PMC

Classifier accuracy (percent of classifications in which evidence for the correct trial type was highest) is plotted separately for each trial type (visual, phonological, semantic). Classifier evidence for each category (color-coded) is also plotted for each trial type. *p<0.005, **p<0.0002

Task procedures. (A) Experiment 2a: subjects performed short-term recognition of words, pseudo-words, or line segments. Both sets of stimuli for each trial were drawn from the same category. (B) Experiment 2b: subjects performed the same task but with each stimulus set drawn from a different category. (C) Experiment 2c: subjects performed short-term recognition for trials with either 2 sets of 2 stimuli each (4 total) or 1 set of 2 stimuli.

Unload effects on RT for behavioral experiments. Data are grouped along the horizontal access according to the length of time between the onset of the cue and the onset of the probe (0.1, 2, or 4 s). The vertical axis shows the difference in RTs (from the first recognition probe) between conditions of high- and low-load of uncued (irrelevant) stimuli. For Exp. 1 and 2, the high-load condition consisted of multiple stimuli in an uncued set, and the low-load condition consisted of a single uncued item. For Exp. 3, however, the high-load condition had two stimuli and the low-load condition had none (i.e., no unloading of UMIs was required).

In Phase 1, participants performed a short-term memory task (A) for items from one of three categories: line segments (visual memory), vowel sounds in pseudowords (phonological memory), or word meanings (semantic memory). In Phase 2, participants performed a two-item short term memory task (B) for items drawn from the same three categories – the two items present on each trial were always from different categories. A cue indicated the behaviorally relevant item before each of the two probes, with half of the trials cuing the same item twice (repeat trials) and half cuing the two items in turn (switch trials, as in the example diagrammed above).

Cross-validation decoding was performed within the Phase 2 task. Classifier sensitivity to the visual category (AUC) is plotted for each k-fold cross validation analysis time window, averaged across subjects. The width of the ribbon corresponds to the standard error of the AUC, calculated across subjects. Width of brackets surrounding significance markers indicates extent of delay period used for statistical analysis – see methods for details. Time is represented on the horizontal axis, with stimulus presentation (circles) from -2 to 0 s, the first cue (triangle) at 5 s, and the first probe (square) at 10.5 s. *p<0.05, **p<0.005.

Mean classifier evidence values are plotted separately for cue repeat (left) and cue switch trials (right). The visual, phonological and semantic categories were collapsed across all trials into new categories defined by the first cue: cued (red) is the category indicated by the first cue, uncued (blue) is the category of the other stimulus which is not selected by the first cue, and absent (gray) is the category not present on that trial. Time is represented on the horizontal axis, with stimulus presentation (circles) from -2 to 0 s, the first cue (triangle) at 5 s, the first probe (square) at 10.5 s, the second cue (triangle) at 14 s and the second probe (square) at 19.5 s. Width of the ribbons represents mean ± SEM, with spline interpolation to create continuous curves. Width of the brackets surrounding significance markers denotes extent of delay period used for statistical analysis: see methods for details. *p < 0.05, **p < 0.005.