Showing papers in "Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology in 1974"

Chasing behaviour of houseflies ( Fannia canicularis )

Abstract: 1. Chases in which male flies (Fannia canicularis) pursue other flies were studied by filming such encounters from directly below. Males will start to chase whenever a second fly comes within 10–15 cm (Fig. 3). 2. Throughout these chases there was a continuous relationship between the angle (θe) made by the leading fly and the direction of flight of the chasing fly, and the angular velocity of the chasing fly (ωf). This relation was approximately linear, with a slope of 20 ° s−1 per degree θe (Figs. 4–7). 3. The maximum correlation between ωf and θite occurs after a lag of approximately 30 ms, which represents the total delay in the system (Fig. 8). 4. In the region close to the chasing fly's axis (θite less than about 35 °) a second mechanism exists in which the angular velocity of the chasing fly (ωf) is controlled by the relative angular velocity of the leading fly (ωe), rather than its relative position. The ratio of ωf to ωe in this region is approximately 0.7. 5. Using the results in 2–4 above, and an empirically determined relation between the angular and forward velocities of the chasing fly, it was possible to simulate the flight path of the chasing fly, given that of the leading fly (Fig. 11). Because these simulations predict correctly the manoeuvres and outcomes of quite complicated chases, it is concluded that the control system actually used by the fly is accurately described by conclusions 2–4. 6. The physiological implications of this behaviour, and the possible function of chasing, are discussed.

Organization of the stomatogastric ganglion of the spiny lobster

Abstract: The Stomatogastric ganglion ofPanulirus interruptus contains about 30 neurons, and controls the movements of the lobster's stomach When experimentally isolated, the ganglion continues to generate complex rhythmic patterns of activity in its motor neurons which are similar to those seen in intact animals

The locust jump

Abstract: The locust jumps by a rapid extension of its metathoracic tibiae. The comparatively slow rate of rise of tension of the extensor tibia muscle means that if it is to shorten rapidly, it must develop tension isometrically prior to the jump by co-contracting with the flexor muscle. The extensor muscle is far stronger than the flexor and thus there has to be considerable structural specialisation of the joint to enable the flexor to prevent the tibia moving under the extensor tension. The geometry of the joint gives the flexor muscle a very large mechanical advantage over the extensor in the fully flexed position. This mechanical advantage decreases rapidly as the joint extends so that the residual flexor tension does not slow down the movement (Fig. 4). There is also a locking device associated with the flexor tendon which is engaged when the tibia is fully flexed and which holds it in this position against the developing extensor force (Fig. 5).

The anatomy and output connection of a locust visual interneurone; the lobular giant movement detector (LGMD) neurone

Abstract: 1. The anatomy of a giant movement detector neurone in the locust lobula (the LGMD) is described on the basis of both intracellular injection of cobalt (Fig. 2) and the reconstruction of osmium-ethyl gallate and silver impregnated serial sections (Fig. 3). 2. It is shown that the LGMD has an anatomically complex junction with a previously described interneurone, the Descending Contralateral Movement Detector (Fig. 4), and that spikes in the LGMD precede 1∶1 with fixed latency spikes in the DCMD (Figs. 1,5). 3. Three separate dendritic subfields are seen in the lobula complex (Figs. 2, 3); these are tentatively ascribed to the three different classes of input to the cell. 4. A large part of the LGMD's terminal arborisation appears to serve only a single functional junction, that with the DCMD (Fig. 4).

Neuronal control of swimming in the medicinal leech. I. Dynamics of the swimming rhythm

Abstract: Leeches swim by undulating their extended and flattened body in the dorsoventral direction, to form a wave that travels backwards along the animal. The troughs and crests of this body wave are produced by a metachronal rhythm of antiphasic contractions of the dorsal and ventral longitudinal musculature of the body wall of successive segments. Cinematographic records of swimming leeches show that over a range of cycle periods from 390 to 1100 msec the animal maintains one full wave along the length of its body. This constant wave form is achieved by compensating for the increase in the cycle period by an increase in the intersegmental travel time of the wave from 19 to 77 msec per segment. Direct muscle tension measurements of the segmental body wall during the swimming movement of a restrained, brainless and partially denervated leech lead to values for the dynamic parameters of the body wave which are in agreement with those abstracted from cinematographic records. In order to study the neuronal control of the swimming movement, a semi-intact leech preparation was developed. This preparation carries out movements that are clearly vestiges of the swimming rhythm while allowing the taking of electrophysiological records from exposed and immobilized parts of its peripheral and central nervous systems. The records reveal a nerve cell activity rhythm whose period matches that of the swimming rhythm. The swimming rhythm and its body wave must be generated by a system of distributed, phase-locked segmental oscillators that cause an antiphasic activity of the motor neurons innervating the segmental dorsal and ventral longitudinal muscles. The cycle of these oscillators can be inferred to consist of a variable time sector whose changes in length are responsible for changes in the cycle period, and of a constant time sector whose length is independent of the cycle period.

