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Using Brain Activation (nir-HEG/Q-EEG) and Execution Measures (CPTs) in a ADHD Assessment Protocol
Chapters
Summary April 1st, 2018
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.
Transcript
The overall goal for this protocol is to present a complete procedure or model of assessment for the diagnosis of Attention Deficit with Hyperactivity Disorder, otherwise known as ADHD. The purpose is to provide a more objective diagnostic procedure for this developmental disorder and to deepen our knowledge of 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.
ADHD is one of the problems that most affects cognitive performance. It is described as a persistent pattern of inattentive, restless, and impulsive behavior, which is more persistent than that of shared in others at the same stage of development. The latest addition of the Diagnostic and Statistical Manual, DSM-IV, this class three types of presentation of this disorder, predominantly hyperactive unenforcive, predominantly inattentive, and a combined presentation.
ADHD has been associated with a dysfunction in the central nervous system, which is characterized as a developmental delay and as a cortical hyperactivity in some brain areas, specifically in the dopaminergic and the androgenic systems. The androgenic system is involved in the regulation of selective attention and in the maintenance of the activation levels that we need in order to perform a task. The dopaminergic system is involved in the ability to control one's behavior both at a motivational and executive levels.
The dysfunction involved in systems, androgenic and dopaminergic systems, is considered to be one of the basis for the center of symptoms of ADHD:impulsiveness, hyperactivity, and lack of attention. One of the most common problems in the identification of the ADHD relates to the operative or diagnostic of this disorder due to the absence of a global protocol. This research group from the University of Oviedo has been working on developing accomplished protocol for assessment this developmental disorder.
This protocol suggests the existing of certain patterns of cortical activation and executive conduct that could be used for identifying more of ADHD. To verify the incidence of activation, cortical activation, and executive control, it is necessary that brain activation variables are recorded in the areas of central and prefrontal cortex as well as to administer different continuous performance tests. We are going to see how to use the continuous performance tests and the cortical activation techniques for the diagnosis of ADHD.
In this protocol, we use two types of continuous performance test, a traditional and widely used test called the test of variables of attention and a test based on virtual reality called Aula Nesplora. Aula Nesplora is a continuous performance test based on a virtual reality environment that reproduces the conditions of a regular classroom. This test evaluates attention, impulsivity, processing speed, and motor activity in children and adolescents aged between six to 16 years of age.
Head movements are registered by sensors located in the 3D virtual glasses, thus the software updates the angle of vision giving the subject the feeling of actually being in a virtual classroom. The duration of the Aula Nesplora test is 20 minutes. The test consists of three phases that are gradually explained by a virtual teacher.
The first phase aims to immerse the participant in the context of virtual reality, and it consists of visually locating balloons and popping them. The second phase is based on the X No paradigm, traditionally known as No/Go paradigm, in which the participant must press a button provided that he or she does not see or hear the stimulus apple. Finally, in the third phase, an X paradigm, or Go paradigm, is also incorporated with participants being asked to press a button whenever they see or hear the number seven, thus not only the delivery response but also its inhibition is assessed.
The test of variables of attention is another continuous performance test for people aged from four to 90. The exercise is based on the presentation of two simple images. The first one presents a square at the bottom of the screen, which is the target condition, and the second one presents a square at the bottom of the screen, the no target condition.
This test has three different stages:instructions, training, and test. The instruction stage explains to the participant the aim of the task as follows. You have to take this button and press it when you see a black square in the upper part.
However, do not press the button when the black square is in the bottom part. The training stage lasts three minutes, and its aim is to ensure the child understands the task. Before starting the test, we always tell the child that the task is long but they have to keep still and concentrate on doing the task.
The test lasts between 20 to 25 minutes. Many approaches have been developed to assist activation. The two measures described here are hemoencephalography, which provides data about blood oxygenation in the prefrontal cortex and quantified electroencephalogram, which provides data about electrical activation.
The quantified electroencephalogram is used to record electrical activity. This is a computerized EEG system that provides information on levels of cortical activation through the relationship of two waves, the beta-theta ratio. It measures the tension in general independently of the task to be performed.
In this procedure, an electrode is place on the subjects corresponding cortical area, CZ or FP1, to record the beta-theta ratio, and two more control electrodes are placed on the subjects left and right earlobe. Lastly, an EMG system is placed on the right forearm to quantify the degree of movement. Hemoencephalography aims to assist blood oxygenation in expressly selected areas of the prefrontal cortex.
The device consists of a band that is placed precisely on the front of the participant's head. The participant has to be quiet and peaceful for the duration of the procedure. The process employs the translucent property of biological tissue and low frequency red and infrared lights with light emitting diodes known as depth diodes.
The lights are emitted alternately onto the surface of the skin. The emitted light penetrates the tissue and is scattered, refracted, and reflected. A small amount of light modified by absorption in the tissue returns to the surface and is measured.
The ratio is calculated by comparing the red light, which is not absorbed as much by oxygenated hemoglobin with infrared light, which is less affected by oxygenation. Before administering the measure, we show the device and the band to the children so they can feel comfortable and safe. Then the participant is informed that they cannot move and must be still.
When we put the band on, it is important that external light cannot enter, so the band must be tight and secure. Also, it is necessary to be sure that it is well-situated in the specific button. To conduct this procedure, we need to introduce in the program the cortical point that we are going to assess, FP1 for assessment of inhibition capacity and FPZ for assessment of attention capacity.
The measure takes 35 seconds for each point. Due to the more complex nature of the stimuli, the Aula Nesplora parameters provide more comprehensive information than other other continuous performance tests. This test gives very useful information because it provides the same variables that other continuous performance tests do:omissions, commissions, response time, and variability.
But it also differentiates these measures by sensory modality, visual versus auditory, presence/absence of distractors, and task type, Go versus No Go.Unlike other tests, the Aula Nesplora Test also provides a reliable indicator of motor activity during performance. Once the test is completed, the program provides a report with a number of different variables. These variables include omissions, response time, commissions, response time variability, D prime, and an ADHD index.
When the obtained standard score is lower than 80, it is interpreted as a deficit in performance. Standard scores in the range of 80 to 85 indicate borderline performance. Poor performance on omissions or reaction time are indicative of an attention deficit, whereas poor performance on variability or commissions is related to hyperactivity and impulsivity.
An obtained beta theta ratio lower than 50%at CZ is associated with a deficit of sustained attention. And if the ratio is also lower in FP1, then the attentional deficit is associated with a lack of executive control attributable to hyperactivity. A ratio of less than 80 is used to indicate a possible deficit in attention or inhibition.
The device also provides an attention index, which indicates when the participant is incapable of increasing the ratio and thereby brain activation. This apparently indicates a lapse in the attentional process. In conclusion, according to the model of assessment reported in the study by Rodriguez and colleagues in 2016.
In this protocol about the ADHD diagnosis, if we consider it, separate the different variables, we can lose a lot of information about our subject and introduce different segments or that are really adaptive to the subjects. A comprehensive assessment has to include different variables but also we need to understand the relationship between these measures. In this case, activation and executive measures.
Overall, it is more or less important in several implications for both clinical and educational context as it allows assessment professionals to have a great information, to adapt the treatments and intervention to the profile of the client.
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