Visual position stabilization in the hummingbird hawk moth, Macroglossum stellatarum L. II. Electrophysiological analysi
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Ó Springer-Verlag 1998
ORIGINAL PAPER
R. Kern
Visual position stabilization in the hummingbird hawk moth, Macroglossum stellatarum L. II. Electrophysiological analysis of neurons sensitive to wide-®eld image motion Accepted: 13 August 1997
Abstract Response properties of neurons in the cervical connectives of the hummingbird hawk moth, Macroglossum stellatarum L., were determined. All neurons described in this account respond directionally selectively to motion in large parts of the visual ®eld of either eye. They respond maximally to bilateral stimulation, preferring either motion as induced on the eyes during translatory movements of the animal or when it turns around one of its body axes. Cells most sensitive to rotational motion either respond best to rotation of the patterns around the vertical axis of the animal or around its longitudinal body axis. Neurons most sensitive to translational pattern motion respond best to either simulated translations of the animal along its vertical or along an oblique axis. Most types of neurons respond tonically and do not habituate. The sensitivity to motion stimuli is not evenly distributed within the receptive ®eld of any investigated neuron. Part of these neurons might play a role in visual position and course stabilization. Key words Vision á Position stabilization á Optomotor neurons á Hawk moth á Insect Abbreviations NPBM non-preferred bilateral motion á PBM preferred bilateral motion á RH-cells neurons that respond best to horizontal rotational motion á RPM rotational pattern motion á RV-cells neurons that respond best to vertical rotational motion á TO-cells neurons that respond best to translational motion along an oblique axis á TPM translational pattern motion á TV-cells neurons that R. Kern Lehrstuhl fuÈr Biokybernetik, UniversitaÈt TuÈbingen, Auf der Morgenstelle 28, D-72076 TuÈbingen, Germany Present address: Lehrstuhl fuÈr Neurobiologie, FakultaÈt fuÈr Biologie, UniversitaÈt Bielefeld, Postfach 10 01 31, D-33501 Bielefeld, Germany Fax: +49 (0)521/106 6038 e-mail: [email protected]
respond best to translational motion along a vertical axis
Introduction The diurnal hawk moth, Macroglossum stellatarum L., sucks nectar from ¯owers while hovering in front of them (Knoll 1922). This peculiar feeding behaviour, which is reminiscent of hummingbirds, requires the ability of the animal to compensate for disturbances of its position relative to the ¯ower in order to keep the proboscis in contact with the nectary. It has been shown in laboratory studies on freely ¯ying animals that they control their position mainly by exploiting visual cues (Pfa and Varju 1991; Farina et al. 1994, 1995; Kern and Varju 1998). Mechanical cues derived via the proboscis were demonstrated to play only a minor role (Zhou 1991). In a companion paper (Kern and Varju 1998), the systems controlling the stabilizing optomotor responses have been analysed by simulating the visual consequences of disturbances experienced by Macroglossum in natural situations. The control s
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