The lateral line mechanoreceptive mesencephalic,diencephalic, and telencephalic regions in the thornback ray,Platyrhinoidis triseriata (Elasmobranchii)

Central lateral line pathways were mapped in the thronback ray, Platyrhinoidis triseriata, by analyzing depth profiles of averaged evoked potentials (AEPs), multiunit activity (MUA), and single unit recordings. Neural activity evoked by contra- or ipsilateral posterior lateral line nerve (pLLN) shock is restricted to the tectum mesencephali, the dorsomedial nucleus (DMN) and anterior nucleus (AN) of the mesencephalic nuclear complex, the posterior central thalamic nucleus (PCT), the lateral tuberal nucleus of the hypothalamus, and the deep medial pallium of the telencephalon (Figs. 2, 3, 4, 6, 7). Neural responses (AEPs and MUA) recorded in different lateral line areas differ with respect to shape, dynamic response properties, and/or latencies (Figs. 9, 10 and Table 1). Ipsilaterally recorded mesencephalic and diencephalic AEPs are less pronounced and of longer latency than their contralateral counterpart (Fig. 9 and Table 1). In contrast, AEP recorded in the telencephalon show a weak ipsilateral preference. If stimulated with a low amplitude water wave most DMN, AN, and tectal lateral line units respond in the frequency range 6.5 Hz to 200 Hz. Best frequencies (in terms of least displacement) are 75-150 Hz with a peak-to-peak water displacement of 0.04 micron sufficient to evoke a response in the most sensitive units (Fig. 11A, B, C). DMN and AN lateral line units have small excitatory receptive fields (RFs). Anterior, middle, and posterior body surfaces map onto the rostral, middle, and posterior brain surfaces of the contralateral DMN (Fig. 12). Some units recorded in the PCT are bimodal; they respond to a hydrodynamic flow field--generated with a ruler approaching the fish--only if the light is on and the eye facing the ruler is left uncovered (Fig. 13).     

The responses of central octavolateralis cells to moving sources

Mechanosensory lateral line units recorded from the medulla (medial octavolateralis nucleus) and midbrain (torus semicircularis) of the bottom dwelling catfish Ancistrus sp. responded to water movements caused by an object that passed the fish laterally. In terms of peak spike rate or total number of spikes elicited responses increased with object speed and sometimes showed saturation (Figs. 7, 14). At sequentially greater distances the responses of most medullary lateral line units decayed with object distance (Fig. 11). Units tuned to a certain object speed or distance were not found. The signed directionality index of most lateral line units was between –50 and +50, i.e. these units were not or only slightly sensitive to the direction of object motion (Figs. 10, 17). However, some units were highly directionally sensitive in that the main features of the response histograms and/or peak spike rates clearly depended on the direction of object movement (e.g. Fig. 9C, D and Fig. 16). Midbrain lateral line units of Ancistrus may receive input from more than one sensory modality. All bimodal lateral line units were OR units, i.e., the units were reliably driven by a unimodal stimulus of either modality. Units which receive bimodal input may show an extended speed range (e.g. Fig. 18).Abbreviations MON medial octavolateralis nucleus - MSR mean spike rate - PSR peak spike rate - p-p peak-to-peak - SDI signed directionality index     

Effects of running water on brainstem lateral line responses in trout,<Emphasis Type="Italic"> Oncorhynchus mykiss</Emphasis>, to sinusoidal wave stimuli

We investigated how single units in the medial octavolateralis nucleus of the rainbow trout, Oncorhynchus mykiss, respond to a 50-Hz vibrating sphere in still and running water. Four types of units were distinguished. Type MI units (N=16) were flow-sensitive; their ongoing discharge rates either increased or decreased in running water, and as a consequence, responses of these units to the vibrating sphere were masked if the fish was exposed to water flow. Type MII units (N=7) were not flow-sensitive; their ongoing discharge rates were comparable in still and running water, and thus their responses to the vibrating sphere were not masked. Type MIII units (N=7) were also not flow-sensitive; nevertheless, their responses to the vibrating sphere were masked in running water. Type MIV units (N=14) were flow-sensitive, but their responses to the vibrating sphere were not masked. Our data confirm previous findings in the goldfish, Carassius auratus, indicating that the organization of the peripheral lateral line is reflected to a large degree in the medial octavolateralis nucleus. We compare data from goldfish and trout and discuss differences with respect to lateral line morphology, lifestyle and habitat of these species.Abbreviations CN canal neuromast - MON medial octavolateralis nucleus - SN superfical neuromast - a.c. alternating current - d.c. direct current     

