National Brain Mapping Lab


General Questions

tES Section

  • 1
    What is tES (Transcranial Electrical Stimulation)?

    Transcranial Electrical Stimulation is a non-invasive stimulation which applies a 1-2mA direct electrical current between anodal and cathodal electrodes to make excitation or inhibition in subsequent brain regions. Different electrode montages are used in various brain regions, and simulation of input and output electrical current helps to improve montage and affects cognition and disease.

  • 2
    What does electrode montage mean?

    It’s determining and positioning electrodes on the brain regions, shoulder and arm to make the desired function and electrical current path. For each treatment and cognitive assessment, there are different electrode positioning.

  • 3
    What facilities can be found in tES laboratory?

    tES facilities are explained in Services and equipment section on our webpage, in detail. https://nbml.ir/EN/services/tDCS-Lab

  • 4
    Which parameters are required for a tES session?

    In direct current stimulation, running a session require information of anode, cathode and reference (if it is needed) electrode position, current intensity, stimulation duration, ramp up and ramp down times. In alternative current stimulation current frequency and phase are needed in addition.

  • 5
    What is tES and TMS differences?

    In TMS there is a magnetic field in the coil which induces an electrical current and field in 0.5 cm2 and about 2cm depth on the brain and can cause cortex activity, e.g., stimulating motor cortex causes muscle activation. In tES a small direct electrical current is used on 1 to 35 cm2 (each electrode) brain region to make effects.

EEG Section

  • 1
    What is Electroencephalography?

    Electroencephalography (EEG) is a non-invasive technique for measurement of the electrical activity of the brain; EEG has a high temporal resolution compared to other brain mapping techniques.

  • 2
    What types of studies can be performed using Electroencephalography?

    Electroencephalography can be used as a tool to evaluate and model brain function during cognitive tasks. Besides, evaluation of medical interventions effects such as (transcranial electrical/magnetic stimulation, medication, and therapeutic consultation) is achievable with pre/post electroencephalography. For more information, please visit the service section on our webpage.

  • 3
    What sorts of stimulus can be presented to the participants?

    We can measure the individual’s response to visual, auditory, somatosensory (vibration, electrical) stimuli.

  • 4
    What are the lab equipment for data recording?

    The lab is equipped with
    - (64+16) 80 channel amplifier g.HIamp (g.tec)
    - 32 channel amplifier g.USBamp (g.tec)
    - 32 channel EEG cap g.Nautilus (g.tec)
    - (64+16) 80 channel MR-compatible amplifier BrainAmp MR Plus (Brain Product)
    - Set of sensors for physiological parameters recording

  • 5
    What are the approaches for stimuli presentation?

    It’s recommended to use common toolboxes such as Psychtoolbox & Cogent to implement various cognitive tasks. Use of any programs or scripts written in other programming languages than MATLAB is approved.

  • 6
    What are the approaches for stimuli presentation?

    Three main approaches can be taken to send synchronization triggers to the digital input of an amplifier?
    1- Sending triggers to the parallel port on the stimulation PC. (Click to receive the sample code for parallel port handling)
    2- Using optical sensors that are sensitive to changes in illumination intensity. (If you put these sensors on a point on the presentation screen that would change simultaneously with an important event in your tasks such as stimulus presentation or user’s response you will have the time tags on your EEG data.
    3- Using Push buttons to mark any desired time points in your data.

  • 7
    What information is achievable at each session?

    Each session, the lab provides you with the recorded signals and synchronization triggers in a single file with .mat format that can be loaded in MATLAB easily.

  • 8
    Are the electrode coordinates on subject’s head available?

    In case you can receive the approximate electrode coordinates from our lab specialist. Also, there is an opportunity to extract the precise electrode locations using the Navigation system available in the TMS lab.

TMS Section

  • 1
    What is repetitive Transcranial Magnetic Stimulation (rTMS)?

    rTMS is an effective, non-invasive alternative for the large number of patients not responding to medication. rTMS does not require anesthesia – and is not to be confused with ECT (Electro Convulsive Therapy). The rTMS system delivers magnetic pulses to stimulate nerve cells in the part of the brain controlling the mood. The rapid change in the magnetic field induces a current, and if the current induced is of sufficient amplitude and duration, it will excite neurons.

