Fig. 4: Supramodal common representations of working memory in the superior parietal cortex.

a To directly compare the representations of braille identity between different tasks and ascertain their correspondence, discrimination indices were derived based on within- and between-braille correlations for each pair of working memory tasks. b–d Discrimination indices for braille identity for each pair of the tasks in SPL and IPS. Significantly positive discrimination indices were found between the two within-modal tasks (TT and VV), as well as between the two cross-modal tasks (TV and VT) (b). Furthermore, positive discrimination indices were observed between task TV and each within-modal task (TV and TT; TV and VV) (c), and between task VT and each within-modal task (VT and TT; VT and VV) (d). e Cross-decoding of braille identity using multi-class classification analysis. An SVM classifier was trained on neural response patterns from one task and tested on patterns from the other task, and vice versa. The classification accuracies in both directions were then averaged. f–h Classification performance between each pair of the tasks in SPL and IPS. The dotted lines indicate the chance level. Consistent with the discrimination index results, significant cross-decoding was observed between the two within-modal tasks (TT and VV), as well as between the two cross-modal tasks (TV and VT) (f). Furthermore, significant cross-decoding was observed between task TV and each within-modal task (TV and TT; TV and VV) (g), and between task VT and each within-modal task (VT and TT; VT and VV) (h). Asterisks above each box, *p < 0.05, **p < 0.01 (one-sample t test, right-tailed, FDR-corrected). Asterisks between two boxes, **p < 0.01 (paired t test, two-tailed). A full list of statistical values is provided in Supplementary Table 2. The lower, middle, and upper lines of each box represent the 25%, 50%, and 75% quartiles, respectively. The upper and lower whiskers extend to the highest and lowest data values within 1.5 times the interquartile range from the hinge. Each dot indicates the mean data value for each participant (b–d: n = 29; f–h: n = 28).