Midterm Flashcards
What’s the difference between the physical world and the psychological dimension
- Physical world = environment that’s outside of us
- Psychological dimension = how we experience things that are outside of us/our minds
Why can’t we see/perceive the different electromagnetic waves?
- Because we don’t have any receptors for them
- Except for the visual spectrum because we have receptors for these (why we can see and perceive them)
What kind of mechanism are receptors compared to?
A lock and key mechanism
What’s perception?
- Whatever your brain makes of the activation of receptors by external stimuli
- OR the experiences that result from stimulation of the senses
- How we experience the world through our senses
- Identified with complex processes that involve higher-order mechanisms such as interpretation and memory that involve activity in the brain
- Ex: identifying the food you’re eating and remembering the last time you had it
What’s sensation?
- Detection of stimulus
- Often identified as involving simple “elementary” processes that occur right at the beginning of a sensory system
- Ex: when light reaches the eye, sound waves enter the ear, or food touches the tongue
Give an example of the easy VS hard problem of consciousness
- Easy problem: figuring out how the detection of colour occurs
- Hard problem: how is that processing of stimuli suddenly turned into the perception of a colour? Neuroscientists don’t know how to answer this
TRUE OR FALSE: Different organisms have different perceptual capabilities
TRUE: Different organisms have different perceptual capabilities -> due to having different receptors
How many steps inside a person’s brain describe the process of perception?
7 steps, plus “knowledge”
What are the steps of the perceptual process?
- Stimulus in the environment
- Stimulus hits the receptors (light is reflected and focused)
- Receptor processes
- Neural processing
- Perception
- Recognition
- Action
+ “Knowledge” inside the person’s brain
What’s transduction?
- Crucial for perception
- In the senses, refers to the transformation of environmental energy to electrical energy
Why does transduction occur with light energy?
The brain doesn’t understand light energy, so it’s transferred into electrical energy which is understood by the brain (electrical-chemical energy)
What steps of the perceptual process correspond to knowledge?
- Perception
- Recognition
Describe distal stimulus
- Actual image
- The stimulus “out there” in the external environment
- “Distant”
Describe proximal stimulus
- The representation of the distal stimulus on the receptors
- Stimulus is “in proximity” to the receptors
- Patterns of wavelengths reflected on retina are the proximal stimulus
What’s environmental stimuli?
All objects in the environment that are available to the observer
What’s the principle of transformation?
When the stimuli and responses created by stimuli are transformed, or changed, between the environmental stimuli (distal stimuli) and perception
What’s neural processing?
- Changes that occur as signals are transmitted through the maze of neurons
- Involves interactions between the electrical signals travelling in networks of neurons
- Operations that transform electrical signals within a network of neurons or that transform the response of individual neurons
What forms the optic nerve?
Retinal ganglion cells
What are sensory receptors?
- Cells specialized to respond to environmental energy, with each sensory system’s receptors specialized to respond to a specific type of energy
- Sort of like a bridge between the external sensory world and your internal (neural) representation of that world
What does transduction do with environmental energy?
It changes environmental energy to nerve impulses
What do rod and cone receptors do with light energy?
They transform it into electrical energy and influence what we perceive
What do visual pigments do?
React to light
TRUE OR FALSE: the primary visual cortex is the only part of the brain that processes visual information
FALSE: The Primary visual cortex is not the only part of the brain that processes visual information -> visual info also goes to the temporal and parietal lobes
- Blindsight happens to people who have damage to their visual cortex
- If they can’t perceive the light, how can they know where the dots are moving or that there are obstacles?
- Because visual info doesn’t only go in the visual cortex but in other brain areas too (leads to processing visual information in an unconscious manner)
Where does recognition take place in the brain?
In the temporal lobe
What part of the brain corresponds with “Vision for action”?
Parietal lobe
Electrical signals are transformed into what?
Conscious experience
Describe the perceptron
- An electronic computer
- “Perceiving machine”
- Expected to be the 1st non-living mechanism able to perceive, recognize & identify its surroundings without human training or control
- The 1st Perceptron could teach itself to distinguish between basic images -> but couldn’t do complex tasks
- Rosenblatt claimed that this computer could “learn to recognize similarities or identities between patterns of optical, electrical, or tonal information, in a manner which may be closely analogous to the perceptual processes of a biological brain
What do many consider to be a key precursor to modern artificial intelligence?
Rosenblatt’s Perceptron
Why can computers still not perceive as well as humans?
