Transcribed:How Seen Movement Appears In The Frog's Optic Nerve

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Transcribed from a reprint

Federation Proceedings Volume 18 Number 1 March 1959 Pages 393 and 354.

H. Maturana, J. Y. Lettvin, W. H. Pitts, W. S. McCulloch

Research Laboratory of Electronics, M.I.T. Cambridge, MA

Part I

The receptive field of a single optic nerve fiber (plotted by the on and off responses to small fixed spots) is often divisible into concentric cones. This suggests that the response of the fiber to a moving spot may be polar with respect to a reference point in the receptive field. Movement is indeed polarly encoded and there exists at least the following four typed of fibers whose rate of firing depends on the centrifugal component of a movement with respect to some point internal to the receptive field (centripetal and tangential movements never cause discharge):

  1. Some fibers have wide receptive fields and low sensitivity. Of these some prefer the moving object darker than background, other prefer it lighter.
  2. A second group has constricted fields and high sensitivity.
  3. A third set shows a directional heavy weighting of the response.
  4. A fourth kind has annular fields.

A fifth variety measures inversely the average intensity of illumination in a region. Its maximum rate is in the dark.

Part II

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