The hippocampus deals largely with memory consolidation, where information from the working memory and short-term memory is encoded into long-term storage for future retrieval. Amnesic patients with damage to the hippocampus are able to demonstrate some degree of unimpaired semantic memory, despite a loss of episodic memory, due to spared parahippocampal cortex. In other words, retrograde amnesics "know" about information or skill, but cannot "remember" how they do. The diencephalon and the surrounding areas role in memory is not well understood. However, this structure appears to be involved in episodic memory recall. The temporal lobes are essential for semantic and factual memory processing. Aside from helping to consolidate memory with the hippocampus, the temporal lobes are extremely important for semantic memory. Damage to this region of the brain can result in the impaired organization and categorization of verbal material, disturbance of language comprehension, and impaired long-term memory. The right frontal lobe is critical for the retrieval of episodic information, while the left frontal region is more active for the retrieval of semantic information. [56] Lesions in the right hemisphere and right frontal lobes result in the impaired recall of non-verbal material, such as music and drawings. Difficulties in studying this region of the brain extends to its duties in comprehension, naming objects, verbal memory, and other language functions.Brain plasticity has helped explain the recovery process of brain damage induced retrograde amnesia, where neuro-structures use different neural pathways to avoid the damaged areas while still performing their tasks.
Reactionary disturbances effect emotional and motivational responses as well, but reflect the failure to cope with environmental demands. Someone with this might withdraw from the environment that they are placed in because they no longer know how to handle the cognitive resources. Nutritional deficiency
RA has been found among alcohol-dependent patients who have Korsakoffs syndrome. Korsakoffs syndrome patients develop retrograde amnesia due to a thiamine deficiency (lack of vitamin B1). Also, chronic alcohol use disorders are associated with a decrease in the volume of the left and right hippocampus.These patients regular diet consists mostly of hard alcohol intake, which lacks the necessary nutrients for typical development and maintenance. Therefore, after a prolonged time consuming primarily alcohol, these people undergo memory difficulties and ultimately develop RA. However, some of the drawbacks of using Korsakoff patients to study RA is the progressive nature of the illness and the unknown time of onset. Infections
Infections that pass the blood–brain barrier can cause brain damage (encephalitis), sometimes resulting in the onset of RA. In the case of patient SS, the infection led to focal or isolated retrograde amnesia where there was an absence of or limited AA. Brain scans show abnormalities in the bilateral medial temporal lobes, including two thirds of the hippocampal formation and the posterior part of the amygdala. Surgery
Henry Molaison had epilepsy that progressed and worsened by his late twenties. The severity of his condition caused him to undergo surgery in an effort to prevent his seizures.