Lecture 5 Flashcards
What is mental imagery?
Internal representation that creates the experience of sense-perception in the absence of appropriate sensory input (visual, auditory, kinaesthetic, proprioceptive, gustatory, olfactory)
What are two main theories of mental imagery?
Functional equivalence
Propositional codes
Functional equivalence (Kosslyn)
Imagery is generated using neural machinery used for sensation and motor control.
Visual imagery relies on visual system
Motor imagery relies on motor system
Propositional codes (Pylyshyn)
Imagery is an epiphenomenal product of propositional codes
Images are manipulated by manipulating symbolic representations, not the image itself
Imagery is independent of sensory and motor systems
Mental scanning as evidence
Memorise a map then imagine the map.
Participants are asked to inspect the map and report whether a feature is present or absent
Time systematically increased with distance and subjectively larger images required more time to scan than did subjectively smaller ones.
When subjects were not asked to base all judgements on examination of their images the distance between an initial focus point and a target did not affect reaction times.
Cognitive neuroscience as evidence
Imagery activates visual areas involved in perception.
Activation depends on the task
High resolution imagery tends to activate early visual areas
Spatial judgements activate more dorsal areas
Non-spatial judgements that do not require high resolution comparisons activate ventral areas
TMS over V1 disrupts visual imagery
Neurophysiological evidence
MS cannot imagine colours
e.g. imagine a summer sky, police box, or the sea. What is the darkest?
Some patients with left neglect hemianopia cannot generate images
Making eye movements…
reduces the intensity of visual imagery
Problems of Tacit knowledge
Pylyshyn modified the mental scanning task. Participants had to report the compass bearing of landmarks. This reaction time was unrelated to the distance of the starting point
Participants perform the task in the same way as they would in the real world
Tacit knowledge
Knowledge that is unconscious or that cannot be articulated
Problem of dissociation
DF shows normal visual imagery abilities:
imagine the letter D, rotate it 90 degrees and put a triangle directly below it. Remove the horizontal line. What is this. ICE CREAM
What type of people have problems with visual imagery?
Hemianopes
Is imagery modular?
Yes
Do different types of imagery activate different parts of the brain?
Yes
Functions of mental imagery: Paivio
Imagery has two functions each with two levels this distinguishes between imagery content and imagery function.
Level: specific, general
Function: cognitive, motivational
