2-Minute Neuroscience: Epilepsy

Epilepsy is a chronic condition characterized by recurrent seizures. Seizures are characterized by excessive neural activity, which is caused by both increased action potential firing rates and increased synchronous firing (i.e. many neurons fire action potentials at the same time). When seizures originate in one area of the brain, they are known as focal seizures. Alternatively, when seizure activity occurs in widespread areas of the brain all at once, it is referred to as a generalized seizure. In this video I discuss these types of seizures and the abnormal brain activity that is associated with them.

TRANSCRIPT:

Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss epilepsy.

Epilepsy is a chronic condition that is characterized by recurrent seizures; seizures are temporary disruptions of normal brain activity caused by excessive neural activity. Epilepsy can have genetic and acquired causes, but in most cases the cause is not known. Seizures can look drastically different depending on the patient, ranging from a brief and subtle interruption in consciousness to violent convulsions.

One characteristic seizures have in common, however, is excessive neural activity. In a healthy brain, different groups of neurons are all firing action potentials at different times. During a seizure, however, firing rates are increased and groups of neurons all fire at the same time, leading to large spikes in neural activity.

In seizures called focal seizures, this excessive activity begins in one specific area of the brain called the seizure focus, but it can also propagate to other areas of the brain. Neurons that are in the seizure focus experience a large and long-lasting depolarization followed by the firing of a train of action potentials. This abnormal activity is referred to as a paroxysmal depolarizing shift. The unusual activity is normally confined to the area it originated in, but during a seizure it can spread due to the failure of inhibitory mechanisms, leading to widespread abnormalities in brain function.

In seizures called generalized seizures, excessive activity seems to arise in widespread areas of the brain all at once. Although the mechanisms underlying this are not fully understood, generalized seizures may involve a pervasive hyperexcitability of neurons throughout the cortex along with abnormalities in neural networks that connect the thalamus to the cortex.

REFERENCE:

Purves D, Augustine GJ, Fitzpatrick D, Hall WC, Lamantia AS, McNamara JO, White LE. Neuroscience. 4th ed. Sunderland, MA. Sinauer Associates; 2008.