The influence of proprioceptive feedback on Locust flight co-ordination

Abstract: The right fore wing of a tethered locust (Locusta migratoria) flying in front of a wind tunnel was moved up and down about its normal axis of rotation. The reaction of the animal was measured by recording muscle potentials from the depressor muscles of all wings. The flight rhythm of an animal can be forced to take a preferred phase with regard to the input rhythm, provided the stimulating frequency does not differ by more than 10 to 15% from the wing beat frequency of the non-driven wings. The reaction is apparently due to phasic proprioceptive feedback from the driven wing which influences the flight rhythm within a few wing beats. This proprioceptive feedback normally increases the precision of co-ordination of the wings among themselves.

Normal fluctuations in the earth's magnetic field influence pigeon orientation

Abstract: In an attempt to determine whether naturally occurring fluctuations in the earth's magnetic field influence homing pigeons' initial bearings, three series of test releases (1970, 1972, 1973) at a site 45.7 miles north of the loft were conducted under an experimental design that controlled for most extraneous variables. The mean bearings for each series showed a significant inverse correlation with the K index of magnetic activity, i.e. the bearings were more to the left when K was high. In a single series of releases at a site 43.6 miles west of the loft, the means again showed a significant inverse correlation with K. Since most of the magnetic fluctuations in all four series were less than 70 gamma, it is concluded that the sensitivity of pigeons to magnetic cues probably approaches that already demonstrated for honeybees. A brief discussion of Lamotte's (1974) paper concerning the effect of bar magnets on initial orientation is appended.

Neuroethology of sound production in gomphocerine grasshoppers (Orthoptera: Acrididae)

Abstract: 1. Sound production of grasshoppers is based upon central motor patterns which are hierarchically organized at various functional levels (Fig. 2). These involve coordination (i) of single motor units belonging to the same muscles, (ii) of muscles relating to one hindleg, and (iii) of laterally homologous muscles moving the left and the right hindleg, respectively. 2. The motor organization at the first two levels has been investigated comparatively in several species. The neuromuscular activity underlying stridulation was recorded in freely moving animals using flexible wire electrodes (diameter 20–30 μm) which allowed the functional identification of individual motor units (Fig. 3). Up to 30 electrodes were chronically implanted into the metathoracic muscles without restricting the behaviour. 3. The motor patterns are based upon certain principles some of which are generally valid for all species: (i) The individual units are characterized by discrete types of activity (Fig. 4). (ii) Motor units and muscles are always recruited in a fixed order (Figs. 1, 3, 10). 4. The co-ordination of single units does not follow a general scheme but it reflects features of the specific song patterns (Fig. 5). The muscles producing the movements of one hindleg are also specifically co-ordinated: (i) In rapidly stridulating species the sets of antagonistic muscles are coupled in an unequivocal (unimodal) manner from which the pattern of leg movements can easily be deduced (Figs. 11, 12, 13). (ii) On the other hand, in slowly stridulating species the antagonistic muscles are coupled in two ways, since several of them are recruited both before the beginning and at the end of the leg strokes (Figs. 7–9). Maximum of motor activity is usually found at the end of the upward movements where the activities of both the elevator and depressor muscles partly overlap (Fig. 7b).

Response to Frequency Shifted Artificial Echoes in the Bat Rhinolophus ferrumequinum

Abstract: In 5 roosting bats the resting frequency, that is the mean frequency of the cf-portion of consecutive sounds, is kept constant with a standard deviation which varies between 30–120 Hz in different bats and at different days. In 15 bats the emitted sounds were electronically shifted in frequency and played back as artificial echoes. Upward frequency shifts were responded by a decrease of the emission frequency. This frequency compensation occurred at frequency shifts of up to 4400 Hz in all bats and up to 6000 Hz in a few bats. The frequency decrease in different bats over the whole compensation range was 50–300 Hz smaller than the frequency shifts in the echoes. The echoes, therefore, returned at a frequency, called the reference frequency, which was by this compensation offset higher than the resting frequency. The standard deviations of the emission frequency in compensating bats were only slightly larger than in roosting bats and the same in the whole compensation range. All bats started to compensate frequency shifts when they were slightly larger than the compensation offset. Downward frequency shifts were not responded by a change of the emission frequency, but the accuracy with which the emission frequency was kept decreased somewhat. From these results it is concluded that the Doppler shift compensation system of the Horseshoe bats compares the echo frequency with the reference frequency and compensates deviations of upward frequency shifts.

