Brain monitoring suggests common link between electrical tremors and mental health disorders

Brain monitoring suggests common link between electrical tremors and mental health disorders

A new review of current literature, conducted by the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, has found that irregular responses in the brain to challenging tasks and mistakes could be key to understanding common links between abnormal behaviours in a range of mental illness and cognitive disorders.

The researchers reviewed studies that measured brief electrical tremors – naturally occurring electrical vibrations produced in areas at the front of the brain – using EEG, an electrophysiological monitoring method to record electrical activity on the scalp.  By collating the findings from the studies they found that brain waves, known as ‘theta activity’, in people with conditions like anxiety, OCD, and ADHD are different following mistakes or challenging situations compared to the theta activity in those with healthy brains.

The results, published today in Biological Psychiatry, show that disorders like anxiety, OCD and ADHD are strongly linked to brainwaves that oscillate in consistently divergent ways from healthy brains in the midfrontal region of the brain. The researchers suggest that with further investigation measurements of theta activity have the potential to improve diagnostic methods and the effectiveness of currently available treatments like CBT.

Oscillations in the theta frequency range are becoming increasingly recognised as related to behavioural and cognitive control, hallmarks of healthy behaviour, and disruption in these oscillations have been connected to a range of psychiatric illnesses. This study establishes that, in more than one type of mental illness, theta-related signals act in ways that diverge from the behaviours seen in healthy brains.

In anxious individuals for example, research suggests that there is a significantly higher degree of frontal-midline theta activity compared to non-anxious individuals, and that could be associated with more reactive control modes of behaviour in the moment rather than proactive behaviours such as planning and preparation.

Many studies use what’s known as the Eriksen Flanker test to investigate this. A participant’s reaction time is measured by asking them to press a correct button while being presented with distractions. In anxious individual’s, their response time is negatively affected following a mistake as their focus is still on the mistake they just made rather than the task at hand. This could explain how the distraction of worries affects behaviour, as it depletes the required mental capacity needed for active maintenance of task rules and goals.

Comparatively, the review found recent studies of ADHD suggest that a dysregulation of theta signals when performing tasks resulted in a different type of negative effect on performance. Again, in tests that measure response times, the theta activity in individuals with ADHD rises either too early or too late for them to make an appropriate decision based on what they perceive. Similar levels of dysregulation are found in those with substance use disorder.

Dr Grainne McLoughlin, the study’s first author from King’s IoPPN said, “From our review, we see that a healthy brain is one in which we see consistent levels of theta activity at the right moments. Theta activity in an anxious person for example is imbalanced over time compared to someone without anxiety. Someone experiencing anxiety, while able to take in new information, isn’t able to alter their cognitive behaviour effectively going forward because they are overfocussed on reacting immediately to environmental stimuli. Consistency and balance in these signals are thought to be essential for effective communication between brain regions, and appropriate and timely responses to our environment.”

Dr Scott Makeig, the study’s Lead Investigator from the University of California San Diego and who has long investigated ways to map and model frontal theta activity, said, “Frontal midline theta complexes in scalp-recorded brain electrical signals play essential roles in these transient theta network events which also seem to synchronize higher-frequency activities to regulate communication between brain executive, sensory and motor areas supporting quick behavioural responses and situational awareness of their consequences. This review suggests a role of abnormalities in these theta network events in producing a range of symptoms associated with mental illness.” 

The investigators propose that this research has the potential to improve diagnostics and help shape future treatments.

Dr McLoughlin said, “Analysis of these brainwaves shows that certain brains may be programmed to respond suboptimally to the environment. Improving the consistency and balance of these signals in the brain may be an important first step as there is the potential to improve the effectiveness of treatments like Cognitive Behavioural Therapy (CBT). Our research shows that without consistency and balance in theta oscillations, it can be difficult to process new information and voluntarily guide behaviour. This research in time could help clinicians to have a greater consideration for how the brain responds to situations so that therapies like CBT can be applied more effectively.”

This study was possible thanks to funding from the Medical Research Council UK.

Ends

For more information, please contact Patrick O’Brien (Senior Media Officer) at Patrick.1.obrine@kcl.ac.uk

Midfrontal theta activity in psychiatric illness: an index of cognitive vulnerabilities across disorders (DOI10.1016/j.biopsych.2021.08.020) (Gráinne McLoughlin, Máté Gyurkovics, Jason Palmer, Scott Makeig) was published in Biological Psychiatry.

About King’s College London and the Institute of Psychiatry, Psychology & Neuroscience

King's College London is one of the top 35 UK universities in the world and one of the top 10 in Europe (QS World University Rankings, 2020/21) and among the oldest in England. King's has more than 31,000 students (including more than 12,800 postgraduates) from some 150 countries worldwide, and 8,500 staff. King's has an outstanding reputation for world-class teaching and cutting-edge research. The Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s is the premier centre for mental health and related neurosciences research in Europe. It produces more highly cited outputs (top 1% citations) on mental health than any other centre (SciVal 2019) and on this metric we have risen from 16th (2014) to 4th (2019) in the world for highly cited neuroscience outputs. World-leading research from the IoPPN has made, and continues to make, an impact on how we understand, prevent and treat mental illness and other conditions that affect the brain.

www.kcl.ac.uk/ioppn @KingsIoPPN

The Medical Research Council is at the forefront of scientific discovery to improve human health. Founded in 1913 to tackle tuberculosis, the MRC now invests taxpayers’ money in some of the best medical research in the world across every area of health. Thirty-three MRC-funded researchers have won Nobel prizes in a wide range of disciplines, and MRC scientists have been behind such diverse discoveries as vitamins, the structure of DNA and the link between smoking and cancer, as well as achievements such as pioneering the use of randomised controlled trials, the invention of MRI scanning, and the development of a group of antibodies used in the making of some of the most successful drugs ever developed. Today, MRC-funded scientists tackle some of the greatest health problems facing humanity in the 21st century, from the rising tide of chronic diseases associated with ageing to the threats posed by rapidly mutating micro-organisms. The Medical Research Council is part of UK Research and Innovation. https://mrc.ukri.org/