Discharge Patterns and Functional Organization of Mammalian Retina Stephen W. Kuffler 1951

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

Theoretical Alternatives 1.The organization is different than that of the frog or limulus. 2.The organization is the same as that of the frog or the limulus 3.It is the same in some ways or different in others. -or more specifically...

Theoretical Alternatives Alternatives for the organization of the retina: Direct Indirect Overlap No overlap

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

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

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

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.

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”

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

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

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

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

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.

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