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W Metzner

Publications and source records attributed to W Metzner.

33 records · Page 2Linked to original sources
PubMed1993

The jamming avoidance response in Eigenmannia is controlled by two separate motor pathways.

The gymnotiform fish Eigenmannia generates weakly electric signals for electrolocation and communication. The signals are produced by electric organ discharges (EODs) that are driven by a medullary pacemaker nucleus. To avoid jamming by neighboring conspecifics with similar frequencies, a fish raises its own EOD frequency if the neighbor's frequency is lower, and it lowers its EOD frequency if the neighbor's frequency is higher (Watanabe and Takeda, 1963). Both the raising and lowering of EOD frequency of this jamming avoidance response (JAR; Bullock et al., 1972) are thought to be controlled by feature-extracting neurons in the diencephalic prepacemaker nucleus (PPn-G) that discriminate the sign of the frequency difference between the jamming signal and the fish's EOD (Kawasaki et al., 1988a; Rose et al., 1988; for review, see Heiligenberg, 1991). These prepacemaker neurons are excited in response to lower jamming frequencies, thereby raising the frequency, and inhibited by higher jamming frequencies, producing a discharge deceleration. The results of experiments presented here, however, suggest a mechanism for the motor control of the JAR that is different from the one described previously (see, e.g., Heiligenberg, 1991). Two prepacemaker nuclei, one PPn-G and one sublemniscal prepacemaker nucleus (SPPn) (Keller et al., 1991 a,b), which provide the only known inputs to the pacemaker, were lesioned selectively. This article explores the effects of these lesions on the JAR. Pharmacological experiments were used to elucidate the transmitter types involved. The results suggest that the JAR is controlled by two separate motor pathways. One controls frequency rises and originates in the dorsal substructure of the nucleus electrosensorius (Keller, 1988). It sends excitatory connections to the diencephalic prepacemaker and finally to the pacemaker nucleus, where AMPA-type receptors mediate the synaptic transmission. The second pathway controls frequency decreases and originates in the ventral substructure of the nucleus electrosensorius. It provides GABAergic input to the SPPn. The SPPn is tonically active and also controls the EOD frequency even in the absence of jamming signals. Its projection to the pacemaker nucleus is mediated by NMDA-type receptors. The results of this study suggest that there is no single population of final, feature-extracting elements or "recognition units" that controls JAR-related shifts of the pacemaker frequency. Instead, the motor control of the JAR consists of an interaction of two independent pathways according to a "push-pull" principle.

Animals↗
PubMed1993

An audio-vocal interface in echolocating horseshoe bats.

The control of vocalization depends significantly on auditory feedback in any species of mammals. Echolocating horseshoe bats, however, provide an excellent model system to study audio-vocal (AV) interactions. These bats can precisely control the frequency of their echolocation calls by monitoring the characteristics of the returning echo; they compensate for flight-induced Doppler shifts in the echo frequency by lowering the frequency of the subsequent vocalization cells (Schnitzler, 1968; Schuller et al., 1974, 1975). It was the aim of this study to investigate the neuronal mechanisms underlying this Doppler-shift compensation (DSC) behavior. For that purpose, the neuronal activity of single units was studied during spontaneous vocalizations of the bats and compared with responses to auditory stimuli such as playback vocalizations and artificially generated acoustic stimuli. The natural echolocation situation was simulated by triggering an acoustic stimulus to the bat's own vocalization and by varying the time delay of this artificial "echo" relative to the vocalization onset. Single-unit activity was observed before, during, and/or after the bat's vocalization as well as in response to auditory stimuli. However, the activity patterns associated with vocalization differed from those triggered by auditory stimuli even when the auditory stimuli were acoustically identical to the bat's vocalization. These neurons were called AV neurons. Their distribution was restricted to an area in the paralemniscal tegmentum of the midbrain. When the natural echolocation situation was stimulated, the responses of AV neurons depended on the time delay between the onset of vocalization and the beginning of the simulated echo. This delay sensitivity disappeared completely when the act of vocalization was replaced by an auditory stimulus that mimicked acoustic self-stimulation during the emission of an echolocation call. The activity of paralemniscal neurons was correlated with all parameters of echolocation calls and echoes that are relevant in context with DSC. These results suggest a model for the regulation of vocalization frequencies by inhibitory auditory feedback.

Adaptation, Physiological↗
PubMed1991

The coding of signals in the electric communication of the gymnotiform fish Eigenmannia: from electroreceptors to neurons in the torus semicircularis of the midbrain.

In the context of aggression and courtship, Eigenmannia repeatedly interrupts its electric organ discharges (EODs) These interruptions contain low-frequency components as well as high-frequency transients and, therefore, stimulate ampullary and tuberous electroreceptors, respectively. Information provided by these two classes of receptors is relayed along separate pathways, via the electrosensory lateral line lobe (ELL) of the hindbrain, to the dorsal torus semicircularis (TSd) of the midbrain. Some neurons of the torus receive inputs from both types of receptors and some respond predominantly to EOD interruptions while being rather insensitive to other forms of signal modulations. This high selectivity appears to result from convergence and gating of inputs from individually less selective neurons.