Responses of brainstem lateral line units to different stimulus source locations and vibration directions

We recorded responses of lateral line units in the medial octavolateralis nucleus in the brainstem of goldfish, Carassius auratus, to a 50 Hz vibrating sphere and studied how responses were affected by placing the sphere at various locations alongside the fish and by different directions of vibration. In most units (88%), stimulation with the sphere from one or more spatial locations caused an increase and/or decrease in discharge rate. In few units (10%), discharge rate was increased by stimulation from one location and decreased by stimulation from an adjacent location in space. In a minority of the units (2%), changing sphere location did not affect discharge rates but caused a change in phase coupling. Units sensitive to a distinct sphere vibration direction were not found. The data also show that the responses of most brainstem units differ from those of primary afferent nerve fibers. Whereas primary afferents represent the pressure gradient pattern generated by the sphere and thus encode location and vibration direction of a vibrating sphere, most brainstem units do not. This information may be represented in the brainstem by a population code or in higher centers of the ascending lateral line pathway.     

Toral lateral line units of goldfish, Carassius auratus, are sensitive to the position and vibration direction of a vibrating sphere

We recorded the responses of lateral line units in the midbrain torus semicircularis of goldfish, Carassius auratus, to a 50-Hz vibrating sphere and determined the unit's spatial receptive fields for various distances between fish and sphere and for different directions of sphere vibration. All but one unit responded to the vibrating sphere with an increase in discharge rate. Only a proportion (25?%) of the units exhibited phase-locked responses. Receptive fields were narrow or broad and contained one, two or more areas of increased discharge rate. The data show that the receptive fields of toral lateral line units are in many respects similar to those of brainstem units but differ from those of afferent nerve fibres. The responses of primary afferents represent the pressure gradient pattern generated by a vibrating sphere and provide information about sphere location and vibration direction. Across the array of lateral line neuromasts, the fish brain in principle can derive this information. Nevertheless, toral units tuned to a distinct sphere location or sensitive to a distinct sphere vibration direction were not found. Therefore, it is conceivable that the torus semicircularis uses a population code to determine spatial location and vibration direction of a vibrating sphere.     

Two-dimensional receptive fields of midbrain lateral line units in the goldfish, <Emphasis Type="Italic">Carassius auratus</Emphasis>

We determined the receptive fields of midbrain lateral line units in goldfish, Carassius auratus, with a 50 Hz vibrating sphere placed at various azimuths and elevations alongside the fish and studied how responses were affected by different directions of sphere vibration. The receptive fields of toral lateral line units, in contrast to those of primary afferent nerve fibers, did not represent the pressure gradient pattern generated by a vibrating sphere. Thus, unlike primary afferents, single toral lateral line units did not code for source location in their spatial discharge patterns. The two-dimensional receptive fields were round, horizontally or vertically stretched, or complex. While some toral lateral line units were sensitive to the direction of sphere vibration others were not.     

Coding of lateral line stimuli in the goldfish midbrain in still and running water

We investigated in goldfish, Carassius auratus, how running water affects the responses of toral lateral line units to a stationary vibrating sphere or to a non-vibrating sphere that moves along the side of the fish. Experiments were conducted in the presence of running water (hydrodynamic noise) to further explore the sensory capabilities of the lateral line with special focus on the morphological sub-modalities. Previous recordings from lateral line nerve fibres in various fish species and the first nucleus of the ascending lateral line pathway in goldfish revealed flow-sensitive and flow-insensitive units. These physiological differences represent, at least in part, the differences in morphology of the lateral line, superficial and canal neuromasts. Following up on these findings we recorded flow-sensitive and flow-insensitive units in the Torus semicircularis of goldfish. In still water, both types of units responded to a vibrating or moving sphere. In running water, neural responses were weaker when the sphere was moved with the flow but were comparable or slightly stronger when the sphere was moved against the flow. In running water, responses of flow-sensitive fibres to the vibrating sphere were masked. In contrast, the responses of units insensitive to water flow were not masked. Our data confirm previous findings but also indicate differences when compared to previous reports. We discuss these differences with respect to lateral line morphology, sub-modalities and convergence of different channels of information at higher brain stations.     

