Visual Imagery II: Imagery and the Brain Flashcards
Single Cell Recording Study?
Electrodes implanted in patient’s brain
- To localize origin of epileptic seizures (rare!)
Medial temporal lobe
- Imagery Neurons (will be on exam) responded to both perception and imagery for specific objects, but not others
Results suggest overlap between object perception and object imagery
Brain Imaging Studies -
Bihanet al (1993) imaged (fMRI) visual cortex while Ps viewed vs. imagined same objects
Results showed visual cortex active for both
Brain Imaging Studies -
Kosslynet al. (1993) imaged (PET) visual cortex while Ps imagined small vs large letters
- Small letter active posterior occipital lobe
- Large letters activated anterorir occipital lobe
Results suggest topographic mapping (will be on exam) of cortex
Mind Reading?
Text describes MVPA –machine-learning on brain image data used to predict imagery
Marvin Chun (Yale) has more impressive version of this
–
Showed Ps specifically crafted faces which help computer learn how features are represented
–
Computer then reconstructs guesses of imagined faces
Mind Reading?
Text describes MVPA –machine-learning on brain image data used to predict imagery
Marvin Chun (Yale) has more impressive version of this
–
Showed Ps specifically crafted faces which help computer learn how features are represented
–
Computer then reconstructs guesses of imagined faces
Brain Lesion Studies
Martha Farah (1993) studied patient (M.G.S.), part of right occipital lobe removed
Mental walk task
Smaller field of view after operation
Suggests visual cortex important for imagery
Brain Lesion Studies - hemineglect cases?
- Italian patients neglected left visual field, even when recalling images from memory (Bisiach& Luzzatti, 1978)
- Same inability to disengage from right visual field in perception and imagery
- Suggests attentional control operates similarly in the outside world and inside imagination
Not all shared mechanisms
Some studies show dissociations
Guarigliaet al. (1993) –patient showed hemineglect in mental imagery, but not perception
Dissociating Perception & Imagery?
- Visual perception involves bottom-up processing; located at lower and higher visual centers
- Imagery is a top-down process; located at higher visual centers
- Difficult to manipulate mental images
Perception is automatic and stable; imagery takes effort and is fragile
Eidetic imagery?
Ability to maintain seemingly clear mental image of an earlier perceptual event
Incidence is higher in children than adults
- With age, verbal codes more efficient to represent abstract concepts
No reliable demonstrations of “photographic” memory!
Method of Loci?
Forming associations between things to-be-recalled things and spatial locations already very familiar
Requires practice
Pegword Technique?
Forming associations between to-be-recalled things and concrete nouns (easy to visualize)
Differences in Visual Imagery? SPATIAL
Some of us are better at imagining spaces, others objects
Spatial imagery:
Ability to imagine spatial relations
Paper Folding Test (PFT):
a paper is folded then a hole is created –what does the unfolded paper look like?
Mental rotation task –spatial imagers did better
Differences in Visual Imagery? OBJECT
Some of us are better at imagining spaces, others objects
Object imagery:
Ability to image details, features or objects
Vividness of Visual Imagery Questionnaire (VVIQ):
Imagine item prompts, how vivid is the image?
“The sun is rising above the horizon into a hazy sky”
Degraded pictures task –object imagers did better
Mental maps?
Cognitive/mental map:
Imaginal representation of the world/environment
You can use either a physical map or a cognitive map to navigate an environment
Distortion in Mental Maps?
Mental maps are not organized as a true picture
Employ a heuristic of making irregular geographic boundaries fit into a kind of grid
Cost = loss of information