Metamorphosis of the Abdominal Ganglia of the Tobacco Hornworm, Manduca sexta

Abstract: 1. Motor neurons in the fourth abdominal ganglion were identified by diffusing cobalt into the ganglion through the cut ends of the peripheral nerves. 2. The ganglion from the last instar larva had a total of 74 motor neurons. These were divided into 10 groups which were characterized by the position of the cell body in the ganglion and the root through which the axon travelled to the periphery. 3. In the transition to the pupal stage, 12 larval neurons were lost and 8 new motor neurons appeared. 4. There was no change in the number of motor neurons during adult development. Most of the larval neurons persist through metamorphosis and are used by the adult at emergence. At this stage there are 70 motor neurons. 5. After adult eclosion there was a loss of 40 motor neurons. Only “larval” neurons degenerated. Those which remained included both those which were larval in origin and those which appeared in the pupa. After emergence the interneuron number dropped from approximately 380 to 200. 6. At the time of emergence the eclosion hormone “turns-off” pupal behavior and “turns-on” adult behavior. It also triggers the breakdown of various muscle groups in the abdomen. It is concluded that the neural death was the end result of this aspect of eclosion hormone action.

Frequency and directional responses of cilia to membrane potential changes inParamecium

Abstract: Ciliary motor reactions and membrane responses to injected current stimulation inParamecium caudatum were recorded with a combined electrophysiological and high-speed cine system to investigate relations between ciliary activity and membrane potential. The power stroke of the cilia normally directed to the right rear rotates clockwise to a more posterior orientation in response to hyperpolarizing stimulation. Depolarization induces a counterclockwise shift, usually leading to the rapid reversal of beat direction toward the anterior end (Fig. 15). Ciliary frequency is increased either with hyperpolarization or with moderate or strong depolarization of the cell membrane. The frequency response is linked to the directional response in such a way that minimal frequency occurs during transition from reversed to normal beating, and that with increasing clock-wise or counterclockwise angular deviation of the power stroke from this sector of transition the frequency of beat is increased. In the course of transition from the reversed to normal beating the cilia are inactivated, i.e. they stick out perpendicularly to the cell surface without a polarized beat. A depression in normal beating activity somewhat resembling inactivation occurs with small depolarizations. Hyperpolarization-induced frequency time courses are significantly slower than those evoked by membrane depolarization. The role of transmembrane calcium fluxes and consequent modification of intraciliary calcium concentrations is considered with regard to the observed ciliary responses.

The behavioral hierarchy of the molluskPleurobranchaea

Abstract: Feeding behavior and the effect of its occurrence on other, unrelated behaviors were studied in the carnivorous marine gastropodPleurobranchaea calif arnica. The threshold of the feeding response is low and stable: it does not change in a circadian fashion (Fig. 1); it does not change during different behavioral states such as mating (Table 4) and quiescence (“sleep” Table 5); the threshold does not change following aversive electric shock to the oral veil (Table 1); and it does not change with repeated application of food stimuli (Fig. 2). In the present paper only two physiological variables were found to elevate the feeding response threshold; excessive mechanical stimulation (Figs. 3, 4) and satiation with food (Fig. 5).

Polarization sensitivity: A phenomenon independent of stimulus intensity or state of adaptation in retinular cells of the crabsCarcinus andCallinectes

Abstract: SummaryPolarization sensitivity of photoreceptors of the crabsCarcinus andCallinectes were measured with intracellular microelectrodes in the dark adapted condition with stimuli of very low intensity and under conditions of selective polarized adaptation. A mean polarization sensitivity ratio of 4.5 to one (n=25) was obtained. The values ranged from 3.2 to one to 9 to one. The value obtained in any given cell was independent of either (a) the intensity of the stimuli employed in its determination, or (b) any conditions of selective adaptation present during the experiment.The results of these experiments are discussed in reference to two hypothetical explanations for the discrepancy between microspectrophotometric measurements of rhabdomeric dichroism and electrophysiological determinations of polarization sensitivity in crustacean photoreceptors. They do not support the hypothesis of Muller (1971, 1973) that the high polarization sensitivity measured in such photoreceptors is due to a passive interaction between the retinular cells which serves to enhance polarization sensitivity imparted by the dichroism of the rhabdom. They do support the hypothesis of Shaw (1966, 1969) and Snyder (1973) which suggest that the dichroic ratio of the rhabdomere and the polarization sensitivity ratio of the cell are similarin situ.

