Within a few seconds, the ring started to fade, and eventually the ring disappeared completely! This is an example of __________
Visual adaptation
In visual object recognition, we must solve with the problems of ________ (correctly separating objects from their background) and __________ (inferring when an object is partially blocked from view).
Segregation, occlusion
Optic Ataxia is caused by damage to the ___________
dorsal pathway
Patient DF was diagnosed with profound visual agnosia. She would be able to do all of the following EXCEPT
Copy a picture of an apple
Because of __________, visual information from the fovea is represented in a ________ region of visual cortex
cortical magnification, larger
what can we conclude about visual development from selective rearing experiments conducted on cats?
The perceptual inputs that young infants do (or do not) receive are very important in their brain development
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Gestalt psychologists
What is orientation tuning? What experiment would a neuroscientists run to determine the orientation turning of a particular neuron in primary visual cortex?
The process by which neurons in the visual cortex respond to the orientation of a visual stimulus. It shows stronger responses as the stimulus gets closer to the preferred orientation. Plotting the data would result in the creation of an "orientation tuning curve." The neuron's firing rate is displayed in this curve for every stimulus orientation. The curve's peak indicates the neuron's most responsive orientation.
Describe the law of similarity and the law or proximity. Give two real-world examples of how your brain might group together objects based on these principles (one example of each).
According to the Law of Proximity, things that are near one another are seen as belonging together. An example of a law of proximity is in contrast to people scattered, people standing or sitting close to one another in a group (such as at a meeting or concert) are perceived as one unit. For the Law of Similarity, We group objects that are similar in appearance (e.g., color, shape, size) as being part of the same set, an example of this is when people wearing the same uniform or color in a group photo are viewed as part of the same team or event.
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Global image information, peripheral vision
People with prosopagnosia have difficulty recognizing _________.
None of the above
Tools
Objects
Scenes
Animals
none of the above
According to __________, objects are recognized as arrangements of simpler 3-d shapes called “geons”.
Recognition by components theory
True of false: Viewing human faces and "greebles" activates the same regions of the fusiform gyrus, and this occurs even when seeing "greebles" for the first time.
false
Region "LO" is on the lateral (outside) part of the fusiform gyrus and is important for processing _________________
objects
Describe the "change blindness" demonstration we did at the end of class on Tuesday. What happened? What did you need to do to notice the change?
Answer:
On Tuesday, A picture on a beach was shown, then a blank blue screen, and then the picture of the beach was shown again. Many of us didn't recognize in that picture shown after the blank that it was a change in a picture. It took us a lot of time to recognize that a group of people on the right side of the disbanded from the photo. The only way we efficiently recognized a difference in both photos was when the blank blue screen was removed. Change blindness is a perceptual phenomenon that occurs when a change in a visual stimulus is introduced and the observer does not notice it. We did not notice the change due to the blank blue screen acting as a distraction which diverted our attention away from the change.
Retinotopy
Visual regions are arranged retinotopically:
Retinotopy is the process of mapping visual information from the retina to the brain. It's also known as retinal mapping. Regions that are adjacent on the retina are processed in adjacent regions of visual cortex
•To summarize: columns
in V1 are organized
spatially based on
•Retinotopy
•Orientation selectivity
•Ocular dominance
cortical magnification
Cortical magnification is how the brain gives more attention to certain parts of what we see. It means more brain cells are used to process things we look at directly (like words on a page) because our central vision (the fovea) has more receptors and needs more brain power to understand details.
retinotopic maps
A retinotopic map is like a brain map that shows how we see the world. It organizes brain cells to match the layout of what we see, so areas next to each other in our vision are processed by nearby brain cells. Scientists can see these maps in the brain’s visual cortex using fMRI scans.