  • 2
    What are the side-effects of rTMS?

    rTMS is well-tolerated and associated with few side-effects and only a small percentage of patients discontinue treatment because of these. The most common side-effect, which is reported in about half of patients treated with rTMS, is headaches. These are mild and generally diminish over the course of the treatment. Over-the-counter pain medication can be used to treat these headaches.
    About one third of patients may experience painful scalp sensations or facial twitching with rTMS pulses. These too tend to diminish over the course of treatment although adjustments can be made immediately in coil positioning and stimulation settings to reduce discomfort.
    The rTMS machine produces a loud noise and because of this earplugs are given to the patient to use during the treatment. However, some patients may still complain of hearing problems immediately following treatment. No evidence suggests these effects are permanent if earplugs are worn during the treatment.
    rTMS has not been associated with many of the side-effects caused by antidepressant medications, such as gastrointestinal upset, dry mouth, sexual dysfunction, weight gain, or sedation.
    The most serious risk of rTMS is seizures. However, the risk of a seizure is exceedingly low. At Johns Hopkins, we follow up-to-date safety guidelines that are designed to minimize the risk of seizures. While rTMS is a safe procedure, it is important to point out that because it is a new treatment, there may be unforeseeable risks that are not currently recognized.

  • 3
    Who cannot get rTMS?

    Patients with any type of non-removable metal in their heads (with the exception of braces or dental fillings), or within twelve inches of the coil should not receive rTMS. Failure to follow this rule could cause the object to heat up, move, or malfunction, and result in serious injury or death. The following is a list of metal implants that can prevent a patient from receiving rTMS:
    • Aneurysm clips or coils
    • Stents in the neck or brain
    • Implanted stimulators
    • Cardiac pacemakers or implantable cardioverter defibrillator (ICD)
    • Electrodes to monitor brain activity
    • Metallic implants in your ears and eyes
    • Shrapnel or bullet fragments in or near the head
    • Facial tattoos with metallic or magnetic-sensitive ink
    • Other metal devices or object implanted in or near the head

  • 4
    Is TMS Therapy uncomfortable?

    No, the most common side effect related to treatment was scalp discomfort during treatment sessions. This side effect was generally mild to moderate, and occurred less frequently after the first week of treatment.
    If necessary, you can treat this discomfort with an over-the-counter analgesic. If these side effects persist, your doctor can temporarily reduce the strength of the magnetic field pulses being administered in order to make treatment more comfortable.
    Less than 5% of patients treated with TMS Therapy system discontinued treatment due to side effects.

  • 5
    What happens during an rTMS procedure?

    For each rTMS session, the patient sits in a specially designed treatment chair, much like the kind used in a dentist’s office. Because rTMS uses magnetic pulses, before beginning a treatment, patients are asked to remove any magnetic-sensitive objects (such as jewelry, credit cards). Patients are required to wear earplugs during treatment for their comfort and hearing protection, as rTMS produces a loud clicking sound with each pulse, much like an MRI machine.
    During the first rTMS session, several measurements are made to ensure that the TMS coil will be properly positioned over the patient’s head. Once this is done, the TMS coil is suspended over the patient’s scalp. The TMS physician then measures the patient’s motor threshold, by administering several brief pulses. The motor threshold is the minimum amount of power necessary to make the patient’s thumb twitch, and varies from individual to individual. Measuring the motor threshold helps the physician personalize the treatment settings and determine the amount of energy required to stimulate brain cells.
    Once the motor threshold is determined, the coil is then brought forward so that it rests above the front region of the patient’s brain. Treatment is then commenced. During the treatment, patients will hear a series of clicking sounds and will feel a tapping sensation under the treatment coil.
    Succeeding treatment sessions do not require that the motor threshold be determined again, unless indicated otherwise, such as when changes in medications are made during the course of the treatment.

  • 6
    Which parameters is needed for an rTMS session?

    For an rTMS session researcher should determine waveform, coil type, coil positioning on brain, intensity in %Motor threshold, frequency, pulse number in each train or train duration, inter-train interval, total number of train according to safety articles.

  • 7
    What does it mean by EMG signal during TMS evaluation?

    We can detect the MEP response of a specific brain area by TMS pulse. The MEP detected with surface electromyography (EMG) quantifies the level of the corticospinal tract and corticobulbar tract excitability (spatially in neurological disorders). For example, when TMS is applied over M1, it can elicit contraction in contralateral muscles.

  • 8
    What are the facilities available for EMG acquisition during TMS?

    There are 3 EMG acquisition systems for concurrent TMS-EMG such as:
    • Magventure EMG system
    • Motion Lab EMG system
    • Wireless and wired Bayamed EMG system

  • 9
    Is EMG signal analysis service available in NBML?

    Yes, we provide EMG signal analysis service in NBML.

  • 10
    What kind of results is accessible after data acquisition session?

    You will be provided by the EMG output files in the .xlsx or .txt formats as well as motor thresholds.

  • 11
    Would you adjust the EMG system parameters such as sampling frequency and … as my research design?

    Yes, we can adjust EMG system parameters as you want such as sampling frequency, number of channels, bandwidth, magnification and ….

fNIRS Section

MRI Section

Signal Processing

cognitive assessment


Image Processing

Virtual Reality