Lecture 7 & 8

Question 1

Motion perception

Answer 1

Continuous environmental uptake and allows us to group objects.

Question 2

What is Illusory motion ?

Answer 2

Apparent motion that is perceived motion in a static stimulus e.g. doodle book, movies

Question 3

Describe illusory motion

Answer 3

Induced motion that uses a stationary frame to create movement.

Question 4

What type of motion produces retinal motion?

Answer 4

Real motion

Question 5

Physiological basis of motion - middle temporal area

Answer 5

(V5) is where almost all neurons are direction selective to process where an object is

Question 6

Newsome and monkeys

Answer 6

Monkey experiment with moving dot displays and measured neuronal firing rate. With increasing coherence between shape direction the more rapidly neurons fire

Question 7

What are middle temporal neurons specialised to do?

Answer 7

Detect motion direction

Question 8

The aperture problem

Answer 8

The direction of moving stimulus through a receptive field is ambiguous.

Question 9

The superior temporal sulcus

Answer 9

Receives projections from the middle temporal area and inferotemporal cortex

Question 10

Biological motion

Answer 10

Self produced motion of a biological being- real motion that produces retinal motion

Question 11

Collary discharge theory

Answer 11

Motion perception depends on retinal motion and eye movements. Eyes have 6 muscles with 3 relevant signals.

Question 12

What are the 3 relevant signals that create motion

Answer 12

Image displacement signal (IDS): an image moves across the retina and successfully stimulates the receptors 
Motor signal (MS): a motion command is sent from the muscle to the eye muscles 
Collary discharge signal: copy of the motor signal

Question 13

Evidence for collary discharge theory

Answer 13

Behavioural evidence: motion perception matches the model predictions
Neural evidence: real motion neurons respond to moving stimuli but not static stimuli

Question 14

Sensation

Answer 14

The un-interpreted sensory impressions created by the detection of stimulus

Question 15

Perception

Answer 15

The physiological process of making sense of a sensation

Question 16

Recognition

Answer 16

The identification of a stimulus as an object we are familiar with

Question 17

Object recognition

Answer 17

If visual input matches the representation there is object recognition.
If visual input does not match the representation there is not recognition

Question 18

Theories of object recognition

Answer 18

Template matching
Feature analysis
Structural analysis

Question 19

Template matching

Answer 19

Visual input is transformed until it matches a template. Problem- large number of templates required

Question 20

Feature analysis

Answer 20

Size or orientation used to distinguish. E.g. P and R

Problem- spartial arrangement of features not taken into account

Question 21

Structural analysis

Answer 21

Objects may differ in their 2D appearance but may become equivalent in 3D space

Question 22

What does visual object (Structural) analysis proceed through

Answer 22

4 levels of representation

1. Raw primal sketch: process brightness
2. Full primal sketch: geometric organisation of intensity changes (edges)
3. 2 1/2 D sketch: spatial location of visible surfaces
4. 3D model: Represents the object independently of the observer’s posision

Question 23

Ellie & Young

Answer 23

use boxes to show functional processing stages
Arrows show direction of information flow
Blue indicates sensory processing
Red is perceptual processing
Green is recognition

Question 24

Testing model predictions- Benson and Greenber

Answer 24

Soldier suffered CO poisoning and could: maintain fixations, name colours, describe sensations, detect changes in brightness, detect movement of small objects
He could not: perceive shape or form, or recognise/name objects

Model predicts that there was no viewer centred representation as there was no perception of basic shapes so all following steps were impaired

Question 25

Testing model predictions- Warrington (Right posterior lesion patients)

Answer 25

Group of patients with right posterior lesions could not: match object size/colour, explain the use of different objects, recognise objects from pictures or recognise objects from unusual views .
Impaired object centred representation so could not recognise objects from unusual views

Question 26

Testing model predictions - Warrington ( cerebral atrophy)

Answer 26

Ongoing loss of neurons and connections between them.
Patient could not distinguish basic shapes, identify colours, numbers, letters, match pictures, name common objects and could not identify meaningful sounds
Object recognition impaired

Question 27

Ellis and Young predictions on patients with visual agnosis.

Answer 27

Inability to recognise objects due to impaired perceptual and semantic stages

Question 28

What does a cognitive model need to do?

Answer 28

Explain the functional components of a mechanism and how they are linked.

Question 29

Apperceptive agnosia

Answer 29

Cannot copy or match simple shapes

Question 30

Associative agnosia

Answer 30

Can copy and match objects but intact perception has no meaning