Correlation between auditory thalamic area evoked responses and species-specific call characteristics

Evoked potentials were recorded from the posterior dorsal thalamus of green treefrogs (Hyla cinerea) in response to single tones and combinations of two and three tones. 1. The responses to two tones were largest when one of the component tones was 500 Hz and when the second component was between 2000 and 4000 Hz (Fig.3). 2. The response to 500 + 3000 Hz showed nonlinear facilitation; i.e., the amplitude of the response was greater than the sum of the responses to the component tones alone (Figs. 4, 5). This result provides evidence that cells functioning as 'AND' gates will be found in this center. 3. When a third tone around 1200 Hz was added to a stimulus of 500 + 3000 Hz a 65% decrease in the evoked response amplitude occurred (Fig. 6). 4. The largest evoked response amplitude to a two-tone stimulus (500 + 3000 Hz) occurred when the rise-time was less than 50 ms (Fig. 7). 5. The two-tone tuning was found to be temperature dependent. The optimal lower frequency tone shifted downward with decreasing temperatures (Fig. 8). 6. When the temperatures of the neurophysiological and the behavioral experiments are matched, the optimal stimuli for evoking a large response are closely correlated to the parameters of the acoustic stimuli preferred by gravid H. cinerea females in discrimination tests. This center therefore appears to be very important for the processing of complex species-specific sounds.     

The nuclei of the lateral lemniscus in the rufous horseshoe bat,Rhinolophus rouxi

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)     

Behavioral and neurophysiological assessment of lateral line sensitivity in the mottled sculpin,Cottus bairdi

1. The unconditioned feeding response of the mottled sculpin, Cottus bairdi, was used to measure threshold sensitivity of the lateral line system to a vibrating sphere as a function of stimulus position (i.e., sphere near head, trunk or tail) and vibration frequency. In addition, extracellular recording techniques were used to measure threshold sensitivity curves for posterior lateral line nerve fibers for the same stimulus positions used for measuring trunk sensitivity in behavioral measurements. 2. For all stimulus positions, behaviorally-measured threshold sensitivity was relatively independent of vibration frequency from 10 to 100 Hz when defined in terms of water acceleration, rather than velocity or displacement. Best thresholds for stimuli placed 15 mm away from the head were around -75 dB re: 1m/s(2), approximately 20 dB less than that for stimuli placed at the same distance near the tail. Trunk sensitivity was intermediate. 3. Physiologically-measured threshold sensitivity, in terms of acceleration, was also relatively independent of of frequency from 10 to 100 Hz in most fibers. A smaller number of fibers showed a decline in acceleration sensitivity after 10-30 Hz, with the rate of decline being equivalent to equal velocity sensitivity. Best sensitivity of all fibers fell between -40 and -70 dB re: 1m/s (2). 4. These results indicate that (a) behavioral thresholds are based on acceleration-sensitive endorgans--most likely lateral line canal (rather than superficial) neuromasts, (b) behavioral performance can be accounted for on the basis of information from a single population of fibers, and (c) sensitivity varies along the fish's body in a manner that corresponds to the size and distribution of neuromasts.     

The function of auditory neurons in cricket phonotaxis

Summary The activity of auditory receptor cells and prothoracic auditory neurons of the cricket,Gryllus bimaculatus, was recorded intracellularly while the animal walked on a sphere or while passive movement was imposed on a foreleg.During walking the responses to simulated calling song is altered since (i) the auditory sensory cells and interneurons discharged impulses in the absence of sound stimuli (Figs. 1, 3) and (ii) the number of action potentials in response to sound is reduced in interneurons (Figs. 2, 3).These two effects occurred in different phases of the leg movement during walking and therefore masked, suppressed or did not affect the responses to auditory stimuli (Figs. 3, 4). Hence there is a time window within which the calling song can be detected during walking (Fig. 5).The extra excitation of receptors and interneurons is probably produced by vibration of the tympanum because (i) the excitation occurred at the same time as the leg placement (Fig. 4), (ii) during walking on only middle and hindlegs, no extra action potentials were observed (Fig. 6), (iii) in certain phases of passive movements receptor cells and interneurons were excited as long as the ipsilateral ear was not blocked (Figs. 8, 9).Suppression of auditory responses seems to be peripheral as well as central in origin because (i) it occurred at particular phases during active and passive leg movements in receptor cells and interneurons (Figs. 1, 4, 9), (ii) it disappeared if the ear was blocked during passive leg movements (Fig. 9) and (iii) it persisted if the animal walked only on the middle and hind legs (Fig. 6).     

