Spontaneous and sensory-evoked activity propagates across spatial scales in the mammalian cortex but technical challenges have generally precluded establishing conceptual links between the function of local circuits of neurons and brain-wide network dynamics. To solve this problem, we developed a method for simultaneous cellular-resolution two-photon calcium imaging of a local microcircuit and mesoscopic widefield calcium imaging of the entire cortical mantle in awake, behaving mice. Our method employs an orthogonal axis design whereby the mesoscopic objective is oriented downward directly above the brain and the two-photon objective is oriented horizontally, with imaging performed through a glass right angle microprism implanted in the skull. In support of this method, we introduce a suite of analysis tools for relating the activity of individual cells to distal cortical areas, as well as a viral method for robust and widespread gene delivery in the juvenile mouse brain. We use these methods to characterize the diversity of associations of individual, genetically-defined neurons with cortex-wide network motifs.

Spontaneous and sensory-evoked activity propagates across varying spatial scales in the mammalian cortex, but technical challenges have limited conceptual links between the function of local neuronal circuits and brain-wide network dynamics. We present a method for simultaneous cellular-resolution two-photon calcium imaging of a local microcircuit and mesoscopic widefield calcium imaging of the entire cortical mantle in awake mice. Our multi-scale approach employs an orthogonal axis design where the mesoscopic objective is oriented above the brain and the twophoton objective is oriented horizontally, with imaging performed through a microprism. We also introduce a viral method for robust and widespread gene delivery in the mouse brain. These approaches allow us to identify the behavioral state-dependent functional connectivity of pyramidal neurons and vasoactive intestinal peptide (VIP)-expressing interneurons with long-Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

The ability to perceive and respond to environmental stimuli emerges in the absence of sensory experience. Spontaneous retinal activity prior to eye opening guides the refinement of retinotopy and eye-specific segregation in mammals, but its role in the development of higher-order visual response properties remains unclear. Here, we describe a transient window in neonatal mouse development during which the spatial propagation of spontaneous retinal waves resembles the optic flow pattern generated by forward self-motion. We show that wave directionality requires the same circuit components that form the adult direction-selective retinal circuit and that chronic disruption of wave directionality alters the development of direction-selective responses of superior colliculus neurons. These data demonstrate how the developing visual system patterns spontaneous activity to simulate ethologically relevant features of the external world and thereby instruct self-organization.

Convenient, efficient and fast whole-brain delivery of transgenes presents a persistent experimental challenge in neuroscience. Recent advances demonstrate whole-brain gene delivery by retro-orbital injection of virus, but slow and sparse expression and the large injection volumes required make this approach cumbersome, especially for developmental studies. We developed a novel method for efficient gene delivery across the central nervous system in neonatal mice and rats starting as early as P1 and persisting into adulthood. The method employs transverse sinus injections of 2–4 μL of AAV9 at P0. Here, we describe how to use this method to label and/or genetically manipulate cells in the neonatal rat and mouse brain. The protocol is fast, simple, can be readily adopted by any laboratory, and utilizes the widely available AAV9 capsid. The procedure is adaptable for diverse experimental applications ranging from biochemistry, anatomical and functional mapping, gene expression, silencing, and editing.

Hamodi AS, Pratt KG. Region-specific regulation of voltagegated intrinsic currents in the developing optic tectum of the Xenopus tadpole. J Neurophysiol 112: 1644 -1655, 2014. First published July 2, 2014; doi:10.1152/jn.00068.2014.-Across the rostrocaudal (RC) axis of the Xenopus tadpole optic tectum exists a developmental gradient. This gradient has served as a useful model to study many aspects of synapse and dendrite maturation. To compliment these studies, we characterized how the intrinsic excitability, the ease in which a neuron can fire action potentials, might also be changing across the same axis. Whole-cell recordings from tectal neurons at different points along the RC axis revealed a graded increase in intrinsic excitability: compared with neurons at the caudal end of the tectum, neurons at the rostral end fired more action potentials in response to current injection and expressed greater peak Na ϩ and K ϩ currents, the major intrinsic currents in these neurons that underlie the action potential. We also observed, along the same axis and in the same direction, a previously described increase in the amount of synaptic drive received by individual neurons (Wu GY, Malinow R, Cline HT. Science 274: [972][973][974][975][976] 1996). Thus as synaptic activity ramps up across the RC axis, so does intrinsic excitability. The reduction of overall circuit activity induced a compensatory scaling up of peak Na ϩ and K ϩ currents only in the caudal portion of the tectum, suggesting a region-specific, compensatory form of plasticity. development; instrinsic currents; optic tectum; region specific; Xenopus tadpole AT THE CAUDAL EDGE OF THE optic tectum of the Xenopus tadpole is a proliferative zone where progenitor cells give rise to tectal neurons. At a rate that is dependent on levels of visually driven activity, these newborn neurons migrate rostrally out of the proliferative zone and into the tectum proper, where they get incorporated into the functioning retinotectal circuit (Sharma and Cline 2010). As new members of the retinotectal circuit, they begin receiving direct synaptic input from retinal ganglion cells of the contralateral eye, the lateral line (via the brain stem), as well as other tectal neurons. This ongoing incorporation of newborn neurons from the proliferative zone creates a spatial developmental gradient, in which the most immature neurons are localized at the caudal end of the tectum, and the most mature are localized to the rostral end (Cline 2001;Lazar 1973;Wu et al. 1996). Many aspects of neural development have been described across this rostrocaudal (RC) axis: tectal neuron dendrites become increasingly complex and arborized (Wu et al. 1999), glutamatergic synapses gain ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (Wu et al. 1996), AMPA receptors gain glutamate receptor 2 (GluR2) subunits (Aizenman et al. 2002), spontaneous synaptic frequency increases (Wu et al. 1996), and GABAergic transmission becomes increasingly hyperpolarizing (Khakhalin and Aizenman 2012)....