The behavioral hierarchy of the molluskPleurobranchaea: II. Hormonal suppression of feeding associated with egg-laying

Abstract: SummarySpontaneous egg-laying in the carnivorous marine gastropodPleurobranchaea californica is accompanied by elevation of the feeding response threshold (Fig. 1), an adaptation that presumably prevents specimens from eating their own eggs. Injection of blood from egg-laying animals induces egg-laying and elevation of the feeding response threshold in non-laying specimens (Fig. 2). Therefore, the causal agent is blood-borne and presumably a hormone(s). Injection of crude extract of whole nervous systems taken from egg-laying specimens induces egg-laying and elevation of the feeding threshold in non-laying specimens (Figs. 3A, 4A, 5, 6, 7). Therefore, the hormone(s) is contained within the central nervous system of egg-laying specimens. Injection of crude extract of whole nervous systems taken from non-laying specimens weakly induces egg-laying, but not elevation of the feeding threshold, in non-laying specimens (Figs. 3B, 4B). Therefore, the hormone(s) may be present, in small quantities, in the central nervous system of non-laying specimens. Injection of sea water into non-laying specimens neither induces egg-laying nor elevates the feeding response threshold (Figs. 3C, 4C). Therefore, the above effects were not caused simply by the trauma of injection. Injection of crude extract of whole nervous systems taken from egg-laying specimens does not influence withdrawal responses (Figs. 8, 9) or righting behavior (Figs. 10, 11). Therefore, the hormone(s) is selective in its suppressive effect, preferentially inhibiting feeding but not other behaviors.These data support the hypothesis that one or more hormone(s) is released by the nervous system into the blood to induce egg-laying and simultaneously and selectively suppress feeding behavior. The study shows that egg-laying occupies a more dominant position than feeding in the behavioral hierarchy ofPleurobranchaea, and suggests that the dominance is mediated hormonally (Fig. 12).

Daily energetics of the Black-capped Chickadee,Parus atricapillus, in winter

Abstract: The Black-capped Chickadee,Parus atricapillus, is a year-round resident of deciduous forests near Ithaca, New York. Chickadees are confronted with high nightly energetic demands, due to their small size (10–12 g) and the subfreezing winter temperatures, which must be met by an adequate energy reserve. The fat stores of Chickadees on midwinter evenings provide slightly more energy then expended overnight, as based on metabolic measurements made in the laboratory.

Physiology of insect rhythms: IV. Role of the brain in the regulation of the flight rhythm of the giant silkmoths

Abstract: Summary1.Male giant silkmoths generally show 3 distinct peaks of flight activity each day: a brief burst of flight after lights-off (α1), a longer bout of activity later in the night (α2), and a lights-on response. Theα1 andα2 activities are under circadian control, whereas the lights-on response occurs in response to an exogenous signal.2.Surgical experiments showed that the brain was necessary for the expression of the flight rhythm. Moreover, an intact neural pathway from the brain to the thoracic motor centers was needed for overt rhythmicity.3.Rhythmic flight activity continued after the removal of the optic lobes but not after excision of the cerebral lobes.4.Extirpation of the compound eyes did not interfere with the entrainment of theα1 andα2 peaks, but it abolished the lights-on response. Ablation of the ocelli had no effect on any of the flight peaks. It was concluded that the flight clock(s) was entrained by an extraretinal photoreceptor.5.Experiments involving covering the head with opaque wax indicated that the extraretinal receptor was in the head.6.When the head was covered with opaque wax but the compound eyes were left exposed, the moths showed free-running activity even though they were in a photoperiod regimen. Consequently, the only pathway of photoperiod information to the locomotor clock is apparently via the extraretinal receptor.7.It was concluded that adult activity was most likely controlled by centers in the cerebral lobe area of the brain. These presumably receive light directly and control activity via neural pathways to the thoracic ganglia.

