Activation of extracellular signal-regulated kinase (ERK) and ΔFosB in emotion-associated neural circuitry after asymptotic levels of active avoidance behavior are attained

Absence of “Warm-Up” during Active Avoidance Learning in a Rat Model of Anxiety Vulnerability: Insights from Computational Modeling

“…Figure 4A shows typical within-session avoidance responding patterns, plotted as trial-by-trial responding averaged across several blocks of training sessions (Perrotti et al, 2013). As illustrated in the figure, avoidance responding typically increases across trials within a session, but particularly in later sessions, SD rats generally make fewer avoidance responses on the first few trials of a session, compared to their performance at the end of the previous session or later in the same session.…”

“…Asterisks indicate significantly greater responding in WKY than SD; crosses indicate significantly less responding by SD on the first two trials of a block than on the last two trials of the preceding block. Adapted from Figure 1 of Perrotti et al (2013). (B) Similarly, warm-up is shown during acquisition by the SD but not WKY model (B1–4) .…”

“…If the animal presses the lever during the warning period, this is defined as an avoidance response: W is terminated, no shocks are delivered, and the trial moves immediately to the ITI. Behaviorally inhibited WKY rats acquire avoidance responses more quickly than SD rats (Servatius et al, 2008; Beck et al, 2011; Jiao et al, 2011b; Perrotti et al, 2013). WKY rats also typically show impaired extinction of responding when W is no longer paired with shock (Servatius et al, 2008; Beck et al, 2011; Jiao et al, 2011b; Perrotti et al, 2013).…”

“…Behaviorally inhibited WKY rats acquire avoidance responses more quickly than SD rats (Servatius et al, 2008; Beck et al, 2011; Jiao et al, 2011b; Perrotti et al, 2013). WKY rats also typically show impaired extinction of responding when W is no longer paired with shock (Servatius et al, 2008; Beck et al, 2011; Jiao et al, 2011b; Perrotti et al, 2013). This impaired extinction indicates that the WKY rat is an overly avoidant animal that is willing to expend energy and continue displaying the avoidance response during extinction rather than occasionally testing whether the reinforcement contingency is still present.…”

“…This phenomenon has been termed “warm-up,” and is shown by a number of species in a range of avoidance paradigms (for reviews, see Kamin, 1963; Spear et al, 1973; Hineline, 1978). In contrast, WKY rats tend to respond on the first trial of each session at approximately the same rate as at the end of the prior session (Servatius et al, 2008; Perrotti et al, 2013). It is possible that the absence of warm-up contributes to the generally faster acquisition, and slower extinction, of avoidance in the WKY rats compared to SD rats.…”