Figure 1.
The schematic illustration for the cued matching tasks.
A: The matching stimuli in the unimodal working memory task (left, high tone - high tone and low tone - low tone) and the crossmodal working memory task (right, high tone - line and low tone - curve); B: The events in a cued matching task trial. The solid arrows after task cue indicate the attended stimulus and the dashed arrows indicate the ignored stimulus according to the feature of task cue. C: the cued unimodal matching task (CUMT): S1 (high tone or low tone) with a duration of 200 ms is followed by a TC (a cycle with light-gray in upper half, 500 ms), the auditory (high or low tone) and visual (line or curve) stimuli are simultaneously presented for 200 ms after the Delay II, the participants are asked to attend the auditory stimulus and ignore the visual stimulus, finally they have to report whether the auditory S2 matches the S1 by pressing a button as correctly and quickly as possible. D: the cued crossmodal matching task (CCMT): the sequences of the CCMT are identical to the CUMT except that the task cue is the cycle with dark-gray in upper half. The participants are asked to attend the visual stimulus and ignore the auditory stimulus, and report whether the visual S2 matches auditory S1 by pressing a button.
Figure 2.
The behavioral performance of the cued matching task.
A: Correct rate; B: Reaction time. CUMT indicates the cued unimodal matching trial. CCMT indicates the cued cross-modal matching trial. The error bars mean the standard deviations; ***p<0.001 (student t-test).
Figure 3.
Brain regions related to initiation of cross-modal working memory retrieval (p<0.001, uncorrected, k = 100).
A: the areas displaying stronger activities in CCMT trials compared to the CUMT trials; B: the areas displaying stronger activities in CUMT trials compared to the CCMT trials. l-LPFC (X = −50): left lateral prefrontal cortex; l-SPL (Z = 44): left superior parietal lobe; Thalamus(X = −10).
Table 1.
Summary of brain areas showing greater activation to task cue in CCMT than CUMT conditions (p<0.001, uncorrected, k = 20).
Figure 4.
The ROI analysis of Brain activations to S1 stimulus and task.
A and B (l-LPFC, X = −50): left lateral prefrontal cortex; C and D (l-SPL, Z = 44): left superior parietal lobe; E and F (Thalamus, X = −10); S1: the first stimulus (high tone or low tone) in the cued matching task; TC: the task cue in the cued matching task; Error bars corresponded to the standard error of mean; *p<0.05, **p<0.01, ***p<0.001 (student t-test).