Module 4 study guide

Depth and size perception

-The visual system uses multiple cues to identify relative depth and size in the environment -our visual systems must re-create the 3D world using essentially flat, 2D retina

motion aftereffect

-a motion-based visual illusion in which a stationary object is seen as moving in the opposite direction of real or apparent motion just observed -suggests that motion neurons in the occipital cortex may have an opponent system, we see movement opposite the direction of the motion we were just watching ex: waterfall illusion, we state downward see the aftereffect that after objects move like its moving upward

MT or V5

-area in the occipital lobe in the dorsal partway critical to the visual perception of motion

How does the visual system correctly perceive the overall motion of objects

-beyond V1 we have area involved in motion perception that is able to verify which objects are shared within all the different apertures -whenever you consider multiple receptive fields that information can be pulled from higher processing pathways -that visual areas will be able to integrate all the hypothesis to get the overall motion of an object

How do we interpret point-light walker display?

-humans are so good at recognizing everything -they can determine the the type and direction of movement, also gender -the way we interpret the dots depends on the overall context -if you add several lights consistent with one person body, you can interpret the dots as a whole and perceive it differently

experiment for LIP region

-monkeys maintain fixation point and need to make fast eye movements when light appear and disappear -find location of neuron in LIP that has a receptive field results: -neurons in LIP fire right before the movement -function is to remember the location and produce a movement to that specific location

optic flow

-motion depth cue that refers to the relative motions of objects as the observer moves forward or backward in a scene -as we move the objects present in the environment -provides information about distance and can be used to aid in our own movement ex: as we move in one direction, object appear to get bigger as they approach us. In addition to this being a cue for depth, it also indicates motion. A driver can judge her speed by the rate at which objects are flowing towards her

motion detection in the retina

-plays an important role in early motion detection -the M and the P pathway at the retina both contribute to motion perception

Which part of the fovea are seeing the motion?

-poor motion thresholds in the foveal regions of our retina -periphery is good at detecting motion -a moving stimulus at the periphery seems to grab the attention, and it may direct the fovea to this stimulus

Reichardt detector

-simple neurons assemblies that are capable of computing motion -try to detect whenever an object moves from place one to place two at a specific speed -if a cell is stimulated at the same time by both receptors then it can detect motion -there are two signals from the receptors: one is delayed and one is fast

optic flow motion cue

-the overall summary of how all the points of an image move coherently as a result of my motion or object in the world -how fast the objects are increasing towards the horizon gives you a mathematical answer of how fast you are traveling and which direction you are turning ex: focus of expansion point doesn't change much. dots in the scene are moving past you as you move forward

corollary discharge theory

-the theory that the feedback we get from our eye muscles as our eyes track an object is important to the perception of motion -in addition to the muscles of the eye, this signal will be sent to areas of the brain responsible for motion detection, and it provides the brain with updated information about locations and speeds of moving objects -means that one of the cues detecting motion is the movement of our own eyes ex: when playing tennis our eyes and head move to track the movement of the ball using smooth-pursuit eye movements

Stimuli used in Newsome and Paré's (1988) experiment

-trained monkeys to respond to a pattern of dots -they slowly diminished the # of dots coherently in a direction -put electrodes in the MT area of the monkey FINDINGS -specific neurons coding for specific information in the world -when they took the MT region out of the monkeys brain they were not able to do the task -HOWEVER after several months they recovered and were able to do the task -SO there are other parts of the brain that can detect motion detection

smooth pursuit eye movements

-voluntary movements we use to track moving objects -use it only when there is an actual moving object in the environment -feedback from visual system allow our eyes to continuously follow motion ex: our eyes move gradually as we follow an airplane across the sky

How slow and how fast to detect motion

-we can usually perceive fast motion even if we cannot detect them -an object must move at least 1 minute of 1 degree across the retina to be detected ex: plants growing or very fast movements are very hard to detect with the human eye

three dimensional movies

-when creating the moving they have separate frames so that the eyes get separate images of the movie -the brain receives the difference in image and combines it so you get that 3D effect

the correspondence problem

-when we see the world through one aperture we cannot tell where the objects are moving -we get a wrong impression of the movement -one single receptive field does not provide the most accurate motion that is happening in the world -whenever you start having more apertures available to you, you are able to say where exactly object are throughout motion

humans have a field of view of about

190 degrees

motion

An object's change in position relative to a reference point.

