Deficits in executive functions, e.g. voluntary selection, are considered central to the attention-deficit/hyperactivity disorder (ADHD). The aim of this simultaneous EEG/fMRI study was to examine associated neural correlates in ADHD patients. Patients with ADHD and healthy subjects performed an adapted go/nogo task including a voluntary selection condition allowing participants to freely decide, whether to press the response button. Electrophysiologically, response inhibition and voluntary selection led to fronto-central responses. The fMRI data revealed increased medial/lateral frontal and parietal activity during the voluntary selection task. Frontal brain responses were reduced in ADHD patients compared to controls during free responses, whereas parietal brain functions seemed to be unaffected. These results may indicate that selection processes are related to dysfunctions, predominantly in frontal brain regions in ADHD patients.
"We included studies that fulfilled the following criteria: (a) employed fMRI and a motor inhibition task (stop-signal or go/no-go), (b) compared ADHD patients with healthy control subjects, (c) analyzed the data to assess motor response inhibition, and (d) reported the coordinates of activation areas normalized into a stereotaxic standardized space (such as Talairach space or Montreal Neurological Institute [MNI] space). We excluded studies on the following grounds: (a) the data analysis was not focused on motor response inhibition but rather on posterrors (Spinelli, Vasa, et al., 2011), inhibitory errors (Spinelli, Joel, et al., 2011), or selection conditions (Karch et al., 2010); (b) included overlapping samples (Suskauer, Simmonds, Caffo, et al., 2008a); or (c) used region-of-interest approaches (Liddle et al., 2011). Based on these criteria, 23 studies (listed in Table 1) were eligible for analysis, including 15 studies that used a go/no-go task (Booth et al., 2005; Dibbets, Evers, Hurks, Marchetta , & Jolles, 2009; Dillo et al., 2010; Durston, Mulder, Casey, Ziermans, & van Engeland, 2006; Durston et al., 2003; Epstein et al., 2007; Kooistra et al., 2010; Ma et al., 2012; Mulligan et al., 2011; Schulz et al., 2004; Schulz, Newcorn, Fan, Tang, & Halperin , 2005; Siniatchkin et al., 2012; Smith, Taylor, Brammer, Toone, & Rubia, 2006; Suskauer, Simmonds, Fotedar, et al., 2008b: and 1 study that used; Tamm, Menon, Ringel, & Reiss, 2004), seven studies that used a stop-signal task (Cubillo et al., 2010; Hart et al., 2014; Passarotti, Sweeney, & Pavuluri, 2010; Rubia et al., 2010; Rubia, Halari, Mohammad, Taylor, & Brammer , 2011; Rubia et al., 1999; Rubia, Smith, Brammer, Toone, & Taylor, 2005), and one study that used both (Sebastian et al., 2012). "
[Show abstract][Hide abstract] ABSTRACT: Attention-deficit hyperactivity disorder (ADHD) has been recognized as a disorder of executive function, and a number of functional MRI (fMRI) studies have been conducted to investigate the altered brain activation patterns between ADHD patients and healthy controls. However, the findings across different studies have been inconsistent, and the different neural mechanisms between adults and children with ADHD remain unclear. The aim of this study was to perform a meta-analysis of fMRI studies to further investigate and compare the abnormalities in adults and children with ADHD during motor response inhibition.
Activation likelihood estimation (ALE) was used to investigate brain activation differences between ADHD patients and controls, and a subtraction meta-analysis was performed to compare adult and child patients.
Twenty-three studies met the inclusion criteria. Meta-analysis using ALE detected significantly decreased activation during response inhibition in ADHD in the supplementary motor area, insula, caudate, and precentral gyrus, as well as increased activation in the postcentral gyrus, inferior frontal gyrus, and precuneus. The activation decreases in the right caudate were greater in child ADHD patients than adult ADHD patients.
