An international team of scientists led by the Indian Institute of Technology Mandi has performed mathematical simulation studies on non-invasive brain stimulation techniques.
The multi-institutional research team, comprising scientists from the National Brain Research Centre and University at Buffalo, US, also developed the mathematical model to understand the physiological effects of non-invasive brain stimulation.
Transcranial electrical stimulation (tES) is a non-invasive brain stimulation technique that passes an electrical current through sections of the brain to study or alter brain function.
In the procedure, multiple electrodes are applied to the scalp of the patient, and current is passed between the electrodes through the soft tissue and skull.
Part of the current penetrates into the brain and affects the nerves, resulting in an altered activity. Beyond being explored as a curative, tES is considered useful to map the functions of the brain, that is, to understand the relationship between the brain part and behaviors/actions.
Given the important nature of the brain, the use of electricity on it can be dangerous if outcomes are not known. The response of various blood vessels in the cranium and various neurological pathways to tES must be clearly understood to get the maximum benefit of the procedure, with minimum damage.
“We simulated a physiologically detailed mathematical model of the neurovascular unit(NVU) with four compartments: synaptic space, astrocyte space, perivascular space, and arteriole smooth muscle cell space, called NeuroVascular Units or NVU,” said Dr. Shubhajit Roy Chowdhury, Associate Professor, School of Computing and Electrical Engineering, IIT Mandi, in the statement.
The mathematical model involved the application of perturbations of varying frequencies (0.1 Hz to 10 Hz) to simulate the electrical field, to the four nested NVU compartmental pathways and analyzed the changes in blood vessel diameter in response to the frequencies.
Three types of non-invasive brain stimulation — transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS) and transcranial oscillatory current stimulation (tOCS) — were modeled to investigate their physiological effects.
The initial tES effects on the blood vessels were also found to occur via the perivascular space — a fluid-filled space surrounding the blood vessels in the brain.
“Our study can help brain- and neuro-specialists plan patient-specific restorative neurorehabilitation activities for stroke, post-traumatic brain injury, mild cognitive impairment, dementia, and other neuropsychiatric disorders,” Chowdhury said.
Such a mathematical model-based quantitative analysis would help in individualized therapeutic protocols for neuropsychiatric disorders. The team has planned experimental studies that involve the blocking of various pathways to validate their modeling results.
The results have been published in the journal Brain Stimulation.