Discharge Patterns and Functional Organization of Mammalian Retina

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Discharge Patterns and Functional Organization of
Mammalian Retina

• Stephen W. Kuffler
• 1951

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Question

• What is the functional organization of the
  mammalian retina?
• How does it differ from that of the frog or the
  Limulus?
• organization of connections, receptive fields

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Theoretical Alternatives

• The organization is different than that of the
  frog or limulus.
• The organization is the same as that of the frog
  or the limulus
• It is the same in some ways or different in
  others.
• -or more specifically . . .

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Theoretical Alternatives

• Alternatives for the organization of the retina
  
• Direct
  Indirect
• Overlap
• No overlap

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Logic

• Stimulate specific areas of the retina and alter
  the parameters of the stimuli, while recording
  from that area with an electrode
• The patterns of discharges from cells in response
  to varying stimuli will give clues as to the
  organization of the retina

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Methods

• Project light stimuli onto retinas of
  anesthetized cats using Multibeam
  Ophthalmoscope, while recording from one
  ganglion cell in that area with a microelectrode.
• Eye was left intact
• Manipulate Parameters of stimulus location,
  size, intensity, duration, background
  illumination, number of points

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Results

• You can record from a single ganglion cell
• Fig 1. Potentials recorded from retina by
  microelectrode.
• 1A. And 1C. Show potential recorded from ganglion
  cells

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Results

• Receptive fields have a functional sub-structure
• Concentric areas within RF in which light
  produces different responses
• on regions
• off regions
• on-off regions
• RFs are more sensitive towards center.

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Results

• Fig. 4. Responses of specific regions within RF.
  (A) on region, (B) off region, (C) on-off
  region
• Fig. 6. Distributions of discharge patterns
  within ganglion cell RF crosses on, circles
  off, circles and crosses on-off

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Results

• Fig. 3. Extent of receptive field showing
  thresholds of stimulus intensity which trigger
  discharge
• Fig. 5. Discharge activity caused by stimulation
  in different regions of center of receptive field

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Results

• When two areas within receptive field are
  stimulated, an interaction produces a different
  pattern of responses.
• Interaction of stimulus parameters also causes
  variation of response

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Results

• Fig. 8. Interaction of 2 separate light spots in
  same RF.

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Interpretation

• Response patterns in RFs of cells reflect
  structural features of retina, i.e. wiring
• There are more receptors in the center of a
  receptive field and less towards the edges.
• Sideways connections in retina provide overlap of
  RFs and inhibition from other areas
• Connections are indirect, fields are overlapping

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Interpretation

• Computation and processing of stimulus is already
  occurring at retinal level
• At no point after light stimulates receptor do we
  have a pure, uninterpreted image of the world
• Mammalian retina in some ways is more like
  invertebrate than frog.

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Problems

• Cats instead of monkeys
• Effects of anesthesia
• Problems with technique/technology
• Really recording from only one cell?
• Oversampling of large ganglion cells.
• Scattering of light inside of eye