12/12/2023 0 Comments Global amnesia eventTake the case of a middle-aged man identified as JG, whose thalamic lesion expanded as he grew older. Similar to other forms of RA, the inability to recall past information characterizes the isolated form. Isolated RA is usually associated with a visible thalamic lesion. With focal RA, the details of a patient's life prior to amnesia onset can be reintroduced, but they are unable to recall how they perceived the experience. Although she could be re-taught information from her past, these memories were not episodic, but rather, semantic. Take a case study of a middle-aged female, for instance, who experienced focal RA after significant head trauma. When an individual experiences focal RA, a combination of their episodic and semantic memories may be affected. Slight differences in the use of these terms to describe a pure form of RA are summarized below:įocal RA generally results from neurological problems like epilepsy and is characterized by memory loss prior to – but not after – injury or disease onset. Focal, Isolated, and Pure RA Īn absence of anterograde amnesia (AA) characterizes pure forms of RA, which fall into three main categories: focal, isolated, and pure RA. Since more hippocampal traces are present for older memories, it is easier for older memories to remain intact when RA occurs. However, this theory has been challenged by the multiple-trace theory, which claims that the brain develops a hippocampal trace each time a memory is retrieved. Therefore, if an individual experiences RA that damages the hippocampus, they will lose more short-term memories according to this theory. As memory processing occurs in the brain over time, neocortical regions can directly communicate with each other, so they do not rely as heavily on the hippocampus for long-term memory storage. Initial theories proposed that the hippocampus and medial temporal lobe are not nearly as important for long-term memories compared to short-term memories. Debate has risen about why this temporal gradient forms in the first place. This type of RA is commonly triggered in individuals with Korsakoff syndrome due to a combination of long-term alcohol use and Wernicke encephalopathy. Memory loss in patients with temporally graded RA strongly follows Ribot's law, meaning that one will experience more memory loss for events closer to the injury or disease onset. Individuals with pure forms of RA like focal, isolated, and pure RA do not have anterograde amnesia (AA). Types Types of RA can be divided into two main categories: temporally graded RA and pure forms of RA. Diagnosing RA generally requires using an Autobiographical Memory Interview (AMI) and observing brain structure through magnetic resonance imaging (MRI), a computed tomography scan (CT), or electroencephalography (EEG). However, memory loss usually follows Ribot's law, which states that individuals are more likely to lose recent memories than older memories. Depending on its severity, RA can result in either temporally graded or more permanent memory loss. RA negatively affects an individual's episodic, autobiographical, and declarative memory, but they can still form new memories because RA leaves procedural memory intact. Although an individual can have both RA and AA at the same time, RA can also occur on its own this 'pure' form of RA can be further divided into three types: focal, isolated, and pure RA. RA differs from a similar condition called anterograde amnesia (AA), which is the inability to form new memories following injury or disease onset. In neurology, retrograde amnesia ( RA) is the inability to access memories or information from before an injury or disease occurred.
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