The neurology of memory and anterograde and retrograde amnesia IntroductionMemory is defined as "the mental capacity to encode, store and retrieve information" (American Psychological Association , 2002). It is part of the means by which human beings function. The process of forming and recalling memories involves various complex neurological processes, and disruptions to these processes can result in memory loss or the inability to form new memories. Amnesia is a memory disorder in which, due to trauma or a head injury, some parts of the memory are inaccessible. The two main types of amnesia are anterograde amnesia and retrograde amnesia. Anterograde amnesia refers to the inability to create new memories (Mastin, 2010). “Retrograde amnesia refers to the loss of memory for information acquired before the onset of amnesia” (Squire & Alvarez, 1995, p. 169). The purpose of this report is to explore the neurology of memory and the processes of encoding, consolidation, storage and retrieval, as well as briefly investigate the two main types of amnesia, anterograde and retrograde amnesia. Neurons and Memory The average brain has approximately 100 billion electrically excitable neurons, and these are the cells involved in the encoding, consolidation, storage, and retrieval of memory (Mastin, 2010). Neurons use electrochemical signals to process and transmit information. Neurons maintain voltage gradients across their membranes, driven by differences in concentrations of sodium, potassium, chloride, and calcium ions within the cell, each of which contains different charges (Mastin, 2010). An electrochemical impulse called an action potential is generated when this voltage gradient changes significantly (Mastin, 2010). This impulse travels rapidly along…the middle of the paper…consolidation, retrograde amnesia, and the hippocampal complex,” Current Opinion in Neurobiology, vol. 7, pp. 217-227, viewed May 11, 2014, .Shrager & Squire , 2008, Amnesia, Scholarpedia, viewed May 11, 2014, Sprenger, 1999, Learning & Memory: The Brain in Action, Association for Supervision and Curriculum Development (ASCD), USA. Squire & Alvarez, 1995, "Retrograde amnesia and memory consolidation: a neurobiological perspective", Current Opinion in Neurobiology, vol. 167, accessed 11 May 2014, (electronic PubMed Central, 2006, 'Chapter 5: encoding and retrieval from long-term memory', consulted on 11 May 2014, .