correspondence problem

In binocular vision, the problem of figuring out which bit of the image in the left eye should be matched with which bit in the right eye

visually guided grasping

Medial intraparietal area (MIP): area that allows to plan and execute a direct movement, approaches the object Anterior intraparietal area: prepares the grasp for the object in the desired way ex: grab and throw vs grab and write differences

saccades

Rapid voluntary movements of the eyes. ex: when you read you make a series of saccades, -vision is suppressed during the actual movement from one object to he next ex: within the 50ms between the movement of your eye from a car to a tree you essentially cannot see anything new

motion parallax

a cue that arises from the motion of a person in the environment. -things that are closer to us will move faster than object that are father away -object between point of focus and me move in an opposite direction. Objects beyond the point of focus moves in the same direction, speed and direction are perfect metric cues ex: the moon looks like it moves with us. actually there is not enough movement we can do to change the relative position of the moon. its so far away that as we move it doesn't change it projection on the eyeball

lateral intraparietal area (LIP)

able to visually guide eye movements -important for preparing, controlling, and controlling the deployment of an eye movement to a specific location

shadows and shading

an object in front of its shadow, and the angle of the shadow can provide some information about how far the object is in front of the background -understand whether the surface is coming out or into the ground ex: light sources are coming from different directions so the shadows change the perception of the image

apparent motion

appearance of real motion from a sequence of still images ex: watching movies, there are separate frames within the film

oculomotor cues

based on sensing the position of the eyes and muscle tension

Weigelt et al.'s (2013) results

compared how the brain would react when people were detecting locations versus the motion results: -founded that attention to motion resulted in a bigger response in MT than did to attention to location

gradient of flow

difference in flow as a function of distance from the observer -object closer to us seem to move faster, whereas more distant object appear to move slowly

diplopia

double vision -results from the images of an object having to much disparity to lead to fusion

deletion

gradual occlusion of a moving object as it passes behind an object -clue that the bookshelf is closer ex: before the book shelf

occlusion

happens when one object partially hides or obstructs the view of a second object -only tells us relative, not metic depth information

induced motion

illusory perception when one moving object may cause another object to look like its moving ex: clouds moving in one direction induce the perception that the moon is moving in the opposite direction

Akinetopsia

inability to see objects in motion -occurs when MT is damaged

real motion

motion in the world created by continual change in the position of an object relative to some frame of reference ex: car passing by, ducks swimming across the pond

crossed disparity

object are in front of the fixation point or horopter

uncrossed disparity

objects are behind fixation point or horopter

atmospheric perspective

objects in the distance appear blurred and tinged with blue

vergence

occurs when the eye rotate inward to see a near object and then bend outward when we look at a more distant object -more useful cue than accommodation, and it can provides the visual system with reliable depth information to about 2 meters in distance

fMRI results from Kaas et al. (2010)

participants imagined moving object -when participants engaged in motion visual imagery larger responses were recorded from the MT -MT is active during visual imagery that involves motion

focus of expansion

point towards which someone in motion is moving but itself does not move

the horopoter

region in space where the two images from an object fall on corresponding locations on the two retinae -a person falls on corresponding points on the retina -when the distance between the projection of the object is the same in the two eyes then we can say the object falls on corresponding points

texture gradients

textures become finer as they recede in the distance

binocular disparity

the difference in the retinal images of the two eyes that provides information about depth ex: when you look at your finger through just your left or right eye your fingers flips in position

relative size

the farther an object is, the smaller is will be on the retina. *if it is bigger it is closer to us

accretion

the gradual reappearance of a moving object as it emerges from behind another object -clue that the bookshelf is closer ex: after the bookshelf

relative height

the higher the object is on a visual plane the farther it tends to be from us *objects closer to the horizon are seen as more distant

What is the concept of Affordance?

the information in the visual world that specifies how that information can be used -perception is determined partially by meaning and function ex: seeing a piano affords playing music, seeing an elevator affords being able to go up and down

monocular/pictorial cues

the perceptual cues of depth (such as relative size and interposition) that can be perceived by one eye alone

linear perspective

the pictorial depth cue that arises from the fact that parallel lines appear to converge as they recede into distance -helped with art

accommodation

the process of adjusting the lens of the eye so that one can see both near and far object easily -the thickness of lens changes through muscles and brain can interpret if objects are near or far from us

Panum's area of fusion

the region of small disparity around the horopter where the two images can be fused into a single perception

stereopsis

the sense of depth that we perceive from the visual system's processing of the comparison of the two different images from each retina

zero desparity

there is zero difference on the retina

familiar size

we judge distance based on our prior knowledge of the sizes of objects -use stored knowledge of how big a watermelon is vs a lemon to see how far away it is from us