Biomedical subjects

Günter Ehret

Publications and source records attributed to Günter Ehret.

6 recordsLinked to original sources

PubMed2003

Spatial map of frequency tuning-curve shapes in the mouse inferior colliculus.

Neurons in the central nucleus of the auditory midbrain inferior colliculus divide into four classes according to the shapes of their receptive fields. Neurons of two of these classes - sharply tuned, inhibition-dominated neurons of class II, and broadly tuned neurons of class III - show systematic gradients in their abundance on isofrequency contours. Sharp tuning is most prevalent in the center, broad tuning in the periphery of the ICC. This new map of tuning-curve shape adds to the six previously described maps of neural response properties on isofrequency contours of the ICC and stresses the fact that very different sensitivities and selectivities to sound properties are combined in local clusters of collicular neurons.

Acoustic Stimulation↗

PubMed2002

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.

Animal Communication↗

PubMed2002

Basic maps in the auditory midbrain.

Topologic maps at consecutive levels of sensory pathways indicate behaviorally relevant features of stimuli at increasing degrees of complexity. In the auditory system, except for tonotopic maps, the nature of represented features is unknown. In a model analogous to visual map formation we show that in the auditory midbrain, layers of neurons with preference to the same frequency (isofrequency planes) may hold maps of two basic, mutually orthogonal parameters--instantaneous amplitude and phase--of basilar membrane displacement at the cochlear location responding to that frequency. The proposed neural tuning to frequency, amplitude, and phase implies that sound is transformed into specific temporal trajectories of neural activation, with consequences for experimental design and interpretation of neural response behavior.

Animals↗

PubMed2002

Sry does not fully sex-reverse female into male behavior towards pups.

Investigations in mice suggest that the Y-chromosomal genes affect certain behaviors. Here, we studied whether a part of the Y chromosome, the Sxr locus, has an effect on induction of motivation for parental care (pup retrieval) or of parental aggression towards pups (infanticide). XX females, XX males with the Sxr locus on the X chromosome, and XY males of the C57BL/6J strain were tested. The induced pup retrieval or infanticide behaviors were genotype-dependent. XX mice always retrieved pups and never were infanticidal. On the first test, significantly more XY males (38%) than XX males (17%) were infanticidal. When the same animals were tested for a second time, all except one of the XX males retrieved pups. Overall, motivation for parental care was highest in XX females, followed by XX males, and lowest in XY mice. On the other hand, the incidence of infanticide was highest in XY males, lower in XX males, and absent in XX females. We conclude that the Sxr locus of the Y chromosome, when operating in a XX background, partially erases but does not fully defeminize motivation for pup retrieval. Further, it induces infanticide to a level higher than that of XX females but significantly lower than that of normal males (XY). Hence, we suggest that genes outside the sex-determining region of the Y chromosome and/or genes on autosomes are necessary for manifestation of full male-type parental behavior.

Animals↗

PubMed2002

Corticofugal modulation of midbrain sound processing in the house mouse.

An understanding of the neural mechanisms responsible for auditory information processing is incomplete without a careful examination of substantial descending pathways. This study focuses on the functional role of corticofugal projections. Our work with the house mouse reveals that the focal electrical stimulation of the primary auditory cortex leads to profound changes in auditory response properties in the central nucleus of the inferior colliculus of the midbrain. Cortical stimulation does not impact on the collicular best frequencies when the best frequencies of stimulated cortical neurons and recorded collicular neurons are similar. Rather, collicular best frequencies are shifted toward the stimulated cortical best frequencies when cortical and collicular frequencies are different. Such a shift is unrelated to the differences in minimum thresholds between cortical and collicular neurons. In addition to frequency-specific shifts in collicular best frequencies, cortical stimulation elevates collicular minimum thresholds and reduces both dynamic ranges and response magnitudes if cortical and collicular best frequencies are different. If cortical and collicular best frequencies are similar but minimum thresholds are different, collicular minimum thresholds are shifted toward the stimulated cortical thresholds; dynamic ranges and response magnitudes may either increase or decrease in this scenario. Our results suggest that the corticofugal adjustment has a centre-surround organization with regard to both cortical best frequencies and cortical minimum thresholds. The midbrain processing of sound components in the centre of cortical feedback is largely enhanced while processing in the surround is suppressed.

Acoustic Stimulation↗

PubMed2001

Mice and humans perceive multiharmonic communication sounds in the same way.

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.

Age Factors↗