Mice and humans perceive multiharmonic communication sounds in the same way Günter Ehret* and Sabine Riecke Proc Natl Acad Sci USA 2002 Jan 8;99(1):479-82 *Department of Neurobiology, University of Ulm, D-89069 Ulm, Germany;
and Department of Biology, University of Konstanz, D-78457 Konstanz,
Germany Abstract: Vowels and voiced consonants of human speech and most mammalian vocalizations
consist of harmonically structured sounds. The frequency contours of formants
in the sounds determine their spectral shape and timbre and carry, in
human speech, important phonetic and prosodic information to be communicated.
Steady-state partitions of vowels are discriminated and identified mainly
on the basis of harmonics or formants having been resolved by the critical-band
filters of the auditory system and then grouped together. Speech-analog
processing and perception of vowel-like communication sounds in mammalian
vocal repertoires has not been demonstrated so far. Here, we synthesize
11 call models and a tape loop with natural wriggling calls of mouse pups
and show that house mice perceive this communication call in the same
way as we perceive speech vowels: they need the presence of a minimum
number of formants (three formants-in this case, at 3.8 + 7.6 + 11.4 kHz),
they resolve formants by the critical-band mechanism, group formants
together for call identification, perceive the formant structure rather
continuously, may detect the missing fundamental of a harmonic complex,
and all of these occur in a natural communication situation without any
training or behavioral constraints. Thus, wriggling-call perception in
mice is comparable with unconditioned vowel discrimination and perception
in prelinguistic human infants and points to evolutionary old rules of
handling speech sounds in the human auditory system up to the perceptual
level. Comment: In a series of elegant experiments with untrained and freely behaving mice, Ehret and Riecke showed that these animals perceive pitch in a similar way as cats, non-human primates, and humans. We now know that also mice group consecutive harmonics for the perception of one unitary pitch. Of particular interest is the finding that also in these small mammals the grouping of harmonics is governed by the critical bandwidth, which is hardwired in the auditory midbrain (inferior colliculus). The molecular mechanism of pitch neurons in this nucleus can now be investigated by the established techniques of gene analysis, which are already highly developed for the mouse. (Comment Martin Braun) |