Die optomotorischen Reaktionen von fixiert fliegenden Bienen bei Reizung mit Spektrallichtern

Abstract: 1. Das optomotorische Verhalten von fixiert fliegenden Honigbienen in einer 2farbigen Drehtrommel wurde untersucht. Die Drehtrommel wurde mit Spektrallichtern (343–615 nm) beleuchtet (Abb. 1). 2. Auf Farben gleicher bienensubjektiver Helligkeit reagieren die Bienen nicht (Abb. 6–8). Parbsehsystem und optomotorisches System sind demnach zwei getrennte Systeme. 3. Eine sehr genaue spektrale Empfindlichkeitskurve wurde gewonnen. Sie ist der Empfindlichkeitskurve des Grunrezeptors der Biene sehr ahnlich (Abb. 9). Die Grunrezeptoren liefern also den dominanten Beitrag zum optomotorischen System der Biene. 4. Der Beitrag der UV- und/oder Blaurezeptoren wird diskutiert. Dabei werden auch Untersuchungen uber richtungsspezifisch bewegungssensible Neuronen der Biene berucksichtigt. 5. Die Konsequenz der Nulldurchgange der Reaktions-Kurven fur in der Literatur beschriebene Modelle zur Versehaltung des optomotorischen Systems wird diskutiert. 6. Vermutlich gilt das Prinzip der Trennung des Farbsehsystems vom Bewegungssehsytem bei Insekten allgemein.

An increased scope for thermal tolerance upon acclimating pupfish (Cyprinodon) to cycling temperatures

Abstract: Pupfish (Cyprinodon nevadensis amargosae), which inhabit shallow, thermally instabile desert waters were acclimated to a series of constant temperatures (15, 25 and 35 ° C) and to a symmetrical fluctuating temperature regime (15–35 ° C). A range or scope of thermal tolerance of 39 ° C between critical thermal maxima and minima exists for this species (Fig. 1). Upon acclimation to cycling temperatures, this tolerance range increased significantly to almost 41 ° C (Fig. 2). Hence, these fish can apparently compensate physiologically for both warm and cold temperatures simultaneously.

Electric organ discharge patterns during dominance related behavioral displays inGnathonemus petersii (Mormyridae)

Abstract: 1. The electric organ discharge (EOD) patterns seen in pairs of mormyrid fishes (Gnathonemus petersii) during displays related to aggression and establishment of dominance are described. 2. A new method of reliably separating the discharges of the two fish was used. In this method a fine wire was attached to the tail of one animal (Fig. 1). 3. Discharge patterns were examined at different stages during the characteristic sequence of overt behavioral events which usually occurred after an intruder was put into a tank in which another fish of the same species had been resident for 1 hour or more. The resident attacked the intruder immediately, the intruder being initially unresponsive. After a few minutes, however, the two fish entered into intense, mutual, antiparallel displays (Fig. 2). The displays occurred repeatedly during a period of 0.5–30 min. This period ended suddenly with one of the fish clearly dominant as shown by one-sided attacks and avoiding behavior by the submissive fish. 4. All attacks were accompanied by a smooth acceleration to a high discharge rate which was usually terminated abruptly (Fig. 3). Anti-parallel behavior was accompanied by similar accelerations in both fish. Interdischarge intervals during these high rates changed discretely between those of about 15 msec and those of about 9 msec (Figs. 3–9). Initial attacks before the antiparallel period usually produced no effect or a brief acceleration in the discharges of the attacked animal. Similar attacks when dominance was well established caused a slowing of the discharge rate of the attacked fish. 5. The echo response in which one fish responds to the EOD of another with a discharge of its own at a latency between 11 and 14 msec was seen at all stages of the encounter. This latency corresponded rather exactly to the gap in the interval histogram between the shorter intervals around 9 msec and the longer ones around 15 (Figs. 11, 12). This correspondence led to a degree of avoidance of near synchronous discharges during those attacks which did not cause either slowing or accelerations in the attacked animal (Fig. 11). A degree of synchrony avoidance also occurred during the mutually high discharge rates of antiparallel behavior. This resulted from the phase locking of the two discharge trains which was often present at these times and which was probably due to the echo responses (Fig. 13). 6. Several features of the individual discharge trains and of their interaction were examined during the period of antiparallel activity. This was done in order to see if some critical parameter could be detected which would allow one to predict the winner of the encounter and which might be used as a signal by the fish themselves. No single feature among those we examined was clearly and consistently related to the outcome of the encounter.

