title: Relationship between individual neuron and network spontaneous activity in developing mouse cortex.
abstract: Spontaneous synchronous activity (SSA) that propagates as electrical waves is found in numerous central nervous system structures and is critical for normal development, but the mechanisms of generation of such activity are not clear. In previous work, we showed that the ventrolateral piriform cortex is uniquely able to initiate SSA in contrast to the dorsal neocortex, which participates in, but does not initiate, SSA (Lischalk JW, Easton CR, Moody WJ. Dev Neurobiol 69: 407-414, 2009). In this study, we used Ca(2+) imaging of cultured embryonic day 18 to postnatal day 2 coronal slices (embryonic day 17 + 1-4 days in culture) of the mouse cortex to investigate the different activity patterns of individual neurons in these regions. In the piriform cortex where SSA is initiated, a higher proportion of neurons was active asynchronously between waves, and a larger number of groups of coactive cells was present compared with the dorsal cortex. When we applied GABA and glutamate synaptic antagonists, asynchronous activity and cellular clusters remained, while synchronous activity was eliminated, indicating that asynchronous activity is a result of cell-intrinsic properties that differ between these regions. To test the hypothesis that higher levels of cell-autonomous activity in the piriform cortex underlie its ability to initiate waves, we constructed a conductance-based network model in which three layers differed only in the proportion of neurons able to intrinsically generate bursting behavior. Simulations using this model demonstrated that a gradient of intrinsic excitability was sufficient to produce directionally propagating waves that replicated key experimental features, indicating that the higher level of cell-intrinsic activity in the piriform cortex may provide a substrate for SSA generation.
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington;
authors.forename: Heather M
authors.initials: HM
authors.lastname: Barnett
authors.affiliation: Center for Brain Science, Harvard University, Cambridge, Massachusetts;
authors.forename: Julijana
authors.initials: J
authors.lastname: Gjorgjieva
authors.affiliation: Undergraduate Neurobiology Program, University of Washington, Seattle, Washington; and.
authors.forename: Keiko
authors.initials: K
authors.lastname: Weir
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington; Undergraduate Neurobiology Program, University of Washington, Seattle, Washington; and.
authors.forename: Cara
authors.initials: C
authors.lastname: Comfort
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington; UW Institute for Neuroengineering, University of Washington, Seattle, Washington.
authors.forename: Adrienne L
authors.initials: AL
authors.lastname: Fairhall
authors.affiliation: Department of Biology, University of Washington, Seattle, Washington; profbill@u.washington.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Moody
mesh_terms: D000818:Animals; D058256:Brain Waves; D020013:Calcium Signaling; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000196:embryology / Q000502:physiology*; D003344:Cortical Synchronization; D054351:Electrical Synapses / Q000502:physiology; D051379:Mice; D008959:Models, Neurological; D009415:Nerve Net / Q000196:embryology / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D066195:Piriform Cortex / Q000196:embryology / Q000502:physiology; D013569:Synapses / Q000502:physiology; D061566:Voltage-Gated Sodium Channels / Q000502:physiology
chemical_list: D061566:Voltage-Gated Sodium Channels
keywords: activity-dependent development; cortex; piriform cortex; spontaneous activity