Topic 6- Movement and Action

Question 1

What is optic flow?

Give an example.

Answer 1

Flow of stimuli in the environment that occurs when you move relative to that environment

Ex- Imagine you’re in a car: as you drive, objects close to you (like trees) appear to move quickly, while distant objects (like mountains) seem to move slowly. This visual motion is optic flow.

Question 2

What are 2 important characteristics of optic flow?

4pts

Answer 2

1. Optic flow is faster near the observer and slower farther from the observer
   –> The gradient of flow; provides information about speed/how fast the observer is moving
2. No optic flow at the destination the observer is moving towards
   –> Focus of expansion (FOE); where the observer will end up if course is not changed

Question 3

What is spatial updating?

Answer 3

Awareness of our position in an environment while we move

Question 4

What is the navigation wayfinding?

3pts

Answer 4

• When we want to travel to distant destinations that aren’t immediately visible.

–> involves perceiving objects in the environment
–> remembering these objects and their relation to the overall scene/environment
–> knowing when to turn and in what direction

Question 5

Objects at corners where a decision needs to be made whether to turn or not.

What type of wayfinding task is this?

Answer 5

Decision-point landmarks

Question 6

Objects that provide no critical information for wayfinding

What type of wayfinding task/landmark is this?

Answer 6

Non-decision-point landmarks

Question 7

What is affordances?

2pts

Answer 7

• Information about how an object can be used

–> What it “offers” or “provides” us

Question 8

Interacting with objects:
What are the first 2 steps and pathways ?

2pts

Answer 8

• Identifying the object involves the ventral (“what”) pathway
• Reaching for the object involves the dorsal (“where”/”how”) pathway, specifically the parietal reach region (PRR)

Question 9

Provides feedback to my visual system about how I need to shape my hand, and which type of grip I should probably use.

Contains neurons that respond best to, and produce, different types of grips

What region of the brain does this?

2pts

Answer 9

Dorsal (where/how region) important for reaching and grasping

• major region in the dorsal pathway is the parietal reach region (PRR)

Question 10

Erroneously predicting weight when perceiving two differently sized objects that have the same weight.

Error occurs because we tend to predict that objects we perceive as being bigger = more force to lift.

What concept is this?

Answer 10

Size-weight illusion

Question 10

The real, physical movement of a stimulus

What type of motion is this?

Answer 10

Real motion

Question 11

What are the 3 types of illusory motion?

Answer 11

• Apparent motion: illusion of continuous movement as a result of rapid successions of still images
• induced motion: Occurs when the motion of one object causes a nearby stationary object appear to move
• Motion aftereffects: Occurs when viewing a moving stimulus causes a stationary stimulus to then appear to move

Question 12

If you’re on a train and look out the window at another train on the adjacent track, and your train starts moving forward, the other train might appear to move backward, even if it’s stationary.

What type of motion is this?

Answer 12

Induced motion

Question 13

If you stare at a waterfall for a while and then look at the surrounding rocks, the rocks will appear to move upwards.

Wat type of motion is this?

Answer 13

Motion aftereffects

Question 14

When Jack walks from left to right, and you move your eyes to follow him, portions of the environment become covered as he walks by them, and then uncovered when he moves on.

Creates a local BLANK in the BLANK BLANK .

Indicates to our visual system that the object (Jack) is moving relative to the environment.

Gets perceived as BLANK.

Answer 14

• local disturbance in the optic array
• motion

Question 15

What are two ways we perceive motion?

Answer 15

• We move our eyes to follow an object
• Our eyes are stationary and looking straight ahead as an object moves across the visual field/retina

Question 16

Motion is perceived when one part of the visual scene moves relative to the rest of the scene, and no motion is perceived when the entire scene moves.

What is the neural basis for this? According to this theory, 3 signals exist:

What theory is this?

4pts

Answer 16

• The corollary discharge theory

1. A motor signal (MS):
   Indicates you have moved your eyes
2. An image displacement signal (IDS): Indicates that an image has moved on the retina/something has moved in the visual field
3. A corollary discharge signal (CDS): A copy of the motor signal

Question 17

What is an important thing to understand about movement being perceived regarding comparators?

2 pts

Answer 17

• Movement is perceived when the comparator receives one and only one of the signals, either the CDS or the IDS
• If the comparator, receives both signals, no movement is perceived

Question 18

You move your eyes to follow Jack.

What type of signal is this and what happens?

Answer 18

• comparator receives a CDS, so movement is perceived

Question 19

You keep your eyes still as Jack walks past, but his image moves across your retina.

What type of signal does the comparator receive and what happens?

Answer 19

• comparator receives a IDS, so movement is perceived

Question 20

You move your eyes right to left and the image of the entire scene moves across your retina.

What type of signal does the comparator receive and what happens?

Answer 20

• comparator receives 2 signals, an IDS and CDS, so no movement is perceived

Question 21

Which part of the brain is associated with motion perception?

BLANK area contains many receptive fields that are BLANK BLANK.

Answer 21

V5- in the middle temporal area (MT)

-MT, directionally selective

Question 22

Occurs when only a portion of a moving stimulus is seen as though viewed through a narrow aperture, or in the view of a single neuron’s receptive field.

Can provide misleading information about the direction in which the stimulus is moving.

What problem is this? What are 2 solution

Answer 22

Aperture problem

• The visual system combines information from multiple neurons to perceive the overall direction of a moving object
• Focusing on the object’s ends for “true” picture of how something is moving