Abstracts

Summary: A bird's-eye view of neural network activity could answer fundamental questions about how seizures start and end, and clarify the differences between interictal and ictal activities. Ideally, this view would include information on the actions of every neuron. Activity-dependent dyes can provide such information from large arrays of cells (e.g. Trevelyan et al. J Neurosci 26:12447), but so far there are no perfect experimental designs. Each dye and imaging technique has unique advantages and disadvantages. The speakers will provide descriptions of their techniques, including pitfalls and potential applications, describe some interesting results, and discuss approaches. Kevin Staley will introduce the workshop and discuss the challenges of organizing and analyzing 3 dimensional datasets using examples from work with chloride and calcium-dependent dyes. Rosa Cossart will discuss calcium imaging of physiological and pathological synchronous discharges in the developing brain. She will show how the analysis of single cell calcium events combined to targeted electrophysiological recordings can help establish a functional connectivity map in cortical slices. In particular she will show how this experimental approach can help finding "hub neurons" with an exceptionally high number of connections playing a key role in synchronization dynamics. John White will describe a new microscopic technique, called targeted-path scanning (TPS), for activity-dependent imaging dozens of neurons simultaneously with single-cell resolution and high temporal resolution. Results from this technique suggest that epileptifom activity in brain slices of entorhinal cortex arises when the chloride gradient breaks down and GABA_A receptors become excitatory. Douglas Coulter will present data derived from voltage- and calcium imaging in hippocampal entorhinal cortical slices, which elucidate the spatiotemporal dynamics of synaptic and cellular activation within hippocampal circuits in epileptic animals. Audience participation should be a particularly important component of this workshop, so please come armed with questions and opinions.