Polarised light detection in the bee,Apis mellifera

Abstract: The ninth cell in each ommatidium is the only retinula cell that acts as a polarised light detector. The ninth cell is a short retinula cell which is found in the proximal third of the ommatidium. This conclusion is based on the following observations: (1) The most frequently found green sensitive cells have either no or very low sensitivity to polarised light. This is caused by electric coupling of cells with different microvilli orientations. The electric coupling was found to be independent of adaptation state. (2) There are two different types of UV receptors: the more frequently found UV cells also have a distinct spectral sensitivity at longer wavelengths (>450 nm) and a small polarisation sensitivity. A very rarely recorded UV receptor type with no sensitivity to longer wavelengths (>450 nm) has a high polarisation sensitivity (average PS = 5, maximal PS = 9). All recordings of these UV cells were made close to the basement membrane in the region of the 9th cell. (3) The short length of the 9th cell, its position in the proximal third of the ommatidium, and the orientation of the microvilli is theoretically consistent with it having a high polarisation sensitivity.

Central Control of Cardiac and Scaphognathite Pacemakers in the Crab, Cancer magister

Abstract: Command fibers located in the circumesophageal connectives which modify scaphognathite and heart rhythms have been mapped and characterized in the crab,Cancer magister. Behavior: Crabs show a variety of responses to external stimuli often including simultaneous cessation of cardiac and scaphognathite “pumping”. Habituation and a return to prestimulus rhythms results from continued stimulation. The response to short stimulus durations, on the other hand, generally outlasts the stimulus indicating the playing-out of a motor program. Neurophysiology: Small bundles of fibers have been isolated from desheathed connectives. Activity in these fibers resulting from stimulation of various anterior sensory receptors was recordeden passant with suction electrodes. When sensory stimulation produced both electrical activity in the nerves under examination and a cardiac and/or scaphognathite response it was assumed such units were involved in inducing this response. This was tested by electrical stimulation delivered through the same electrode. Those units which produced similar responses to natural and artificial stimulation were deemed “command fibers”. It was invariably found that the minimum stimulating frequency needed to mimic naturally induced responses was much greater than the frequency at which the units discharged in response to those stimuli. During mapping experiments, command fibers were characterized with respect to their positions in the connectives and by the responses they produced at different frequencies of stimulation. 68% of the fibers identified affected both cardiac and scaphognathite systems, 29% the scaphognathites alone and 3% the heart alone. The frequency-response profiles of single bivalent command fibers were often different from the heart and scaphognathites. These findings help explain the responses of both systems to natural stimuli and also indicate that the circulatory and respiratory systems not only perform in concert, but are often under common control.

Circadian rhythms in cockroaches

Abstract: The driving oscillator, which mediates circadian locomotor rhythms in cockroaches, appears to reside in the protocerebrum of the brain. The evidence indicates that the optic lobes are crucial elements in this circadian system, and that control of rhythmicity is mediated through electrical, rather than hormonal, channels. Lesions were placed at various sites within the optic lobes in order to localize the areas controlling rhythmicity. It appears that the two innermost synaptic areas (the lobula and the medulla) constitute the crucial optic lobe elements. The outer synaptic area of the optic lobe (the lamina) is not necessary for the expression of rhythmicity, but does function as a coupling through which light cycles, transduced by the compound eyes, entrain the circadian clock.

Manipulation of frequency analysis in the cochlear ganglion of the guinea pig

Abstract: 1. Recordings of extracellular activity were obtained from single cells in the spiral ganglion of the basal turn of the guinea pig cochlea. 2. The spatial distribution of characteristic frequencies of cells in the ganglion was consistent with published data on the location of displacement maxima on the basilar membrane. 3. Large variations in the sharpness of single cell tuning curves were seen between animals. These variations were closely linked to sensitivity differences. 4. The tuning curves of single cells could be made less sharp by slowing the rate of artificial ventilation. These tuning curve changes were reversible and intimately associated with alterations in sensitivity and spontaneous activity. 5. The data point either to the presence of a mechanical non-linearity, or a physiologically vulnerable second filter, as the explanation for the sharpness of neural tuning curves in cochlear nerve fibres.

Detection of polarized light by the homing pigeon, Columba livia

Abstract: Of 12 homing pigeons tested, four could be trained to discriminate between a linearly polarized light source with a rotating axis of polarization and the same light source with a stationary axis of polarization. Initially, all 12 pigeons were trained to discriminate between rotating and nonrotating crosshairs. The crosshairs were gradually faded until only polarized light remained. The response was a classically conditioned increase in heart rate. An additional control series was performed using neutral density filters. This is the first evidence for polarized light detection in birds.