Simple cortical cells
A simple cell in the primary visual cortex is a cell that responds primarily to oriented edges and gratings (bars of particular orientations). Torsten Wiesel and David Hubel discovered these cells in the late 1950s. •Simple cortical cells in V1 respond best to a narrow bar of light with a particular orientation
orientation tuning curve
An orientation tuning curve is a graph that shows how a neuron responds to different orientations. It's used to study how neurons in the visual cortex process lines and edgesshowing stronger responses as the stimulus gets closer to the preferred orientation
adaptation
To find behavioral evidence of orientation selectivity we can use selective adaptation (Selective adaptation is a phenomenon in psychology where prolonged exposure to a specific stimulus results in a temporary decrease in sensitivity to that stimulus. It is a form of sensory adaptation that occurs in various sensory systems, including vision, hearing, and touch)
When a neuron fires over and over it gets fatigued, and, for a short time, is less able to respond
type of cell
ocular dominance
•Whether input comes from the left eye or the right eye
Ocular dominance is the tendency of the brain to prefer visual input from one eye over the other.
Experience Dependent Plasticity
Selective Rearing - When animals are deprived of visual inputs, early in development, the neurons that respond to that feature gradually disappear
When deprived of horizontal inputs as kittens, they don’t respond to horizontal rods as adult cats
When deprivation occurs in a critical period it is permanent and the animals don’t recover
Ventral pathway
the downward pathway that processes “what” information about the environment
Damage causes problems in visual object recognition (visual agnosia)
dorsal pathway
the upward pathway that processes “where” and “how” information about objects
Damage causes difficulty localizing and interacting with objects (optic ataxia)
visual agnosia optical ataxia gripping experiment
RV- dorsal lesion optical ataxia
DF- ventral lesion visual agnosia
Segregation
Objects need to be separated from their background
grouping
We need to figure out which elements are connected (and which aren’t)
occlusion
We need to correctly infer when an object is partially blocked from view
Gestalt psychologists
•Rather than segregating the elements of perception, Gestalt psychologists focused on the integration of objects and sensations to create meaning
•Holism – the whole is greater than the sum of the parts
•Identified common cognitive tools we use to organize and categorize objects
law of common region
The principle of common region says that items within a boundary are perceived as a group and assumed to share some common characteristic or functionality
a website layout where different sections of content are clearly separated by distinct boxes or borders, making it easy for users to perceive each section as a separate group
law of continuity
The Gestalt Principle of Continuity states that we are more likely to see continuous and smooth flowing lines rather than broken or jagged ones.
Movies: The brain stitches together many individual shots into a continuous storyline.
law of closure
if there is a break in the object, we perceive the object as continuing in a smooth pattern. For example, in the circle below, we tend to see a complete circle with something over top of it.
law of good figure
the law of symmetry and order is also known as prägnanz, the German word for “good figure.” What this principle says is that your brain will perceive ambiguous shapes in as simple a manner as possible
Olympic Logo: The Olympic logo, with its five interlocking rings, is perceived as a series of overlapping circles, not a collection of connected curved lines.
phi phenomena
The phi phenomenon is an optical illusion in psychology that creates the perception of motion when stationary objects are presented in rapid succession
viewing flip book images that seem to be moving as you turn the pages quickly
Common Fate
Objects moving in parallel with the same velocity are grouped together
flock of birds flying in formation
Uniform Connectedness
•A connected region with the same color, texture, or lightness is treated as a single unit
. One example of this is when you can see the image that will be made on a connect the dots picture before you connect the dots.
Figure and Ground
•An object (or figure) has to be perceptually segregated from its surroundings (the ground)
•Figures are more memorable and often perceived as “in front” of the ground
•Border ownership - The border separating the two appears to belong to the ground, defining its shape
•Figures usually appear “above” the ground
•Earth vs. sky
geons
Geons are simple, three-dimensional shapes like cylinders, cones, and blocks that serve as the basic building blocks of all objects we recognize. According to Recognition-by-Components (RBC) Theory, proposed by Irving Biederman, objects are recognized by breaking them down into their component geons and understanding the relationships between them.
all geons shared
no geons shared
Biederman cooper 1991
evidence for recognition by components theory
•For each complementary pair, no edges are shared
•But the top pair looks much more similar than the bottom pair, and this top pair results in more priming
•Faster to recognize one after being previously exposed to the other
•This suggests that geons are being stored in memory, not edges
Scene Recognition
We can recognize scenes extremely rapidly, identifying their gist (the general impression of a familiar location, e.g. kitchen) within a fraction of a second
Rather than identifying lots of objects, we likely use global image features to recognize scenes
Color, texture, naturalness, openness
( in the ventral stream)
rossel et al 2022
Rossel et al. (2022) had participants adjust how blurry an object looked until it matched a blurry reference image. They found that when the object was in a fitting scene (like a printer in an office), participants made the object blurrier than needed. This happened because the brain was using the familiar scene to make the object seem clearer than it actually was, so participants added more blur to compensate for this perceptual boost from the context.
