Published online by Cambridge University Press: 15 April 2015
Early in development, before the onset of vision, the retina establishesdirection-selective responses. During this time period, the retina spontaneouslygenerates bursts of action potentials that propagate across its extent. Theprecise spatial and temporal properties of these “retinalwaves” have been implicated in the formation of retinal projectionsto the brain. However, their role in the development of direction selectivecircuits within the retina has not yet been determined. We addressed this issueby combining multielectrode array and cell-attached recordings to examine micethat lack the CaV3.2 subunit of T-type Ca2+ channels(CaV3.2 KO) because these mice exhibit disrupted waves during the period thatdirection selective circuits are established. We found that the spontaneousactivity of these mice displays wave-associated bursts of action potentials thatare altered from that of control mice: the frequency of these bursts issignificantly decreased and the firing rate within each burst is reduced.Moreover, the projection patterns of the retina demonstrate decreasedeye-specific segregation in the dorsal lateral geniculate nucleus (dLGN).However, after eye-opening, the direction selective responses of CaV3.2 KOdirection selective ganglion cells (DSGCs) are indistinguishable from those ofwild-type DSGCs. Our data indicate that although the temporal properties of theaction potential bursts associated with retinal waves are important foractivity-dependent refining of retinal projections to central targets, they arenot critical for establishing direction selectivity in the retina.