This meta-analysis identified dysfunction in several areas of the motor inhibition network that may play a role in the abnormal neural mechanisms of response inhibition in ADHD. The comparison of child and adult subgroups raises the possibility that the persistence of functional abnormalities of the caudate may be an important factor in whether ADHD persists. (PsycINFO Database Record
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"This approach is also designated " integration-byprediction " regarding that single-trial EEG/fMRI analyses usually employ EEG-derived regressors as predictors of the fMRI BOLD responses (for more detail see Debener et al., 2006; Eichele et al., 2009; Bland et al., 2011). In the process of isolating taskrelated single-trial EEG activity, different routines have been used: single-trial EEG features are extracted from single independent components (ICs) reflecting best the EEG component of interest (Debener et al., 2005; Feige et al., 2005; Mobascher et al., 2009), from artifact-cleaned EEG data using several electrodes (Eichele et al., 2005; Novitskiy et al., 2011) or single electrodes (Bénar et al., 2007; Mulert et al., 2008; Warbrick et al., 2009; Karch et al., 2010; Scheibe et al., 2010; Juckel et al., 2012; Baumeister et al., 2014). However, in the majority of studies components of interest were identified by visual inspection, which depends on subjective evaluation and can be biased by inter-and intra-individual variations of the evaluator. "
[Show abstract][Hide abstract] ABSTRACT: Due to its millisecond-scale temporal resolution, EEG allows to assess neural correlates with precisely defined temporal relationship relative to a given event. This knowledge is generally lacking in data from functional magnetic resonance imaging (fMRI) which has a temporal resolution on the scale of seconds so that possibilities to combine the two modalities are sought. Previous applications combining event-related potentials (ERPs) with simultaneous fMRI BOLD generally aimed at measuring known ERP components in single trials and correlate the resulting time series with the fMRI BOLD signal. While it is a valuable first step, this procedure cannot guarantee that variability of the chosen ERP component is specific for the targeted neurophysiological process on the group and single subject level. Here we introduce a newly developed data-driven analysis procedure that automatically selects task-specific electrophysiological independent components (ICs). We used single-trial simultaneous EEG/fMRI analysis of a visual Go/Nogo task to assess inhibition-related EEG components, their trial-to-trial amplitude variability, and the relationship between this variability and the fMRI. Single-trial EEG/fMRI analysis within a subgroup of 22 participants revealed positive correlations of fMRI BOLD signal with EEG-derived regressors in fronto-striatal regions which were more pronounced in an early compared to a late phase of task execution. In sum, selecting Nogo-related ICs in an automated, single subject procedure reveals fMRI-BOLD responses correlated to different phases of task execution. Furthermore, to illustrate utility and generalizability of the method beyond detecting the presence or absence of reliable inhibitory components in the EEG, we show that the IC selection can be extended to other events in the same dataset, e.g., the visual responses.
Frontiers in Neuroscience 07/2014; 8(8):175. DOI:10.3389/fnins.2014.00175 · 3.66 Impact Factor
"The experiment consisted of an adapted auditory go/no-go task [see also Ref. (35)]: during the go condition subjects were instructed to press a response button as quick as possible while minimizing errors; during the no-go condition, this response was to be inhibited. In the voluntary selection condition, participants were allowed to freely decide, whether to press the response button or not. "
[Show abstract][Hide abstract] ABSTRACT: Deficits in executive functions, including voluntary decisions are among the core symptoms of attention deficit/hyperactivity disorder (ADHD) patients. In order to clarify the spatiotemporal characteristics of these deficits, a simultaneous EEG/functional MRI (fMRI) study was performed. Single-trial coupling was used to integrate temporal EEG information in the fMRI analyses and to correlate the trial by trial variation in the different event-related potential amplitudes with fMRI BOLD responses. The results demonstrated that during voluntary selection early electrophysiological responses (N2) were associated with responses in similar brain regions in healthy participants as well as in ADHD patients, e.g., in the medial-frontal cortex and the inferior parietal gyrus. However, ADHD patients presented significantly reduced N2-related BOLD responses compared to healthy controls especially in frontal areas. These results support the hypothesis that in ADHD patients executive deficits are accompanied by early dysfunctions, especially in frontal brain areas.
Frontiers in Psychiatry 04/2014; 5:41. DOI:10.3389/fpsyt.2014.00041
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