By analyzing the fluctuations of different brain states , neuroscientists from the Synapsy National Research Center (Switzerland) have identified a new neurological marker of attention deficit hyperactivity disorder (ADHD).
The results, published in the journal 'Biological Psychiatry: Cognitive Neuroscience and Neuroimaging', provide evidence for a stronger biomarker of ADHD and thus contribute to psychiatry becoming a more precise medical discipline.
ADHD affects five percent of adults, which makes it one of the most common psychological disorders . The current clinical diagnosis is based solely on questionnaires that focus primarily on the symptoms of inattention and impulsivity.
However, neuroscientists speculate that the causes of ADHD , although still not well understood , have a biological and genetic basis, which suggests that there could be biomarkers that aid in their diagnosis.
This was the objective of this new study supported by Synapsy, a research center that has combined psychiatry and neurosciences for the last twelve years to understand the neural bases of different psychological disorders in the hope of creating better means to diagnose and treat them.
With the support of the University of Geneva (UNIGE), the Center for Biomedical Imaging (CIBM) and the Geneva University Hospital (HUG), they focused their attention on a new electroencephalographic approach called microstates to identify the 'neurological signatures 'del attention deficit hyperactivity disorder (ADHD).
The microstate technique is used to observe the combined spatial and temporal aspects of brain activity. Using this technique, the research team found that a certain state of brain activity associated with sleep and attention lasted longer among people with ADHD.
IN SEARCH OF A BETTER RESEARCH TOOL
Electroencephalograms (EEG), a test that uses a network of electrode sensors placed on the subject's scalp to measure electrical fields generated by large-scale neural networks, could be used to detect ADHD.
In fact, recent studies have revealed abnormal EEG activity among ADHD patients, suggesting that abnormal brain development may be the cause of attention deficit hyperactivity disorder (ADHD).
However, the data vary too much from one study to another, which makes them unreliable markers of ADHD. «These variations are due, either to the great heterogeneity of the causes of ADHD, or to the fact that traditional EEG analyzes are not a good tool to delve into the matter, since they do not take into account the spatio-temporal aspects of the states cerebral “, says Tomás Ros, researcher at the Department of Psychiatry and Neuroscience of the Faculty of Medicine of UNIGE.
THE BRAIN MICROSTATES REVEAL TWO BIOMARKERS
Brain activity fluctuates successively from one state to another while at rest, manifesting different spatial configurations in the electric field of the EEG. Neuroscientists mostly speak of five main 'micro' states or configurations, ranging from A to E.
These different states remain stable for about one hundred milliseconds and change from one to another, hence their name 'microstates'. An EEG can detect them and extract their frequency, duration and order of appearance from the recordings.
Using this approach, the researchers found differences between adult patients with and without attention deficit hyperactivity disorder (ADHD). Brain ‘microstate’ A appears to have a shorter duration among patients diagnosed with ADHD.
“When comparing this observation with the data from the clinical questionnaires, we observe that this state is inversely correlated with the symptoms of inattention,” says Víctor Férat, researcher at the Functional Brain Mapping Laboratory and first author of the study.
Interestingly, the team observed that microstate D lasted longer in ADHD patients, and that this was associated with greater sleep disturbance, a typical ADHD symptom.
CONTROLLED RELIABILITY
As scientific findings must be reproduced in the field, the research team repeated their analyzes with a different cohort of patients to verify the generalizability of their findings.
In collaboration with Professor Martijn Arns, director of the Brainclinics institute in the Netherlands, the first collection of data from sixty-six patients diagnosed with attention deficit hyperactivity disorder (ADHD) and sixty-six people from the control group was validated by another cohort of twenty-two ADHD patients and twenty-two control subjects, registered with the HUG by the ADHD unit led by Professor Nader Perroud, co-author of the study. “In this case, we have replicated the results for microstate D, but not those for microstate A,” says Victor Férat.
Therefore, microstate D appears to be a replicable brain biomarker for ADHD. Furthermore, it appears to be associated with sleep disorder in this population, a key aspect of ADHD. These findings thus reveal a valuable tool for research, diagnosis and even treatment. “This biomarker could be monitored in real time during brain training with 'neurofeedback', for example,” concludes Ros.
