In neurology, retrograde amnesia (RA) is a loss of memory-access to events that occurred or information that was learned in the past. It is caused by an injury or the onset of a disease. It tends to negatively affect episodic, autobiographical, and declarative memory, while keeping procedural memory intact without increasing difficulty for learning new information. RA can be temporally graded, or more permanent based on the severity of its cause. It is usually consistent with Ribot's law. The law states that subjects are more likely to lose memories closer to the traumatic incident than more memories that happened further from the incident. The type of information that is forgotten can range from a specific memory, such as a single event, or a more general memory. This would resemble generic amnesia. Anterograde amnesia is a similar condition that deals with the inability to form new memories following the onset of an injury or disease. Cause RA commonly results from damage to regions of the brain that are associated with episodic and declarative memory, including autobiographical information. In extreme cases, individuals may completely forget who they are. Generally, this is a more severe type of amnesia known as global, or generalized amnesia. However, memory loss can also be selective or categorical, manifested by a person's inability to remember events related to a specific incident or topic. Patients also differ in durations of RA (how long they can't recall information) and durations of what is forgotten (past time frame for which information is unavailable). Temporally graded retrograde amnesia In temporally graded retrograde amnesia, patients eventually recover most memories following the onset of RA. This suggests that the hippocampal formation/ consolidation, the process of coding new information, is only used in systematic consolidation for temporary storage, and short periods of time. Systemic consolidation then moves the information and long-term consolidation takes place in other brain structures. The fact that damage to the hippocampal formation can eventually overcome RA suggests that other brain structures are able to take over the jobs of the malfunctioning regions. RA can also progress and further deteriorate memory recollection, as in the case of Korsakoff syndrome and Alzheimer's disease, due to the ongoing nature of the damage caused by the illnesses. The degree to which different patients recover from RA differs in time (some take a few days while others a few decades) and content (some will only remember