This work presents a new protocol for the assessment of Attention Deficit Hyperactivity Disorder (ADHD) by providing a more objective diagnostic procedure for this developmental disorder based on the use of innovative tools. It also analyzes the relationship between activation measures and executive function measures.
Attention Deficit Hyperactivity Disorder (ADHD) is a problem that impacts academic performance and has serious consequences that result in difficulties in scholastic, social and familial contexts. One of the most common problems in the identification of this disorder relates to the apparent over diagnosis of the disorder due to the absence of global protocols for assessment. The research group of School Learning, Difficulties and Academic Performance (ADIR) from the University of Oviedo, has developed a complete protocol that suggests the existence of certain patterns of cortical activation and executive control for identifying ADHD more objectively. This protocol takes into consideration some of the hypothetical determinants of ADHD, including the relationship between activation of selected areas of the brain, and differences in performance on various aspects of executive functioning such as omissions, commissions or response times, using innovative tools of Continuous Performance Testing (based on Virtual Reality CPT and Traditional CPT) and brain activation measures (two different tools, based on Hemoencephalography- nirHEG; and Quantified Electroencephalography –Q-EEG, respectively). This model of assessment aims to provide an effective assessment of ADHD symptomatology in order to design an accurate intervention and make appropriate recommendations for parents and teachers.
The overall goal of the present protocol is to develop a complete procedure or model of assessment for the diagnosis of Attention Deficit Hyperactivity Disorder, otherwise known as ADHD. ADHD is one of the problems that impacts academic performance. It is understood to be a disorder characterized by problems with attention, inhibitory control and hyperactivity, whose performance is significantly lower than their peers1,2. The latest version of the Diagnostic and Statistical Manual of Mental Disorders (DSM)1 includes different updates from the previous version: ADHD has been categorized as a neurodevelopmental disorder; the age of appearance of the symptoms has been increased so now the symptoms can manifest before 12 years of age; the term ADHD presentation should be used instead of subtype (predominantly hyperactive/impulsive; predominantly inattentive; and combined presentation, and); finally, it has been accepted as a comorbidity with autism spectrum disorders.
There are different estimations of prevalence rates depending on the country or region analyzed3,4,5. An international global systematic3 review observed an average prevalence rate of 5.29%. However, applying criteria from the Diagnostic and Statistical Manual of Mental Disorders4, the percentage ranges from 5.9 to 7.1%. Similarly, a meta-analysis of ADHD in a Spanish population provided an average of 6.8%5. The variations in prevalence rates could be due to the different assessment protocols used.
Although there is a considerable body of research suggesting a neurological basis for ADHD, the origins of this disorder remain unclear. Several studies have associated the ADHD symptomatology to brain cortical hypoactivation, which is related to a deficit in the dopaminergic and noradrenergic systems6. The noradrenergic system modules the selective attention and the activation levels needed to carry out a task. On the other hand, the dopaminergic system is responsible for inhibitory control, both at an executive and motivational level. The low cortical activation related to the dopaminergic and noradrenergic systems is presumed to be the basis for the inhibitory and attentional deficits presented in the ADHD. In this sense, children with ADHD show low cortical activation in the dopaminergic and noradrenergic systems, which is manifested by different profiles of electro cortical activity in a state of rest, evidenced by increased theta -and decreased beta- activity7,8 as well as low levels of blood oxygenation in the Fp1 (front left side of the frontal lobe), and FPz/Cz (central zone of the pre-frontal cortex) regions.
Blood oxygenation is measured using nir-HEG, which uses functional near-infrared spectroscopy to measure color changes in the blood in the brain to indicate oxygen saturation areas; oxygenated blood is bright red whereas de-oxygenated blood is a deep, almost purplish crimson. Cortical activation is measured using quantified electroencephalography (Q-EEG). This is a computerized EEG system that records electrical activity in the brain to provide levels of cortical activation through the beta/theta ratio. It measures attention in general, independently of the task being performed. Other studies have focused on the existence of an executive function (EF) impairment in the ADHD population9, which would explain the difficulty children with ADHD have controlling impulsive responses, resisting interference or distraction, organizing activities in a sequential manner, and sustaining cognitive effort while performing an activity.
