Ernst Kramer

The orientation of walking honeybees in odour fields with small concentration gradients

The behaviour of walking honeybees in small gradient odour fields was investigated by means of a simulation technique. The bee was kept in one place by a locomotion compensator (‘running sphere’). This compensator allowed for a precise reconstruction of the bees actual locomotion on the sphere, and presented the bee with a stimulating odour whose concentration was controlled by feedback from the reconstructed locomotion. This rendered possible the application of well‐defined odour fields and revealed that: (1) honeybees are capable of finding odour sources in the absence of optical cues and with concentration gradients too small to allow tropotactic or klinotactic orientation; (2) bees are capable of memorizing odour concentrations with a high degree of accuracy; (3) this orientation system is based on a switching over from negative to positive anemotaxis at a ‘reference’ concentration; (4) this reference is a function of the odour concentration at which a sugar reward is given. The results do not support any hypothesis for an orientation system based on the detection and comparison of successive values of odour concentration. A hypothesis on the nature of the ‘reference value’ is discussed and supported by experiments.

Investigations and considerations of directional perception during voluntary saccadic eye movements.

SummaryThis investigation attempts to examine the change of retinal local signs during voluntary horizontal saccadic eye movements. The method used was to expose the S. to a short light stimulus (electronic flash) of approximately one degree angular width during or after a 16 degree eye movement. The stimulus was released by the eye movement itself via the retino-corneal potential. The S.s task was to localize the stimulus on a fixed luminous scale.Clear translatory illusions occurred in these experiments. They depended systematically on the spot on the retina stimulated, and on the time elapsed between the onset of the saccade and the release of the stimulus. These illusions are best interpreted as due to the shift of a “coordinate system” across the retinal field. The shift is initiated by the coordinate of the retinal spot on which the target of the eye movement was projected before the saccade began. This coordinate rapidly swings into the fovea. The processes on the retinal hemisphere opposite to the target occur at a much slower rate. Moreover, temporary changes of the topology of the coordinate system may take place during the saccade. Their origin is still unclear.The results of the experiments are discussed in terms of a special model based on the previous explanations of the phenomenon of directional constancy (especially the reafference principle, the attention theories, and MacKays theory).ZusammenfassungDie vorliegende Arbeit hatte das Ziel, die „Umstimmung der retinalen Raumwerte“ während willkürlicher horizontaler Blicksprünge (Sakkaden) zu untersuchen.Die Methodik bestand darin, während oder nach der Augenbewegung kurzzeitig einen ca. 1° großen Lichtreiz (Elektronenblitz) im Gesichtsfeld der Vp zu exponieren, den diese in bezug auf eine kopffeste Skala zu lokalisieren hatte. Die Auslösung des Lichtreizes erfolgte auf elektrookulographischem Weg durch die Augenbewegung selbst.Bei diesen Versuchen traten in systematischer Abhängigkeit vom retinalen Ort des Reizes und von der zwischen Sakkadenbeginn und Reizexposition verstrichenen Zeit deutliche Verlagerungstäuschungen auf. Sie lassen sich am besten interpretieren, wenn man die Umwertungsprozesse als „Wanderung“ eines lokalisatorischen Bezugssystems über ein zentralnervöses Projektionsfeld der Retina auffaßt. Diese Wanderung wird eingeleitet und angeführt durch ein rasches Einschwingen der Koordinate des Zielpunktes der Blickbewegung in die Fovea; in der zielabgekehrten Netzhauptperipherie vollzieht sich die Umwertung wesentlich langsamer. Dabei kann es vorübergehend zu topologischen Veränderungen des Bezugssystems kommen, deren Genese noch unklar ist.Ausgehend von den bislang vorliegenden Ansätzen zur Erklärung der Richtungskonstanz (insbesondere vom Reafferenzprinzip, den Aufmerksamkeitstheorien und der Theorie MacKays) wird ein eigenes Modell entwickelt, in dessen Rahmen die Versuchsergebnisse diskutiert werden.

Search and anemotactic orientation of cockroaches

Abstract Orientation of three species of cockroaches, Blattella germanica, Periplaneta americana and Blaberus craniifer , was monitored in still air and in wind using a servosphere device. In the absence of wind the cockroaches exhibited search behaviour characterized by species-specific patterns of looping and straight locomotory segments. In wind the cockroaches alternated turning left and right rather than looping. Relatively straight course directions were maintained in wind, primarily upwind in B. craniifer and downwind in B. germanica; P. americana ran upwind at low wind velocities and downwind at high wind velocities. The antennae perceive the direction of air currents; for all three species the threshold of wind perception is between 0.015 and 0.03 m/sec.

Stabilization of altitude and speed in tethered flying gypsy moth males: influence of (+) and (‐)‐disparlure

ABSTRACT. Changes in lift and thrust were elicited in tethered male gypsy moths, Lymantria dispar L. (Lepidoptera, Lymantriidae), by visual pattern elements moving radially either towards or from the point directly beneath their body, if the sex‐pheromone, (+)‐disparlure, was present. The sign of these changes was such as to counteract the pattern movements, which were generated by a rotating spiral beneath the moth. By restricting the area of spiral visible to the moth to either transverse or longitudinal sectors, flight altitude was affected by the centrifugal/centripetal movements in the lateral sectors, whereas flight speed was affected by those in the frontal sector. It is deduced that in free flight these compensatory reactions are responsible for the stabilization of flight altitude and speed, respectively. Surprisingly, without pheromone present these responses were usually not detectable: a wide range of flight altitude and speed was then observed. In the presence of (+)‐disparlure, however, these responses were always strongly pronounced, the animal keeping within a narrow range of speed and altitude. These compensatory reactions were blocked by the attraction‐inhibiting (‐)‐disparlure if presented in racemic mixture with the (+) form: the range of speed and altitude shown by the moth was then the same as without any pheromone. Under closed‐loop conditions, the mean flight speed was reduced by the racemic mixture as well as by (+)‐disparlure alone, however.

