Enhancing Sleep Dependent Consolidation by Non-invasive Brain Stimulation

Study Overview
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Brief Summary
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Stroke, one of the most common causes for acquired adult disability, is not only a burden for the individual but also for his or her close relatives and caregivers. Functional recovery is commonly associated with the re-acquisition of lost skills. This skill (re-)acquisition is separated into different phases during which learning takes place while the skill/movement is actively performed - so called online learning - or during the time of non-performance between the training - so called offline learning or consolidation. During the initial phase of training, performance improvements are commonly steep (online learning). During the following processes of consolidation, which often depend on sleep, memory traces are being modified and stored for long-term memory retention leading to a further improvement without additional training (offline learning). Previous studies focusing on individuals after stroke could show a beneficial effect of sleep on motor skill acquisition. As an intervention, transcranial electrical stimulation (tES) with motor tasks could show beneficial effects on motor skill acquisition. tES is a method to stimulate an area of the brain non-invasively and this is done by applying low voltage current to the scalp that lies in close proximity to the target brain region. In the current study, stimulation is performed during sleep and types of stimulation resemble natural sleep physiology: slow-wave and spindles. As slow-wave and spindles are shown to be important for memory consolidation, it is hypothesized that applying physiologically-inspired stimulation could enhance memory consolidation in individuals after stroke. It is known that patterns of sleep physiology change in older individuals, thus, this population is also investigated in the current study. It is interpreted and discussed that older individuals do not benefit from sleep as much as younger individuals do. Thus, it is hypothesized that applying physiologically-inspired stimulation could enhance memory consolidation in healthy older individuals.

Official Title
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Enhancing Sleep Dependent Consolidation by Non-invasive Brain Stimulation to Boost Motor Skill Acquisition in Individuals After Stroke

Conditions
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Stroke, Aging

Intervention / Treatment
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* Other: Non-invasive brain stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: right handed (healthy older) healthy (healthy older) monohemispheric stroke (individuals after stroke) at least 6 months since diagnosis stroke (individuals after stroke) Exclusion Criteria: Unable to provide informed consent Pregnancy Known or suspected non-compliance, drug or alcohol abuse Inability to follow the procedures of the study, e.g., due to language problems, psychological disorders, dementia, etc. of the participant Non-compliance to the instructions of the experimenter or an inappropriate behaviour hindering the normal progress of the experiment Previous enrolment into the current study Exclusion criteria tES, and transcranial magnetic stimulation (TMS) Use of psychoactive medication, which might influence the study results Request of not being informed in case of incidental findings Recurrent stroke / multiple strokes (individuals after stroke) Cerebellar stroke (individuals after stroke)

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Slow-wave-like transcranial direct current stimulation (tDCS)<br>tDCS during sleep | Other: Non-invasive brain stimulation<br>* based on sleep-physiology (slow-wave and spindles)<br>|
| Experimental: Spindle-like transcranial alternating current stimulation (tACS)<br>tACS during sleep | Other: Non-invasive brain stimulation<br>* based on sleep-physiology (slow-wave and spindles)<br>|
| Sham Comparator: Sham stimulation during sleep<br>Sham | Other: Non-invasive brain stimulation<br>* based on sleep-physiology (slow-wave and spindles)<br>|
| Active Comparator: Wake in case participants could not take a nap<br>Active Comparator (with stimulation), in case participants could not take a nap | Other: Non-invasive brain stimulation<br>* based on sleep-physiology (slow-wave and spindles)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Behavioural motor score (session 1) | It is a computer-based score, which determines (compound) measure of accuracy and speed and can therefore be seen as a measure of performance improvement at session 1 | 15 minutes | 
| Behavioural motor score (session 2) | It is a computer-based score, which determines (compound) measure of accuracy and speed and can therefore be seen as a measure of performance improvement at session 2 | 15 minutes | 
| Behavioural motor score (session 3) | It is a computer-based score, which determines (compound) measure of accuracy and speed and can therefore be seen as a measure of performance improvement at session 3 | 15 minutes | 
| Behavioural motor score (session 4) | It is a computer-based score, which determines (compound) measure of accuracy and speed and can therefore be seen as a measure of performance improvement at session 4 | 15 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Behavioural motor score (session 5) | It is a computer-based score, which determines (compound) measure of accuracy and speed and can therefore be seen as a measure of performance improvement at session 5 | 15 minutes | 
| Functional magnetic resonance imaging (fMRI) during behavioral motor score evaluation | Blood oxygen level dependent contrast among sessions (sessions 1-5) | 15 minutes | 
| Electroencephalography (EEG) during sleep | Sleep spindle density (spindle per minute) | 1 hour |