Figure 1. Task and recording sites.

(a) In the task, sets of consonants are presented and have to be memorized. The set size (4, 6, or 8 letters) determines working memory workload. In each trial, presentation of a letter string (encoding period, 2 s) is followed by a delay (maintenance period, 3 s). After the delay, a probe letter is presented. Participants indicate whether the probe was in the letter string or not. (b) Response accuracy decreases with set size (71 sessions). (c) Reaction time increases with set size (53 ms/item). (d) The tip locations of the hippocampal local field potentials electrodes for all participants (N=15) are projected in a hippocampal surface.

Figure 1—figure supplement 1. Hippocampal contact locations.

The recording location of the hippocampal local field potentials electrode of each participant is projected in a left hippocampal surface.