Effect of Non-invasive Magnetic Stimulation of the Brain on Breathlessness in Healthy Individuals. (AHrTMS)

Effect of Repetitive Transcranial Magnetic Stimulation (rTMS) of the Dorsolateral Prefrontal Cortex (DLPFC) on Hypercapnic Air Hunger Induced in Healthy Individuals.

The purpose of this study is to see if the front part of the brain called the "Dorsolateral Prefrontal Cortex" (DLPFC) has a role in our ability to feel breathlessness. The experiment will use a device that sits on the top of the head which produces a magnetic field that penetrates the scalp and excites the brain tissue directly under it. This procedure is called repetitive transcranial magnetic stimulation (rTMS), it is a painless procedure and known to be safe in healthy individuals. Previous research has shown that the pain felt when capsaicin, the active ingredient in 'chilli' powder, is applied to the hand is reduced by applying the rTMS on the scalp directly above the DLPFC part of the brain. In this experiment we want to see if breathlessness is also reduced. We will use a breathing task that will generate a moderate amount of breathlessness by adding a small amount of carbon dioxide to the inhaled air, while preventing the increase in the amount of breathing we would normally see in response to this. If we find that breathlessness produced by this breathing task is reduced after rTMS over the DLPFC, this may lead to new drugs that target this part of the brain in patients suffering from breathlessness due to heart or lung disease. The study will also improve our knowledge of how the brain enables us to feel breathlessness

Following a practice session, there will be 3 intervention arms presented in random order on 3 separate days. The three arms will be: (i) 10-20mins of 5Hz rTMS over left DLPFC (Arm 1), (ii) 5Hz rTMS over right DLPFC (Arm 2), (iii) sham rTMS (Arm 3). A standard steady state air hunger test will be conducted before and immediately after each intervention.

Masking will only be applied to the participants in relation to whether they receive sham or actual rTMS.

Administered immediately following pre and post intervention air hunger tests in relation to the "test just completed"

Inclusion Criteria: healthy individuals, over 18 years old, with no history of heart, lung or neurological conditions Exclusion Criteria: Any history of respiratory problems (including Asthma that involves regular use of inhalers) Any history of heart or circulatory problems (e.g. palpitations, arrhythmias, angina, BP) Any history of epilepsy, convulsions or seizures, migraines, or fainting Any history of anxiety disorders (e.g. panic attacks) Any history of serious head injury or brain surgery Any metal parts in the head (except dental wire) Any implants (e.g. pacemaker, insulin pump, neurostimulator) Pregnancy or problems with alcohol or drug abuse.

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