Attractivity of pheromone surpassed by time-patterned application of two nonpheromone compounds

Strong support is given to the thesis that an unmodulated level of pheromone does not evoke orientation toward the source in male silkmoth Bombyx morieven if the concentration is high. The bombykol-related compound (Z,E)-4,6-hexadecadiene, which is known to elicit a firing of bombykol receptors that is maintained for many minutes after the removal of the stimulus, was used for the tests, together with linalool, which inhibits the response of the bombykol cells. Neither hexadecadiene nor linalool is known to release the typical behavior of orientation in these moths. The experiments, however, show that if the uniform firing after a hexadecadiene stimulus is modulated by a suitable sequence of linalool pulses, the males immediately display orientation behavior and approach the source even faster and more directed than with pulsed bombykol.

Anemotactic orientation of gypsy moth males and its modification by the attractant pheromone (+)-disparlure during walking

ABSTRACT. Tracks of dewinged gypsy moth males, Lymantria dispar L. (Lymantriidae), walking upwind in an airstream without pheromone consist of marked alternations between more or less straight upwind segments, partly with an arcadic structure, and twisted segments. This apparently complicated behaviour can, however, simply be explained by a superposition of noise and two turning commands: an upwind turning tendency, derived from the anemoreceptive system, which represents an average of the moths angular positions over a period of time; and an internal turning tendency which consists of strong but brief bursts. These bursts are produced intermittently; successive bursts do not necessarily alternate polarity. Amputation of one antenna increases the probability of bursts towards the amputated side; therefore a separate burst source is postulated for each antenna. In the presence of the attractant pheromone (+)‐disparlure, the anemotactic signal is weighted higher; twisted segments are, therefore, less pronounced.

Untersuchungen und berlegungen zur Richtungswahrnehmung bei willkrlichen sakkadischen Augenbewegungen@@@Investigations and considerations of directional perception during voluntary saccadic eye movements

SummaryThis investigation attempts to examine the change of retinal local signs during voluntary horizontal saccadic eye movements. The method used was to expose the S. to a short light stimulus (electronic flash) of approximately one degree angular width during or after a 16 degree eye movement. The stimulus was released by the eye movement itself via the retino-corneal potential. The S.s task was to localize the stimulus on a fixed luminous scale.Clear translatory illusions occurred in these experiments. They depended systematically on the spot on the retina stimulated, and on the time elapsed between the onset of the saccade and the release of the stimulus. These illusions are best interpreted as due to the shift of a “coordinate system” across the retinal field. The shift is initiated by the coordinate of the retinal spot on which the target of the eye movement was projected before the saccade began. This coordinate rapidly swings into the fovea. The processes on the retinal hemisphere opposite to the target occur at a much slower rate. Moreover, temporary changes of the topology of the coordinate system may take place during the saccade. Their origin is still unclear.The results of the experiments are discussed in terms of a special model based on the previous explanations of the phenomenon of directional constancy (especially the reafference principle, the attention theories, and MacKays theory).ZusammenfassungDie vorliegende Arbeit hatte das Ziel, die „Umstimmung der retinalen Raumwerte“ während willkürlicher horizontaler Blicksprünge (Sakkaden) zu untersuchen.Die Methodik bestand darin, während oder nach der Augenbewegung kurzzeitig einen ca. 1° großen Lichtreiz (Elektronenblitz) im Gesichtsfeld der Vp zu exponieren, den diese in bezug auf eine kopffeste Skala zu lokalisieren hatte. Die Auslösung des Lichtreizes erfolgte auf elektrookulographischem Weg durch die Augenbewegung selbst.Bei diesen Versuchen traten in systematischer Abhängigkeit vom retinalen Ort des Reizes und von der zwischen Sakkadenbeginn und Reizexposition verstrichenen Zeit deutliche Verlagerungstäuschungen auf. Sie lassen sich am besten interpretieren, wenn man die Umwertungsprozesse als „Wanderung“ eines lokalisatorischen Bezugssystems über ein zentralnervöses Projektionsfeld der Retina auffaßt. Diese Wanderung wird eingeleitet und angeführt durch ein rasches Einschwingen der Koordinate des Zielpunktes der Blickbewegung in die Fovea; in der zielabgekehrten Netzhauptperipherie vollzieht sich die Umwertung wesentlich langsamer. Dabei kann es vorübergehend zu topologischen Veränderungen des Bezugssystems kommen, deren Genese noch unklar ist.Ausgehend von den bislang vorliegenden Ansätzen zur Erklärung der Richtungskonstanz (insbesondere vom Reafferenzprinzip, den Aufmerksamkeitstheorien und der Theorie MacKays) wird ein eigenes Modell entwickelt, in dessen Rahmen die Versuchsergebnisse diskutiert werden.