Figure 1. Paradigm sequence, stimuli and timing in a single trial.

Schematic representation of an example of a single ‘Medium’ load true positive trial in the Combined task. Each box represents a trial component with duration of each denoted (in seconds). Each fMRI trial consisted of a) an instruction screen indicating task component to be remembered (either Picture, or Position, or Picture and Position); b) a pre-encoding fixation grid; c) a study screen during which sets of targets were presented for participants to remember (encoding phase); d) a fixation mask consisting of a grid masked with grey squares to minimise perceptual after-effects (maintenance phase); e) a response screen during which another set of stimuli were displayed and participants indicated with a button press (yes/no) if any one of the targets had been present in the immediately preceding study screen (retrieval phase) and f) the inter-trial interval with duration jittered. Multicoloured abstract designs represent target stimuli to be remembered (either the picture itself; or the position in which the picture is placed; or both). Curved green shape represents non-target (filler) items.