PMC5462969_01
PMC5462969_02
Examples of different trials in each condition of the visual working memory task. For details, see "Experimental Design and Stimuli" Section.
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F1
This task involves two sets of stimuli, one with black shapes, used to evaluate memory for shapes; and a second one with colored shapes, assessing shape-color binding in working memory (see Figure 1).
Enhanced working memory binding by direct electrical stimulation of the parietal cortex. (A) Mean performance of the subject during the real (posterior parietal cortex, PPC) or sham (sham) stimulation in the shape-only (shapes) and shape-color binding (binding) conditions, compared to the performance of seven matched control participants. Error bars represent standard deviations (SD) from the mean. (B) Schematic brain localization of the reported contact sites. Red nodes represent the stimulated site and black nodes show the ROIs were stimulation propagation was detected. (C) Intracranial event related potentials (iERP) activity from significant ROIs comparing real and SHAM stimulation in the shape-color binding condition. Shadowed bars around potentials indicate SEM. For visualization purposes, the signal was renormalized, filtered and smoothed. p < 0.005, permutation test with bootstrapping and false discovery rate correction, minimum length of windows with significant differences: 100 ms.
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F2
Relative to controls ("Behavioral Analysis" Section), the subject only reached normal STM binding performance upon stimulation (Crawford's t = 0.20, p = 0.84, Zccc = 0.21; Figure 2A). In addition, compared with the SHAM condition, electrical stimulation during the binding condition significantly enhanced performance (Crawford's t = -2.93, p = 0.02, Zccc = -3.31; Figure 2A). Moreover, the subject's performance in the shapes condition did not significantly differ from that of controls, in any of the treatments (PPC: Crawford's t = 1.33, p = 0.23, Zccc = -1.42; SHAM: Crawford's t = 2, p = 0.08, Zccc = 2; Figure 2A). The intracranial event related potentials (iERP) showed maximal effects in parietal regions, followed by the cuneus, the posterior cingulate, the postcentral gyrus, the middle frontal gyrus, and the hippocampus, in a constant decreasing fashion (all ps < 0.005, permutation test with bootstrapping and false discovery rate correction; Figure 2C).