Aura
A sensation sometimes experienced before a tonic clonic seizure . It can be anything from a sound, smell, feeling, taste, change in body temperature or disturbance in vision. Auras can occur hours / days before a tonic clonic seizure, given the person enough warning to take necessary action e.g. lie down to prevent injury.

The type of aura experienced varies from person to person, because auras are themselves simple partial seizures. They are not always followed by a tonic clonic seizure, but where this does happen, it is known as a
secondary generalised seizure.

Cortical dysplasia
A congenital abnormality, whereby the neuron networks in a particular area of the brain fail to form properly during development, and some neurons grow to be larger than normal in certain regions. This causes the signals sent through these neurons to misfire, which can lead to seizures.

Gap junction
A specialized connection between certain types of cell, which allows ions such as calcium (Ca2+), sodium (Na+) and potassium (K+) to pass freely between cells.

Gene expression
The process whereby the information held in a gene is used to create a functioning protein (gene product). If a gene is under-expressed, less of the gene product will be produced than normal, whereas if the gene is over-expressed, more of the product will be formed than normal.

Hemichannel
A gap junction is made of two hemichannels, which connect to each other across the space between the two cells.

Hippocampus
This is an important memory centre in the brain, located on the inner part of the temporal lobe.

Ion channels
Pores that help to control electrical activity in cells, by allowing the flow of ions such as calcium (Ca2+), sodium (Na+) and potassium (K+) into or out of the cell. A channel that allows the passage of potassium is known as a potassium channel and so forth.

Neurons
Excitable cells that are a core component of the brain and spinal cord. Neurons receive, process and transmit information, and they play a vital role in all of our functions. Information travels down neurons as electrical signals, which are created by the movement of ions into and out of the cell membrane, via ion channels.

The image below shows the structure of a neuron:

Neurotransmitter
A chemical that carries signals between a neuron and another cell, across a synapse.

A neurotransmitter is stored in a small package at the end of a neuron, near the edge of a synapse. On the surface of the next cell are special receptors for the neurotransmitter. When the neurotransmitter combines to its receptor, a chain of events is triggered that causes the signal to be transferred over.

A neurotransmitter can be excitatory, meaning that it triggers the next cell to become active; or inhibitory, meaning that it suppresses activity in the next cell.

The major excitatory neurotransmitter in the brain is called glutamate, whilst the main inhibitory neurotransmitter is known as GABA.

Receptor
A structure or site, found on the surface of a cell or within a cell, that can bind to a particular hormone, antigen or neurotransmitter. The binding of a substance to its receptor begins a chain of biochemical reactions that lead to changes in the cell. For example it might cause an influx of a particular ion, of a change in enzyme activity.

Refractory epilepsy
When two or more anti-epileptic drugs have failed to control a person's seizures, and he / she has experienced at least one seizure per month for 18 months.

If the neurotransmitter released into a synapse is excitatory, the synapse is called an excitatory synapse. if the neurotransmitter released is inhibitory, the synapse is known as an inhibitory synapse.

Thalamus