Asymmetrical stimulus generalization following differential fear conditioning

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Abstract

Rodent ultrasonic vocalizations (USVs) are ethologically critical social signals. Rats emit 22 kHz USVs and 50 kHz USVs, respectively, in conjunction with negative and positive affective states. Little is known about what controls emotional reactivity to these social signals. Using male Sprague–Dawley rats, we examined unconditional and conditional freezing behavior in response to the following auditory stimuli: three 22 kHz USVs, a discontinuous tone whose frequency and on–off pattern matched one of the USVs, a continuous tone with the same or lower frequencies, a 4 kHz discontinuous tone with an on–off pattern matched to one of the USVs, and a 50 kHz USV. There were no differences among these stimuli in terms of the unconditional elicitation of freezing behavior. Thus, the stimuli were equally neutral before conditioning. During differential fear conditioning, one of these stimuli (the CS+) always co-terminated with a footshock unconditional stimulus (US) and another stimulus (the CS) was explicitly unpaired with the US. There were no significant differences among these cues in CS+-elicited freezing behavior. Thus, the stimuli were equally salient or effective as cues in supporting fear conditioning. When the CS+ was a 22 kHz USV or a similar stimulus, rats discriminated based on the principal frequency and/or the temporal pattern of the stimulus. However, when these same stimuli served as the CS, discrimination failed due to generalization from the CS+. Thus, the stimuli differed markedly in the specificity of conditioning. This strikingly asymmetrical stimulus generalization is a novel bias in discrimination.

Section snippets

General introduction

Rodent ultrasonic vocalizations (USVs) have been studied for many decades (Anderson, 1954, Blanchard et al., 1991, Brudzynski et al., 1993, Knutson et al., 2002, Sales and Pye, 1974, Sewell, 1967, White et al., 1990, Zippelius and Schleidt, 1956). USVs serve as ethologically critical social signals (Brudzynski, 2005, Litvin et al., 2007) and offer a unique window into the emotional state of the animal (Borta et al., 2006, Brudzynski, 2007, Knutson et al., 2002, Panksepp, 2007). Rats emit USVs

Experiment 1

Although USVs are thought to be critical social signals in rats and other rodents, little is known about the role of experience in determining emotional or defensive responses to these vocalizations. Using naı¨ve rats, Experiment 1 examined unconditional freezing responses to pre-recorded USVs and some simpler, synthetic stimuli. The results demonstrated that USVs are as “neutral” as tones in experimentally naı¨ve, male, Sprague–Dawley rats.

Experiment 2

Genetic variations have been shown to affect the production of USVs (Brunelli, 2005, Brunelli et al., 1997, Burgdorf et al., 2005, Hahn et al., 1987, Sales and Smith, 1978), but there have been few studies of the possible influence of genetic and environmental variables in determining reactivity to these social signals (see Allen et al., 2007, Brudzynski, 2007, Endres et al., 2007). Although the stimuli used in Experiment 1 were equally neutral, as measured by unconditional freezing, they might

Experiment 3

Experiment 2 demonstrated that fear generalizes toward USV-like cues (centripetal spread) more than it does from these cues (centrifugal spread). Experiment 3 explored what happens when both cues are USVs. As in Experiment 2, the focus was on how well the rats discriminated between the cue pairs (d in Eq. (1)) and whether there was a discrimination bias (AG in Eq. (4)). The first cue pair consisted of two 22 kHz USVs. These were selected from our library of recorded USVs to differ maximally in

Experiment 4

In Experiments 2 and 3, rats displayed asymmetrical stimulus generalization of fear. The direction of the asymmetry was consistently toward the 22 kHz USV or similar cue (see discussion of Eq. (4)). In principle, this interesting phenomenon might reflect non-associative sensitization to 22 kHz USV-like stimuli. Experiment 4 asks whether cue-specific sensitization can account for the discrimination bias. This experiment specifically evaluated the possibility that rats might become sensitized by

Summary of five main findings

The present study was the first examination of differential fear conditioning to natural auditory stimuli in rodents. The auditory stimuli consisted of 22 kHz USVs, a 50 kHz USV, and various synthetic stimuli that were designed to “deconstruct” the 22 kHz USVs into simpler acoustic features. We focused on three categories of auditory features: principal frequency, discontinuity, and frequency/amplitude modulations. Five main findings emerged.

First, 22 kHz USVs did not differ from 50 kHz USVs,

General conclusions

The asymmetrical stimulus generalization reported here is a novel form of “biological preparedness” (Seligman, 1970, Seligman, 1971) in the auditory fear conditioning system. Rats appear to have a predisposition to generalize acquired fear toward 22 kHz USVs or similar stimuli. Just as with other preparedness phenomena (see Cusato and Domjan, 1998, Domjan et al., 2004, Krause et al., 2003), asymmetrical stimulus generalization is unpredicted by conventional animal learning theories. Our brief

Acknowledgments

We thank Dr. Michael Domjan for useful discussion. This research was supported by National Institutes of Health Grants MH58405 and AG19645 (T.H.B.) and Yale University.

References (96)

  • S.M. Brudzynski

    Ultrasonic calls of rats as indicator variables of negative or positive states: Acetylcholine-dopamine interaction and acoustic coding

    Behavioural Brain Research

    (2007)
  • S.M. Brudzynski et al.

    Behavioural responses of laboratory rats to playback of 22 kHz ultrasonic calls

    Physiology & Behavior

    (1995)
  • S.M. Brudzynski et al.

    Acoustic characteristics of air puff-induced 22-kHz alarm calls in direct recordings

    Neuroscience and Biobehavioral Reviews

    (2005)
  • S.M. Brudzynski et al.

