What is EEG?

Electroencephalography, or EEG, is a commonly used non-invasive brain imaging technique. When neurons in the brain communicate with each other, they emit electrical signals. If many neurons in a certain region of the brain emit an electrical signal at the same time, that signal can be picked up by sensors, or electrodes, placed on top of your head. This brain activity naturally occurs all the time – for example, when you are trying to remember what to pick up at the grocery store or when you are closing your eyes to relax.

Preparing for an EEG session is quite simple. Please arrive with clean and dry hair without product, such as hairspray, gel or excessive conditioner. Thoroughly remove facial makeup before the session. Because the EEG records signals from your scalp, we ask that you remove any tightly woven hair, such braids or dreadlocks. You may bring snacks if you choose. We provide water.

EEG has been used for decades in scientific research and medicine to image the brain. It is considered a safe and non-invasive procedure. A seldom-recorded side effect is a slight itching or burning sensation where the gel touches the skin. In order to minimize this, the researchers thoroughly remove any gel residue with cleansing alcohol pads after the EEG session. If you experience a slight itching or burning sensation after the session and it persists, please consult your primary care physician.

Researchers typically record EEG activity while you are completing a series of tasks on a computer or mobile device. An EEG cap will be fitted to your head and you will be asked to wear this cap for the duration of the session. You will not feel anything from the recording other than the sensation of the cap on your head and the gel when it is applied. These sessions can last a few hours; however, the researcher will provide breaks upon request. We provide shampoo, conditioner, a towel, and a hairdryer for you to use after the EEG session to thoroughly wash your hair of any remaining gel before leaving our lab.

What is tACS/tDCS?

Transcranial alternating current stimulation (tACS) and transcranial direct current stimulation (tDCS) are two forms of non-invasive brain stimulation that modulates brain activity via weak electrical currents. The major focus on tACS/tDCS at Neuroscape is to assess whether these technologies may be used to enhance various cognitive functions. Although both technologies hold potential to enhance cognition, the main difference is that tDCS applies a constant electrical current, whereas tACS alternates current between stimulation electrodes in a frequency-specific manner. In either case, the current generated is approximately the same as that drawn by a hearing aid. Due to the weak currents used, the application of both tDCS and tACS have been found to be very low-risk. Although there is the possibility for mild discomfort during the stimulation such as tingling, itching, and skin redness in the area of stimulation, it is generally well tolerated.

Unless otherwise specified, no special preparation is needed prior to tDCS/tACS studies, and you may follow your regular daily routine. However, just like EEG, tACS/tDCS does not necessarily work well with tightly woven hair such as braids or dreadlocks. As such, you may need to unweave such hairstyles.

The modern use of tACS/tDCS has been around for over a decade and is generally considered safe. However, participants with any of the following conditions should not participate these types of studies:

• history of seizures
• history of neurological or psychiatric disorders
• cochlear implant
• unexplained loss of consciousness
• metal in the head
• frequent or severe headaches or neck pain
• implanted brain medical devices.

The effects of transcranial electrical stimulation on fetuses have not been fully investigated. For this reason, pregnant or potentially pregnant women should not participate in these studies.

A tACS/tDCS device (as pictured above) will be placed on your head and small dots of gel will be placed in your hair at each electrode site. The gel is water-based so it should wash out easily and will not change your hair color. Each study visit will last approximately 2.5 – 3.5 hours but the total time of stimulation will not be longer than 40 minutes in a single visit. You may stop the stimulation at any time.

What is TMS?

Transcranial magnetic stimulation (TMS) is a method applied at the scalp to briefly alter the normal processes of neurons on the outer surface of the brain that receive stimulation. Different frequencies and intensities of magnetic pulses are applied to cause either excitatory or inhibitory firing of neurons in a narrowly focused area of the brain. Because TMS directly causes only transient changes in the brain, it has been safely adopted for many therapeutic as well as experimental applications.

Feeling comfortable and rested when the session begins is important. Be sure to have a full night’s rest before the date of treatment, as well as your normal meal pattern up until about 90 minutes before treatment. If you are ill, congested or noticeably fatigued on the day of treatment, delay your appointment until you are recovered to fully normal. Receiving TMS stimulation should not produce effects that linger more than a few minutes once treatment ends. You will be fully capable of operating equipment, driving or thinking as soon as you leave your treatment session.

At the beginning of TMS sessions, we deliberately assess the minimum intensity required to cause effects at the targeted brain region. Using this approach, we can be completely confident that TMS treatment is entirely safe. Many, many thousands of clinical and experimental sessions using TMS procedures have been conducted without adverse outcomes over the past decade. We will screen your health history carefully to be sure you have no medical risks that preclude TMS treatment for you. Although there is theoretical risk that seizure may result from unusual neuronal stimulation, such adverse events have not been reported in association with TMS using our approach.