RESEARCHERS AT MIT FIND NEW WAY TO ELECTRICALLY STIMULATE BRAIN TISSUE WITHOUT OPENING THE SKULL
For the last twenty-years deep brain stimulation (DBS) has been used to treat Parkinson’s Disease.
The process, which involves implanting a device in the brain that delivers electrical pulses to the subthalamic nucleus, alleviates many of the physical symptoms of Parkinson’s.
Whilst DBS is generally quite safe, it is nevertheless still a surgical procedure. DBS requires highly invasive surgical technique that requires a surgeon to drill small holes in the patient’s skull, through which electrodes are then inserted. It is because of the surgical nature of the procedure, that problems such as infection, stroke and bleeding on the brain can occur.
However, new research from the Massachusetts Institute of Technology has developed a method that can stimulate the brain non-invasively. By using multiple electric fields applied from outside of the brain, the new method can selectively stimulate deep brain structures in live mice ‘without affecting the activity of cells in the overlying regions’ and can also easily adjust ‘to evoke movements by stimulation of the motor cortex.’
Temporal interference, is the act of using two opposing fields that are applied to the brain with differing frequencies. Thus, whenever the frequency fields cross paths, an ‘envelope’ is produced. For example, when applying two opposing fields with frequencies with 3000 and 3010Hz, an envelope field with a frequency of 10Hz is created whenever the two high frequency fields cross paths.
Using this theory, Nir Grossman and his team at the Massachusetts Institute of Technology supposed that by generating a low frequency electric field envelope inside the brain, they could stimulate the nerve cells in the envelopes without stimulating the exposed to either of the high frequency fields.
The researchers used computer models to simulate the effects of the method and then tested the technique on anaesthetised mice. Automated patch clamping was used to exemplify that stimulation activates cells in the envelope, before the researchers dissected the brains of the mice and used fluorescent antibodies to show c-Fos in the region targeted by the researchers.
To conclude the research, the scientists tested how safe the procedure was. When stimulating the hippocampus in awake mice they found the method did not change the density of neurons, dying cells or alter the brain tissue temperature beyond the average range. Another benefit to the new technique found that none of the mice experienced seizures during or after the procedure.
Clearly, the new technique purveyed by researchers at MIT holds some advantages over DBS. However, it also holds some advantages over other non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). Speaking on the research, Ed Boyden, professor of Biological Engineering and Brain and Cognitive Sciences at the MIT Media Lab and the McGovern Institute for Brain Research, said:
“With TMS and tDCS you can activate deep regions, but you also can activate overlying ones, and that could cause unwanted side effects. Targets for disorders such as depression, Alzheimer’s, PTSD, and so forth, are deep in the brain, and they might be more selectively stimulatable with our method.”
“We’ve already begun some human stimulation trials with normal healthy volunteers, although it’s very early days and very exploratory, and we are now reaching out to experts on epilepsy, tinnitus, depression, and other disorders to see if we can help.”
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