Oscillations in Reward-guided Behavior

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.


Eligibility Criteria:
General Inclusion Criteria:

* signed informed consent
* Age 18-40 years
* Normal physical and mental status (i.e. no neurological, musculoskeletal, neuromuscular, cognitive, or psychiatric disorders)
* If a participant already took part in the experiment with the same decision-making task

Exclusion Criteria for TI electrical stimulation:

* pregnancy
* epilepsy
* head traumas
* implants (cochlear, neurostimulators, cardiac pacemakers, medication infusion device)
* metal in the brain or skull
* work in the metal industry
* scars or inflammations on the regions, where the stimulation electrodes are placed
* administration of antipsychotic or anti-epileptic medication
* hearing problems or ringing in the ears
* syncope or fainting spells in the last 5 years
* severe side-effects after transcranial magnetic stimulation (TMS) or electrical stimulation if participant underwent it before
* the inability to comply with magnetic resonance imaging (MRI) inclusion criteria if participant underwent it before

Exclusion Criteria for MRI experiments:

* pregnancy
* claustrophobia
* history of brain surgery
* family member that suffers from epilepsy
* suffering from medication abuse for more than a year or drug intake
* taking medications for medical reasons for more than a month
* receiving of depot injections
* one or more of the following materials in the body: metallic objects (e.g., dental implants, a metallic splinter in the eye, but not braces); wire, pacemaker or implanted defibrillator; artificial heart valves; vascular grafts; bio-stimulator or nerve stimulator; aneurysm or intracranial clip; cochlear implant; other prostheses or orthoses; implanted medication pump (insulin or pain pump); medicated patch (e.g., nitro-patch, pain patch, nicotine patch, hormone patch, motion sickness patch); other implants; tattoo or jewelry
* history of any of these illnesses: brain thrombosis, stroke, traumatic brain injury, meningitis, heart attack, prolonged loss of consciousness, migraine, epilepsy