IIT Mandi scientist develops mathematical models to study non-invasive brain simulation methods

Three types of non-invasive brain stimulation – transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS) and transcranial oscillatory current stimulation (tOCS)

A collaborative research team comprising scientists from the Indian Institute of Technology Mandi and National Brain Research Centre, India and University at Buffalo, USA, performs mathematical simulation studies on non-invasive brain simulation techniques.

The results of the team’s recent work in the area have been published as an abstract in the journal, Brain Stimulation. The abstract has been co-authored by Dr Shubhajit Roy Chowdhury from IIT Mandi, Dr Yashika Arora from National Brain Research Centre, India, and Dr Anirban Dutta of University at Buffalo.

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. This is not a new concept, and dates back even before the discovery of electricity. In the first century AD, the Roman physician Scribonius Largus applied the black torpedo, an electric shock producing fish, to the head of the emperor to alleviate his headache. Soon after the discovery of electricity in the 18th century, portable electrostimulation devices were designed to treat various neurological syndromes including headaches.

In modern day tES, 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 altered activity. Beyond being explored as a curative, tES is considered useful to map the functions of the brain, i.e., to understand the relationship between the brain part and behaviours/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 maximum benefit of the procedure, with minimum damage. The multi-institutional research team has developed a mathematical model to understand the physiological effects of non-invasive brain stimulation.

Highlighting his research, Dr. Shubhajit Roy Chowdhury, Associate Professor, School of Computing & Electrical Engineering, IIT Mandi, said, “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.” 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 analysed 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 modelled 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,” said the lead researcher. Such a mathematical model based quantitative analysis would help in individualized therapeutic protocols for neuropsychiatric disorders. The team has planned experimental studies that involve blocking of various pathways to validate their modelling results.

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