Role of Working Role of Working Memory in Visual Memory in Visual

Selective AttentionSelective Attention

de Fockert, Rees, Frith, Lavie (2001)

OutlineOutline

• Definition of Selective Attention• Definition of Working Memory• Previous research• Current research

– Methodology & Results•Behavioural Task• Imaging Study

• Discussion

Selective AttentionSelective Attention

• A system that focuses on relevant information by filtering out irrelevant information from the available stimuli

• The purpose is to reduce the load on cognitive processing systems

Downing, 2000

Working MemoryWorking Memory

• A system used for short-term storage & “executive processes”

Smith & Jonides, 1999

Short-term MemoryShort-term Memory

• Performing active maintenance of a limited amount of information for a matter of seconds

Smith & Jonides, 1999

Executive ProcessesExecutive Processes

• Attention & Inhibition (Competition)

• Task Management• Planning• Monitoring• Coding

Smith & Jonides, 1999

Low Working Memory Low Working Memory LoadLoad

Attention & Inhibition

Task Management

Coding

Monitoring & Updating

Planning

*adapted from Smith & Jonides, 1999

High Working Memory High Working Memory LoadLoad

Attention & Inhibition

Task Management

Coding

Monitoring & Updating

Planning

Working Memory LoadWorking Memory Load

As working memory load increases, processing of irrelevant stimuli also

increases, and vice versa.

Previous ResearchPrevious Research

• Working memory may provide top-down modulation of selective attention

• Active maintenance of objects in working memory caused selective attention to shift towards that object

Downing, 2001

LeBar et al (1999)LeBar et al (1999)

• Physiological overlap between working memory and visuospatial attention tasks

• Concluded that spatial attention and working memory use common cognitive features

• This would require dynamic shifting of attentional resources

Current PaperCurrent Paper

HypothesisHypothesis

• Selective Attention relies on Working Memory to prioritize stimuli to process relevant stimuli

*BUT if Working Memory is busy than Selective Attention will process irrelevant stimuli to a greater degree

MethodologyMethodology

Behavioural Task

500 ms

500 ms

3000 ms

1500 ms

850 ms

500 ms

1250 ms

Response Interval

1250 ms

Response Interval

Example of Example of High Working High Working Memory Load Memory Load condition with condition with two Selective two Selective Attention Attention tasks.tasks.

PredictionsPredictions

Distractor Faces Low WM Load High WM Load

Congruent No effect No effect

Incongruent No effectIncreased RT and Error

Working Memory Load

ResultsResults

Behavioural Data

ResultsResults

Task Low WM Load High WM Load

Selective Attention Manipulation (Response 1)

739 ms (er=5%)

752 ms (er=5.5%)

Working Memory Manipulation* (Response 2)

214 ms (er=4%)

642 ms (er=8%)

Working Memory Load

*significant main effect

Distractor Effects by Working Memory Load

0

100

200

300

400

500

600

700

800

Low WM Load High WM Load

Working Memory Load

Dis

trac

tor

Effec

ts (

ms)

SelectiveAttentionManipulation

WorkingMemoryManipulation

Distractor Distractor Interference/CongruencInterference/Congruenc

y Effectsy Effects

• Low working memory load = 46 ms (error rate=3%)

• High working memory load = 78 ms (error rate=4%)

• F(1,9) = 13.36, P<0.01

MethodologyMethodology

Imaging Task

PredictionsPredictions

Selective Attention Task Low WM Load High WM Load

No distractor facesNo distractor processing

No distractor processing

Distractor faces present & incongruent

No distractor processing

High distractor processing

Working Memory Load

DetailsDetails

• 6 participants (4 males, 2 females)

• 2T Siemens VISION system measured BOLD signal

• 32 contiguous 3-mm axial slices per volume

• Acquired every 2800 ms• Total of 720 volumes acquired in

six runs

Epoch SequenceEpoch Sequence

Low WM load and face incongruent

High WM load and face incongruent

Low WM load and face absent

High WM load and face absent

Run1

Run2

Run3

Run4

Run5

Run6

5 memory trials and 15 attention displays

} Block Design

Results Results

Imaging Data

Significant Significant activations activations related to related to Working Working

Memory Load- Memory Load- LHLH

Superior temporal gyrus

Precentral gyrus

Inferior frontal gyrus

Significant Significant activations activations related to related to Working Working

Memory Load- Memory Load- RHRH

Precentral gyrus

Superior temporal gyrus

Superior parietal lobe

Significant activations related to Significant activations related to the interaction between the interaction between

selective attention and working selective attention and working memory load include:memory load include:

• Bilateral fusiform gyri• Right inferior occipital lobe• Left lingual gyrus

Significant Significant activations related to activations related to

the interactionthe interaction

Occipitotemporal gyrus (Fusiform gyrus) (bilateral)

Lingual gyrus (left)

Occipital Lobe (right)

Low WM

High WM

Percent signal change for face Percent signal change for face presence versus absencepresence versus absence

• Graph represents the maxima of interaction in right fusiform gyrus, separated by working memory load

DiscussionDiscussion

• It is concluded that working memory and the prefrontal cortex plays an important role in controlling selective attention

The EndThe End

Perceptual vs Working Perceptual vs Working Memory LoadMemory Load

Perceptual LoadAs perceptual load increases, processing of irrelevant stimuli decreases, and vice versa.

Previous WorkPrevious Work

• Physiological overlap between areas involved in working memory and interference resolution (Binge et al, 2001)

Analysis using SPMAnalysis using SPM

• Voxel-based• Images are spatially

normalised into standard space and smoothed