Functional organization of the electroreceptive midbrain in an elasmobranch (Platyrhinoidis triseriata)

The response properties of 322 single units in the electroreceptive midbrain (lateral mesencephalic nucleus, LMN) of the thornback ray, Platyrhinoidis triseriata, were studied using uniform and local electric fields. Tactile, visual, or auditory stimuli were also presented to test for multimodality. Most LMN electrosensory units (81%) are silent in the absence of stimulation. Those with spontaneous activity fired irregularly at 0.5 to 5 impulses/s, the lower values being more common. Two units had firing rates greater than 10/s. Midbrain electrosensory units are largely phasic, responding with one or a few spikes per stimulus onset or offset or both, but the adaptation characteristics of some neurons are complex. The same neuron can exhibit phasic or phasic-tonic responses, depending upon orientation of the electric field. Tonic units without any initial phasic over-shoot were not recorded. Even the phasic-tonic units adapt to a step stimulus within several seconds. Unit thresholds are generally lower than 0.3 microV/cm, the weakest stimulus delivered, although thresholds as high as 5 microV/cm were recorded, Neuronal responses reach a maximum, with few exceptions, at 100 microV/cm and decrease rapidly at higher intensities. LMN neurons are highly sensitive to stimulus repetition rates: most responded to frequencies of 5 pulses/s or less; none responded to rates greater than 10/s. Three distinct response patterns are recognized. Best frequencies in response to sinusoidal stimuli range from 0.2 Hz (the lowest frequency delivered) to 4 Hz. Responses decrease rapidly at 8 Hz or greater, and no units responded to frequencies greater than 32 Hz. Most LMN neurons have small, well defined excitatory electroreceptive fields (RFs) exhibiting no surround inhibition, at least as detectable by methods employed here. Seventy-eight percent of units recorded had RFs restricted to the ventral surface: of these, 98% were contralateral. The remaining 22% of units had disjunct dorsal and ventral receptive fields. Electrosensory RFs on the ventral surface are somatotopically organized. Anterior, middle, and posterior body surfaces are mapped at the rostral, middle, and caudal levels, respectively, of the contralateral LMN. The lateral, middle, and medial body are mapped at medial, middle, and lateral levels of the nucleus. Moreover, the RFs of all units isolated in a given dorsoventral electrode track are nearly superimposable. About 40% of LMN, measured from the dorsal surface, is devoted to input from ventral electroreceptors located in a small region rostral and lateral to the mouth.(ABSTRACT TRUNCATED AT 400 WORDS)     

Peripheral lateral line responses to amplitude-modulated sinusoidal wave stimuli

This report describes the responses of single afferent fibers in the posterior lateral line nerve of the goldfish, Carassius auratus, to pure tone and to amplitude-modulated sinusoidal wave stimuli generated by a dipole source (stationary vibrating sphere). Responses were characterized in terms of output-input functions relating responses to vibration amplitude, peri-stimulus time histograms relating responses to stimulus duration, and the degree of phase-locking to both the carrier frequency and the modulation frequency of the amplitude-modulated stimulus. All posterior lateral line nerve fibers responded to a pure sine wave with sustained and strongly phase-locked discharges. When stimulated with amplitude-modulated sine waves, fibers responded with strong phase-locking to the carrier frequency and, in addition, discharge rates were modulated according to the amplitude modulation frequency. However, phase-locking to the amplitude modulation frequency was weaker than phase-locking to the carrier frequency. The data indicate that the discharges of primary lateral line afferents encode both the carrier frequency and the modulation frequency of an amplitude-modulated wave stimulus. Accepted: 2 June 1999     

Lateral line reception in still- and running water

The lateral line of fish is composed of neuromasts used to detect water motions. Neuromasts occur as superficial neuromasts on the skin and as canal neuromasts in subepidermal canals. Fibres of the lateral line nerves innervate both. There have been extensive studies on the responses of lateral line nerve fibres to dipole stimuli applied in still water. However, despite the fact that many fish live in rivers and/or swim constantly, responses of lateral line nerve fibres to dipole stimuli presented in running water have never been recorded. We investigated how the peripheral lateral line of still water fish ( Carassius auratus) and riverine fish ( Oncorhynchus mykiss) responds to minute sinusoidal water motions while exposed to unidirectional water flow. Both goldfish and trout have two types of posterior lateral line nerve fibres: Type I fibres, which most likely innervate superficial neuromasts, were stimulated by running water (10 cm s(-1)). The responses of type I fibres to water motions generated by a vibrating sphere were masked if the fish was exposed to running water. Type II fibres, which most likely innervate canal neuromasts, were not stimulated by running water. Consequently, responses of type II fibres to a vibrating sphere were not masked under flow conditions.     

