[Abstract Title]. - Society for Neuroscience

Support: DFG SFB 509
Title: Development of the neural substrate of the optokinetic reflex in macaque monkeys
Authors: *C. DISTLER, K.-P. HOFFMANN;
Dept Zoology & Neurobiol, Ruhr Univ. Bochum, D-44780 Bochum, Germany
Abstract: In infant macaques, monocular horizontal OKR (mhOKR) can be elicited both in
temporo-nasal and, at lower gain, in naso-temporal direction already shortly after birth.
Symmetry depends on stimulus velocity: mhOKR at low stimulus velocities becomes
symmetrical at about 3 weeks of age, at higher stimulus velocities it reaches symmetry at about
4-5 months of age (Distler, Vital-Durand, Korte, Korbmacher, Hoffmann, Vis Res. 39: 3909-
3919, 1999).
We recorded from retinal slip neurons in the nucleus of the optic tract and dorsal terminal
nucleus (NOT-DTN) of 4 anaesthetized and paralyzed infant macaques (age: P9, P12, P14, P60).
As in adults, retinal slip neurons in the NOT-DTN were already direction selective for
ipsiversive stimulus movement shortly after birth (P9). The large majority (96%) of NOT-DTN
neurons in P9, P12 and P14 were binocular (OD groups 2, 3, and 4). However, more neurons
were dominated by the contralateral eye (OD group 2) in infants than in adults which could
explain the mild asymmetry of mhOKR at that age. Already in the youngest animals, NOT-DTN
neurons responded well to different stimulus velocities, their velocity tuning, however, was
narrower than in adults, trunkated towards low stimulus velocities.
Already at P12, electrical stimulation in V1 elicited orthodromic responses both in the superior
colliculus and the NOT-DTN. However, the incidence of orthodromically activated neurons was
much lower in infants (40-60% of the tested NOT-DTN neurons) than in adults (97%).
Orthodromic latencies from V1 were significantly longer in P14 (x=12.2ms ± 8.9) than in adults
(x=3.51ms±0.81). By contrast, electrical stimulation in motion sensitive area MT was
significantly more efficient in activating NOT-DTN neurons (80% of the tested cells) and
yielded shorter latencies than V1 (x= 7.8ms ± 3.02; adult x= 2.99ms ± 0.85).
Thus, cortical input in addition to bilateral retinal input to retinal slip neurons in the NOT-DTN
is present at latest at 2 weeks after birth. The lower incidence of orthodromically activated cells
and the long latencies indicate that the cortical projection to the NOT-DTN is quite immature at
that point. The projection from motion sensitive are MT is more efficient than that from V1.
Disclosures: C. Distler , None; K. Hoffmann, None.
Poster
264. Eye Movements: Smooth Pursuit
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 264.12/DD29