Generally, these characteristic symptoms of ADHD have serious consequences which result in difficulties in scholastic, social and familial contexts. Children with ADHD have a higher probability of repeating a grade and/or completing fewer grades at school than children without ADHD. Moreover, dropping out of high school is three times more likely among youth with ADHD10,11.
Considering the modifications and the new categorization of ADHD in the current version of the Diagnostic and Statistical Manual of Mental Disorders 1, results relevant to establish the relationship between cortical activation levels in specific brain areas, executive functions, and diagnosis-related variables7,8,11,12 (i.e., differences between the three types of ADHD presentations).
One of the most common problems in the identification of ADHD is the over diagnosis of the disorder due to the absence of global protocols for assessment. The fact that professionals do not have a general protocol based on objective variables is causing a large percentage of false positive and false negative cases of ADHD. This situation highlights the need for professionals and clinicians to have a clear protocol that considers not only the relevant variables but also the relationships between them.
For this reason, the research group of School Learning, Difficulties and Academic Performance (ADIR) from the University of Oviedo has been working on developing a complete protocol to identifyprofiles of cortical activation and executive control to provide a more objective diagnosis of ADHD than what is currently in use. This protocol is particularly important because it takes into account the fact that cortical activation in the frontal and prefrontal cortex impacts the executive function. The current protocol will be useful for clinicians who are interested in performing a complete assessment that considers the interaction between relevant variables in the diagnosis. To that end, the protocol is based on the assessment model from a recent study proposed by Rodriguez et al. which takes into consideration the interaction between cortical activation and executive variables (Figure 1).
In summary, the purpose of this protocol is to provide a more objective diagnostic procedure for this developmental disorder than is currently available, and to analyze in depth the relationship between activation measures and executive function measures. The procedure will also take into consideration some of the hypothetical determinants of ADHD, both in the relationship between activation of selected areas of the brain and differences in performance on various aspects of executive functioning such as omissions, commissions or response times.
The present study was conducted according to the Declaration of Helsinki, which establishes the ethical principles for research involving human beings. The study's aims, scope and procedure were also approved by the Ethics Committee of the University of Oviedo and University Hospital of Asturias.
1. Parents Report
2. Cognitive Measures
3. Executive Measures Using Continuous Performance Tests
4. Cortical Activation Measures in Fp1 and Fpz/Cz Regions (Hemoencephalography, and Quantified Electroencephalography) 17
Using the assessment procedure presented here, it is possible to carry out an effective assessment about ADHD symptomatology in order to design an accurate intervention and make recommendations for parents and teachers. Below are a series of representative results of a participant with ADHD and a participant without ADHD, which will allow professionals to see the differences between the two profiles.
Once clinicians had the informed consent from the families, a cognitive scale (WISC IV) was administered to the children in order to exclude those participants who present low or high capacities. The following steps then compiled an attentional profile of the children using the Continuous Performance Test and Activation Cortical Techniques (Q-EEG and nir-HEG). Figure 7 shows the results of children with and without ADHD in the Virtual Reality CPT. These results show the children with ADHD have more omissions and commissions errors, as well as higher motor activity and larger response times.
Similarly, Figure 8 shows the results obtained by the Traditional CPT showing how the child with ADHD presented larger percentages in omissions, commissions, response times and in the variability of the response. While the child without ADHD showed the best scores at the end of the tasks, the child with ADHD did not show improvement in any of the four blocks.
Figure 9 shows an example of the Cortical Activation collected by nir-HEG in a child affected by ADHD who obtained 24.5 percentage points below the average in Fp1 region.
Similarly, an example of the measures collected by Q-EEG in a child with ADHD (FP1 region) are shown in Figure 10 that evidences how the symptoms of ADHD cause a decreased in cortical activation (ratio beta/theta under 0.5).