The problem is that computers don’t have the huge storehouse of information that humans begin accumulating as soon as they’re born
Perception starts with _____ and then moves on to the _____
- The detectors (located in the eyes, ears, skin, tongue, nose and mouth)
- The “computer” (the brain)
TRUE OR FALSE: the mechanisms responsible for perception are extremely complex
True
What are some medical applications that depend on an understanding of perception?
- Devices to restore perception to people who have lost vision or hearing
- Treatments for pain
What are some applications of the understanding of perception in the real-world?
- Autonomous vehicles
- Face recognition systems
- Speech recognition systems
- Highway signs
Everything we see, hear, taste, feel, or smell, is the result of what?
The activity in our nervous system and our knowledge gained from past experience
Perception depends on what?
The properties of the sensory receptors
What’s the difference between sensation and perception?
Sensation involves detecting elementary properties of a stimulus and perception involves the higher brain functions involved in interpreting events and objects
What’s the perceptual process?
A sequence of steps leading from the environment to perception of a stimulus, recognition of the stimulus and action with regard to the stimulus
What’s the difference between distal stimulus and proximal stimulus?
Information about the stimulus in the environment (distal stimulus) hits the receptors, resulting in the proximal stimulus
What are receptor processes?
They include transduction and the shaping of perception by the properties of the receptors
What’s the retinotopic map?
- Map of the retina on the cortex
- This organized spatial map means that two points that are close together on an object and on the retina will activate neurons that are close together in the brain
Why is the spatial representation of the visual scene on the cortex considered distorted?
Because there’s more space in the cortex being allotted to images located near the fovea than to images located in the peripheral retina
What’s cortical magnification?
- Occurs when a disproportionately large area on the cortex is activated by stimulation of a small area on the receptor surface
- Ex: the relatively large area of visual cortex that is activated by stimulation of the fovea.
- Although the fovea accounts for only 0.01% of the retina’s area, signals from the fovea account for 8-10% of the retinotopic map on the cortex
What’s the cortical magnification factor?
The size of the cortical magnification effect
How has cortical magnification been determined in the human cortex using brain imaging?
- Robert Dougherty and coworkers (2003) had participants in the fMRI scanner look at stimuli
- The participant looked directly at the center of the screen, so the dot at the center fell on the fovea
- During the experiment, stimulus light was presented in two places: (1) near the center, which illuminated a small area near the fovea; and (2) farther from the center, which illuminated an area in the peripheral retina
- This illustrated cortical magnification because stimulation of the small area near the fovea activated a greater area on the cortex than stimulation of the larger area in the periphery
What’s the purpose of cortical magnification in the visual system?
- The extra cortical space allotted to letters and words at which the person is looking provides the extra neural processing needed to accomplish tasks such as reading that require high visual acuity
- Also, when you look at a scene, information about the part of the scene you are looking at takes up a larger space on your visual cortex than an area of equal size that is off to the side
- That more space on the cortex translates into better detailed vision rather than larger size which is an example of the fact that what we perceive doesn’t exactly match the “picture” in the brain
Who carried out a series of experiments in which they recorded from neurons they encountered as they lowered electrodes into the visual cortex?
Hubel and Wiesel
What did Hubel and Wiesel find when they inserted an electrode perpendicular to the surface of a cat’s cortex?
- They found that every neuron they encountered had its receptive field at about the same location on the retina
- Also that these neurons all preferred stimuli with the same orientation
What did Hubel and Wiesel conclude about location columns in the striate cortex?
They concluded that the striate cortex is organized into location columns that are perpendicular to the surface of the cortex, so that all of the neurons within a location column have their receptive fields at the same location on the retina (they overlap)
What are location columns?
A column in the visual cortex that contains neurons with the same receptive field locations on the retina
What did Hubel and Wiesel conclude about the cortex and orientation columns?
They concluded that the cortex is also organized into orientation columns, with each column containing cells that respond best to a particular orientation
What are orientation columns?
A column in the visual cortex that contains neurons with the same orientation preference
What did Hubel and Wiesel conclude when they moved an electrode through the cortex obliquely, so that the electrode cut across orientation columns?
- They found that the neurons’ preferred orientations changed in an orderly fashion, so a column of cells that respond best to 90 degrees is right next to the column of cells that respond best to 85 degrees
- They also found that as they moved their electrode 1 mm across the cortex, their electrode passed through orientation columns that represented the entire range of orientations
What’s the size of one location column?
- 1mm
- Meaning that one location column is large enough to contain orientation columns that cover all possible orientations
What’s a hypercolumn?