Behavioural responses of juvenile cuttlefish (Sepia officinalis) to local water movements

Physiological studies have shown that the epidermal head and arm lines in cephalopods are a mechanoreceptive system that is similar to the fish and amphibian lateral lines (Budelmann BU, Bleckmann H. 1988. A lateral line analogue in cephalopods: Water waves generate microphonic potentials in the epidermal head lines of Sepia officinalis and Lolliguncula brevis. J. Comp. Physiol. A 164:1-5.); however, the biological significance of the epidermal lines remains unclear. To test whether cuttlefish show behavioural responses to local water movements, juvenile Sepia officinalis were exposed to local sinusoidal water movements of different frequencies (0.01-1000 Hz) produced by a vibrating sphere. Five behavioural responses were recorded: body pattern changing, moving, burrowing, orienting, and swimming. Cuttlefish responded to a wide range of frequencies (20-600 Hz), but not to all of the frequencies tested within that range. No habituation to repeated stimuli was seen. Results indicate that cuttlefish can detect local water movements (most likely with the epidermal head and arm lines) and are able to integrate that information into behavioural responses.     

Directionality of antennal sweeps elicited by water jet stimulation of the tailfan in the crayfish Procambarus clarkii

Summary Directionality and intensity dependence of antennal sweeps elicited by water jet stimulation of the tailfan in tethered, reversibly blinded adult and juvenile crayfish (Procambarus clarkii) were analyzed.Resting crayfish keep their antennae at about 50° symmetrically to the longitudinal body axis (Figs. 2 bottom, and 3).In adults, tailfan stimulation elicits synchronous backward sweeps of both antennae, which increase for more caudal stimulus directions (Figs. 2–4 and 5A). Directions differing by 30°–60° are significantly distinguished (Fig. 4). The mean sweep of the ipsilateral antenna significantly overrides that of the contralateral antenna for rostrolateral stimulation at 40–200 mm/s stimulus velocity and lateral to caudolateral stimulation at 40 mm/s and thus lateralization of the stimulus is revealed (Figs. 2 top, 4 and 5A). Mean antennal sweeps at a given stimulus direction and distance increase with increasing stimulus velocity (40–250 mm/s, Fig. 5A).In juveniles, the directional dependence of antennal sweeps is reduced compared to that of adults, while a similar intensity dependence is found (Fig. 5B).The pronounced directionality of the antennal response in adult crayfish vanishes and response latencies increase after reversibly covering the tailfan with a small bag or the telson with waterproof paste (Figs. 6 and 7). Thus, tailfan and especially telson mechanoreceptors play an important role in the localization of water movements elicited by predators or prey behind the crayfish.     

Tonotopic organization and functional characterization of the auditory thalamus in a songbird,the European starling

1. The diencephalic auditory nucleus of the European starling, the nucleus ovoidalis, shows rostrocaudal and dorsoventral diameters of 500-800 microns and a mediolateral diameter of 800-1000 microns. This small and sharply delimited nucleus is composed of densely packed neurons. 2. Its tonotopic organization consists of evenly spaced isofrequency contours, with best frequencies decreasing ventrally. The frequency range was found to be 150 Hz to 7030 Hz. 3. Apart from tonotopic organization, other characteristics of single units demonstrate the uniformity of the neuronal population. Units have high spontaneous activities (mean 61 pps; Fig. 4a), and show mainly stimulus correlated tonic discharge patterns. In most cases, excitatory frequency bands are enclosed by inhibitory frequency bands. 4. Single units were tested, applying various stimulus classes differing in time structure (BPN, sine, FM up, FM down, SFM, SAM) but sharing a common frequency band. All neurons tested responded to all classes. Evaluation of stimulus class preference, however, revealed that BPN and SFM caused the strongest responses, whereas FM and SAM were less effective. 5. Comparison of the single unit responses in the ovoid nucleus with those known for avian auditory forebrain and midbrain centres strongly suggests a relay function for the diencephalic nucleus.     