Figure 1. Model of ADHD assessment
Based on Hemoencephalograpy (nir-HEG), Quantified Electroencephalography (Q-EEG), and Traditional CPT (CPT). Variables included: HEG-Fp1(nir-HEG ratio from left pre-frontal cortex); HEG-FpZ (nir-HEG ratio from central pre-frontal cortex); Q-EEG-Fp1(beta-theta ratio from left pre-frontal cortex); Q-EEG-CZ (beta-theta ratio from central cortex); CPT-OMIS (omissions committed in CPT ); CPT-COMIS (commissions committed in CPT); CPT-VAR (Response Variability during CPT tasks); CPT-RT (Response Time obtained in CPT); CPT-DPR (D prime Index provided by CPT); ADHD-INDEX (ADHD Index provided by CPT). This model reflects a stronger association between activation (central and left prefrontal) and execution in ADHD children than their peers without the disorder. Low cortical activation (by QEEF) and blood oxygenation (by nir-HEG) in Fp1 region, are related to low performance in CPT. Similarly, normal levels of electrical activation and blood oxygenation are associated to normal results from CPT. Provided by Rodríguez et al.11. Please click here to view a larger version of this figure.
Figure 2. Head Mounted Display(HMD) glasses of the Virtual Reality CPT.
The image shows the Head Mounted Display (HMD) glasses, the headphones and the button which must be held with the dominant hand. The image also shows the virtual classroom which is shown to the participant via the glasses and to the therapist via the computer screen. Please click here to view a larger version of this figure.
Figure 3. Virtual classroom provided by the Virtual Reality CPT.
Virtual classroom environment where the participant does the tasks which are explained by a virtual teacher. Please click here to view a larger version of this figure.
Figure 4. Images present in the Traditional CPT.
The right-hand picture shows the non-target stimulus and the left-hand picture shows the target stimulus. Please click here to view a larger version of this figure.
Figure 5. Participant wearing the nir-HEG band.
The image shows the nir-HEG band placed in the Fp1 region and the hardware connected.
Figure 6. Participant with electrodes of Q-EEG.
The image shows the blue electrode in the Cz region and the red one in the Fp1 region. The control electrodes: black and white, have been placed on the participant´s left and right earlobes, applying electrode gel. Finally, an electromyogram was placed on the right forearm.
Figure 7. Performance and motor activity during the Virtual Reality CPT.
The Y axis shows the standardized scores from the Virtual Reality CPT (scores above 60 mean low performance in the variable studied and scores below 60 mean good performance of the variables studied. The X axis shows the different variables provided by the Virtual Reality test. The colors: yellow, orange and red, represent the grade of severity: low, medium and high in the performance of different variables. A and C illustrate the performance of a participant without ADHD (A) and a participant with ADHD (C).
Images B and D represent the subject´s head movement (motor activity) throughout the test. The green square refers to the blackboard and the yellow square represents the area in which the virtual blackboard can be inside the visual range for detecting the stimulus. If child move out of the yellow square, it makes impossible to perform the visual task properly. The dot diagram provides a graphic which represents the child's attention towards the blackboard and to the general task. Image B represents the motor activity in a participant without ADHD and image D represents the motor activity of a participant with ADHD.
Figure 8. Profile provided by the Traditional CPT in the main variables.
Figure A represents the profile of a student with ADHD while Figure B shows the execution of a child with a performance similar to the normative group. The term "SS" refers to Standardized scores. Standardized scores below 80 represent low performance. "Q1"(25%), "Q2"(50%), "Q3"(75%) and "Q4"(100%) represent the four quartiles of the CPT tasks. This division is useful in order to see whether the subject's attention decreases during the activities or not.
Figure 9. Activation measure with the nir-HEG.
This Figure shows the ratio indicator of the oxygenation of the blood at specific point (Fp1/Fpz) and an attention index which is expressed as percentage (a percentage below 50% represents a low attentional index).
Figure 10. Cortical activation measures in FP1.
The Figures show the output from Q-EEG. The top part shows beta/theta waves measured individually, and the bottom part shows the beta/theta ratio in the Cz region and electromyography results from the right forearm. The CZ beta/theta ratio is shown on the left (in this case is 0.55), cortical activation is good when the ratio is above 0.50. The electromyography from the right forearm is used to ensure that the participant is relaxed at a muscular level, and is on the right (in this case the value of EMG is 4.22). Good values in electromyography are below 5.0. Please click here to view a larger version of this figure.
