Session I - cognitive part: The cognitive parts involves the well-known oddball and Eriksen flanker tasks, which are expected to elicit P300 and ERN, respectively. Both tasks will be performed in one session unless the patient will be tired, in which case they will be performed in two sessions (in two different days). In the oddball task patients will be shown a sequence of simple geometrical shapes, including a standard blue circle, a large blue circle and a square. The probability of these shapes will be 80%, 10% and 10%, respectively. Each shape will appear for 100mse every 1500-2000msec. Patients will be asked to press the space-bar (with the unaffected hand) when the large blue circle appears. There will be 3 blocks of 400 shapes each. This task will last one hour with breaks between the blocks. In the Eriksen flanker task patients will be shown a sequence of congruent, non-congruent and neutral stimuli. Each stimulus will include a central pair of arrows, flanked at the top and bottom by two other pairs of either arrows or squares. In congruent and non-congruent stimuli the top and bottom pairs include arrows that are either in the same (congruent) or opposite (non-congruent) direction as the central pair, while in neutral stimuli the top and bottom pairs are squares. Each stimulus will appear for 200msec every 1500-2000msec. Patients will be asked to press the left or right arrow on the keyboard (with the unaffected hand) according to the direction of the arrows in the central pair as fast as possible. There will be 8 blocks of 64 stimuli each and will last 45-60min, including breaks.