Emergence of dominant initiation sites for interictal spikes in rat neocortex

Abstract

populations with unbalanced inhibition can generate interictal spikes (ISs), where each IS starts from a small initiation site and then spreads activation across a larger area. We used in vivo voltage-sensitive dye imaging to map the initiation site of ISs in rat visual cortex disinhibited by epidural application of bicuculline methiodide. Immediately after the application of bicuculline, the IS initiation sites were widely distributed over the entire disinhibited area. After ϳ10 min, a small number of sites became "dominant" and initiated the majority of the ISs throughout the course of imaging. Such domination also occurred in cortical slices, which lack long-range connections between the cortex and subcortical structures. This domination of IS initiation sites may allow timing-related plasticity mechanisms to provide a spatial organization where connections projecting outward from the dominant initiation site become strengthened. Understanding the spatiotemporal organization of IS initiation sites may contribute to our understanding of epileptogenesis in its very early stages, because a dominant IS initiation site with strengthened outward connectivity may ultimately develop into a seizure focus.

Capturing remote activation of epilepsy source?

“…Before proceeding further, it is worth noting that similar phenomena, i.e. spontaneous PSs, their spatial nucleation, and related 'UP states' of network spiking have been repeatedly observed in organotypic brain slice cultures [93][94][95][96][97][98][99][100][101]. Unlike the cultured networks of initially dissociated neurons, these systems essentially retain the specific (and unknown) network connectome and cell-type neighborhood, and have relatively high cell density.…”

‘Blue’ voltage-sensitive dyes for studying spatiotemporal dynamics in the brain: visualizing cortical waves

“…2,[7][8][9][10][11] The VSD signals of spontaneous cortical activity are about 0.1% of the resting light intensity [ Fig. 2(b)], much smaller than the ∼0.5% of pulsation artifacts of a nonblue dye RH795 [ Fig.…”

“…1 Among many contributions to neuroscience achieved by the Grinvald group, the blue dyes have advanced the imaging of the mammalian cortex. [2][3][4][5][6][7][8][9][10] The excitation wavelength of blue dyes has minimal overlap with the absorption of hemoglobin, and hence has minimal pulsation artifacts. 1 This advantage leads to high signal-to-noise ratio optical recordings of cortical activity, with sensitivity as good as that of local field potential (LFP) recordings.…”