  Epileptic seizures are considered as abnormally hypersynchronous neuronal
activities of the brain. Do hypersynchronous neuronal activities in a brain
region lead to seizure or the hypersynchronous activities take place due to the
progression of the seizure? We have examined the ECoG signals of 21 epileptic
patients consisting of 87 focal-onset seizures by three different measures
namely, phase synchronization, amplitude correlation and simultaneous
occurrence of peaks and troughs. Each of the measures indicates that for a
majority of the focal-onset seizures, synchronization or correlation or
simultaneity occurs towards the end of the seizure or even after the offset
rather than at the onset or in the beginning or during the progression of the
seizure. We also have outlined how extracellular acidosis caused due to the
seizure in the focal zone can induce synchrony in the seizure generating
network. This implies synchronization is an effect rather than the cause of a
significant number of pharmacologically intractable focal-onset seizures. Since
all the seizures that we have tested belong to the pharmacologically
intractable class, their termination through more coherent neuronal activities
may lead to new and effective ways of discovery and testing of drugs.
