1. Kimron Shapiro & Frances Garrad-Cole The University of Wales, Bangor
Age-Related Deficits and Involvement of Frontal Cortical Areas as Revealed by the Attentional Blink
Kimron Shapiro & Frances Garrad-Cole
The University of Wales, Bangor

2. Abstract

3. Introduction
Deficits in divided attention have been well characterised in young to middle-aged adult populations
Less is known about such deficits in younger individuals
Development of frontal cortex continues until ~ 20 yrs.
Thus we predicted that developmental trends might appear in a divided attention task that requires the frontal cortex
We studied such a task in 7-15 yr. old children that is known to index the speed with which attention can be deployed to a target then re-deployed to another target
The task we chose is known as the attentional blink (AB) task
AB task requires two target items to be processed then stored briefly for report

4. Attentional Blink Method

5. Attentional Blink Results
100 80 60
% Correct T2 Detection 40
single-task 20
dual-task 1 2 3 4 5 6 7 8
0 ms
90 ms
180 ms
270 ms
360 ms
450 ms
540 ms
630 ms
720 ms
Relative Serial Position of T2

6. Experiment 1: Rationale
Will developmental of frontal cortex be revealed in the degree of attentional blink?
To evaluate this, we tested participants in 4 age groups in the AB task: 7, 12, 15, and adult.
AB task modified to not require reading.
Used shapes with an orientation judgement as target tasks (see next slide).

7. Experiment 1: Method & Stimuli
Participant Age groups:
7 (mean age = 7 yr 6 mo) N=16
12 (mean age = 12 yr 5 mo) N=16
15 (mean age = 15 yr 6 mo) N=16
Adult (age range = 18-43) N=16
Stimulus size (see fig.) 120 x 120 pixels
T1 (blue isosceles triangle) judged to point “up or down”
T2 (red isosceles triangle) judged to point “left or right”
Distractors were random coloured shapes (not red/blue triangles)
Stimuli presented at rate of ~ 10 per sec. T2
variable lag T1
7-15 items
Fixation

8. Experiment 1: Results & Conclusions
AB magnitude (single - dual target condition) decreases to baseline for all groups except 7 yr. olds
Lack of recovery in 7 yr. olds could be due to two factors:
Distractors fail to be effectively inhibited
Insufficient (lag) time for recovery
Hypotheses examined in Experiments 2 and 3

9. Experiment 2: Rationale, Method, Results, Conclusions
Investigated hypothesis that distractor stream causes more interference in 7-yr. old group
Removed distractor stream leaving only two masked targets, separated by lag
Method produces a “standard” AB outcome
Results reveal same pattern as before, suggesting distractors not having more of an effect in this age group
T1 mask T1
T2 mask T2

10. Experiment 3: Rationale, Method, Results, Conclusions
Investigated hypothesis that lag was insufficient to reveal recovery
Extended lag to ~ 2 sec
Same AB paradigm used as in Experiment 1
Results show recovery to baseline, suggesting AB is longer in 7 yr. olds
Results of Experiment 1 not simply due to general dual-task deficit

11. Experiment 4: Rationale & Method
Results from AB task suggest developmental trend as predicted by development of frontal cortex
Given that frontal areas known to be involved in working memory (WM), predicted a similar developmental trend should be revealed in a WM task
Same 4 age groups (and participants) as in AB task
Participants required to remember 2 or 6 rules regarding an arbitrary stimulus-response (i.e., left - right) mapping
Task should utilise visual short-term memory component of WM without a confounding influence of verbal memory

12. Experiment 4: Results & Conclusions
Significant effect of age and task on WM
Post-hoc tests reveal significant differences between 7 yr. olds and both 15 yr. olds and adults on both 2- and 6- shape tasks
Data suggest WM capacity differs for youngest age group in accordance with prediction from AB task

13. Experiment 5: Rationale & Method
Is the ‘attention’ shown to be lacking in the (temporal) AB task the same as that required in a (spatial) visual search task?
Tested 7-yr. old participants (N=8) and adults (N=8) in a visual search feature and conjunction task using same shapes from Exp. 1
Set size was 2, 10, or 20
In the feature search task the target was a different colour from similarly shaped distractors
In the conjunction search task the target shared features in common with the distractors
Feature
Search
Conjunction
Search

14. Experiment 5: Results & Conclusions
Results show a significant 4-way interaction among age, search condition (feat. vs. conj.), set size, and target (presence vs. absence)
Post-hoc tests reveal increased slopes in the conjunction search task in the younger group
Results suggest that attention shown to be lacking in AB task is also lacking in spatial task
Adult
7-yr

15. General Results and Conclusions
AB task reveals developmental trend consistent with development of frontal areas of the brain
Largest deficits shown in youngest (age 7) participants
Results are consistent with data from individuals with frontal lesions showing large AB deficits (Richer & Lepage, 1996)
Results also consistent with recent MEG data revealing frontal activity during the AB task that is synchronised with temporo-parietal area (Shapiro, et al. 2003)
AB effect does not appear to be due to increased interference from distractor stream
AB outcome ‘correlates’ with decreased WM capacity
Attention required by AB task seems to be the same as that required by visual search task

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