Inverted faces
•are difficult to recognize
•This provides evidence for face expertise (in a particular orientation), and that we process faces holistically as arrangements of features rather than individual elements
•Certain regions of the temporal cortex become specialized for face recognition
•The fusiform face area-a part of the human visual system that is specialized for facial recognition. It is located in the inferior temporal cortex
prosopagnosia
•Individuals with prosopagnosia are unable to recognize people from their faces alone
•But have no difficulty recognizing other complex objects
greebles
Participants were trained to identify novel non-face objects (“greebles”) over 10 days. Over time, they started to show fMRI activation to greebles in the same regions of fusiform cortex used for face processing
This region is now tuned to identify and distinguish these complex objects
selective attention
•selecting only a subset of sensory information for further processing
•Involves boosting the strength of relevant information
•And “filtering out” or suppressing irrelevant information
Attention Theories: Spotlight Model
•Attention is often described as a “visual spotlight”
•We can focus our conscious attention on a subset of the visual field
•Anything outside of the spotlight is not processed as deeply (and might not be recognized or remembered)
•Spotlight and eye location aren’t always the same– we can see without directly looking
overt attention
the position of our eyes
covert attention
the focus on our mind
change blindness
•When we fail to notice a major change in a visual scene because it was outside our scope of attention
•Particularly common when there’s a flicker between images
change blindness studies
•Addicts are faster to detect the disappearance of an object of addiction in a flickering scene
•e.g. alcoholics detect a disappearing vodka bottle sooner than a control object, Jones et al (2006)
•Change blindness also occurs in other senses
•A voice changing to another person in a phone conversation Vitevich (2003)
dichotic listening
•: When different messages are played to the left and right ear
•Participants are often asked shadow one ear: repeat what they hear
•People remember almost none of the
content from the unattended ear
•But they do notice: Changes in speaker pitch/gender
cocktail party affect
The cocktail party effect is the ability to focus on a single sound while ignoring other sounds.
example hearing your name over multiple sounds/voices
attention affects early sensory processing
Selective spatial attention affects early sensory brain response (Luck, Woodman & Vogel, 2000)
The study explored how paying attention to a specific area affects the brain's early response to visual information. Participants were asked to focus their attention on one side of the screen while keeping their eyes fixed on the center (using "covert attention"). The results showed that when visual flashes appeared on the side they were attending to, the brain responded more strongly than when the flashes appeared on the side they ignored. This effect occurred very quickly, within 100 milliseconds. The study com the start.hallenges earlier theories, like Deutsch & Deutsch's (1963), which suggested that attention only influences memory, not how we perceive things. The findings indicate that attention actually shapes how we process visual information right fr
Attention affects responses
of individual neurons
•Attended stimuli cause 1) stronger, 2) more sustained, and 3) more consistent neural responses than unattended stimuli
•When we attend to a task, the neurons that code for the attended stimulus are more likely to fire together (in synchrony)
•Helps explain how attention helps “bind” different features of an object (e.g. color and shape)
Attention makes neurons more sensitive, and lowers detection thresholds for faint stimuli
Attentional Guidance
•Attention can be directed by top-down goals
•Locations that are “cued” or that receive greater rewards will quickly attract our attention
•Targets appearing in an attended location are processed more quickly and accurately
•Attention can also be captured automatically by salient or contrasting stimuli
eye tracking
•We can use eye-tracking to monitor people’s eye-movements and attention in real time
ADHD
•Attention Deficit Hyperactivity Disorder (ADHD) is marked by executive dysfunction
•Inattention – an inability to focus one’s attention for sustained periods or plan for future goals
•Impulsivity – an inability to control or regulate one’s emotions or behavior
•Hyperactivity – Excessive talking and motor activity in inappropriate situations
•These differences are pervasive and disabling, causing problems with employment, academic performance, and relationships
eye movements
•Our eyes rest on one point briefly (fixation) for 200-300ms and then jump suddenly to a new location (saccade)
•200,000 new fixations per day!
