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

Abstract

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

Attentional Blink Method

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

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).

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

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

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

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

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

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

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

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

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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