Expansion of the half retinal projection to the tectum in goldfish: An electrophysiological and Anatomical study

The topographical retino-tectal projection of goldfish was electrophysiologically mapped at various intervals after surgical removal of the nasal half of the retina and pigment epithelium. The remaining projection was initially restricted to the appropriate rostral half of the tectum, even if the nerve was crushed and allowed to regenerate. But later, after 137 days or more, it showed a progressive expansion onto the foreign caudal half of the tectum. The magnification factor, the number of micrometers of tectum per degree in the visual field, doubled in the rostro-caudal but not in the medio-lateral direction. Analysis of the sequence of the expansion showed that a few fibers originally projecting nearest the denervated area were the first to spread over it. Then, progressively more fibers moved caudally until a nearly uniform representation of the half retina was established on the tectum. Radioautography also demonstrated that retinal fiber terminals had invaded the caudal tectum. The retinae of these fish were also examined histologically. The density of ganglion cells had not increased, but they consistently showed the axonal reaction. This was not found to be associated with any initial surgical trauma, but rather with the movement of their fiber terminals within the tectum. Frozen sections, through half retinal and normal eyes, were cut and photographed for comparison of ocular geometry. Operated eyes were normal except for a slight but consistent loss of ocular volume. Analysis of the optical geometry showed that recording with fish in air produced two effects: Myopia (10° blur circle, or less) and enlargement of the visual field by 15% to 20%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50003/1/901770206_ftp.pd

Relative modulation sensitivities of the red and green color mechanisms

The sensitivities of the human green and red cone mechanisms to sinusiodally flickering light were found to be near equal and independent of field size and estimation method. No wavelength dependency of modulation sensitivity was found. An observer who lacks the red cone pigment (protanope) did not show unusually high flicker sensitivity to green light of 525 nm. The modulation transfer function for the normal observer measured with a green flickering test on a red background is identical to that on a green background when the backgrounds have been equated for the green cones by the protanope. The same is true for the contrast transfer function of the normal observer when determined with a green grating on the red and green backgrounds equated by the protanope.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22781/1/0000336.pd

Opponent-process additivity--I: Red/green equilibria

A red/green equilibrium light is one which appears neither reddish nor greenish (i.e. either uniquely yellow, uniquely blue, or achromatic). A subset of spectral and nonspectral red/green equilibria was determined for several luminance levels, in order to test whether the set of all such equilibria is closed under linear color-mixture operations.The spectral loci of equilibrium yellow and blue showed either no variation or visually insignificant variation over a range of 1-2 log10 unit. There were no trends that were repeatable across observers. We concluded that spectral red/green equilibria are closed under scalar multiplication; consequently they are invariant hues relative to the Bezold-Brucke shift.The additive mixture of yellow and blue equilibrium wavelengths, in any luminance ratio, is also an equilibrium light. Small changes of the yellowish component of a mixture toward redness or greeness must be compensated by predictable changes of the bluish component of the mixture toward greenness or redness. We concluded that yellow and blue equilibria are complementary relative to an equilibrium white; that desaturation of a yellow or blue equilibrium light with such a white produces no Abney hue shift; and that the set of red/green equilibria is closed under general linear operations.One consequence is that the red/green chromatic-response function, measured by the Jameson-Hurvich technique of cancellation to equilibrium, is a linear function of the individual's color-matching coordinates. A second consequence of linear closure of equilibria is a strong constraint on the class of combination rules by which receptor outputs are recoded into the red/green opponent process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22247/1/0000683.pd

Control of eye movements while recording from single units in the pigmented rat

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23073/1/0000647.pd

Lateral spread of light adaptation in the rat retina

Recordings from the rat optic tract fibers were used to assess changes in sensitivity under various conditions of adaptation. An adapting background which excites only a small fraction of the rods can yet cause a several-fold change in sensitivity. A small adapting spot much more effectively decreases the cell's sensitivity to a superimposed test than to test spots in positions far from the adapting locus. Thus, adaptation spreads laterally but not uniformly throughout the ganglion cell center. Scattered light does not account for the spread, since a displaced adapting spot can be more effective than one superimposed on the test spot.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23063/1/0000635.pd