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Neuronal circuits in cephalopod vision
Williamson, R.; Ichikawa, M.; Matsumoto, G. (1994). Neuronal circuits in cephalopod vision. Neth. J. Zool. 44(3-4): 272-283
In: Netherlands Journal of Zoology. E.J. Brill: Leiden. ISSN 0028-2960, more
Peer reviewed article  

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  • Williamson, R.
  • Ichikawa, M.
  • Matsumoto, G.

    Cephalodops have a sophisticated visual system that is comparable in overall performance to many vertebrate visual systems. Although the eyes of cephalopods and vertebrates have strong similarities, their central processing systems seem anatomically very different. In this paper we investigate the mechanism used by cephalopods for analysing visual signals, with a view to comparing this with vertebrate systems. The cephalopod retina is comparatively simple containing only photoreceptors, supporting cells, and a efferent innervation. The retina is topographically mapped onto the optic lobe via a chiasma that inverts the visual map. Within the optic lobe most photoreceptor axons terminate in a complex neuropil area, the outer plexiform zone. This zone recieves connections from many different cell types and stains positively for most of the major neurotransmitters; this is undoubtely an important processing area. Using 400 µm slices from the optic lobe, field potentials were imported from this erea in response to stimulation of the optic nerves; these showed a complex potential in the plexiform layers, indicating synaptic activity in this zone. This activity could be abolished by synaptis blocking agents. The spatial extent of this activity was revealed by an optical recording method, whereby the slice was stained with a voltage-sensitive dye and a fast video system was used to image the responses to electrical stimulation. This confirmed that the activity from the retinal photoreceptors excites follower cells in the plexiform zone, probably the small amacrine cells, and that this spreads along the margin of the zone to cover a distance of about 400 µm. The signal could not be followed further in transverse slices. These experiments provide evidence for the first steps in our understanding of visual processing in cephalopds and demonstrate the adventages of combining electrical and optical recordings in the analyses of complex neural processing.

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