The Journal of Neuroscience, April 1, 2002, 22(7):2626-2636
Spontaneous Retinal Activity Is Tonic and Does Not Drive Tectal
Activity during Activity-Dependent Refinement in Regeneration
Bradley J.
Kolls and
Ronald L.
Meyer
Department of Developmental and Cell Biology, University of
California, Irvine, California 92697
During development, waves of activity periodically spread across
retina to produce correlated activity that is thought to drive
activity-dependent ordering in optic fibers. We asked whether similar
waves of activity are produced in the retina of adult goldfish during
activity-dependent refinement by regenerating optic fibers.
Dual-electrode recordings of spontaneous activity were made at
different distances across retina but revealed no evidence of retinal
waves in normal retina or during regeneration. Retinal activity was
tonic and lacked the episodic bursting associated with waves.
Cross-correlation analysis showed that the correlated activity that was
normally restricted to near neighbors (typically seen across 100-200
µm and absent at >500 µm) was not altered during regeneration. The
only change associated with regeneration was a twofold reduction in
ganglion cell firing rates. Because spontaneous retinal activity is
known to be sufficient to generate refinement during regeneration in
goldfish, we examined its effect on tectal activity. In normal fish,
acutely eliminating retinal activity with TTX rapidly reduced tectal
unit activity by >90%. Surprisingly, during refinement at 4-6 weeks,
eliminating retinal activity had no detectable effect on tectal
activity. Similar results were obtained in recordings from torus
longitudinalis. After refinement at 3 months, tectal activity was again
highly dependent on ongoing retinal activity. We conclude that
spontaneous retinal activity drives tectal cells in normal fish
and after regeneration but not during activity-dependent
refinement. The implications of these results for the role of
presynaptic activity in refinement are considered.
Key words:
goldfish; retinotectal system; tectum; spontaneous
activity; regeneration; visual system; retinal activity; presynaptic
activity
Copyright © 2002 Society for Neuroscience 0270-6474/02/2272626-11$05.00/0