Retinal slip neurons in the nucleus of the optic tract and dorsal terminal nucleus in cats with congenital
strabismus
C. Distler & K.-P. Hoffmann
Journal of Neurophysiology, 75:1483-1494, 1996
- 1. Visual response properties of neurons in the nucleus of the optic tract (NOT) and dorsal terminal nucleus
of the accessory optic tract (DTN) were electrophysiologically investigated in five congenitally strabismic cats
and compared to normal adult cats and 3-4 week old kittens.
2. As in normal cats, NOT-DTN cells of strabismic cats preferred horizontal ipsiversive stimulus movement. However,
NOT-DTN neurons in strabismic cats altered their activity to a lesser amount per degree change of stimulus direction
than do normal adult cats. In addition, NOT-DTN cells in strabismic cats exhibited a broader directional tuning,
i.e. they increase their activity to a broader range of directions than control NOT-DTN cells.
3. Spontaneous activity and activity difference between preferred and non-preferred direction were significantly
lower in NOT-DTN neurons of strabismic than in normal adult cats and resembled that found in 3 week old kittens.
Maximal stimulus related activity was lower than in normal adult cats but higher than in kittens.
4. Visual latencies to onset of movement in the preferred direction were indistinguishable in strabismic and in
normal adult cats. Visual latencies to onset of movement in the non-preferred direction, however, were shorter
in strabismic than in normal adult cats.
5. The average velocity tuning curve of NOT-DTN cells in strabismic cats was very flat without a well-defined optimal
stimulus velocity. Thus, it closely resembled data from 3 week old kittens.
6. Binocular convergence was significantly altered to a stronger dominance of the contralateral eye in NOT-DTN
of strabismic cats. This reduction of binocular neurons was less pronounced than in cats with artificially induced
strabismus or in 3 week old kittens.
7. In conclusion, the data presented here for retinal slip neurons in the NOT-DTN of strabismic cats closely resemble
those from 3 week old kittens where no functional cortical input to the NOT-DTN is present. However, the elevated
stimulus driven activity and the still relatively high degree of binocularity give a clear indication for a functional
albeit weak and abnormal cortical input to the NOT-DTN in these naturally strabismic cats.
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