Classical conditioning of vocalizations in the rat: Acoustic characteristics of the CR and UCR

Classically conditioned shock-elicited vocalizations in the adult rat were acoustically analyzed and described, The fundamental frequency of the CRs ranged between 2,000 and 3,600 Hz, with overtones that extended well into the ultrasonic range and with durations lasting approximately 1÷2 sec. Major differences between CR and UCR signals were apparent. The CR vocalizations had little frequency variation and little or no noise, while the UCR vocalizations were associated with highly irregular frequencies and broad-band noise. Post-shock vocalizations had combined features of the CR and UCR sounds. It is suggested that the differences between the CR and UCR are related to the CR being the emotional cry and the UCR the pain cry.