Differential effects of forward or simultaneous conditioned stimulus-unconditioned stimulus intervals on the defensive behavior system of the Norway rat (Rattus norvegicus).

Abstract

To test several predictions derived from a behavior-systems approach, the authors assessed Pavlovian fear conditioning in rats after 30 trials of forward, simultaneous, or unpaired training. Direct evidence of conditioned fear was collected through observation of flight and freezing reactions during presentations of the conditioned stimulus (CS) alone. The authors also tested the CS's potential to reinforce an instrumental escape response in an escape-from-fear paradigm. On the one hand, rats that received forward training showed conditioned freezing, but no conditioned flight was observed. On the other hand, rats that received simultaneous training showed conditioned flight, but no conditioned freezing was observed. Rats that received either forward or simultaneous pairings showed instrumental learning of the escape-from-fear response. Implications for several theories of Pavlovian conditioning are discussed.

Design of a Neurally Plausible Model of Fear Learning

“…Although some procedures, demonstrate the possibility of simultaneous or backward pairing or even the superiority of the latter for producing associations (Mowrer and Aiken, 1954; Heth and Rescorla, 1973; Mahoney and Ayres, 1976; Rescorla, 1980; Ayres et al, 1987; Matzel et al, 1988; Albert and Ayres, 1997; Esmoris-Arranz et al, 2003; Leising et al, 2007), it appears to us that for the sorts of experiments modeled by FRAT, forward pairing produces considerably more substantial and reliable conditioned fear than do non-forward procedures when fear is measured by CS-produced suppression of an ongoing operant, aversion, or freezing (Mowrer and Aiken, 1954; Heth and Rescorla, 1973; Mahoney and Ayres, 1976; Ayres et al, 1987; Albert and Ayres, 1997; Esmoris-Arranz et al, 2003). We have chosen to approximate this situation by making the model produce freezing only after forward pairing.…”

An automatic recording system for the study of escape from fear in rats

“…The basic procedure was adopted from Esmoris-Arranz et al (2003) who showed that a simultaneous conditioning paradigm (CS and US occur simultaneously at the beginning of each conditioning trial) is better than a forward conditioning one (CS is followed by US) in inducing EFF. After 3 days of handling (2 min/day) and 4 days of habituation (20 min/day) to the shuttle boxes, rats were randomly assigned to two groups: paired and unpaired, and subjected to 4 days of fear conditioning.…”

“…The fear conditioning commenced 3 min later. The CS was a compound stimulus consisting of the onset of an 85 dB 2800 Hz pure tone and offset of two houselights (tone+light off) for 15 s, similar to the compound CS used in Esmoris-Arranz et al (2003). The US was a 3 s 0.5 mA electrical footshock.…”

“…Fleeing (active avoidance) in order to get away from the CS or terminate it requires animals to make an overt motor action and is a voluntary and intentional motor response to danger, thus, it is deemed as a “ conditioned active fear response” (Amorapanth, LeDoux, and Nader 2000). Evidence suggests that conditioned reactive and active fear responses are mediated by distinct neural systems involving different sub-regions of the amygdala (Amorapanth, LeDoux, and Nader 2000), that they are sensitive to different classes of psychotherapeutic drugs (Li et al 2004; Mead, Li, and Kapur 2008), and are best induced under different CS-US temporal relations (Esmoris-Arranz, Pardo-Vazquez, and Vazquez-Garcia 2003). …”

“…Unlike conditioned fear reactions, it is also difficult to be recorded automatically. Often times, an experimenter has to manually manipulate animals and count the number of EFF, which inevitably introduces variability among animals (Amorapanth, LeDoux, and Nader 2000; Crawford and Masterson 1982; Esmoris-Arranz, Pardo-Vazquez, and Vazquez-Garcia 2003). In the present study, we described a computer controlled automatic recording system that is suitable to the study of EFF.…”