week 6 - perception and action Flashcards
optic flow
appearance of objects as observer moves past them
What are the two features of optic flow?
gradient of flow and focus of expansion
gradient of flow
- difference in flow as a function of distance from observer
- objects closer to focus of expansion appear to move quicker
- objects far from focus of expansion seem to move slower
focus of expansion
point in distance where there is no flow
Gibson plane experiment
- red dots characterized focus of expansions
- blue arrows represented different aspects of gradient of flow
- pilots would want to land where there is no movement aka focus of expansion
How does movement create perceptual information?
- as we are moving, we are presented with various kinds of stationary objects
- movement creates more perceptual information
invariant information
properties that remain constant while the observer is moving (such as the focus of expansion)
self-produced information
flow is created by the movement of the observer
Describe how movement from a car creates perceptual information?
- movement from car creates optic flow
- creating optic flow gives us more visual information
- flow: object moving relative to car
- flow provides information for guiding further movement
Why is a novice gymnast able to do a backflip with their eyes closed better than an advanced gymnast?
Advanced gymnast learns to rely on focus of expansion and are very reliant on the visual information that comes in while doing a backflip
Lee and Anderson experiment (infant swinging room)
- 13-16 month children placed in swinging room
- the movement of a stationary floor and a wall/ceiling that swings back and forth created optic flow
- researchers manipulated optic flow information which infants were heavily reliant on
What were the results of the Lee and Anderson experiment?
showed that vision has a powerful effect on balance and even overrides other senses that provide feedback about body placement and posture
optic flow neurons
neurons in the medial superior temporal area (MST) that respond to flow patterns
Britten and van Wezel experiment
monkeys were trained to view flow of dots on a screen and report which way they perceived the optic flow of information
What were the results from the Britten and van Wezel experiment? (monkey and dots)
- were able to find subset in temporal lobe reacting as a result as well as particular neural response
- specific neurons were essentially responding to particular patterns of movement or different optic flow patterns
What occurred when specific MST neurons were microstimulated?
judgements were shifted in the direction of the stimulated neuron
Land and Lee experiment (car)
fitted car with different instruments to measure angle of steering wheel, speed of vehicle, and driver’s direction of gaze
What did Land’s and Lee’s experiment suggest?
- rather than focusing on focus of expansion, we pay attention to different focus points to gain different optic flows of information to determine where we will move
- drivers also use other info to determine their heading
blind walking experiment
- participants viewed target, were blindfolded, and were prompted to walk to target
- participants were able to make it to the target for the most part
- showed that people can navigate without any visual stimulation from the environment
landmarks
objects on a route that serve as cues to indicate where to turn
Mary Heyho experiment (maze landmarks)
- subjects were placed in a virtual maze containing non-decision and decision point landmarks
- measured eye tracking to record what they focused on
What were the results of Mary Heyho’s experiment?
- When all landmarks were present, performance did not differ. Least fixated landmarks (non-decision landmarks) did not contribute much to performance. But most fixated (decision landmarks) had a bit of increase in maze performance.
- when half of the non-decision point landmarks were removed, their maze performance was not affected
- when half of the decision point landmarks were removed, their performance decreased
What part of the brain is highly active when we encounter landmarks?
parahippocampal gyrus (place area)
Janzen and van Turennout experiment (virtual museum)
- observers studied a film that moved through a virtual museum and were told to act as guide
- exhibits appeared at both decision points where turns were necessary and non-decision points
- observers were given a recognition task while in an fMRI and were presented with objects seen in exhibits and objects they had not seen
What were the results of the Janzen and van Turennout experiment?
- observers claimed they did not recognize objects from exhibit, however, there was still a high amount of brain activation
- results showed that the greatest activation for objects at decision points (landmarks) in the parahippocampal gyrus
Restrosplenial cortex damage
- study with someone who had damage to RC
- took pictures of her own garden and asked where the shots were taken from
- even having lots of experience with her own garden, she still had issues determining directions (where picture was taken)
Maguire experiment (taxi driver)
- taxis drivers have a larger and more connected hippocampus (helpful for wayfinding)
- taxi driver with damage to hippocampus had trouble finding their way around the neighborhood
affordances
affordances of objects are made up of information that indicates what an object is used for
brain damage and affordances
people with certain types of brain damage may not be able to nam objects but they can still describe how they are used
affordances cup of coffee example
- perception of cup: ventral stream
- reaching for cup: dorsal
- grasping cup: both
Connolly experiment
- evidence for parietal reach region (PRR)
- used monkeys to find that neurons in PRR were responding specifically to different types of grasps
- monkeys looked at fixation light, light turned on sees object and then they are off, and monkeys had to grasp object
Connolly experiment results
- for each different types of grips, a specific neuron will respond
- neurons in PRR respond to different kinds of grips which helps us out with locating a particular object
Fattori
- found that 3 different regions are used while grasping
- when monkey is adjusting grip in the dark, they use the neuron to facilitate its movement
Schindler experiment (cylinder)
- obstacle avoidance is controlled by parietal regions
- two patients with parietal lobe and damage and control subjects were given two cylinders and asked to reach between them to touch gray strip behind them
What were the results of Schindler’s experiment?
- control group: moved hand in order to avoid cylinders and touch strip
- two patients: did not differ in movement; not able to use dorsal stream and did not do well on task
- parietal lobe does not only allow us to make appropriate hand grips, but is also helps us avoid particular obstacles
mirror neurons
- located in frontal lobe
- respond when watching someone perform an activity as if we were doing the activity ourself
mirror neurons in monkeys’ cortex experiment
- respond when a monkey grasps an object and when experimenter grabbed object
- response to observed action “mirror” the response of actually grasping
- diminished response when object is grabbed by a tool
What are the possible functions of mirror neurons?
- to help understand another animal’s actions and react to them appropriately
- to help imitate the observed action
audiovisual mirror neurons
- respond to action and the accompanying sound
- mirror neurons fire the same way in monkeys when they watch the experimenter break the peanut, when they hear the peanut being broken, and when they break the peanut themselves
Lacoboni experiment
- mirror neurons can be influenced by intentions
- had subjects look at shot film clips and showed different context clips as well as action clips
- intent of action was different based on circumstance
What were the results of the Lacoboni experiment?
- singal changes based on intent (drinking vs. cleaning)
- more active for cleaning/drinking than the actual action
