Fig 1.
SPIRIT schedule of enrolment, interventions and assessments.
Fig 2.
There will be two assessments with similar setups. Only during the second assessment, participants will receive high definition-transcranial direct current stimulation (HD-tDCS) for 20 minutes with 1 milliamp.
Fig 3.
Participants will need to indicate the direction of a central arrow by button press. Flanking arrows (congruent or incongruent to the central arrow) or squares will need to be ignored. Arrows can be preceded by a cue or not. If a cue is present, it can appear at the centre (central cue) or both above and below the centre (double cue). It can also appear either above or below the fixation at which the arrow is going to appear (single cue).
Fig 4.
As an ongoing task, participants will need to indicate via button press whether two words belong to the same category or not. In addition, when a letter string appears, they will need to memorize the letter as well as its font colour (in the example ‘c’ and ‘green’). Whenever one of the following word pairs will be presented in the same colour as the letter string (here: green), participants will need to press the respective letter key (here: ‘c’).
Table 1.
Naturalistic prospective memory tasks used in our study.
Fig 5.
Electrode montage and current flow for high-definition transcranial direct current stimulation.
We will modulate the right inferior frontal lobe (FC6; A), the left inferior frontal lobe (FC5; B), or the right superior parietal lobe (P4; C). Simulation illustrates current flow through the brain. Positive values (red) indicate an increase, negative values (blue) a decrease in excitability of neurons. Simulations were created with SimNIBS (version 3.2.6) [47].