Behavior of Rats with High and Low Levels of Freezing in Defensive Situations and on Selection of Food Reinforcement

Behavior in rats with different levels of freezing in a classical defensive conditioned reflex was compared on acquisition of conditioned passive and active avoidance reflexes and on selection of food reinforcement of different values. Rats with prolonged freezing acquired the passive avoidance reflex better and retained it longer during extinction than animals with shorter freezing. At the same time, the active avoidance reflex in the shuttle box was acquired more easily by animals with short periods of freezing. Rats with prolonged freezing preferred a delayed and more valuable reinforcement in the model of choosing food reinforcements of different values (low level of impulsivity), while animals with short freezing preferred the low-value reinforcement without a delay (high level of impulsivity). The thresholds of pain sensitivity were no different in rats of the different groups. Thus, rats with prolonged freezing demonstrated a passive behavioral strategy in defensive situations and a low level of impulsivity, while rats with short freezing used an active behavioral strategy and showed a high level of impulsivity.