Time-Critical Integration of Formants for Perception of Communication Calls in Mice

Brain mechanisms in humans group together acoustical frequency components both in the spectral and temporal domain, which leads to the perception of auditory objects and of streams of sound events that are of biological and communicative significance. At the perceptual level, behavioral data on mammals that clearly support the presence of common concepts for processing species-specific communication sounds are unavailable. Here, we synthesize 17 models of mouse pup wriggling calls, present them in sequences of four calls to the pups' mothers in a natural communication situation, and record the maternal response behavior. We show that the biological significance of a call sequence depends on grouping together three predominant frequency components (formants) to an acoustic object within a critical time window of about 30-ms lead or lag time of the first formant. Longer lead or lag times significantly reduce the maternal responsiveness. Central inhibition seems to be responsible for setting this time window, which is also found in numerous perceptual studies in humans. Further, a minimum of 100-ms simultaneous presence of the three formants is necessary for occurrence of response behavior. As in humans, onset-time asynchronies of formants and formant durations interact nonlinearly to influence the adequate perception of a stream of sounds. Together, these data point to common rules for time-critical spectral integration, perception of acoustical objects, and auditory streaming (perception of an acoustical Gestalt) in mice and humans.