•Rapid eye-movements allow us to quickly sample information in the environment
corollary discharge
When we move our eyes, the image on our retina becomes blurry and smeared. However, we don’t feel like the world is moving along with our eyes. To avoid this, the brain compares two signals: one from the visual field image displacement (the sudden shift in what we see) and one from a copy of the signal that tells our eyes to move (the corollary discharge).For example, when you move your eyes to the right, your brain sends a corollary discharge to other parts of the brain to let them know that the movement is self-generated, not caused by something outside (like a person or an object moving). If the image shift doesn't match what the brain predicted from the eye movement signal, we perceive movement in the world around us.
visual attention and reading
When we read, our eyes stop (or "fixate") on individual words, usually just to the left of the center of the word.
Sometimes, our eyes move too far or not far enough when jumping to the next word.
If we don’t understand a sentence or make a mistake, our eyes often move back to earlier words (called "regressions" or "backward saccades").
We spend more time looking at words that are: 1) longer, 2) less common, or 3) harder to predict.
Words we don’t focus on closely aren’t processed for meaning (we don’t understand them deeply).
However, even if we don’t focus on a word, it can still help us understand a nearby word we're trying to read.
Object-based Attention
Object-based attention describes a type of visual attention where the focus is on individual objects within a scene, rather than on specific locations or features.
feature based attention
•We also have feature-based attention that helps us detect certain features, regardless of location (e.g. color, direction of motion)
spatial neglect
Damage to the parietal lobe can cause spatial neglect for one-half of the visual field
Normal vision, but trouble attending and responding to objects to one side
This applies not just to physical objects but also to scenes in the “mind’s eye”
object based attention
A: Attending to entire objects rather than specific spatial locations, providing a same-object advantage in detection.
Q: What did Egly et al. (1994) discover about object-based attention? A: Participants responded faster to targets within the same object compared to equally distant targets on different objects. In other words, attention doesn't just focus on a specific point in space; it can also be focused on an entire object.
What did Luck, Woodman & Vogel (2000) demonstrate about attention and neural responses?
Visual flashes produce stronger neural responses at attended locations, indicating early sensory processing is affected by attention.
What does the ERP method show about attended stimuli?
Attended stimuli cause stronger, more sustained, and more consistent neural responses than unattended stimuli.
What is the Posner Cueing Paradigm?
A method to study spatial attention by cueing specific locations, revealing faster responses when targets appear at cued spots.
What is optic flow?
Optic flow is the motion of objects across the retina as we move in space. Near objects appear to move more quickly than those farther away, indicating speed and direction.
What is the focus of expansion (FOE) in optic flow?
FOE is the point from which objects appear to flow outward, indicating our destination.
What did the blindfolded gymnast study (Bardy & Laurent, 1998) demonstrate?
: It showed that movements are more accurate when combining information from multiple senses rather than relying on motor information alone
What are the key cues for motion perception?
A: Vision, body senses (muscles and joints), and vestibular senses (balance sense from the inner ear).
What did the swinging room study (Lee & Aronson, 1974) show?
Visual cues alone can induce optic flow, causing people to overcompensate and even fall over without true motion.
How accurately do humans walk in a straight line when lost? (Souman et al., 2009)
Humans walk straight only when the sun or moon is visible. In darkness or blindfolded, they walk in tight circles due to noise buildup in perceptual systems.
What is a cognitive map
It is a mental representation of our environment and current location used for navigation rather than simple stimulus-response associations.
What are place cells and grid cells?
A: Place cells in the hippocampus fire when entering a particular location in a familiar area. Grid cells in the entorhinal cortex fire in a hexagonal grid pattern, tracking distance and direction through space.
affordance
•Affordance – an object’s potential for action
: What are affordances in object perception?
