Scientists have completed a successful human trial using new high-frequency technology to stimulate neurons in the hippocampus, the area responsible for forming, organizing and retrieving memories. This non-invasive, painless treatment is now being trialed in older individuals with cognitive impairment, as a potential way to improve memory loss and function caused by Alzheimer's disease and other forms of dementia.
The research, led by scientists at Imperial College London (ICL), is known as temporal interference (TI) brain stimulation. It involves delivering two harmless high-frequency electric fields into the brain. The beams are set at 2,000 Hz and 2,005 Hz, and where they cross they create a third 5-Hz current. This current is the key – it is at the same frequency at which brain cells fire.
This 5-Hz current will be stimulated in the hippocampus and does not affect healthy brain tissue in any other regions. It’s here scientists hope that diseased neurons will be ‘sparked’ back into action and revive the cell-powering mitochondria, which become damaged by Alzheimer’s.
“Until now, if we wanted to electrically stimulate structures deep inside the brain, we needed to surgically implant electrodes which of course carries risk for the patient, and can lead to complications,” said study lead Nir Grossman, from the Department of Brain Sciences at ICL. “With our new technique we have shown for the first time, that it is possible to remotely stimulate specific regions deep within the human brain without the need for surgery. This opens up an entirely new avenue of treatment for brain diseases like Alzheimer’s which affect deep brain structures."
Following research on post-mortem brain measurements to ensure the electric fields would deliver the precise interference in the hippocampus, which is found deep inside the organ, the TI stimulation was delivered to 20 healthy volunteers. During treatment, participants were given a task of memorizing pairs of faces and names. Functional magnetic resonance imaging (fMRI) then showed that TI had selectively affected specific hippocampal activity directly related to memory.
Researchers from ICL’s UK Dementia Research Institute (UK DRI) and the University of Surrey then extended the TI session to 30 minutes, and it was observed that memories formed during stimulation endured upon re-testing, though the rate at which they were forgotten was similar in a control cohort. As such, further studies into treatment session length and long-term analysis is still needed.
“The ability to selectively target deep brain areas using a non-invasive approach is very exciting as it provides a tool to investigate how the human brain operates and opens possibilities for clinical applications,” said first author Ines Violante, from the University of Surrey. “The combination of non-invasive imaging and brain stimulation will help us unravel the processes that support our cognitive functions, such as memory and learning. Knowledge of these processes and how they can be altered is essential to develop better individualized strategies to treat or delay the onset of diseases.”
A trial testing TI on dementia patients is now underway through the UK Dementia Research Institute. The three-week London-based study has recruited individuals aged 50-100 years with mild cognitive impairment and probable, non-familial Alzheimer’s disease in its early stages.
“We hope this work will help to scale up the availability of deep brain stimulation therapies by drastically reducing cost and risk,” said Grossman. “We are now testing whether repeated treatment with the stimulation over the course of a number of days could benefit people in the early stages of Alzheimer’s. We hope that this will restore normal brain activity in the affected areas, which could improve symptoms of memory impairment.”
A second paper from researchers in École polytechnique fédérale de Lausanne (EPFL) in Switzerland, has independently validated the technology. This study was published simultaneously with the ICL paper.
Both studies were published in the journal Nature Neuroscience.
Source: Imperial College London