Open Research Europe presents an interview with Pantelis Lioumis, a co-author of ‘Local brain-state dependency of effective connectivity: a pilot TMS-EEG study’, in this month’s Research Spotlight to understand how magnet stimulation could affect brain activity. Read on to find out more about the research.
Can you share a summary of your Brief Report?
When stimulating the brain with transcranial magnetic stimulation (TMS), it is possible to disturb ongoing activity of neuronal populations in the brain. This evoked brain activity can be recorded with electroencephalography (EEG), and we can use this method to measure the cortical excitability (the measure of how the cortex responds to stimuli) and reactivity of the stimulated brain region. In addition to local effects, this activity spreads from the stimulated brain region to other regions as well, through the white matter and the corpus callosum.
However, both the evoked and propagated activity can be variable. One parameter that may determine this variability is the brain state prior to brain stimulation. A way to identify this state includes the oscillatory pattern in an EEG signal, commonly known as a brain rhythm. Brain rhythms are the result of synchronous neuronal firing, and they differ between areas of the brain. These rhythms also represent various functional brain states as they can be influenced by different phases of sleep as well as various neurological and psychiatric disorders.
Previous research has shown that the brain rhythms (oscillatory phase) at the time of TMS delivery affects the degree of cortical excitability. Our research hypothesized and examined how different phases of pre-stimulus oscillations in two brain regions may determine the way that the TMS-evoked brain activity propagates to the rest of the brain, which can make the mechanism of communication between different brain areas in health and disease much easier to determine.
What inspired you to investigate this?
Brain rhythms impact signal transmissions from one area of the brain to another. Psychiatric and neurological disorders, such as major depressive disorder and Alzheimer’s disease, are due to a brain-wide network failure rather than a dysfunction of one brain area.
This study allows us to investigate the mechanisms that underpin the miscommunications between the different nodes of brain networks, so that we can improve brain treatments with brain stimulation. Thus, we need to know how different aspects of ongoing brain activity affect the generation and propagation of TMS-evoked responses.
What were the outcomes of your research?
We found that the oscillations that occur at the site of TMS stimulation could determine where the evoked activity will spread to. However, we observed high variability between the patients of our study, indicating that we still need more data before drawing definitive conclusions.
Why is open research important to you and your co-authors?
Our work is most beneficial when open to all. Availability allows others to utilize our methods and findings in different populations and conditions for further research and understanding.
What motivated you to publish with Open Research Europe?
Open Research Europe seemed to be a very good platform to communicate our new methodological approach in the pilot stage of our research, since the platform has very open procedures in all stages before publishing.
What are your next steps?
On this topic, we are working on recording and analyzing more data from more brain targets as well as carrying out studies on larger groups of patients to consolidate our results. We also aim to deepen the analysis in order to gain more detailed understanding of this preliminarily observed phenomenon.
Read the full Brief Report today on Open Research Europe to dive deeper into Pantelis Lioumis’ study and findings.