A: Affordances are an object's potential for action, quickly activated in dorsal sensorimotor regions (~200ms).
What is the affordance interference effect? A: It occurs when responding to an object with a different grip than the one typically used, resulting in slower responses.
•In the dorsal pathway, the parietal reach region encodes an object’s location in space and what grip we need to use to interact with it
what is proprioception
Proprioception is the sense of body position and movement, essential for coordination and balance.
vestibular sense
Sense of balance and movement that helps you maintain your equilibrium and orientation. It's also known as the gravity sense.
What happens when proprioceptive inputs are lost?
People struggle to coordinate movements unless they visually monitor their body, highlighting the role of prediction and corollary discharge.
What are mirror neurons?
Mirror neurons respond both when we perform an action and when we see someone else perform the same action. They are found in frontal and parietal regions.
What did the taxi driver study (Maguire, 2006) show?
Taxi drivers, particularly those navigating difficult cities like London, have increased volume in the posterior hippocampus compared to bus drivers.
What are individual differences in navigation strategies? (Boone et al., 2019)
Some people prefer using landmarks, others use cardinal directions. Men are more likely to take shortcuts, even with explicit instructions.
Which of the following is NOT true?
Visual attention is determined only in a bottom-up fashion by salient information in our environment
Eye movements in a visual scene are affected by ____________________
All of the above
Answers:
Salience and low-level contrast
Our goals or current task (e.g. remember clothing)
The presence of meaningful or interesting objects
Which of the following is NOT a common symptom for individuals with attention deficit hyperactivity disorder (ADHD)?
A lack of empathy or inability to understand other’s emotions
Eye-movements are made up of _________ (when the eyes pause briefly on a location) and ________ (rapid jumps to a new location).
Fixations, saccades
Which of the following is true about reading?
We plan regressive eye movements when we have difficulty understanding a sentence
tell you to attend to things appearing on the left side of your vision. To perform this task, you would mainly need to use _______
Spatial attention
Based on our discussion of attention and driving, which of these is probably the most dangerous to do while behind the wheel?
Looking down to quickly send a text message
A spatial neglect patient has difficulty attending to objects in their LEFT visual field. They likely have damage to ________________.
The right parietal cortex
As we move through space, there is no optic flow at the _________, which indicates our ultimate destination.
focus of expansion
Tolman’s maze study demonstrated the existence of __________ in rats
cognitive maps
object affordances and their sensori-motor associations are mainly processed in the _____
dorsal stream
Explain the “corollary discharge” in vision. How can this explain why we see we perceive that the world is holding still, even as we move our eyes rapidly around a scene?
When our eyes move, the image on our retina becomes blurry, but we don’t feel like the world is moving. This happens because our brain has a way of canceling out the effects of eye movements. It does this by creating a copy of the signal it sends to move our eyes, called the corollary discharge. When our eyes move, the entire visual scene shifts, which is known as image displacement. The brain compares the corollary discharge, which is its prediction of the movement, with the actual image displacement. If the shift matches the prediction, the brain knows it’s caused by our eye movements and ignores it. However, if there’s a mismatch, the brain detects it as real movement happening in the world. This process allows us to see a stable world even when our eyes are constantly moving.
When we are in motion, we combine information from multiple senses to track our location and movement in space. Describe an experiment or case study we discussed in class that demonstrates this principle.
The study by Bardy and Laurent (1998) with blindfolded gymnasts demonstrates how we combine information from multiple senses to track our location and movement in space. In this experiment, gymnasts performed complex movements, such as somersaults, while being blindfolded. Without visual input, they had to rely heavily on other senses, particularly their vestibular (balance) system and proprioceptive (body position) cues, to maintain orientation and control their movements.
The findings showed that experienced gymnasts were still able to perform the movements with impressive accuracy despite the lack of visual information. This suggests that the brain effectively integrates sensory information from the vestibular system and proprioception to monitor motion and spatial orientation. It also highlights how the brain can adapt to the absence of one sense (vision) by enhancing its reliance on other sensory inputs to maintain balance and spatial awareness
