Figure 1.
Flowchart describing the procedure.
Figure 2.
Group averaged P1-N1-P2 complexes recorded from electrode site Cz.
Regardless of stimulus type (“mba” or “ba”), P2 peak amplitudes significantly increased across three sessions for Group 2 (exposure + task) but not Group 1 (exposure only). Sessions 1 and 2 were conducted on two consecutive days. Session 3 was conducted one week later.
Figure 3.
Results from Mean-Centering PLS analyses.
(A) Electrode Montage. To report PLS results, Electrode locations were classified into 11 sagittal layers indicated by the dotted lines: three lateral (lat1–3), two medial layers (med1–2) in the two hemispheres, and one midline layer (mid). (B) Contrast weights identified for the first significant LV. For each stimulus type, the largest difference was observed between Sessions 1 and 3, in the P2 latency range, for both groups, but the degree of difference was greater in Group 2. (C) Spatiotemporal patterns of electrode saliencies and bootstrap results corresponding to the design LV shown in (B). The x-axis represents time in milliseconds (ms) starting at the stimulus onset marked as 0 ms. The y-axis represents electrodes organized in 11 blocks corresponding to the 11 sagittal layers in the montage shown in (A). Within each block, electrodes are ordered from top to bottom representing anterior to posterior sites. Each horizontal color bar represents temporal patterns of the electrode saliencies for a given electrode. Warm (more red) color illustrates time points with positive differences expressed in the design contrasts; cool (more blue) color expresses those of negative. Positive saliencies (warm color), and negative saliencies (cool color) indicate time points at which the amplitude of the AEP was enhanced over three experimental sessions. Saliencies are scaled with the singular value. For each electrode, horizontal black bars (comprised of individual “x”s) are plotted over the color contrasts to identify the time points at which differences expressed in the contrasts were stable across participants (bootstrap ratios >3).
Figure 4.
Results from Non-rotated PLS analyses and AEP waveforms for selected electrodes.
Saliencies are displayed as waveforms and the circles on the top or bottom of each waveform indicate time points at which bootstrap ratios were above threshold. Larger and reliable saliencies were observed in the time range of P2 responses. Topographical maps illustrate the scalp distribution of the session effect on P2 responses. Displayed are AEP differences between Sessions 1 and 3 averaged over 190–290 ms.
Table 1.
Electrodes showing the largest and reliable saliencies from MC-PLS in the P2 latency time range.
Figure 5.
P2 amplitude changes across Sessions at three ROIs.
Increases in P2 amplitude were most prevalent within the temporal-occipital region for both Groups across sessions. This session effect was not observed at anterior-central areas as well as at vertex (Cz) for Group 1.
Figure 6.
Individual P2 peak amplitude data are shown for all four Sessions in response to the stimulus “mba”. Results shown are from electrode site TP9. When looking at individual subjects, enhanced P2 amplitudes can be seen for many individuals (in Group 2) even though they had not heard these sounds for many months.
Figure 7.
Group d-prime scores and standard error bars are shown for each test session.