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Health and Safety Services

Psychology - Brain and Behaviour Lab
EEG / ERP and TMS Codes of Practice

The Brain and Behaviour Lab conducts research into human brain function on the basis of electroencephalogram (EEG) and other neuroscientific measures such as transcranial magnetic stimulation (TMS).

The EEG / ERP and TMS Codes of Practice are supplementary to the Health and Safety Policy for the School of Psychology.

ERP (event-related potentials) Experiments
In ERP experiments, the EEG voltage fluctuations generated by the brain, in response to particular stimuli or cognitive tasks, are recorded, in order to investigate cognitive processes such as visual selective attention, cross-modal attention and motor preparation. Participants are paid volunteers, over 18 years of age.

On first contact with the Lab, potential participants are informed about the experiments and the method used to place electrodes on the head, and they are shown around the experimental booth and the electrode placement room, so that they can decide whether they are still interested in participating.

Before taking part in an experiment, participants are given a consent form to read and sign which informs them that they are free to ask questions, that they can opt out at any time and that their identity will be kept confidential. Once they have given their consent, then an electrode cap is placed on their head, secured by a chin strap, and an electrode is fixed to each ear. If a participant finds the chin strap uncomfortable then a chest belt is available as an alternative.

 The skin in the centre of each electrode is first cleaned and degreased with a cotton bud dipped in alcohol and then gently rubbed with a cotton bud dipped in a chlorided, slightly abrasive, electrolyte gel. The purpose of this is to lower the impedance of the skin and so improve conductivity between the skin and the electrode. Participants are encouraged to tell us if this rubbing action is uncomfortable and if so, it is stopped and not repeated. Great care is taken to not damage the skin of the participants’ scalps.

After placement of the electrode cap, participants move to the booth where the experiment takes place. An experiment typically involves pressing a button or making a verbal reply in response to a stimulus presented on a computer screen or via loudspeakers or tactile stimulators. Participants are instructed about the particular task and about how long the experiment will take. The experiment then begins and participants are encouraged to take breaks whenever needed. Refreshments (tea, coffee, water, biscuits) are provided.

On completion of the experiment, participants return to the electrode placement room where the electrode cap and ear electrodes are removed. In order to remove the electrolyte gel, participants wash their own hair using the thermostatic electric shower, clean towels, shampoo, conditioner and hair dryer provided.

Electrodes and electrode caps are disinfected in alcohol after every experimental session.

Towels are used once only by a participant and then washed.

Disposable gloves are available for wear by the researchers.

The alcohol is stored in a flammable cupboard.

In the event of a fire, the building’s fire alarm can be clearly heard from within the experimental booths.

EEG / ERP involves recording (not stimulation) so is completely harmless as a method.

TMS Experiments

 In TMS experiments, a coil is held against the participant’s head. A change in electric current in this coil generates a magnetic field which activates neurons beneath the stimulation site and induces an electric current to flow in the brain. Single pulse TMS is generally believed to be safe. Repetitive stimulation (rTMS) carries a small risk of inducing a seizure during the rTMS study or immediately after if certain guidelines are not followed. We therefore adopt the following precautionary measures.

• Individuals at increased risk of having a seizure or at increased risk in the event of a seizure are excluded from participating. The researcher conducting the study goes through a detailed screening questionnaire with each potential participant before an individual is allowed to take part in the study.

• The levels of stimulation used by our Lab are far below the upper level of agreed safety guidelines developed by investigators using rTMS and have never been the subject of adverse reports.

• Any member of our Lab performing TMS has undergone a first aid emergency responder course and is trained in diagnosing and treating a seizure.

The coil produces a loud clicking noise as it discharges its magnetic pulses. Participants are always offered earplugs to wear to protect their hearing and minimize discomfort.

If the coil is held over an area of scalp containing facial muscles then a participant may experience facial twitches. Participants are warned of this and reminded that they can opt out of the experiment at any time they wish. Sometimes it is possible for the researcher to change the angle of the TMS coil in order to reduce discomfort.

It is widely agreed that a single TMS session has no long-term effects. However, repeated TMS sessions may have effects – either adverse or positive. Therefore, we do not perform experiments with the same participant many times in a short interval (no more than three consecutive days of testing, and less than 1500 pulses in a day).

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