Infant Rodent Ultrasounds ? A Gate to the Understanding of Sound Communication

Abstract

Components of the communication system between infant and adult rodents based on ultrasonic vocalizations (USVs) of infants are analyzed. USVs are most often emitted from a pup lost outside the nest in response to changes of: (i) body temperature, (ii) contact with adults/littermates, (iii) handling, and (iv) smell. These changes modulate the state of arousal and the emotional/motivational states and, as a result, USVs are produced. Acoustic properties of USVs seem to reflect the degrees of changes in arousal and emotion/motivation. Adult rodents are aroused by perceiving the USVs, locate the sender and show a phonotaxic approach to the sender. Acoustic properties of USVs in the frequency and time domains are described based on which adult rodents discriminate the USVs from other ultrasounds and take the USVs or adequate models of them as preferred goals of their phonotaxic approach. The preferred approach to adequate USVs is modulated by emotions/motivations, the sex of the receiver, hormonal states, experience with pups and neurotransmitter systems of the brain. The phonotaxis can be understood as the appetitive component of a pup-caring instinct. The consummatory act of the instinct is the retrieval of the lost pup. This retrieval is independent of USV presence, but it closes the communication loop activated by the emission of USVs. Communication with USVs can be used as a tool to investigate genetic and brain mechanisms of behavioral control.

Modeling fragile X syndrome in the <i>Fmr1</i> knockout mouse

“…Rodent pup ultrasonic vocalizations are considered to be biologically meaningful (155,156), as they are emitted in young pups during stressful situations (157) and elicit retrieval behaviors by the parents. Adult male mice and rats emit ultrasonic vocalizations during interaction with females and in response to urine from estrus females (158).…”

What can mice tell us about Foxp2 function?

“…These calls are innate, not modulated by auditory feedback (mouse pups <10 days old are deaf), and thought to be an involuntary response to altered arousal state. Pup ultrasonic isolation calls (USIs) elicit retrieval by the mother [53] and homozygotes that lack functional Foxp2 emit very few compared to wild-type littermates [21,22 ,23,54]. However, under conditions of elevated arousal (applying gentle pressure to the tail while lifting the animal) homozygotes do produce ultrasonic calls, albeit of lower intensity [22 ,54].…”

Olfactory cues are sufficient to elicit social approach behaviors but not social transmission of food preference in C57BL/6J mice

“…Visual and auditory deprivation both depress normal aggressive behavior in mice [59]. Ultrasonic vocalizations in separated pups elicit retrieval behaviors by parents [18,25,58]. Adult mice of both sexes will vocalize in social situations such as aggressive encounters or copulation, and vocalizations can be elicited by exposing mice to urine or environments conditioned to be viewed as social [27,48,50].…”