Movement sensitivities of cells in the fly's medulla

Summary Intracellular recordings were made in the medullae of intact, restrained females ofCalliphora vicina that faced a hemispherical, minimum-distortion surface upon which moving patterns and spots were projected from the rear (Fig. 2). In the distal medulla, noisy hyperpolarizations to light, most likely recorded in terminals of laminar (L) cells, had flicker-like oscillations to moving gratings of 15° spatial wavelength but not of 2.5° spatial wavelength (Fig. 3). Medullary (M) cells penetrated distally responded to grating movements with similar but depolarizing oscillations, in one cell 180° out of phase with a nearby laminar response (Figs. 4–6).A characteristic movement response recorded from most medullary cells consisted of abrupt, maintained nondirectional depolarizations in response to movements of gratings, often with directional ripple or spikes superimposed. When directions of movement reversed, there were brief repolarizations, but when movements stopped, depolarizations decayed away more slowly (Figs. 7 and 8). Magnitude of responses increased with increasing speeds of both 15° and 2.5° gratings (Figs. 9–11). In some cells, there were delayed decays of responses after stopping (Fig. 12). Still other cells seemed to receive inhibition from other, characteristically responding cells (Fig. 13).Receptive fields tested were simple and usually large, with only a suggestion of surround inhibition (Fig. 14). In general, intensity and position were interchangeable over a cell's receptive field (Figs. 15 and 16). Moving edges and dark spots elicited responses primarily within receptive field centers (Figs. 18–20).It is argued that waveforms of characteristic movement responses can be explained by multiplicative inputs from L- and M-cells to movement detectors (Figs. 21–26).Abbreviations L cells laminar (monopolar) cells - M cells medullary cells     

Behavioral and electrophysiological evidences that the lateral line is involved in the inter-sexual vibrational communication of the himé salmon (landlocked red salmon,Oncorhynchus nerka)

Characteristic vibrational signals are suggested to be exchanged between the sexes during the spawning behavior in the himé salmon (landlocked red salmon, Oncorhynchus nerka). To check whether the lateral line is used to detect and process these vibrational signals, we examined how Co²⁺, which is known to block the mechano-electrical transduction in the lateral line detector, affects both the spawning behavior and lateral line response of the male himé salmon. The results showed that Co²⁺ blocked both the spawning behavior towards the vibrating model (Fig. 2) and the lateral line response to the vibrational stimuli (Figs. 5, 6), if the fish were forced to swim in the water containing 1.0 mM Co²⁺ for 1 to 1.5 h or longer in the presence of 0.25 mM Ca²⁺. 0.1 mM Co²⁺ had similar but weaker effects. These results indicate that the vibrational signals from the vibrating model are detected and processed by the lateral line system to elicit the spawning behavior. These are the first experimental evidences that the lateral line sense is involved in the communicational behavior of the fish.     

Frequency as a releaser in the courtship song of two crickets,Gryllus bimaculatus (de Geer) and Teleogryllus oceanicus: a neuroethological analysis

1. The courtship behavior of male field crickets, Gryllus bimaculatus (De Geer) and Teleogryllus oceanicus, is a complex, multimodal behavioral act that involves acoustic signals (a courtship song; Fig. 1A,B). The dominant frequency is 4.5 kHz for T. oceanicus song (Fig. 1A) and 13.5 kHz for G. bimaculatus (Fig. IB).
2. When courting males are deprived of their courtship song by wing amputation, their courtship success declines markedly but is restored when courting is accompanied by tape-recordings of their courtship songs or a synthetic courtship song with only the dominant frequency of the natural song; other naturally occurring frequency components are ineffective for restoring mating success (Figs. 4, 5).
3. It has been suggested that an identified auditory interneuron, AN2, plays a critical role in courtship success. Chronic recordings of AN2 in an intact, tethered female show that AN2's response to the natural courtship song and synthesized songs at 4.5 and 13.5 kHz is similar in T. oceanicus. By contrast, in G. bimaculatus, AN2's response to the natural courtship song and synthesized song at 13.5 kHz, but not at 4.5 kHz, is similar (Figs. 2,3).
4. In behavioral experiments, playback of a 30 kHz synthetic courtship song in G. bimaculatus does not restore courtship success, yet this same stimulus elicits as strong a response from AN2 as does the normal courtship song (Fig. 6). Thus, contrary to earlier work by others, we conclude AN2 is not, by itself, a critical neural link in the courtship behavior of these two species of crickets.