PT  - JOURNAL ARTICLE
AU  - L Federico Rossi
AU  - Robert C Wykes
AU  - Dimitri M Kullmann
AU  - Matteo Carandini
TI  - Focal cortical seizures start as standing waves and propagate respecting homotopic connectivity
AID  - 10.1101/080598
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 080598
4099  - http://biorxiv.org/content/early/2017/06/30/080598.short
4100  - http://biorxiv.org/content/early/2017/06/30/080598.full
AB  - Focal epilepsy involves excessive cortical activity that propagates both locally and distally. Does this propagation follow the same routes as normal cortical activity? We pharmacologically induced focal seizures in primary visual cortex (V1) of awake mice, and compared their propagation to the retinotopic organization of V1 and higher visual areas. We used simultaneous local field potential recordings and widefield imaging of a genetically encoded calcium indicator to measure prolonged seizures (ictal events) and brief interictal events. Both types of event are orders of magnitude larger than normal visual responses, and both start as standing waves: synchronous elevated activity in the V1 focus and in homotopic locations in higher areas, i.e. locations with matching retinotopic preference. Following this common beginning, however, seizures persist and propagate both locally and into homotopic distal regions, and eventually invade all of visual cortex and beyond. We conclude that seizure initiation resembles the initiation of interictal events, and seizure propagation respects the connectivity underlying normal visual processing.