sLORETA and fMRI Detection of Medial Prefrontal Default Network Anomalies in Adult ADHD

Abstract

Attention deficit hyperactivity disorder (ADHD) is a developmental psychiatric disorder thought to affect approximately 5 to 10% of school-age children, of whom 30 to 65% continue to exhibit symptoms into adulthood. The prevalence of ADHD in adults is also an estimated 4%, second only to depression. Across studies there appear to be significant network dysfunctions involved in ADHD. Typically the foci of interest in ADHD included the insular cortices, frontal lobes, basal ganglia, and cerebellum. More recently, attention has been directed to the default network of the brain and its functional integrity in ADHD with focus on the precuneus and parietal lobes and interactions with medial prefrontal cortices. Functional magnetic resonance imaging (fMRI) measures neurovascular coupling as measured by the blood oxygenated level dependent signal (BOLD). Electroencephalogram (EEG) measures brain electrical information. Because fMRI is an indirect measure of neuronal activity and EEG is a direct measure, combining the results from these two imaging modalities under the same task conditions may provide a more complete story as to the what (EEG) and where (fMRI) activity exists. This article discusses the benefits of using standardized low resolution electromagnetic tomography (sLORETA) analysis of the EEG as compared to fMRI. The goal of the study, the data from which we use for our justification, was to discover the functional differences in ADHD and non-ADHD brains with different brain imaging modalities. We hoped to elucidate functional connectivity patterns by interpreting the data acquired with the EEG using sLORETA and the data acquired with the fMRI scans. We further hoped to find correlation with the sLORETA and fMRI interpretations so as to confirm that EEG is an adequate stand-alone methodology to evaluate ADHD. Participants included 6 ADHD and 7 non-ADHD subjects. They were initially interviewed by phone and administered the Connors Rating Scale and the Mini International Neuropsychiatric Interview to determine accuracy of symptom reporting and to rule out psychological comorbidities. Exclusion criteria consisted of previous head trauma, recent drug or alcohol abuse (14 days), or neurological syndromes. We recorded sequential 19-channel EEG and fMRI during the eyes-open and eyes-closed states and while performing the Stroop test. The QEEG results were evaluated with comparison to a normative database and with sLORETA analysis.Functional connectivity was assessed using the seed-based approach in sLORETA. The fMRI results were evaluated using Brain Voyager TM and other neuroimaging software packages. sLORETA and fMRI data identify a region in medial Brodmann Area (BA) 10 of the default network. Furthermore, regional frontal differences extend to medial BA 32 with more emphasis to left prefrontal. sLORETA determines there is less current source density at BA 10 in the ADHD participants than controls. sLORETA is adequate in localizing the sources of the EEG in the default network as contrasted with fMRI. It is impor...

Pilot Data Assessing the Functional Integrity of the Default Network in Adult ADHD with fMRI and sLORETA

“…A fiber optic keypad was used for participant responses. All parameters for data collection can be found in Cannon, Kerson, et al (2011). Subjects were instructed about the tasks they were to perform in the scanner.…”

“…Given indications from our previous work (Cannon, Kerson, et al, 2011) showing that medial BA 10 showed significant difference in activation between ADHD and control groups, we extracted the time-course from medial Brodmann area (BA) 10 region of interest (ROI 9 in Table 1) using the SPM VOI function, which pulls out the first eigenvector (principal component) of all voxels within a sphere across time (10 mm) based at the ROI coordinates. We then generated a psychological function based on rest versus task.…”

“…sLORETA has been used to examine EEG sources in depression (Pizzagalli, Oakes, & Davidson, 2003), epilepsy (Zumsteg, Andrade, & Wennberg, 2006), and evaluating temporal changes associated with differential task specific default network activity . Recently, sLORETA and fMRI were shown to localize DMN regions with complementary accuracy (Cannon, Kerson, & Hampshire, 2011). This study was conducted with one apriori hypothesis and two exploratory aims.…”

“…Next, we sought to examine connectivity between parieto-occipital and medial prefrontal regions, with special attention directed toward alpha and theta frequency domains between individuals with ADHD and controls. Finally, we sought to explore the utility of consecutive measurements using fMRI and sLORETA for improving our understanding of the relationship and meaning of the EEG and fMRI in the DMN Cannon, Kerson, et al 2011).…”

Electrophysiological evidence during episodic prospection implicates medial prefrontal and bilateral middle temporal gyrus

“…Previous research has demonstrated a direct connection in resting state functional connectivity between the DMN as identified by fMRI blood-oxygen-level dependent (BOLD) signals and EEG oscillations in very low frequency (Hiltunen et al, 2014), and higher frequency domains (Laufs et al, 2003;Mantini, Perrucci, Gratta, Romani, & Corbetta, 2007). Strong association between fMRI BOLD signals and EEG oscillations have been observed in anterior MPFC, one of the DMN hubs, during cognitive task performance in both healthy volunteers (Meltzer, Negishi, Mayes, & Constable, 2007;Scheeringa et al, 2009), and a clinical sample with attention-deficit/hyperactivity disorder (ADHD; Cannon, Kerson, & Hampshire, 2011;Cannon, Kerson, Hampshire, & Garner, 2012). Taken together, EEG offers an ideal platform to investigate brain oscillations during episodic prospection.…”