Some Controversies On The Theory Of Anterograde Amnesia
July 23, 2009
Semantic memory versus episodic memory:
Patients with Anterograde amnesia have tendency of an extensive variety of forgetfulness. Patients with this disease have declarative memory. Now, declarative memory gets additionally subdivided to “semantic” and “episodic” memory.
Episodic memory as the name suggests characterizes in remembering in episodes. This memory is medically or clinically illustrated as one which recollects all autobiographical information in a chronological or sequential context.
The Semantic memory however, follows the practice of reminding realistic information with a complete no link with the history, geography, or the language. For example there has been a patient who has anterograde amnesia which goes to back the childhood days.
In such a patient research demonstrates that the individual is successful in retaining the “semantic memory” wherein the same person suffers an extreme mutilation of the episodic memory.
The confusion is on the basis of something like this –whether the neural circuits that are parts of the episodic and the semantic memory overlap completely or partially or they are completely independent in their activities.
The above mentioned patient’s diencephalic, and the hippocampal structures on the left and right sides were detached. When the individual arrived for medication the primary complaint was that of forgetfulness that involved both episodic and semantic memory.
After performance of a series of “neuropsychological” examinations it was determined that the patient’s semantic memory is in a complete healthy condition. While the episodic part of the patient’s memory was far below average.
Nevertheless, the examination conducted here or the others outside have a vulnerability to subjectivity as there is no clear line separating semantic and episodic memory.
The similarity and the memory fractionation:
We already know that the right side of the hippocampus is responsible for the similarity in “spatial” tasks, wherein the left part of the hippocampus works for the similarity based recalling of the “verbal” tasks.
Now the problem began when some researchers have started to claim that hippocampus is the portion only responsible for recovery of memories, wherein the familiarity or similarity based memories are supported by the “adjacent cortical regions”.
Another incident of a patient who had a damaged “fornix” that left the hippocampus ineffective excluding the “adjacent cortical areas” -those were untouched. It can be stated as a one of its kind injury.
Now when the person faced a test which the individual contained certain similarities the person successfully scored well. However, in general it should be noted that this person had extremely damaged episodic memory, however with some capability of learning the semantic part.
Amnesia –what causes the devil to dwell and some different effects?
The disease amnesia has multiple root causes for its origin and existence in a human brain. In most cases we can trace the root cause to be that of brain damage associated with disease, physical trauma, alcohol abuse, drug, diminished flow of blood to brain –“vascular insufficiency”, and infection.
For example, the injury that takes place of the memory center of the brain can be a resultant of malnutrition, alcohol, or even infections infecting the brain and damaging it, like the herpes and encephalitis. If a state of amnesia has psychological origins is phrased “psychogenic”.
However, the most common associated factors leading to amnesia are brain damage from injury, or erosion of the cells in “dementia”. In all such cases it results in loss of the brain cells. And as the neural network connecting the cells inside brain is too complex these losses are irreversible.
Major brain hemorrhages occur due to brain injuries that result from car accidents or as a resultant of a blow or fall. These shocks lead to a confusing state with an often loss in memory.
I learned that anterograde amnesics have working procedural memory (in LTM) but not declarative (which is semantic and episodic)