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Information in our brain is exchanged in two forms. Neurons--the fundamental units, that is the brain cells--communicate with each other through two “courier” services: through 'chemicals' and 'electricity'. These chemical and this electric exchanges work in harmony to help us the experience and create of the world we live in. In an imbalance in the chemical communication or a malfunction in electrical exchange in between neurons, adversely affects the functions of mind and body. Sometimes such disturbances, especially of the mind, cause people to experience their world in ways that do not match with that of others people around them. Such abnormal experiences require medical attention and are studied and treated in the branch of Psychiatry. Psychotropic drugs often help in course correction of the chemical imbalances in the brain. However, they are not always fool-proof.
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This is where weak intensity brain stimulation come in. In addition to psychotropic drugs, weak intensity brain stimulation techniques address the 'electrical' dysregulation in the brain to shift a person's experience towards the 'normal' spectrum from the 'abnormal' one. These techniques are also helpful in cognitive re-training whereby brain areas responsible for deficiency in mental function like attention, memory, processing speed, etc. in patients are stimulated to perform better.
Under the WISER Neuromodulation Program, the following weak intensity stimulation are offered. All of the techniques mentioned below are safe, well-tolerated with relatively mild or no side-effects. The participant is awake and alert throughout the procedure. The most common side effects are temporary itching and redness of the skin at the site of stimulation. These techniques are administered through safety certified battery-powered current generating devices. Specifically, the tDCS/tACS/tRNS/tPCS devices are connected to electrodes which are usually conductive rubber pads wrapped in saline-soaked sponge pockets. The electrodes are made of sponge because it’s perforated and non-conductive, thus ideal for the purpose of establishing contact with human skin. These sponge pockets (functioning as electrode covers) are then held in place by a non-conducting rubber montage affixed around the head. These devices are capable of generating a weak current of strength up to 4 mA, however common treatment and investigative neuromodulation protocols use typically 1–2.5 mA, for 10–30 minutes.
At present, due to the small number of experiments conducted so far, the underlying mechanisms of tDCS, HD-tDCS, tACS, tRNS and ta-VNS are yet not sufficiently clear. These neuromodulation techniques are being probed through the WISER Neuromodulation Program.
Under the WISER Neuromodulation Program, the following weak intensity stimulation are offered. All of the techniques mentioned below are safe, well-tolerated with relatively mild or no side-effects. The participant is awake and alert throughout the procedure. The most common side effects are temporary itching and redness of the skin at the site of stimulation. These techniques are administered through safety certified battery-powered current generating devices. Specifically, the tDCS/tACS/tRNS/tPCS devices are connected to electrodes which are usually conductive rubber pads wrapped in saline-soaked sponge pockets. The electrodes are made of sponge because it’s perforated and non-conductive, thus ideal for the purpose of establishing contact with human skin. These sponge pockets (functioning as electrode covers) are then held in place by a non-conducting rubber montage affixed around the head. These devices are capable of generating a weak current of strength up to 4 mA, however common treatment and investigative neuromodulation protocols use typically 1–2.5 mA, for 10–30 minutes.
At present, due to the small number of experiments conducted so far, the underlying mechanisms of tDCS, HD-tDCS, tACS, tRNS and ta-VNS are yet not sufficiently clear. These neuromodulation techniques are being probed through the WISER Neuromodulation Program.
Transcranial Direct Current Stimulation (tDCS)
It is a neuromodulatory technique that delivers low intensity, direct current to cortical areas facilitating or inhibiting spontaneous neuronal activity. Current flows between two electrodes placed on the scalp over the target areas. tDCS manipulates brain excitability by effecting membrane polarization. Cathodal stimulation hyperpolarizes while anodal stimulation depolarizes resting membrane potential and the induced after-effects depend on polarity, duration and intensity of the stimulation. Prolonged passage of current (e.g. >10 min) to brain areas can lead to lasting changes in neuronal excitability of those areas. Stimulation protocols for tDCS consist of a fade-in phase in which current is ramped up to the desired intensity (typically <30 s), the main stimulation phase at target intensity (typically 1–2.5 mA, for 10–20 min), and a fade-out phase. One of the drawback is the need to balance the returning current, that is--to stimulate a brain area (anodal current), another area has to be inhibited (cathodal current) or vice-versa.
High definition tDCS (HD-tDCS)
HD-tDCS, as the name indicates, is an advancement of the tDCS method discussed above. This technique uses smaller electrodes and in ring-configuration (4x1 montage—1 central electrode, surrounded by 4 electrodes of opposing polarity). The distribution of current is unequal unlike tDCS; for example, if the central electrode injects a current of strength -2 mA, each of the four return electrodes surrounding it (in a ring configuration) carry a current strength of 0.5 mA. In essence, this technique enables unipolar stimulation—that is, inhibition or stimulation of a brain area by applying negative or positive current through the central electrode. This overcomes the problem of 'balancing the returning current' faced with conventional tDCS.