- A location column that a receives information about all possible orientations that fall within a small area of the retina
- Any oriented edge or line that falls within the location column’s area on the retina will be able to be represented by some of the neurons in this location column
- It’s therefore well suited for processing information from a small area in the visual field
TRUE OR FALSE: The cortical representation of a stimulus does not have to resemble the stimulus
TRUE: The cortical representation of a stimulus does not have to resemble the stimulus; it just has to contain information that represents the stimulus
What’s tiling?
- The adjacent (and often overlapping) location columns working together to cover the entire visual field (similar to covering a floor with tiles)
What’s the extrastriate cortex?
- Collective term for visual areas in the occipital lobe and beyond known as V2, V3, V4, and V5
- Referred to as the extrastriate cortex, since they are outside of the striate cortex
What happens as we move from V1 to higher-level extrastriate areas?
- The receptive field sizes gradually increase
- The representation of the visual scene builds as we move up this hierarchy of extrastriate cortex areas, adding more and more aspects of the visual scene such as corners, colors, motion, and even entire shapes and objects
What happens when the visual signal leaves the occipital lobe?
It continues through different “streams” or pathways that serve different functions
What did Leslie Ungerleider and Mortimer Mishkin find with their research on visual pathways?
They presented evidence for two streams serving different functions that transmit information from the striate and extrastriate cortex to other areas of the brain
What technique did Ungerleider and Mishkin (1982) use to better understand the functional organization of the visual system?
Ablation (aka lesioning)
What’s ablation?
- Destruction or removal of an area of the brain (or of tissue in the nervous system)
- This is usually done in experiments on animals to determine the function of a particular area
- AKA lesioning
Describe the method of brain ablation (lesioning)
- The goal of a brain ablation experiment is to determine the function of a particular area of the brain
- First, an animal’s ability to carry out a specific task is determined by behavioral testing
- Once the animal’s performance on a task has been measured, a particular area of the brain is ablated (removed or destroyed), either by surgery or by injecting a chemical that destroys tissue near the place where it is injected
- After ablation, the monkey is retested to determine how performance has been affected by the ablation
Why are brain lesioning experiments usually conducted on monkeys?
Because of the similarity of their visual system to that of humans and because monkeys can be trained in ways that enable researchers to determine perceptual capacities such as acuity, color vision, depth perception, and object perception
In their experiments on visual pathways, what two behavioural tasks did Ungerleider and Mishkin present monkeys with?
- Object discrimination problem
- Landmark discrimination problem
Describe the object discrimination problem in Ungerleider and Mishkin’s experiment with monkeys
- A monkey was shown one object, such as a rectangular solid, and was then presented with a two-choice task which included the “target” object (the rectangular solid) and another stimulus, such as the triangular solid
- If the monkey was able to discriminate between the two objects and thus push aside the target object, it received the food reward that was hidden in a well under the object
- When part of the temporal lobe was removed in some monkeys, behavioral testing after lesioning (ablation) showed that the object discrimination problem was very difficult for these monkeys
Describe the landmark discrimination problem in Ungerleider and Mishkin’s experiment with monkeys
- The monkey’s task was to remove the cover of the food well that was closest to the “landmark”—in this case, a tall cylinder
- When monkeys had their parietal lobes removed, they had difficulty solving the landmark discrimination problem
What did Ungerleider and Mishkin call the pathway leading from the striate cortex to the temporal lobe?
- The “what” or ventral pathway
- Since their results indicate that the pathway that reaches the temporal lobe is responsible for determining an object’s identity
What did Ungerleider and Mishkin call the pathway leading from the striate cortex to the parietal lobe?
- The “where” or dorsal pathway
- Since their results indicate that the pathway that leads to the parietal lobe is responsible for determining an object’s location
What’s the ventral pathway?
- Pathway that conducts signals from the striate cortex to the temporal lobe
- Also called the “what” pathway because it is involved in recognizing objects
What’s the temporal pathway?
- Pathway that conducts signals from the striate cortex to the parietal lobe
- Has also been called the where, the how, or the action pathway by different investigators
What did researchers discover about the relationship between the dorsal and ventral streams and the retina and LGN?
- Using the techniques of both recording from neurons and ablation, they found that properties of the ventral and dorsal streams are established by two different types of ganglion cells in the retina, which transmit signals to different layers of the LGN
- The cortical ventral and dorsal streams can actually be traced back to the retina and LGN
In what direction do signals flow along the dorsal and ventral visual pathways?
