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Abstract

Spontaneous network activity constitutes a central theme during the
development of neuronal circuitry [1, 2]. Before the onset of vision,
retinal neurons generate waves of spontaneous activity that are relayed
along the ascending visual pathway [3, 4] and shape activity patterns
in these regions [5, 6]. The spatiotemporal nature of retinal waves is
required to establish precise functional maps in higher visual areas,
and their disruption results in enlarged axonal projection areas (e.g.,
[7-10]). However, how retinal inputs shape network dynamics in the
visual cortex on the cellular level is unknown. Using in vivo
two-photon calcium imaging, we identified two independently occurring
patterns of network activity in the mouse primary visual cortex (V1)
before and at the onset of vision. Acute manipulations of spontaneous
retinal activity revealed that one type of network activity largely
originated in the retina and was characterized by low synchronicity
(L-) events. In addition, we identified a type of high synchronicity
(H-) events that required gap junction signaling but were independent
of retinal input. Moreover, the patterns differed in wave progression
and developmental profile. Our data suggest that different activity
patterns have complementary functions during the formation of synaptic
circuits in the developing visual cortex.