Fig. 5.

Statistical evaluation of the effects of reversed contingences on the spectro-temporal profile of NB-induced memory. This analysis revealed statistically significant CS-specific associative responses at different latencies for initial pairing and reversed contingencies. Statistical analysis was accomplished by calculating confidence levels for the corresponding data shown in Fig. 4D–F. The data were thresholded at two levels, (A) 99% (p <.01) and (B) 99.9% (p <.001). The confidence intervals were calculated individually for each plot based on the data representing RCI values from within the 22 × 9 points X–Y matrix (X-axis = time: 2 s before to 20 s following stimulus onset; Y-axis = tone frequency, 1.00, 2.75, 4.50, 6.25, 8.00, 9.75, 11.50, 13.25 and 15.00 kHz). Black-filled areas on the plots represent spectro-temporal regions that equal or exceed the values of the mean plus either the 99% (A) or the 99.9% (B) confidence intervals; none of the points in the matrices fell below the mean minus the confidence intervals. Before training, groups IP and IU differed little (A) or not at all (B). After initial training (IP paired, IU unpaired), the IP group had significantly larger responses than the IU group at and immediately adjacent to the CS frequency (horizontal line) with a latency of ~1–3 s (A); at the 99.9% confidence interval, the difference was confined to the CS frequency band, at ~6.25 kHz, with the same short-latency (B). Following contingency reversal (IU minus IP group data), associative responses were also confined to the CS band ~6.25 kHz, but at a much longer latency of ~7–9 s. (To directly compare the shift in latency, the significant S–T regions in the middle row are projected onto the bottom row as dashed outlines.) Vertical dashed lines at tone onset and 13 s delineate the area of respiration responses where they were most pronounced (see Fig. 4D–F), and are provided as references.