Fig 1.
Timeline, procedure, and stimuli of the visuospatial working memory task of experiment 1.
Participants received a 2 gram dose of either choline bitartrate or placebo in 2 separate sessions (cross-over design). A half hour after ingestion participants were allowed to eat some fruit and another half hour later they performed a visuospatial memory task (a). Mood & arousal, heart rate, and blood pressure (MA,HR,BP) were assessed 3 times during each session. The memory task was divided into 3 test blocks per session. In each block, participants completed 5 trials in which they had to memorize and consecutively indicate each of the location of the 9 target pictures. Pictures were shown for 10 seconds during which participants were supposed to memorize the locations of each picture (b). Pictures were then masked for 4 seconds and participants could subsequently indicate the location of the targets (random presentation order) with a computer mouse. Feedback was given by changing the target in a green (correct location) or red (incorrect location) patch. Pictures were shown in color but are here displayed in grayscale. The background color was grey during the experiment but is here displayed in white for aesthetical reasons.
Fig 2.
Results of visuospatial working memory task of experiment 1.
Average percentage correctly memorized picture locations across participants (chance = ~11%) per supplementation condition (C = choline, P = placebo; n.s. = no significant difference).
Fig 3.
Procedure and stimuli of declarative memory task of experiment 2.
Participants first memorized 50 pictures in an encoding phase (a). Next, the same pictures were presented intermixed with 50 new pictures (b). Participants indicated with 2 arrow buttons on a keyboard whether a presented picture was new (i.e., not presented during memorization) or old (i.e., previously presented).
Fig 4.
Results of declarative memory task of experiment 2.
Average percentage of correctly classified pictures (chance = 50%) as old or new stimuli in the test phase across participants per choline and placebo condition.
Fig 5.
Procedure and stimuli of verbal working memory task of experiment 3.
A total of 24 verbal animal species (a) were read out in 2 second intervals (b). Next, the participant had to recall and type in all the names they remembered. Unrecalled words (misses) were read out again until the participant was able to recall all words or until they had gone through 4 trial iterations.
Fig 6.
Results of memory tasks of experiment 3.
Average percentage of correctly memorized picture locations in the visuospatial working memory task (a), percentage of correctly classified pictures as old or new stimuli in the declarative retrieval task (b), and number of forgotten items in the verbal working memory task (c) per choline and placebo condition.