Article Figures & Data
Figures
- Figure 1.
Task paradigm for Experiment 1. Each trial began with a fixation cross presented on screen for 1000 ms. Subsequently, a visual search of either low (display a) or high (display b) perceptual load was presented for 100 ms. On a random selection of half the trials, the visual display was accompanied by a 100 ms pure tone. After stimulus presentation, a blank screen was displayed for 1900 ms, during which time participants made a speeded response as to the identity of the target letter (X or Z, displays a and b in the figure both show an example of a Z target).
- Figure 2.
Evoked responses before and after DSS analysis. A, Data for the auditory alone condition and the low- and high-load visual and auditory conditions (AVL, AVH) before DSS were applied (left, grand RMS over auditory sensors; right, source analysis). The RMS plot demonstrates a weak auditory signal in the AVL and AVH conditions, likely due to an overlap with concurrent visual activity. Source analysis confirms dispersed activation in the AVL and AVH conditions relative to the A responses. There was additional activity in the visual cortex (BA17 and BA18) bilaterally (not visible due to slice selection) that had activity to a similar extent as that shown in C. B, The same conditions, but after the DSS analysis was applied. The auditory responses across the three conditions are similar in shape (but with a clear effect of load, discussed further in Fig. 3). Source analysis confirmed clear auditory activity, with no remaining activity in the visual cortex. C, Data from the VL and VH conditions, when the visual stimuli were presented without an accompanying tone. D, DSS-derived visual response from the AVL and AVH trials. Both the evoked responses and the source analysis results are comparable to those in C. The load effects reported here are based on the data in D.
- Figure 3.
Load effect on visual and auditory responses. A, Control (passive viewing) data. No significant differences were observed. B, Visual evoked response from the experimental group (conditions AVL and AVH). C, Auditory evoked response from the experimental group (conditions AVL and AVH). A–C, Left, Grand RMS responses across selected visual or auditory channels, for low- and high-load conditions. Shaded areas indicate intervals where response amplitudes differ significantly (see Materials and Methods). Inset, Scalp field maps of a representative participant at the peaks of the vM100 (A, B) and aM100 and P3 (C) responses. Right, Source localizations, computed from t = 70–170 ms. B and C show areas where there was a significant difference between activation in low and high load; A shows aggregate activity for low and high load, since there were no areas which showed a difference in the contrast.
Tables
Condition Anatomical description Brodmann area(s) Peak MNI coordinates p value (FWE corrected) x y z Visual low-load activity, 100–170 ms Bilateral cuneus, precuneus, lingual gyrus BA17, BA18, BA19 −12 −98 −10 <0.001 Visual high-load activity, 100–170 ms Bilateral cuneus, precuneus, lingual gyrus BA17, BA18, BA19 −6 −82 −18 0.001 Auditory alone activity, 100–170 ms Left STG BA21, BA22, BA42 −60 −28 8 0.012 Right STG BA21, BA22, BA42 64 −34 8 0.012 Auditory activity low load, 100–170 ms Left STG, MTG BA21, BA22, BA42 −62 −26 4 <0.001 Right STG, MTG BA21, BA22, BA42 52 −34 8 <0.001 Auditory activity high load, 100–170 ms Left STG, MTG BA21, BA22, BA42 −54 −30 8 0.036 Right STG, MTG BA21, BA22, BA42 56 −44 14 0.032 Left IFG BA11, BA47 −46 28 −14 0.031 Right IFG BA11, BA47 48 26 −10 0.031 Auditory activity low load, 250–300 ms Left STG, MTG BA21, BA22, BA42 −62 −26 4 <0.001 Right STG, MTG BA21, BA22, BA42 52 −34 8 <0.001 Auditory activity high load, 250–300 ms Left STG, MTG BA21, BA22, BA42 −54 −30 8 0.036 Right STG, MTG BA21, BA22, BA42 56 −44 14 0.032 Left IFG BA11, BA47 −46 28 −14 0.031 Right IFG BA11, BA47 48 26 −10 0.031 For each condition, clusters which were significant at p < 0.05 (FWE corrected) are detailed. Each entry gives the anatomical description of the region(s) the cluster covers, the Brodmann area(s) in the cluster, its peak MNI coordinates, and the p value associated with the cluster.
Contrast Anatomical description Brodmann area(s) Peak MNI coordinates p value (FWE corrected) x y z Visual activity, 100–170 ms, high load > low load Right lingual gyrus BA18 30 −94 −12 <0.001 Left postcentral gyrus BA2, BA3 −32 −68 50 0.027 Right SMG BA40 58 −52 30 0.030 Left SMG BA40 −48 −48 20 0.047 Right SPL/IPS BA7 44 −32 60 0.044 Auditory activity, 100–170 ms, low load > high load Left MTG, STS BA21 −66 −26 −6 <0.001 Right MTG, STS BA21 50 −36 −6 <0.001 Auditory activity, 250–300 ms, low load > high load Left STG, MTG BA22, BA41 −48 −24 4 0.012 Right STG, MTG BA22, BA41 46 −40 2 0.004 The table shows regions where contrasts between high and low load indicate significant differences in activation. For each contrast, clusters that were significant at p < 0.05 (FWE corrected) are detailed. Each entry gives the anatomical description of the region(s) the cluster covers, the Brodmann area(s) in the cluster, its peak MNI coordinates, and the p value associated with the cluster.
