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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

(Top) Regions showing significantly greater activation related to the contrast of SO > SI in the ASD than the control group. (Bottom) Regions showing activation in the contrast of SO > SI when the two groups are pooled. Results are plotted on a sagittal slice of the participants’ mean normalized structural scan (top: x = 0, bottom: x = 2, so that each slice displays the relevant peak voxel). Mean contrast estimates are plotted at the peak BA 10 voxel for each contrast (top: 0, 48, 2; bottom: 2, 64, 28) separately for the ASD and control groups. Error bars indicate standard errors.
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fig6: (Top) Regions showing significantly greater activation related to the contrast of SO > SI in the ASD than the control group. (Bottom) Regions showing activation in the contrast of SO > SI when the two groups are pooled. Results are plotted on a sagittal slice of the participants’ mean normalized structural scan (top: x = 0, bottom: x = 2, so that each slice displays the relevant peak voxel). Mean contrast estimates are plotted at the peak BA 10 voxel for each contrast (top: 0, 48, 2; bottom: 2, 64, 28) separately for the ASD and control groups. Error bars indicate standard errors.

Mentions: Inspection of Tables 4 and 5 suggests differences between the ASD and control groups not only in the overall level of medial rostral PFC activation associated with the SO > SI contrast, but also in the location of activation peaks. Specifically, the peak medial rostral PFC activations appear to be relatively caudal in the ASD group, compared with the control group. In order to test for such differences, the peak medial rostral PFC co-ordinate for the SO > SI contrast was extracted individually for each participant (see Gilbert, Williamson, et al., 2007, for a similar approach). Medial rostral PFC was defined here as −8 ≤ x ≤ 8, y > 40, −12 ≤ z ≤ 30, as in our previous study (Gilbert, Williamson, et al., 2007). Analysis of these data confirmed that peak co-ordinates were indeed more caudal in the ASD group than the control group (ASD: mean y = 52.9; control: mean y = 58.4; F(1, 31) = 4.8, p < .05). However, a similar analysis of the medial rostral PFC peaks associated with the Baseline > Random contrast did not produce a significant group difference (ASD: mean y = 53.3; control: mean y = 55.1; F < 1). The results from the SO > SI contrast are illustrated in Fig. 6, which displays regions showing greater activity associated with the SO > SI contrast in the ASD than the control group, along with results from the SO > SI contrast in an analysis where the two groups were combined. It can be seen that the more caudal medial PFC region activated in the subtraction between the groups is activated in the ASD but not in the control group. By contrast, the more rostral medial PFC region activated when the groups were combined shows similar levels of activity in the two groups. It therefore seems likely that the ASD group showed more widespread activity related to the SO > SI contrast than the control group.


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)

(Top) Regions showing significantly greater activation related to the contrast of SO > SI in the ASD than the control group. (Bottom) Regions showing activation in the contrast of SO > SI when the two groups are pooled. Results are plotted on a sagittal slice of the participants’ mean normalized structural scan (top: x = 0, bottom: x = 2, so that each slice displays the relevant peak voxel). Mean contrast estimates are plotted at the peak BA 10 voxel for each contrast (top: 0, 48, 2; bottom: 2, 64, 28) separately for the ASD and control groups. Error bars indicate standard errors.
© Copyright Policy
Related In: Results  -  Collection

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

fig6: (Top) Regions showing significantly greater activation related to the contrast of SO > SI in the ASD than the control group. (Bottom) Regions showing activation in the contrast of SO > SI when the two groups are pooled. Results are plotted on a sagittal slice of the participants’ mean normalized structural scan (top: x = 0, bottom: x = 2, so that each slice displays the relevant peak voxel). Mean contrast estimates are plotted at the peak BA 10 voxel for each contrast (top: 0, 48, 2; bottom: 2, 64, 28) separately for the ASD and control groups. Error bars indicate standard errors.
Mentions: Inspection of Tables 4 and 5 suggests differences between the ASD and control groups not only in the overall level of medial rostral PFC activation associated with the SO > SI contrast, but also in the location of activation peaks. Specifically, the peak medial rostral PFC activations appear to be relatively caudal in the ASD group, compared with the control group. In order to test for such differences, the peak medial rostral PFC co-ordinate for the SO > SI contrast was extracted individually for each participant (see Gilbert, Williamson, et al., 2007, for a similar approach). Medial rostral PFC was defined here as −8 ≤ x ≤ 8, y > 40, −12 ≤ z ≤ 30, as in our previous study (Gilbert, Williamson, et al., 2007). Analysis of these data confirmed that peak co-ordinates were indeed more caudal in the ASD group than the control group (ASD: mean y = 52.9; control: mean y = 58.4; F(1, 31) = 4.8, p < .05). However, a similar analysis of the medial rostral PFC peaks associated with the Baseline > Random contrast did not produce a significant group difference (ASD: mean y = 53.3; control: mean y = 55.1; F < 1). The results from the SO > SI contrast are illustrated in Fig. 6, which displays regions showing greater activity associated with the SO > SI contrast in the ASD than the control group, along with results from the SO > SI contrast in an analysis where the two groups were combined. It can be seen that the more caudal medial PFC region activated in the subtraction between the groups is activated in the ASD but not in the control group. By contrast, the more rostral medial PFC region activated when the groups were combined shows similar levels of activity in the two groups. It therefore seems likely that the ASD group showed more widespread activity related to the SO > SI contrast than the control group.

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