Global Hyper-synchronous Spontaneous Activity in the Developing Optic Tectum

Abstract

Studies of patterned spontaneous activity can elucidate how the organization of neural circuits emerges. Using in vivo two-photon Ca2+ imaging, we studied spatio-temporal patterns of spontaneous activity in the optic tectum of Xenopus tadpoles. We found rhythmic patterns of global synchronous spontaneous activity between neurons, which depends on visual experience and developmental stage. By contrast, synchronous spontaneous activity between non-neuronal cells is mediated more locally. To understand the source of the neuronal spontaneous activity, input to the tectum was systematically removed. Whereas removing input from the visual or mechanosensory system alone had little effect on patterned spontaneous activity, removing input from both systems drastically altered it. These results suggest that either input is sufficient to maintain the intrinsically generated spontaneous activity and that patterned spontaneous activity results from input from multisensory systems. Thus, the amphibian midbrain differs from the mammalian visual system, whose spontaneous activity is controlled by retinal waves.

Emergence of Selectivity to Looming Stimuli in a Spiking Network Model of the Optic Tectum

“…It is known that principal neurons in the tectum receive strong recurrent excitation (Pratt et al, 2008; Liu et al, 2016) that supports spontaneous neuronal activity during development (Pratt and Aizenman, 2007; Imaizumi et al, 2013; James et al, 2015). Principal tectal neurons also demonstrate prominent and rapid inactivation of spiking (Aizenman et al, 2003; Ciarleglio et al, 2015), which allowed us to suggest that together these two phenomena may underlie, or at least contribute to collision detection (Khakhalin et al, 2014).…”

Modeling human neurodevelopmental disorders in theXenopustadpole: from mechanisms to therapeutic targets

“…Time-lapse imaging of radial glia in the tectum has provided the first in vivo description of how neural activity affects the structure and function of these cells (Tremblay et al, 2009), and advances in morphometric software (Liu et al, 2009; Chen et al, 2012) have allowed for an improved ability to track and measure all processes in 3D across short intervals over long periods of time (Hossain et al, 2012). Furthermore, calcium imaging in tadpoles can be carried out readily (Tao et al, 2001; Junek et al, 2010; Xu et al, 2011), including in vivo recordings from intact awake animals (Chen et al, 2012; Podgorski et al, 2012; Imaizumi et al, 2013). Expression of genes of interest can also be achieved in vivo , using electroporation-based protocols (Haas et al, 2001; Haas et al, 2002; Bestman et al, 2006), or by mRNA injection into appropriate cells of the early embryo (Demarque and Spitzer, 2010).…”