A mechanism to explain zero-delay bilateral seizure synchronization.

Synchronization in bilateral CA3 regions via fimbria-fornix-hippocampal commissures system (FFHC) in rodent hippocampus has revealed that bilateral seizures can sometimes be synchronized with very small delays (< 1 ms). This observed small time delay at the start of afterdischarges between the left and right CA3 regions is unexpected given the propagation time across the hemispheres (> 6 ms). The possibility of a common source was first eliminated by in-vitro brain slices experiments. We then tested the hypothesis that, in the presence of noise, synchronization can take place before the seizure activity is sufficient large to be detected generating an apparent zero-delay between the two sides. This hypothesis was tested with computer simulation with a network of interconnected hippocampal neurons. These results provide an explanation for this aberrant simultaneous seizure detection and indicate the importance of noise in the interpretation of the timing of neuronal events.