Bereavement is a highly disruptive experience that is usually followed by a painful but time-limited period of acute grief. An unfortunate minority of individuals experience prolonged and impairing complicated grief, an identifiable syndrome that differs from usual grief, major depression, and other DSM IV diagnostic entities. Underlying processes guiding symptoms are not well understood for either usual or complicated grief. We propose a provisional model of bereavement, guided by Myron Hofer's question "What exactly is lost when a loved one dies?" We integrate insights about biobehavioral regulation from Hofer's animal studies of infant separation, research on adult human attachment, and new ideas from bereavement research. In this model, death of an attachment figure produces a state of traumatic loss and symptoms of acute grief. These symptoms usually resolve following revision of the internalized representation of the deceased to incorporate the reality of the death. Failure to accomplish this integration results in the syndrome of complicated grief.

Two-week-old rats were found to emit very little ultrasound in their cage except during arrivals and departures of the mother, when average peak rates of approximately 1 ultrasonic pulse/rat/min were detected. However, when all pups except one were removed from the home cage, the remaining isolated pup emitted ultrasound at a mean rate of 12 pulses/min for at least 30 min. When young rats of this age were placed alone in an unfamiliar test area, the ultrasound pulse rate was approximately 25/min, whereas groups of 4 littermates in the same situation emitted only occasional ultrasonic pulses. If an isolated pup in the novel environment was allowed access to a single anesthetized littermate or mother this also significantly reduced the rate of ultrasound emission, whereas a warm clay model did not.

The ultrasonic vocalization (USV), or isolation calling response, of infant rats and mice has been studied as a measure of the intensity of an aversive affective state and as an early communicative behavior between pup and mother. The four protocols described in this unit are for the basic isolation testing procedure, and for elicitation of the contact quieting response to littermates and/or dam, the potentiation of isolation calling response by a prior brief maternal interaction and the predator-induced suppression of USV by the scent of an unfamiliar male. These procedures for the elicitation of USV, and for its regulation by different kinds of social interaction, provides the basis for experimental research on the early development of emotion and communication in an animal model system.