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While people are reading, talking or playing computer games, their brain cells elicit electrical signals so they could perform these actions. The firing of these cells is not random but is organized in a temporal pattern, such that a group of cells are simultaneously active at a particular frequency. The researchers can read the frequency of brain signals and identify their location using different brain-imaging tools like EEG and fMRI. These methods are applied to healthy individuals and do not pose any danger.
The investigators of this project would like to use these techniques to study the brain signals, while healthy participants are making the decisions choosing between 2 rewards, e.g., 2 food items. Participants who have depression show different behavior while performing decision-making tasks and the investigation of processes that underlie them will lead to a better understanding of this disease.
Furthermore, there is another category of tools, which help to study the brain. This category includes electrical stimulation, which mimics the electrical pattern that brain cells elicit. Application of external electrical stimulation can enhance this pattern or disrupt it and this process will affect the behavior of a person. Recent investigations have led to the development of a new stimulation technique that allows targeting deep brain regions. The investigators of this project want to apply this method to change the performance of healthy participants in the tasks on decision-making. If this experiment is successful, then stimulation can be used as a therapy for participants with depression.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| TI stimulation | Experimental | Temporal interference (TI) stimulation is a type of low-intensity transcranial electrical stimulation with alternating current (tACS). In case of TI stimulation, 2 electric fields in kHz range are delivered to 4 electrodes, which are placed on the surface of the skull, to modulate neural oscillations. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| TI transcranial electrical stimulation | Device | Participants will undergo transcranial electrical stimulation, which will be delivered with low current amplitudes (<= 2 mA) established with international safety guidelines for electrical stimulation. Threshold for the current amplitude will be established by participants themselves, such that they cannot distinguish when stimulation is applied and not applied. Duration of stimulation will not last longer than 30 minutes. |
| Measure | Description | Time Frame |
|---|---|---|
| Accuracy | Accuracy will be collected with a keyboard and a mouse | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Reaction time | Reaction time will be collected with a keyboard and a mouse | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Fixations | Fixations of the gaze on the screen will be recorded with an eye-tracker. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Saccades | Saccades (a type of the eye movement) will be recorded with an eye-tracker. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Blood oxygenation level dependent (BOLD) | BOLD signal is measured with functional magnetic resonance imaging (fMRI) experiment. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Brain oscillations in delta band | Oscillations within the range from 0.5 Hz to 4 Hz will be measured with electroencephalography (EEG). | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Brain oscillations in theta band |
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| Measure | Description | Time Frame |
|---|---|---|
| Safety outcome (Headache) | Headache severity will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
General Inclusion Criteria:
Exclusion Criteria for TI electrical stimulation:
Exclusion Criteria for MRI experiments:
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| Name | Affiliation | Role |
|---|---|---|
| Rafael Polania, PhD | ETH Zürich | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| ETH Zurich | Zurich | Schweiz | 8057 | Switzerland |
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The same participants receive placebo/sham stimulation and active stimulation on different sessions separated with 1 week or within the same session.
The sequence of sham/placebo and active stimulation will be randomized.
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Participants will be not informed which stimulation they receive active or placebo/sham. They will be debriefed at the end of the experiment.
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Oscillations within the range from 4 Hz to 8 Hz will be measured with EEG.
| Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Brain oscillations in alpha band | Oscillations within the range from 8 Hz to 12 Hz will be measured with EEG. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Brain oscillations in beta band | Oscillations within the range from 12 Hz to 30 Hz will be measured with EEG. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Brain oscillations in low gamma band | Oscillations within the range from 30 Hz to 70 Hz will be measured with EEG. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Brain oscillations in high gamma band | Oscillations within the range from 70 Hz to 250 Hz will be measured with EEG. | Continuously while participants perform a cognitive task (circa 2 hours) with and without TI stimulation. |
| Safety outcome (Scalp pain) | Scalp pain severity will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Tingling) | Tingling severity will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Itching) | Itching severity will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Burning) | Burning sensations will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Discomfort) | Discomfort sensations will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Nausea) | Nausea sensations will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Fatigue) | Fatigue sensations will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Acute mood change) | Acute mood change will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Phosphenes) | Phosphenes/light sensations will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |
| Safety outcome (Sleeplessness) | Sleeplessness will be collected with a questionnaire that contains a scale on which participant can rate this side-effect: (1) absent, (2) mild, (3) moderate, (4) severe. After this question, participant is asked to estimate relationship of this side-effect to intervention: (1) none, (2) remote, (3) possible, (4) probable, (5) definite. | This outcome will be recorded after each experiment with TI stimulation. One experiment lasts around 2 hours. These experiments will be held with different participants throughout the whole study (around 3 years). |