Timing and the transition between modes in the defensive behavior system

Abstract

Antipredator defense is organized in a way that mirrors Timberlake's feeding behavior system because the goal of defense is to thwart predatory behavior. Each predatory mode has a corresponding antipredator mode. Like appetitive behavior systems, the defensive behavior system is organized around distinct modes along a spatiotemporal continuum we call the predatory imminence continuum. Behavior systems theory directs investigation toward the factors that lead to transitions between modes. In the feeding and sex systems the time between Conditional Stimulus (CS) and Unconditional Stimulus (US; e.g., CS-US interval or CS duration) is an important factor. Short CSs elicit conditional responses (CR) characteristic of more terminal modes and long CSs provoke CRs belonging to initial modes. Therefore, we asked if short CSs (10 s) would provoke CRs like the vigorous activity bursts and escape-like responses characteristic of the terminal mode of the predatory imminence continuum (Circa-Strike Behavior). Also, via analogy to appetitive systems, long CSs (3 min) were predicted to favor the intermediate mode, post-encounter behavior, which is characterized by freezing. Instead we found that both CSs produced freezing but not activity burst CRs and that freezing was actually greater with the short CS. We suggest that this difference between behavior systems flows from selection pressure that favors moving toward terminal modes in appetitive systems but away from terminal modes in the antipredator system. In addition, since appetitive reinforcers are more likely to be repeatedly experienced than predators, the learning of timing may be less relevant to defense. We also found that shock produced activity bursts and argue that when you are in the post-encounter mode (freezing) a sudden change in stimulation causes an immediate transition to circa-strike (terminal) behavior.

Keywords: CS duration; CS-US interval; Escape; Fear; Flight; Freezing; Panic.

Figure 1:

The Predatory Imminence Continuum Model. Based on Fanselow & Lester, 1988.

Figure 2:

Acquisition: The mean (±S.E.M) percent time spent freezing during the training session. Baseline (BL) is the 3 minutes prior to shock. Data show freezing during the 3 tones presented during training. The shock only group shows 10 sec that corresponded to the time when the short CS group received the tone. ***p<0.001 Short vs. Long and Shock Only; #p<0.050 Long vs. Short and Shock Only.

Figure 3:

The mean (±S.E.M) freezing during the test session in the novel context. Panel 1: Freezing (percent time) during the initial 3 min baseline period. Panel 2: Freezing during the first 10 sec of the tone. All groups received a 3 min tone regardless of training condition. Panel 3: The percent time spent freezing averaged over the full 3 minutes of the CS test. *p<0.050; **p<0.010.

Figure 4:

The mean (±S.E.M) freezing during the test session in the training context. Panel 1: Freezing (percent time) during the initial 3 min baseline period. Panel 2: Freezing during the first 10 sec of the tone. All groups received a 3 min tone regardless of training condition. Panel 3: The percent time spent freezing averaged over the full 3 minutes of the CS test. *p<0.050; **p<0.010.

Figure 5:

The activity burst, expressed as the mean (±S.E.M) Peak Activity Ratio (PAR), during the tone test in the novel context. Panel 1: PAR for the first 10 sec of the 3 min tone test. Panel 2: PAR for the last 10 sec (170–180 sec) of the 3 min tone test. Ratios are with respect to the 10 sec period prior to tone onset. **p<0.010.

Figure 6:

The activity burst, expressed as the mean (±S.E.M) Peak Activity Ratio (PAR), during the tone test in the training context. Panel 1: PAR for the first 10 sec of the 3 min tone test. Panel 2: PAR for the last 10 sec (170–180 sec) of the 3 min tone test. Ratios are with respect to the 10 sec period prior to tone onset.

Figure 7:

Shock-elicited activity bursts expressed as the mean (±S.E.M) Peak Activity Ratio. Panel 1: PAR comparing the 10 sec prior to shock to the subsequent 10 sec that began with a 2 sec shock. Panel 2: A comparison of the PAR to the first tone onset (both short and long CS groups are combined) to the PAR from the first shock presentation (Shock Only group). ***p<0.001.