- Signals flow not only “up” the pathway from the occipital lobe toward the parietal and temporal lobes but “back” as well
- AKA feedback
- The “backward” flow of information provides information from higher centers that can influence the signals flowing into the system
TRUE OR FALSE: the dorsal and ventral pathways are completely separate from each other
FALSE: the pathways are not totally separated but have connections between them
- In our everyday behavior we need to both identify and locate objects, and we routinely coordinate these two activities every time we identify something and notice where it is
- Thus, there are two distinct pathways, but some information is shared between them
What did Milner and Goodale propose about the dorsal stream?
- They proposed that the dorsal stream is for taking action, such as picking up an object
- Taking this action would involve knowing the location of the object, consistent with the idea of where, but it goes beyond where to involve a physical interaction with the object
- Thus, reaching to pick up a pen involves information about the pen’s location plus information about how a person should move his or her hand toward the pen
- According to this idea, the dorsal stream provides information about how to direct action with regard to a stimulus
Where is evidence supporting the idea that the dorsal stream is involved in how to direct action provided?
- It’s provided by the discovery of neurons in the parietal cortex that respond when a monkey looks at an object and when it reaches toward the object
- The most dramatic evidence supporting the idea of a dorsal “how” or action stream comes from neuropsychology
What’s neuropsychology?
The study of the behavioral effects of brain damage in humans
One of the basic principles of neuropsychology is that we can understand the effects of brain damage by determining what?
Double dissociations
What’s an example of double dissociations?
- The monkey with damage to the temporal lobe was unable to discriminate objects (function A) but had the ability to solve the landmark problem (function B). The monkey with damage to the parietal lobe was unable to solve the landmark problem (function B) but was able to discriminate objects (function A)
- The fact that object discrimination and the landmark task can be disrupted separately and in opposite ways means that these two functions operate independently of one another
Describe patient D.F.
- A 34-year-old woman who suffered damage to her ventral pathway from carbon monoxide poisoning caused by a gas leak in her home
- One result of her brain damage was that D.F. was not able to match the orientation of a card held in her hand to different orientations of a slot
- But when D.F. was asked to “mail” the card through the slot, she could do it! Even though D.F. could not turn the card to visually match the slot’s orientation, once she started moving the card toward the slot, she was able to rotate it to match the orientation of the slot
- These results for D.F. are part of a double dissociation because there are other patients whose symptoms are the opposite of D.F.’s
What method did Milner and Goodale use to study patient D.F?
They used the method of determining double dissociations
What did Milner and Goodale conclude from their observations of patient D.F.?
- D.F. performed poorly in the static orientation-matching task but did well as soon as action was involved
- Thus, Milner and Goodale interpreted D.F.’s behavior as showing that there is one mechanism for judging orientation and another for coordinating vision and action
- They hence suggested that the ventral pathway should still be called the what pathway, but that a better description of the dorsal pathway would be the how pathway, or the action pathway, because it determines how a person carries out an action
What do psychophysical experiments that measure how people perceive and react to visual illusions demonstrate?
They have demonstrated the dissociation between perception and action that was evident for D.F.
In our normal daily behavior, why aren’t we aware of the two visual processing streams?
Because they work together seamlessly as we perceive objects and take actions toward them
Describe Tzvi Ganel and coworkers’ experiment designed to demonstrate a separation of perception and action in non-brain-damaged participants
- Used a visual illusion task where line 1 was longer than line 2 but in the illusion line 2 appears longer
- They presented participants with two tasks:
1) a length estimation task in which they were asked to indicate how they perceived the lines’ length by spreading their thumb and index finger
2) a grasping task in which they were asked to reach toward the lines and grasp each line by its ends - Sensors on the participants’ fingers measured the separation between the fingers as the participants grasped the lines
- These tasks were chosen because they depend on different processing streams: the length estimation task involves the ventral or what stream & the grasping task involves the dorsal or where/how stream
What were the results of Tzvi Ganel and coworkers’ experiment designed to demonstrate a separation of perception and action in non-brain-damaged participants with the use of a visual illusion
- The results of this experiment indicate that in the length estimation task, participants judged line 1 (the longer line) as looking shorter than line 2, but in the grasping task, they separated their fingers farther apart for line 1 to match its longer length
- Thus, the illusion works for perception (the length estimation task), but not for action (the grasping task)
- These results support the idea that perception and action are served by different mechanisms
What’s the inferotemporal (IT) cortex?
- An area of the brain outside Area V1 (the striate cortex), involved in object perception and facial recognition
- Located in the temporal lobe
- Neurons in the IT cortex have the largest receptive fields—large enough to encompass whole objects in one’s visual field
What do IT neurons respond to?
They respond to more complex objects that occupy a larger portion of the visual field