Here we present an effective protocol for assessing ADHD from 6-16 years of ages. Given the symptomatic complexity of ADHD and its high prevalence rates, professionals must have reliable and valid instruments to diagnose this disorder. Generally, questionnaires based on behavioral observations are widely used. However, the use of these instruments as the sole assessment measure has certain limitations, including potential subjectivity on the part of the observer18.
As the results show, this protocol placed emphasis on highlighting the differences between a participant with ADHD against a participant without ADHD. More specifically, it could be seen that a participant with ADHD had lower scores in attentional variables from both CPTs (omissions, commissions, response times and motor activity) as well as lower cortical activation and blood oxygenation in Fp1 and Fpz/Cz brain regions. For this reason, it is very relevant to contrast the information obtained by observation scales with the cognitive profile of the children and the performance in CPTs. Professionals can then perform a more realistic and reliable assessment and, thus provide recommendations for parents and teachers that are more specifically adapted to the individual needs of each child.
However, a critical step of this protocol is the management of exclusion criteria; professionals must ensure the ADHD symptoms are not due to another cause such as perceptive, emotional or social problems19.
A minor limitation of this protocol is the time required to complete each assessment. Generally, this protocol is best divided into several sessions to ensure participant well-being. The applicability of this method has been presented in previous studies11,12 which showed the effectiveness of the assessment model for getting an accurate diagnosis of ADHD according to the Diagnostic and Statistical Manual of Mental Disorders criteria.
Future lines of research would be based on the inclusion of neurological tools for getting an objective assessment of ADHD, considering functional and structural neuroimaging methods. Although, this research used quantitative analysis from Quantified Electroencephalography and Hemoencephalography (nir-HEG), it would be positive the inclusion of other instruments to contrast neuropsychological measures. Moreover, this type of study helps the clinicians to detect specific profiles of cortical activation (Q-EEG) and CPT (executive control) to differentiate the three types of ADHD presentations.
The authors have nothing to disclose.
This work has been supported by a project of the Principality of Asturias (FC-15-GRUPIN14-053) and a predoctoral grant from the Severo Ochoa Program (BP14-030). We would like to thank Anna Bujnowska for her contribution and Heather Marsh and Nigel Marsh for their help.
EDAH | TEA Company | It is a Scale for the Assessment of ADHD that was administered to families and/or teachers. It comprises 20 items that provide information on the presence of symptoms relating to attention deficit and hyperactivity/impulsivity, and helps differentiate between the threes subtypes of ADHD. A score above 90% in its subscales indicates attention deficit, hyperactivity/ impulsivity problems, or both. |
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Wisc-IV R | TEA Company | The WISC-IV by Wechsler (2005) is a tool that assesses individual intelligence in children and adolescents between the ages of 6 years and 16 years 11 months. |
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QEEG | Neurobics pocket | Q-EEG (quantified electroencephalogram) is a computerized EEG system, adapted by Toomin, which provides levels of cortical activation through the beta/theta ratio. It measures attention in general, independently of the task to be performed. |
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NIR-HEG | Brain trainer company | it is a tool used to measure blood oxygenation in expressly selected areas. The nir-HEG employs the translucent property of biological tissue, and low-frequency red and infrared lights with light emitting diodes (LED optodes). | |
AULA Nesplora | Nesplora Company | It is a Continuous Performance Test that evaluates attention, impulsivity, processing speed, and motor activity in participants between 6 and 16 years of age. The task is performed in a virtual reality environment, which is shown through three-dimensional (3D) glasses (Head Mounted Display, HMD) equipped with motion sensors and headphones. |
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T.O.V.A (Test of Variables of Attention) | The T.O.V.A. Company | T.O.V.A. 8 kit | T.O.V.A. is an objective, accurate, and FDA cleared continuous performance test (CPT) that measures the key components of attention and inhibitory control. The T.O.V.A. is used by qualified healthcare professionals as an aid in the assessment of attention deficits, including attention-deficit/hyperactivity disorder (ADHD), in children and adults. |