Spatial integration in polarization-sensitive interneurones of crickets: a survey of evidence, mechanisms and benefits.
Many insects exploit the polarization pattern of the sky for compass orientation in navigation or cruising-course control. Polarization-sensitive neurones (POL1-neurones) in the polarization vision pathway of the cricket visual system have wide visual fields of approximately 60 degrees diameter, i.e. these neurones integrate information over a large area of the sky. This results from two different mechanisms. (i) Optical integration; polarization vision is mediated by a group of specialized ommatidia at the dorsal rim of the eye. These ommatidia lack screening pigment, contain a wide rhabdom and have poor lens optics. As a result, the angular sensitivity of the polarization-sensitive photoreceptors is very wide (median approximately 20 degrees ). (ii) Neural integration; each POL1-neurone receives input from a large number of dorsal rim photoreceptors with diverging optical axes. Spatial integration in POL1-neurones acts as a spatial low-pass filter. It improves the quality of the celestial polarization signal by filtering out cloud-induced local disturbances in the polarization pattern and increases sensitivity.
Labhart
T
T
Zoologisches Institut der Universität, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. labhart@zool.unizh.ch
Petzold
J
J
Helbling
H
H
D000818:Animals; D006135:Gryllidae / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D008027:Light; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology; D013028:Space Perception / Q000502:physiology*