Anatomy of locust ocellar interneurons: Constancy and variability

Abstract: 1. The anatomy of the ocellar interneurons in the brain of the locust,Scchstocerca vaga, was revealed by axonal iontophoresis of cobalt chloride. The normal bilaterally symmetric anatomy, as represented in 41 of 50 preparations, includes 17 large and identified ocellar interneurons (Fig. 1). Each ocellar nerve contains the axons of 7 large interneurons (Fig. 2), 4 of the interneurons having axons in two ocellar nerves. 2. The anatomy of each large interneuron is described (Fig. 5). Only one, with an axon in the median ocellar nerve, projects bilaterally; all others are confined to one side of the brain and have contralateral homologues. Two interneurons run between each lateral ocellus and the median ocellus. Their axons run through the brain without branching, except for the neurite, and they may be the “efferent” units previously described. Several pairs of interneurons are described with effectively identical gross morphology. 3. Individual variation of the same cell in different preparations is described (Fig. 6), showing constancy of general shape but with variation in fine branching patterns characteristic of most preparations. 4. Major asymmetric variations were found in 9 of 50 preparations, including cases in which axons of identified cells extended into lobes of the brain in which they normally were not found (Fig. 7), cases in which normally occuring cells sent extra axons into ocellar nerves in which they normally were not represented, and cases in which extra cells occured which were anatomical duplicates of normally occuring cells (Fig. 9).

The structure of tonic flexor motoneurons in crayfish abdominal ganglia

Abstract: 1. The tonic flexor motoneurons were filled with cobalt dye via the cut ends of their axons. All six physiologically defined cells were identified anatomically (Figs. 2–4). 2. The cell somata are widely scattered in the ventral rind of the ganglia; three cells have ipsilateral and three cells have contralateral somata in reference to their axons; cells with contralateral somata tend to be more rostral in the ganglion (Figs. 2, 11). 3. All cells have bilateral dendritic domains (Figs. 5, 6, 8, 10). Each soma is connected to a long, thin neurite which travels dorsally and enlarges into a thick process (neuropilar segment) that crosses the midline in the posterior outer commissure (Figs. 8, 9) except for fl, which crosses anteriorly (Fig. 10). Many branches emerge from the neuropilar segment; the proximal portions of these branches and the neuropilar segment contribute to the coarse dorsal neuropile. Distal branches are found in the fine ventral neuropile (Figs. 9, 10). No recurrent collaterals were observed. 4. Most of the neuropilar segments converge into a narrow arc that sweeps across the dorsal neuropile (Figs. 8, 9). The close correspondence of the processes, especially of contralateral homologues (Figs. 10, 12) provides an anatomical basis for functional interactions among the tonic flexors. The main masses of finer processes that run along the longitudinal axis are located laterally. 5. Bilateral, serial and interanimal homologies of soma position all showed similar degrees of variation. Positions were relatively constant but might vary by up to 100 μ relative to external landmarks (Fig. 11). 6. Dendritic geometries were sufficiently similar to permit unambiguous identification of homologues, but variability in the number and shape of branches is common.

Behavioral thresholds to electric signals in high frequency electric fish

Abstract: 1) The behavioral thresholds ofApteronotus andEigenmannia to imposed sine wave electric fields were measured as a function of stimulus frequency using operant conditioning techniques. 2)Apteronotus responds to a broad range of frequencies. Its threshold—frequency curve is complex, showing three distinct threshold dips at: <5–15 Hz, 0.6–0.9 μV/cm; 200–300 Hz, 0.9 μV/cm; and 700–2200 Hz to 0.2 μV/cm. The high frequency dip itself is bimodal, with a primary minimum at the fish's electric organ discharge (EOD) fundamental, and a secondary minimum at its second harmonic. 3) The threshold—frequency curve forEigenmannia differs in several respects, being unimodal and sharpely tuned to the fish's EOD frequency with a sensitivity of 0.2–0.3 μV/cm.Eigenmannia shows a lack of keen low frequency perception, and no marked sensitivity increase at the second harmonic of its EOD. 4) The EOD wave forms ofApteronotus andEigenmannia were Fourier analysed:Eigenmannia's EOD approximates a sine wave, whileApteronotus' EOD contains considerable power at harmonic frequencies. 5) It is proposed that behavioral thresholds to frequencies within ca. 50–100 Hz of the fish's EOD fundamental or second harmonic are improved by the fish's extraction of, and preference for, low frequency beats of its EOD with the stimulus. This is suggested by the sharp, EOD specific tuning demonstrated by bothEigenmannia andApteronotus and the second harmonic sensitivity peak ofApteronotus, which are not predicted by known receptor response characteristics. Such a beat extraction capability might provide a mechanism for improving the resolution of conspecific electrocommunication. 6) The influence of water resistivity on the behavioral thresholds ofApteronotus was measured. High frequency sensitivity increases as a power function with decreasing water resistivity down to 1 k Ohm · cm, below which it remains constant. Low frequency sensitivity increases progressively from 100 k Ohm · cm down to 10 k Ohm · cm, but decreases again below this value. Thus low frequency eleotroreceptors are maximally sensitive in 10 k Ohm · cm water, while high frequency receptors function best in water below 1 k Ohm · cm.

