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Intraindividual variability in inhibitory function in adults with ADHD--an ex-Gaussian approach.

Gmehlin D, Fuermaier AB, Walther S, Debelak R, Rentrop M, Westermann C, Sharma A, Tucha L, Koerts J, Tucha O, Weisbrod M, Aschenbrenner S - PLoS ONE (2014)

Bottom Line: We did not find higher numbers of commission errors in aADHD, while the number of omissions was significantly increased compared with controls.In contrast to increased mean RT, the distributional parameter mu did not document a significant slowing in aADHD.Moreover, we found a significant correlation between tau and the number of omission errors.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Psychology and Neuropsychology, SRH Klinikum, Karlsbad-Langensteinbach, Germany.

ABSTRACT

Objective: Attention deficit disorder (ADHD) is commonly associated with inhibitory dysfunction contributing to typical behavioral symptoms like impulsivity or hyperactivity. However, some studies analyzing intraindividual variability (IIV) of reaction times in children with ADHD (cADHD) question a predominance of inhibitory deficits. IIV is a measure of the stability of information processing and provides evidence that longer reaction times (RT) in inhibitory tasks in cADHD are due to only a few prolonged responses which may indicate deficits in sustained attention rather than inhibitory dysfunction. We wanted to find out, whether a slowing in inhibitory functioning in adults with ADHD (aADHD) is due to isolated slow responses.

Methods: Computing classical RT measures (mean RT, SD), ex-Gaussian parameters of IIV (which allow a better separation of reaction time (mu), variability (sigma) and abnormally slow responses (tau) than classical measures) as well as errors of omission and commission, we examined response inhibition in a well-established GoNogo task in a sample of aADHD subjects without medication and healthy controls matched for age, gender and education.

Results: We did not find higher numbers of commission errors in aADHD, while the number of omissions was significantly increased compared with controls. In contrast to increased mean RT, the distributional parameter mu did not document a significant slowing in aADHD. However, subjects with aADHD were characterized by increased IIV throughout the entire RT distribution as indicated by the parameters sigma and tau as well as the SD of reaction time. Moreover, we found a significant correlation between tau and the number of omission errors.

Conclusions: Our findings question a primacy of inhibitory deficits in aADHD and provide evidence for attentional dysfunction. The present findings may have theoretical implications for etiological models of ADHD as well as more practical implications for neuropsychological testing in aADHD.

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Related in: MedlinePlus

Frequency of intraindividual RTs with fitted ex-Gaussian probability functions exemplary for a control (left) and an ADHD (right) subject.NOTE: Please keep in mind that RTs in ADHD encompass a broader range (200<RT<1000 ms) compared with controls (200<RT<500 ms) resulting in broader frequency bins for the ADHD subject. Both subjects are comparable with regard to relevant demographic variables.
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pone-0112298-g003: Frequency of intraindividual RTs with fitted ex-Gaussian probability functions exemplary for a control (left) and an ADHD (right) subject.NOTE: Please keep in mind that RTs in ADHD encompass a broader range (200<RT<1000 ms) compared with controls (200<RT<500 ms) resulting in broader frequency bins for the ADHD subject. Both subjects are comparable with regard to relevant demographic variables.

Mentions: Ex-Gaussian parameters were estimated for every single subject. A comparison of chi-square fitting statistics indicated a comparable fit to RT data for both subjects with aADHD and controls (z = 1.77, p = .077) allowing further between group comparisons of distributional parameters. The parameter μ did not differ significantly between groups (z = 1.81, p = .070, d = 0.4). However, we found significant differences for the parameters σ (z = 2.43, p = .015; d = 0.54) and τ (z = 2.48, p = .013; d = 0.68) indicating higher variability around the mean and a higher number of occasional slow reaction times in aADHD (see Figure 3 below).


Intraindividual variability in inhibitory function in adults with ADHD--an ex-Gaussian approach.

Gmehlin D, Fuermaier AB, Walther S, Debelak R, Rentrop M, Westermann C, Sharma A, Tucha L, Koerts J, Tucha O, Weisbrod M, Aschenbrenner S - PLoS ONE (2014)

Frequency of intraindividual RTs with fitted ex-Gaussian probability functions exemplary for a control (left) and an ADHD (right) subject.NOTE: Please keep in mind that RTs in ADHD encompass a broader range (200<RT<1000 ms) compared with controls (200<RT<500 ms) resulting in broader frequency bins for the ADHD subject. Both subjects are comparable with regard to relevant demographic variables.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4257533&req=5

pone-0112298-g003: Frequency of intraindividual RTs with fitted ex-Gaussian probability functions exemplary for a control (left) and an ADHD (right) subject.NOTE: Please keep in mind that RTs in ADHD encompass a broader range (200<RT<1000 ms) compared with controls (200<RT<500 ms) resulting in broader frequency bins for the ADHD subject. Both subjects are comparable with regard to relevant demographic variables.
Mentions: Ex-Gaussian parameters were estimated for every single subject. A comparison of chi-square fitting statistics indicated a comparable fit to RT data for both subjects with aADHD and controls (z = 1.77, p = .077) allowing further between group comparisons of distributional parameters. The parameter μ did not differ significantly between groups (z = 1.81, p = .070, d = 0.4). However, we found significant differences for the parameters σ (z = 2.43, p = .015; d = 0.54) and τ (z = 2.48, p = .013; d = 0.68) indicating higher variability around the mean and a higher number of occasional slow reaction times in aADHD (see Figure 3 below).

Bottom Line: We did not find higher numbers of commission errors in aADHD, while the number of omissions was significantly increased compared with controls.In contrast to increased mean RT, the distributional parameter mu did not document a significant slowing in aADHD.Moreover, we found a significant correlation between tau and the number of omission errors.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Psychology and Neuropsychology, SRH Klinikum, Karlsbad-Langensteinbach, Germany.

ABSTRACT

Objective: Attention deficit disorder (ADHD) is commonly associated with inhibitory dysfunction contributing to typical behavioral symptoms like impulsivity or hyperactivity. However, some studies analyzing intraindividual variability (IIV) of reaction times in children with ADHD (cADHD) question a predominance of inhibitory deficits. IIV is a measure of the stability of information processing and provides evidence that longer reaction times (RT) in inhibitory tasks in cADHD are due to only a few prolonged responses which may indicate deficits in sustained attention rather than inhibitory dysfunction. We wanted to find out, whether a slowing in inhibitory functioning in adults with ADHD (aADHD) is due to isolated slow responses.

Methods: Computing classical RT measures (mean RT, SD), ex-Gaussian parameters of IIV (which allow a better separation of reaction time (mu), variability (sigma) and abnormally slow responses (tau) than classical measures) as well as errors of omission and commission, we examined response inhibition in a well-established GoNogo task in a sample of aADHD subjects without medication and healthy controls matched for age, gender and education.

Results: We did not find higher numbers of commission errors in aADHD, while the number of omissions was significantly increased compared with controls. In contrast to increased mean RT, the distributional parameter mu did not document a significant slowing in aADHD. However, subjects with aADHD were characterized by increased IIV throughout the entire RT distribution as indicated by the parameters sigma and tau as well as the SD of reaction time. Moreover, we found a significant correlation between tau and the number of omission errors.

Conclusions: Our findings question a primacy of inhibitory deficits in aADHD and provide evidence for attentional dysfunction. The present findings may have theoretical implications for etiological models of ADHD as well as more practical implications for neuropsychological testing in aADHD.

Show MeSH
Related in: MedlinePlus