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Atypical recruitment of medial prefrontal cortex in autism spectrum disorders: an fMRI study of two executive function tasks.

Gilbert SJ, Bird G, Brindley R, Frith CD, Burgess PW - Neuropsychologia (2008)

Bottom Line: Behaviourally, there were no significant differences between the two groups.However, on a new test of executive function (selection between stimulus-oriented and stimulus-independent thought), the ASD group exhibited significantly greater signal-change in medial rostral prefrontal cortex (especially Brodmann Area 10) in the comparison of stimulus-oriented versus stimulus-independent attention.These results underline the heterogeneity of different tests of executive function, and suggest that executive functioning in ASD is associated with task-specific functional change.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience and Department of Psychology, University College London, London, UK. sam.gilbert@ucl.ac.uk

ABSTRACT
Recent studies have suggested an uneven profile of executive dysfunction in autism spectrum disorders (ASD). For example, some authors have reported deficits on newly developed tests of executive function sensitive to rostral prefrontal function, despite spared, or even superior, performance on other tests. We investigated the performance of a group of high-functioning participants with ASD (N=15) and an age- and IQ-matched control group (N=18) on two executive function tests, whilst undergoing functional magnetic resonance imaging (fMRI). Behaviourally, there were no significant differences between the two groups. In a classical test of executive function (random response generation), BOLD signal differed between the groups in the cerebellum but not in the frontal lobes. However, on a new test of executive function (selection between stimulus-oriented and stimulus-independent thought), the ASD group exhibited significantly greater signal-change in medial rostral prefrontal cortex (especially Brodmann Area 10) in the comparison of stimulus-oriented versus stimulus-independent attention. In addition, the new test (but not the classical test) provided evidence for abnormal functional organisation of medial prefrontal cortex in ASD. These results underline the heterogeneity of different tests of executive function, and suggest that executive functioning in ASD is associated with task-specific functional change.

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Related in: MedlinePlus

Behavioural data from the alphabet task. Left graph shows mean response time (RT) and right graph shows mean error rate, in each of four conditions depending on whether the phase was stimulus-oriented (SO) or stimulus-independent (SI), and whether the trial-type was switch (i.e. different phase to the previous trial: Sw) or non-switch (NS). Error bars indicate standard errors.
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fig2: Behavioural data from the alphabet task. Left graph shows mean response time (RT) and right graph shows mean error rate, in each of four conditions depending on whether the phase was stimulus-oriented (SO) or stimulus-independent (SI), and whether the trial-type was switch (i.e. different phase to the previous trial: Sw) or non-switch (NS). Error bars indicate standard errors.

Mentions: Mean RTs and error rates are displayed in Fig. 2. Mean RTs were examined in an ANOVA with within-subject factors Phase (Stimulus-Oriented [SO] or Stimulus-Independent [SI]) and Switch (Switch trial – i.e. immediately following a switch between the SO and SI phases – or Non-switch trial) and between-subjects factor Group (ASD or Control). There were main effects of Phase, SI trials being slower than SO trials, and Switch, Switch trials being slower than Non-switch trials, along with a Phase × Switch interaction, because the RT difference between Switch and Non-switch trials was larger in the SI phase than the SO phase (F(1, 31) > 21; p < .0001). However, although there was a trend towards slower RTs in the ASD group, neither the main effect of Group nor any of its interactions approached significance (F(1, 31) < 1.7, p > .2). A similar analysis of error rates revealed a main effect of Phase and a Phase × Switch interaction of the same type as the RT data (F(1, 31) > 9.7; p < .005). However, again there was no significant main effect or any significant interactions involving the Group factor (F(1, 31) < 4.1), p > .05).


Atypical recruitment of medial prefrontal cortex in autism spectrum disorders: an fMRI study of two executive function tasks.

Gilbert SJ, Bird G, Brindley R, Frith CD, Burgess PW - Neuropsychologia (2008)

Behavioural data from the alphabet task. Left graph shows mean response time (RT) and right graph shows mean error rate, in each of four conditions depending on whether the phase was stimulus-oriented (SO) or stimulus-independent (SI), and whether the trial-type was switch (i.e. different phase to the previous trial: Sw) or non-switch (NS). Error bars indicate standard errors.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2648877&req=5

fig2: Behavioural data from the alphabet task. Left graph shows mean response time (RT) and right graph shows mean error rate, in each of four conditions depending on whether the phase was stimulus-oriented (SO) or stimulus-independent (SI), and whether the trial-type was switch (i.e. different phase to the previous trial: Sw) or non-switch (NS). Error bars indicate standard errors.
Mentions: Mean RTs and error rates are displayed in Fig. 2. Mean RTs were examined in an ANOVA with within-subject factors Phase (Stimulus-Oriented [SO] or Stimulus-Independent [SI]) and Switch (Switch trial – i.e. immediately following a switch between the SO and SI phases – or Non-switch trial) and between-subjects factor Group (ASD or Control). There were main effects of Phase, SI trials being slower than SO trials, and Switch, Switch trials being slower than Non-switch trials, along with a Phase × Switch interaction, because the RT difference between Switch and Non-switch trials was larger in the SI phase than the SO phase (F(1, 31) > 21; p < .0001). However, although there was a trend towards slower RTs in the ASD group, neither the main effect of Group nor any of its interactions approached significance (F(1, 31) < 1.7, p > .2). A similar analysis of error rates revealed a main effect of Phase and a Phase × Switch interaction of the same type as the RT data (F(1, 31) > 9.7; p < .005). However, again there was no significant main effect or any significant interactions involving the Group factor (F(1, 31) < 4.1), p > .05).

Bottom Line: Behaviourally, there were no significant differences between the two groups.However, on a new test of executive function (selection between stimulus-oriented and stimulus-independent thought), the ASD group exhibited significantly greater signal-change in medial rostral prefrontal cortex (especially Brodmann Area 10) in the comparison of stimulus-oriented versus stimulus-independent attention.These results underline the heterogeneity of different tests of executive function, and suggest that executive functioning in ASD is associated with task-specific functional change.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience and Department of Psychology, University College London, London, UK. sam.gilbert@ucl.ac.uk

ABSTRACT
Recent studies have suggested an uneven profile of executive dysfunction in autism spectrum disorders (ASD). For example, some authors have reported deficits on newly developed tests of executive function sensitive to rostral prefrontal function, despite spared, or even superior, performance on other tests. We investigated the performance of a group of high-functioning participants with ASD (N=15) and an age- and IQ-matched control group (N=18) on two executive function tests, whilst undergoing functional magnetic resonance imaging (fMRI). Behaviourally, there were no significant differences between the two groups. In a classical test of executive function (random response generation), BOLD signal differed between the groups in the cerebellum but not in the frontal lobes. However, on a new test of executive function (selection between stimulus-oriented and stimulus-independent thought), the ASD group exhibited significantly greater signal-change in medial rostral prefrontal cortex (especially Brodmann Area 10) in the comparison of stimulus-oriented versus stimulus-independent attention. In addition, the new test (but not the classical test) provided evidence for abnormal functional organisation of medial prefrontal cortex in ASD. These results underline the heterogeneity of different tests of executive function, and suggest that executive functioning in ASD is associated with task-specific functional change.

Show MeSH
Related in: MedlinePlus