    Analysis of 22 kHz ultrasonic vocalization in laboratory rats: Long and short calls

    Physiology & Behavior

    (1993)
  • J. Burgdorf et al.

    Tickling induces reward in adolescent rats

    Physiology & Behavior

    (2001)
  • M.R. Ciucci et al.

    Qualitative changes in ultrasonic vocalization in rats after unilateral dopamine depletion or haloperidol: A preliminary study

    Behavioural Brain Research

    (2007)
  • V. Cuomo et al.

    Ultrasonic vocalization in response to unavoidable aversive stimuli in rats: Effects of benzodiazepines

    Life Sciences

    (1988)
  • B. Cusato et al.

    Special efficacy of sexual conditioned stimuli that include species typical cues: Tests with a conditioned stimuli pre-exposure design

    Learning and Motivation

    (1998)
  • G.C. Davey et al.

    Differential aversive outcome expectancies for high- and low-predation fear-relevant animals

    Journal of Behavior Therapy and Experimental Psychiatry

    (2003)
  • T. Endres et al.

    Are rats predisposed to learn 22 kHz calls as danger-predicting signals?

    Behavioural Brain Research

    (2007)
  • K.A. Goosens et al.

    Auditory-evoked spike firing in the lateral amygdala and Pavlovian fear conditioning: Mnemonic code or fear bias?

    Neuron

    (2003)
  • B. Knutson et al.

    High-frequency ultrasonic vocalizations index conditioned pharmacological reward in rats

    Physiology & Behavior

    (1999)
  • Y. Litvin et al.

    Rat 22 kHz ultrasonic vocalizations as alarm cries

    Behavioural Brain Research

    (2007)
  • J.M. Mateo

    The development of alarm call response behaviour in free living juvenile Belding’s ground squirrels

    Animal Behaviour

    (1996)
  • J.M. Mateo et al.

    Development of alarm-call responses in Belding’s ground squirrels: The role of dams

    Animal Behaviour

    (1997)
  • M.Y. McGinnis et al.

    Characterization of 50-kHz ultrasonic vocalizations in male and female rats

    Physiology & Behavior

    (2003)
  • R.J. McNally et al.

    Preparedness and resistance to extinction to fear-relevant stimuli: A failure to replicate

    Behaviour Research and Therapy

    (1986)
  • S. Mineka et al.

    Phobias and preparedness: The selective, automatic, and encapsulated nature of fear

    Biological Psychiatry

    (2002)
  • J. Panksepp

    Neuroevolutionary sources of laughter and social joy: Modeling primal human laughter in laboratory rats

    Behavioural Brain Research

    (2007)
  • J. Panksepp et al.

    50-kHz chirping (laughter?) in response to conditioned and unconditioned tickle-induced reward in rats: Effects of social housing and genetic variables

    Behavioural Brain Research

    (2000)
  • G.D. Sales

    The effect of 22 kHz calls and artificial 38 kHz signals on activity in rats

    Behavioural Processes

    (1991)
  • M.E.P. Seligman

    Phobias and preparedness

    Behavior Therapy

    (1971)
  • J.L. Wiley et al.

    Effects of SR141716A on diazepam substitution for delta9-tetrahydrocannabinol in rat drug discrimination

    Pharmacology, Biochemistry, and Behavior

    (1999)
  • A.J. Wintink et al.

    The related roles of dopamine and glutamate in the initiation of 50-kHz ultrasonic calls in adult rats

    Pharmacology, Biochemistry and Behavior

    (2001)
  • J.W. Anderson

    The production of ultrasonic sounds by laboratory rats and other mammals

    Science

    (1954)
  • R.J. Barfield et al.

    Sexual behavior: Ultrasonic postejaculatory song of the male rat

    Science

    (1972)
  • R.J. Blanchard et al.

    Antipredator defensive behaviors in a visible burrow system

    Journal of Comparative Psychology

    (1989)
  • P.M. Boguszewski et al.

    Machine analysis of conditional and unconditional freezing behavior in rats

    Society for Neuroscience Abstract

    (2007)
  • S.M. Brudzynski

    Principles of rat communication: Quantitative parameters of ultrasonic calls in rats

    Behavior Genetics

    (2005)
  • S.A. Brunelli

    Selective breeding for an infant phenotype: Rat pup ultrasonic vocalization (USV)

    Behavior Genetics

    (2005)
  • S.A. Brunelli et al.

    Five generations of selective breeding for ultrasonic vocalization (USV) responses in N: NIH strain rats

    Developmental Psychobiology

    (1997)
  • J. Burgdorf et al.

    Breeding for 50-kHz positive affective vocalization in rats

    Behavior Genetics

    (2005)
  • J.S. Choi et al.

    Central amygdala lesions block ultrasonic vocalization and freezing as conditional but not unconditional responses

    Journal of Neuroscience

    (2003)
  • J. Cohen

    Statistical power analysis for the behavioral sciences

    (1988)
  • D.R. Collins et al.

    Differential fear conditioning induces reciprocal changes in the sensory responses of lateral amygdala neurons to the CS(+) and CS(−)

    Learning & Memory

    (2000)
  • M. Cook et al.

    Observational conditioning of fear to fear-relevant versus fear-irrelevant stimuli in rhesus monkeys

    Journal of Abnormal Psychology

    (1989)
  • M. Cook et al.

    Selective associations in the observational conditioning of fear in rhesus monkeys

    Journal of Experimental Psychology: Animal Behavior Processes

    (1990)
  • F.R. D’Amato et al.

    Pups call, mothers rush: Does maternal responsiveness affect the amount of ultrasonic vocalizations in mouse pups?

    Behavior Genetics

    (2005)
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