Acetylcholine: Neurotransmitter acting in  both the peripheral nervous system (PNS) and central nervous system (CNS). It is linked to memory and learning.

Axon: A long fiber of a nerve cell (a neuron) that acts somewhat like a fiber-optic cable carrying outgoing messages.

Cholinergic system : It is a neurotransmitter system involved in the regulation of memory and learning, acetylcholine is used for transmitting nerve impulses trough nerve cells.

COMPASS : acronym for Computerised Mental Performance Assessment System. It is a battery of tests to measure mood and cognitive performance.

Myelin: A white, fatty material, composed of lipids and lipoproteins, that surrounds  and protects the axons of nerves.

Neurotransmitter: substance which transmits a signal between a neuron and another cell. That signal can be modulated.