Fig. 6.

Transformation of the pattern of AbN activity from late-E (pre-I) bursting to biphasic-E discharge during hypercapnic anoxia (7% CO₂, 93% N₂, 0% O₂). The top three traces show integrated activity (arbitrary units not shown) of PN, cVN and AbN. The bottom trace represents the index of post-I activity calculated as an averaged activity in cVN during the expiratory phase in each cycle (an example is shown as the gray area in the cVN trace); the expiratory phase was defined by the absence of activity in the PN trace (the vertical dashed line across the first cycle of integrated activity indicates the onset of expiration for the first cycle shown in this example). In the first half of the recorded episode, only late-E bursts were present in AbN. The post-I component of cVN gradually decreased. The transition of AbN bursts to a biphasic-E discharge pattern (with pre-I and post-I components) occurred after a significant suppression of the cVN post-I activity (indicated by vertical and horizontal dash-dotted lines)