It is a neuromodulatory technique that delivers low intensity, direct current to cortical areas facilitating or inhibiting spontaneous neuronal activity. Current flows between two electrodes placed on the scalp over the target areas. tDCS manipulates brain excitability by effecting membrane polarization. Cathodal stimulation hyperpolarizes while anodal stimulation depolarizes resting membrane potential and the induced after-effects depend on polarity, duration and intensity of the stimulation. Prolonged passage of current (e.g. >10 min) to brain areas can lead to lasting changes in neuronal excitability of those areas. Stimulation protocols for tDCS consist of a fade-in phase in which current is ramped up to the desired intensity (typically <30 s), the main stimulation phase at target intensity (typically 1–2.5 mA, for 10–20 min), and a fade-out phase. One of the drawback is the need to balance the returning current, that is--to stimulate a brain area (anodal current), another area has to be inhibited (cathodal current) or vice-versa.
High definition tDCS (HD-tDCS)
HD-tDCS, as the name indicates, is an advancement of the tDCS method discussed above. This technique uses smaller electrodes and in ring-configuration (4x1 montage—1 central electrode, surrounded by 4 electrodes of opposing polarity). The distribution of current is unequal unlike tDCS; for example, if the central electrode injects a current of strength -2 mA, each of the four return electrodes surrounding it (in a ring configuration) carry a current strength of 0.5 mA. In essence, this technique enables unipolar stimulation—that is, inhibition or stimulation of a brain area by applying negative or positive current through the central electrode. This overcomes the problem of 'balancing the returning current' faced with conventional tDCS.
Transcranial Alternating Current stimulation (tACS)
This technique electrically stimulates the brain in with sinusoidally applied alternating current that interferes with intrinsic brain oscillations and alters cortical excitability. Effects of tACS are dependent on frequency of stimulation. In tACS is usually delivered as specific frequency however a combination of frequencies can be given. tACS can synchronize (by one single resonance frequency) or desynchronize (by application of several frequencies) cortical oscillations. With increase in the number of frequencies involved in tACS, the effect of stimulation gets closer to that of Transcranial Random Noise stimulation (tRNS). tRNS is a special form of tACS.
tACS and tRNS are thought to affect neural membrane resting potential by oscillatory electrical stimulation with specific and random frequencies. Since, both tACS and tRNS are thought to interact with ongoing cortical rhythmic activity during cognitive processes; they are suitable for use as investigative tools in exploring human cognition. In contrast to tDCS, they might be able to specifically alter task-related oscillatory activity, and thus tackle—beyond cortical activity alterations—another important physiological determinant of cognitive processes.
This technique electrically stimulates the brain in with sinusoidally applied alternating current that interferes with intrinsic brain oscillations and alters cortical excitability. Effects of tACS are dependent on frequency of stimulation. In tACS is usually delivered as specific frequency however a combination of frequencies can be given. tACS can synchronize (by one single resonance frequency) or desynchronize (by application of several frequencies) cortical oscillations. With increase in the number of frequencies involved in tACS, the effect of stimulation gets closer to that of Transcranial Random Noise stimulation (tRNS). tRNS is a special form of tACS.
tACS and tRNS are thought to affect neural membrane resting potential by oscillatory electrical stimulation with specific and random frequencies. Since, both tACS and tRNS are thought to interact with ongoing cortical rhythmic activity during cognitive processes; they are suitable for use as investigative tools in exploring human cognition. In contrast to tDCS, they might be able to specifically alter task-related oscillatory activity, and thus tackle—beyond cortical activity alterations—another important physiological determinant of cognitive processes.
Trans-auricular Vagal Nerve Stimulation (ta-VNS)
The vagus nerve (VN) can be stimulated noninvasively by transcutaneous vagus nerve stimulation (tVNS). This can be done in two ways. One is by stimulating the VN at the neck and this is called cervical vagus nerve stimulation (cVNS), Another way is by stimulation of a certain potion (cymba concha, tragus) of the ear and is called trans-auricular vagus nerve stimulation (ta-VNS). In ta-VNS, tiny electrodes are stuck at the ears. Some devices come with a pre-built mechanism to attach it to the ear in the desirable area. These electrodes are then connected to a device that electrically stimulates the portion of the ear. Its parameters are adjustable. Commonly, a small amount of current (2 mA) is used. The stimulation may give a tickling, tingling or/and vibrating sensation. At times saline water or a special gel is used to decrease electrical resistance and make the process smoother. About 20-30 minutes of stimulation is commonly given, although this may vary.
The vagus nerve (VN) can be stimulated noninvasively by transcutaneous vagus nerve stimulation (tVNS). This can be done in two ways. One is by stimulating the VN at the neck and this is called cervical vagus nerve stimulation (cVNS), Another way is by stimulation of a certain potion (cymba concha, tragus) of the ear and is called trans-auricular vagus nerve stimulation (ta-VNS). In ta-VNS, tiny electrodes are stuck at the ears. Some devices come with a pre-built mechanism to attach it to the ear in the desirable area. These electrodes are then connected to a device that electrically stimulates the portion of the ear. Its parameters are adjustable. Commonly, a small amount of current (2 mA) is used. The stimulation may give a tickling, tingling or/and vibrating sensation. At times saline water or a special gel is used to decrease electrical resistance and make the process smoother. About 20-30 minutes of stimulation is commonly given, although this may vary.