Aggression↗
PubMed1991

Structure and function of neurons in the complex of the nucleus electrosensorius of the gymnotiform fish Eigenmannia: detection and processing of electric signals in social communication.

The complex of the diencephalic nucleus electrosensorius (nE) provides an interface between the electrosensory processing performed by the torus semicircularis and the control of specific behavioral responses. The rostral portion of the nE comprises two subdivisions that differ in the response properties and projection patterns of their neurons. First, the nEb, which contains neurons that are driven almost exclusively by beat patterns generated by the interference of electric organ discharges (EODs) of similar frequencies. Second, the area medial to the nEb, comprising the lateral pretectum (PT) and the nE-acusticolateralis region (nEar, 1 B-D), which contains neurons excited predominantly by EOD interruptions, signals associated with aggression and courtship. Neurons in the second area commonly receive convergent inputs originating from ampullary and tuberous electroreceptors, which respond to the low-frequency and high-frequency components of EOD interruptions, respectively. Projections of these neurons to hypothalamic areas linked to the pituitary may mediate modulations of a fish's endocrine state that are caused by exposure to EOD interruptions of its mate.

Aggression↗
PubMed1989

A possible neuronal basis for Doppler-shift compensation in echo-locating horseshoe bats.

The auditory system of the horseshoe bat is finely tuned to the bat's individual vocalization frequency. To compensate for flight-induced Doppler shifts in the echo frequency, the horseshoe bat adjusts the frequency of its echo-location call to maintain the echo frequency within the narrow range to which its auditory system is best tuned. In this report I describe neurons in the midbrain tegmentum of the horseshoe bat, with properties that strongly indicate their involvement in this Doppler-shift compensation. The activity of these neurons was influenced by both sound emission and auditory stimuli. Neuronal discharges in response to vocalization, however, differed from those in response to purely auditory stimuli that mimicked the bat call. When an auditory stimulus was temporally locked to a preceding vocalization, the response was dependent on the time delay between the two. This delay-sensitivity completely disappeared when vocalizations were simulated acoustically. Only those vocalization and 'echo' parameters were encoded that occur in Doppler-shift compensation. In conclusion, I suggest a model for the regulation of the vocalization frequency through auditory feedback.

Animals↗
PubMed1987

The nuclei of the lateral lemniscus in the rufous horseshoe bat, Rhinolophus rouxi. A neurophysiological approach.

In the rufous horseshoe bat, Rhinolophus rouxi, responses to pure tones and sinusoidally frequency modulated (SFM) signals were recorded from 289 single units and 241 multiunit clusters located in the nuclei of the lateral lemniscus (NLL). The distribution of best frequencies (BFs) of units in all three nuclei of the lateral lemniscus showed an overrepresentation in the range corresponding to the constant-frequency (CF) part of the echolocation signal ('filter frequency' range): in the ventral nucleus of the lateral lemniscus (VNLL) 'filter neurons' represented 43% of all units encountered, in the intermediate nucleus (INLL) 33%, and in dorsal nucleus (DNLL) 29% (Fig. 2a). Neurons with best frequencies in the filter frequency range had highest Q10dB-values (maxima up to 400, Fig. 2c) and only in low-frequency units were values comparable to those found in other mammals. On the average, filter neurons in ventral nucleus had higher Q10dB-values (about 220) than did those in intermediate and dorsal nucleus (both about 160, Fig 2d). Response patterns and tuning properties showed higher complexity in the dorsal and intermediate nucleus than in the ventral nucleus of the lateral lemniscus (Figs. 4 and 6). Multiple best frequencies were found in 12 neurons, nine of them with harmonically related excitation maxima (Fig. 5c, d). Best frequencies of six of these harmonically tuned units could not be correlated with any harmonic components of the echolocation signal. Half of all multiple tuned neurons were located in the caudal dorsal nucleus the other half in the caudal intermediate nucleus. Synchronization of responses to sinusoidally frequency modulated (SFM) signals occurred in VNLL-units in the average up to modulation frequencies of 515 Hz (maximum about 800 Hz) whereas in the intermediate and dorsal nucleus of the lateral lemniscus responses were synchronized in the average only up to modulation frequencies of about 300 Hz (maximum about 600 Hz) (Figs. 7 and 8). A tonotopic arrangement of units was found in the intermediate nucleus of the lateral lemniscus with units having high best frequencies located medially and those with low best frequencies laterally. In the dorsal nucleus the tonotopic distribution was found to be fairly similar to that in the intermediate nucleus but much less pronounced. In more rostral parts of the dorsal nucleus additionally higher best frequencies predominated whereas in caudal areas of that nucleus and also of the intermediate nucleus low BFs were found more regularly.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