Organization of the stomatogastric ganglion of the spiny lobster: III. Coordination of the two subsets of the gastric system

Abstract: SummaryThe neurons of the gastric system form two discrete subsets which drive the median and lateral teeth of the gastric mill. These two subsets can each produce alternating contractions of antagonistic muscles when the other subset is not active, but whenever the two are active simultaneously their motor patterns are coordinated.This coordination is produced by synaptic connections between motor neurons in the two subsets, and by the interneurons common to both subsets. One of the neurons driving the lateral teeth, LGN, inhibits several of the neurons driving the medial tooth—DGN (Fig. 1) and each of the GMs. LGN and the GMs are also electrotonically coupled (Fig. 2). The GMs are electrotonically coupled to all the motor neurons of the lateral teeth subset (Figs. 2, 3, and 9). These synaptic connections are reflected in the spontaneous motor patterns generated by the ganglion. In addition, there are several interactions (Figs. 4–8 and 11b) which may not be the products of direct synaptic connections which nonetheless have been demonstrated experimentally and are reflected in the spontaneous motor patterns (Figs. 14–17).Two hypothesis about the mechanism generating one of the two types of motor patterns observed are proposed. One uses observations of synaptic depression at particular synapses to explain overlapping bursts of reciprocally inhibitory neurons. The other draws on observations of accommodation and postinhibitory rebound to explain how the repetition rate of the pattern might be determined.

Der Polarisationsempfänger im Bienenauge: ein Ultraviolettrezeptor

Abstract: 1. Das Experiment, mit dessen Hilfe Karl v. Frisch die Polarisations-Wahrnehmung der Biene entdeckte, wurde so abgewandelt, das ein Wirkungsspektrum fur die spektrale Empfindlichkeit des Polarisationsempfangers im Bienenauge aufgenommen werden konnte. Auf horizontaler Wabe wurden die Tanze von Bienen beobachtet, die einen mehrere hundert Meter entfernten Futterplatz besuchten. Wahrend der Tanze hatten die Bienen keinen Ausblick auf die Sonne oder den naturlichen Himmel; stattdessen wurde ihnen im Zenit unter einem Sehwinkel von 17° ein Feld monochromatischen, polarisierten Lichtes geboten, dessen Wellenlange, Intensitat und Polarisationsrichtung variierbar waren. Die Bienen verhielten sich unter diesen Versuchsbedingungen bei ihren Tanzen so, als ob sie Ausblick auf ein entsprechend groses Feld blauen Himmels im Zenit hatten. 2. Die Orientiertheit der Tanze konnte uber die Streuung der Tanzwinkel (Richtungen der einzelnen Schwanzellaufe) quantitativ erfast werden. Nur im kurzwelligen Wellenlangen-Bereich bis etwa 430 nm konnten sich die Bienen nach der Polarisationsrichtung orientieren (Abb. 5). Je hoher die Intensitat des polarisierten Lichtes bei einer festgehaltenen Wellenlange dieses Bereichs war, umso besser waren die Tanze ausgerichtet (Abb. 6, 7). Daraus lies sich das Wirkungsspektrum der Polarisations-Wahrnehmung entnehmen (Abb. 8). 3. Ein Vergleich des Wirkungsspektrums mit einer Rhodopsin-Absorptions-Normkurve zeigt, das die Polarisations-Wahrnehmung ein Empfindlichkeitsmaximum bei etwa 345 nm besitzt. Der Polarisationsempfanger im Bienenauge ist also ein Ultraviolett-Rezeptor. Die Ergebnisse unserer Experimente sind mit beiden Deutungen vereinbar; die erstaunlich hohe Empfindlichkeit spricht moglicherweise nicht zugunsten der ersten Hypothese.