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Visual Working Memory

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Visual Working Memory From Perception to Memory Hans Sup r Department Visual System Analysis AMC/NORI Types of Memory Types of Memory Concept of Working Memory ... – PowerPoint PPT presentation

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Title: Visual Working Memory


1
Visual Working Memory
  • From Perception to Memory
  • Hans Supèr
  • Department Visual System Analysis
  • AMC/NORI

2
Types of Memory
MEMORY (Long short term)
DECLARATIVE (Explicit, Episodic)
NON-DECLARATIVE (Implicit, Procedural)
PRIMING
FACTS
EVENTS
SKILLS/HABITS
  • facilitation by repetition

- dates, names
- experience
- routine
NON-ASSOCIATIVE LEARNING
SIMPLE CLASSICAL CONDITIONING
- habituation
- Pavlovs dog
3
Types of Memory
MEMORY (Long short term)
DECLARATIVE (Explicit, Episodic)
NON-DECLARATIVE (Implicit, Procedural)
PRIMING
FACTS
EVENTS
SKILLS/HABITS
  • facilitation by repetition

- dates, names
- experience
- routine
NON-ASSOCIATIVE LEARNING
SIMPLE CLASSICAL CONDITIONING
- habituation
- Pavlovs dog
4
Concept of Working Memory
Central Executive
Visual sketchpad
Phonological loop
Long-term memory
Baddely, Trends Cognit Sci, 2000
5
Functions of Working Memory
Physiology
  • To combine different modalities (e.g. visual and
    auditory).
  • For a correct internal representation of the
    object.
  • To bridge the gap between perception and action.
  • For correct behavioral responses.

Psychology
  • Learning.
  • Planning.
  • Reasoning.

6
Visual Working Memory
  • Maintaining a mental representation
  • Two components
  • Storage of information
  • Retrieval of information
  • Manipulate this information
  • Limited capacity
  • Spatial and object based working memory
  • Can lead to long-term memory

7
Visual System
8
Visual Perception
Perception of object
9
Memory Storage
Storage of object
10
Memory Retrieval
Retrieval of object
11
Definition of Visual Working Memory
  • Storage of a perceptual representation for a
    short period.
  • Requires first the sensory/perceptual processing
    of the stimulus.
  • Subsequent maintenance of its representation
    after stimulus removal.
  • This information is required for later use.
  • It is only stored when needed and is thus an
    active process.

12
Localization of Visual Working Memory
Parietal lobe (Goldberg, Haxby)
  • Frontal lobe
  • (Fuster Goldman Rakic)

Occipital lobe (Jonides, Supèr)
Temporal lobe (Squire, Desimone)
13
Specialization of Visual Working Memory
Parietal lobe
Spatial based
  • Frontal lobe

Domain specific - Spatial cognition in
Dorsolateral PFC - Object cognition in
Ventrolateral PFC
Occipital lobe
Temporal lobe
Sensory based
Object based
14
Medial Temporal Lobe System
Hippocampus
Rhinal areas
15
Measuring Visual Working Memory
  • Object matching (identity of objects)
  • Spatial memory(position of objects)

Screen 1
Screen 2
Screen 3
16
How Is Working Memory Implemented in the Brain?
time
Spike rate
Low (tonic)
High (burst)
Spike interval
Neuron 1
Neuron 2
Synchronized
De-synchronized
17
Neural Correlates of Working Memory
  • Coherent (synchronized) activity of neurons.
  • Neurons are active at the same moment.
  • Low and high frequency range.
  • Between neurons in different cortical areas.

Fell et al., Nat. Neurosci. 2001
18
Neural Correlates of Working Memory
  • Delay activity, I.e. Enhanced responses during
    memory period.
  • This is found in parietal and frontal areas.

( Chafee Goldman-Rakic, J. Neurophysiol, 1998)
19
Synaptic Plasticity
  • LTP/LTD
  • Mainly NMDA dependent
  • Observed in several cortical areas
  • Ionotropic/Metabotropic glutamate receptors
  • Calcium, Calcium Binding Proteins
  • Kinases (PKC, CAMKII)
  • Transcription factors
  • Early genes (c-fos, zif-268)
  • Neuro-modulators (stress hormones)
  • Protein synthesis
  • Pre post synaptic membrane proteins
  • Morphological changes

Synapse
spine
20
Summary
  • Working memory is a cognitive (i.e. internal)
    process.
  • Neural correlate of working memory is found in
    (poly-) sensory and association, and limbic
    areas.
  • Different domains of working memory in the
    prefrontal cortex.
  • During memory coding neurons show coherent
    activity (spike activity and EEG).
  • During memory period some neurons (delay cells)
    have an enhanced firing rate.
  • Synaptic plasticity strengthening and weakening
    of synapses.

21
  • !How is the perceptual information transferred
    into a working memory component?

Storage of object
Perception of object
22
The Visual System
Feedfoward
Feedback
23
Experimental Setup Perception
Average neural response
24
Experimental Setup Perception
Average neural response
25
Figure Positions
Positions relative to the receptive fields of the
recorded neurons
26
Eye Positions and Reaction Time
Window of analysis
Start Saccade
Eye position
27
Probing Perception
28
Perceptual Correlate
Object (figure) is represented by enhanced
activity (colored area)
(Lamme Roelfsema, TINS 2000)
(Supèr et al, Nat. Neurosci, 2001)
29
Performance
30
Modulation Strength and Figure-ground Contrast
31
Reaction Times
Window of analysis
Start Saccade
Eye position
32
Response Strength
33
Experimental Setup Working Memory
Average neural response
34
Experimental Setup Working Memory
Average neural response
35
Experimental Setup Working Memory
Average neural response
36
Probing Working Memory
37
Visual Stimulation
38
Performance of Memory Task
39
Results Memory Task
Figure Response
Memory Correlate
Ground Response
Supèr et al, Science, 2001
40
Remembered Vs Forgotten
41
Task Probing Active Storage
Figure Target
Figure Distractor
End of trial t 1500 ms.
End of trial t 1500 ms.
Saccade
Saccade
Cue on t 1000 ms.
Cue on t 1000 ms.
Distractor on t 500 ms.
Target on t 500 ms.
Fixation
Fixation
Target off t 28 ms.
Distractor off t 28 ms.
Target on t 0 ms.
Distractor on t 0 ms.
Start fixation
Start fixation
42
Results Active Storage
Figure Target
Figure Distractor
Modulation Index
Memory trace is maintained
Memory trace disappears
43
Transformation of Memory to Motor Activity.
44
Conclusions
  • Perception/Visual working memory is represented
    by enhanced firing rate and coherent activity.
  • Visual working memory is the active storage of
    perceptual information.
  • Visual working memory is a distributed process
    throughout the brain.
  • Sequence of correlate of perception, memory, and
    motor-related activity.
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