Scientific title:
Investigating the use of closed-loop auditory stimulation during sleep to improve memory in stroke survivors
University of Oxford
Principal investigator:
Triin Ojakäär
Grant value:
Research ID:
SA PGF 23\100006
Research area:
Start date:
Sunday 8 October 2023
End date:
Wednesday 7 October 2026
3 years
Year awarded:

Why is this research needed?

When we sleep, we typically go through a predictable series of stages, from lighter sleep to deeper sleep, then back into lighter sleep. These stages can be seen as changes in our brain’s electrical activity and are visible using brain scanning techniques like electroencephalography (EEG).

A full cycle of all the stages takes up about 90 minutes, of which about 30 minutes are light sleep and 60 minutes are deep sleep. However, many stroke survivors experience sleep problems, and from previous research, we know that that stroke survivors often spend much less than 60 minutes in the deep stages of sleep.

Sleep is vitally important to learning and memory. Stroke rehabilitation involves a lot of learning and re-learning, from figuring out how to walk again, to adapting to vision problems, to working out how to deal with the emotional impact of stroke. Learning and recovery have the same physical basis: your brain’s amazing ability to re-wire itself.

Triin’s research is about a particular stage of deep sleep called slow wave sleep, which is known to have a key role in learning and memory. In her PhD, she is testing a new piece of technology that she thinks will improve the quality of slow wave sleep, helping the brains of stroke survivors rewire themselves more quickly and speeding up the process of rehabilitation.

What are the aims of this research?

First, Triin needs a deeper understanding of what sleep is like for stroke survivors. To do this, she has been asking stroke survivors and people who’ve never had a stroke to wear an EEG headband that records their brain activity while they’re sleeping in their own bed. Participants are also asked to fill out questionnaires so that Triin can look at sleep quality and factors which could influence sleep, like stroke severity and medication. She predicts that stroke survivors’ brain activity in slow wave sleep will be different from that of people who’ve never had a stroke.

Triin, standing, is placing a black strap that holds the EEG headband around the head of a participant, seated.
Triin fits the EEG headband on a participant

Then, Triin will test the new technology, called a closed-loop auditory stimulation headset. This combines the EEG headband and built in bone conduction headphones. When the headset detects slow wave sleep brain activity, the headphones will deliver short bursts of noise in time with the brain activity. Past research has shown that doing this can change brain activity during sleep and, after waking, improve performance on some types of memory tasks. Triin will test whether it can improve memory for two new tasks – hand movement sequences, and locations of objects on a computer screen. To start with, she will trial the procedure with people who haven’t had a stroke to check for any problems with the headset or the tasks. Then she will trial it again with stroke survivors, comparing how they do on the tasks on nights when the headset delivers noise and nights when it doesn’t. She’ll also look at whether their brain activity changes when the noise is being played.

A large white box with four different coloured buttons is in the foreground. Someone's hand is pressing one of the buttons. Behind, Triin sits watching the person using the button box.
A participant tries the hand movement sequence memory task while Triin watches

What is the benefit of this research?

Triin’s Postgraduate Fellowship is a proof-of-principle study – for the headset, which is a new piece of technology, and for the effects of closed-loop auditory stimulation on sleep and memory in stroke survivors.

If her work and later larger trials are successful, the closed-loop headset could become a low-cost, home-based way for stroke survivors to improve their sleep and memory. In turn, this should make the rehabilitation process go much faster, leading to a quicker return to independence and better quality of life for stroke survivors.

Triin says, “In the long term, this research holds the promise of enhancing well-being through improved recovery for countless individuals affected by stroke. I look forward to dedicating my time to this vital field of study and making it the cornerstone of my research journey.”

What PSP priorities does this research link to?

From 2019 to 2021, we worked with the James Lind Alliance on the Stroke Priority Setting Partnership (PSP). During the PSP process, we collaborated with people with lived experience of stroke and stroke professionals to find out what they thought were the top priorities in stroke research. From this, we identified the top ten priorities in two areas: prevention, diagnosis and short-term care, and rehabilitation and long-term care.

Now, when researchers apply to us for funding, we require that their work addresses at least one of these priorities, or a priority from the Childhood Neurological Disabilities PSP Top 10 as it relates to childhood stroke.

Triin’s project addresses the following priority from the Stroke PSP:

  • Rehabilitation and long-term care 9: Interventions to improve strength and fitness, promote recovery and prevent secondary stroke

Meet the researcher

Image of Triin Ojakäär

Triin is a PhD student in the Department of Clinical Neurosciences at the University of Oxford. From 2022-2023, she did her PhD part time while also working as a research assistant in the same team and as the Regulatory Affairs Manager for a digital therapeutics company. Funding from the Stroke Association means that Triin is now able to work on her PhD full time.

After her PhD, Triin plans to run a larger-scale clinical trial on the closed-loop auditory headset to help build the evidence needed to get it into clinical practice.

Triin’s supervisors are Dr Melanie Fleming and Professor Heidi Johansen-Berg, both at the University of Oxford.