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epileptogenic zone, the site of seizure origin (Figure 1, C). During the actual seizure, neurons then generate continuous high-frequency discharges over many seconds and recruit the surrounding neurons (ultimately adjacent cortical areas) into the seizure discharge. The continuous high-frequency discharge of many neurons creates a marked increase in the concentration of potassium ions and a decrease in the concentration of calcium ions within the extracellular fluid, which further increase neuronal excitability and promote seizure spread. The spread of the seizure discharge through the brain gives rise to the symptoms of an epileptic attack. Once a full-blown seizure begins, excitation may spread rapidly to adjacent cortex, to cortex in the opposite hemisphere, and to subcortical structures (Figure 4). The spread of the seizure reflects in part the strength of the connections of the epileptogenic zone to other brain sites. This spread of the discharge allows the focal seizure to generalize secondarily. When the
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  • Fall '15
  • temporal lobe, Seizure, motor cortex

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