Moscow: According to a new study, the existing approach for brain stimulation to rehabilitate patients after a stroke does not take into account the diversity of lesions and the individual characteristics of patients’ brains and proposed a new approach.
In recent decades, non-invasive neuromodulation methods such as electric and magnetic stimulation of various parts of the nervous system have been increasingly used to rehabilitate patients after a stroke.
Stimulation selectively affects different parts of the brain — functionally enhancing activity in some areas while suppressing unwanted processes in others that impede the restoration of brain functions. This is a promising mean of rehabilitation after a stroke. However, its results in patients remain highly variable.
Authors of the study, which was published in the journal ‘Frontiers in Neurology’, argued that the main reason for the lack of effectiveness in neuromodulation approaches after a stroke is an inadequate selection of patients for the application of a particular brain stimulation technique.
They said the existing approach does not take into account the diversity of lesions after a stroke and the variability of individual responses to brain stimulation as a whole.
The researchers have proposed two criteria for selecting the optimal brain stimulation strategy.
The first is an analysis of the interactions between the hemispheres. Now, all patients, regardless of the severity of injury after a stroke, are offered a relatively standard treatment regimen. This approach relies on the idea of interhemispheric competition.
“For a long time, it was believed that when one hemisphere is bad, the second, instead of helping it, suppresses it even more,” said Maria Nazarova, researcher at the HSE Institute of Cognitive Neurosciences.
“In this regard, the suppression of the activity of the ‘unaffected’ hemisphere should help restore the affected side of the brain. However, the fact is that this particular scheme does not work in many patients after a stroke. Each time it is necessary to check what the impact of the unaffected hemisphere is — whether it is suppressive or activating,” she said.
According to the researchers, the second criterion is the neuronal phenotype. This is an individual characteristic of the activity of the brain, which is ‘unique to each person like their fingerprints’.
Such a phenotype is determined, first by the ability of the brain to build effective structural and functional connections between different areas (connectivity) and the individual characteristics of neuronal dynamics, including its ability to reach a critical state.
This is the state of the neuronal system in which it is the most plastic and capable of change.