A report on Amnesia

Amnesie

Deficit in memory caused by brain damage or disease, but it can also be caused temporarily by the use of various sedatives and hypnotic drugs.

- Amnesia
Amnesie

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Overall

Retrograde amnesia

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Loss of memory-access to events that occurred or information that was learned in the past.

Loss of memory-access to events that occurred or information that was learned in the past.

This would resemble generic amnesia.

Hippocampus (brain)

Anterograde amnesia

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Hippocampus (brain)

In neurology, anterograde amnesia is a loss of the ability to create new memories after the event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact.

Overview of the forms and functions of memory.

Memory

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Faculty of the mind by which data or information is encoded, stored, and retrieved when needed.

Faculty of the mind by which data or information is encoded, stored, and retrieved when needed.

Overview of the forms and functions of memory.
Olin Levi Warner, Memory (1896). Library of Congress Thomas Jefferson Building, Washington, D.C.
The working memory model
The garden of oblivion, illustration by Ephraim Moses Lilien.
Regulatory sequence in a promoter at a transcription start site with a paused RNA polymerase and a TOP2B-induced double-strand break
Brain regions involved in memory formation including medial prefrontal cortex (mPFC)
Regulatory sequence in a promoter at a transcription start site with a paused RNA polymerase and a TOP2B-induced double-strand break

Memory loss is usually described as forgetfulness or amnesia.

Long-term memory

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Stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely.

Stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely.

Research by Meulemans and Van der Linden (2003) found that amnesiac patients with damage to the medial temporal lobe performed more poorly on explicit learning tests than did healthy controls.

Humans have two hippocampi, one in each hemisphere of the brain. They are located in the medial temporal lobes of the cerebrum. In this lateral view of the human brain, the frontal lobe is at the left, the occipital lobe at the right, and the temporal and parietal lobes have largely been removed to reveal one of the hippocampi underneath.

Hippocampus

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Major component of the brain of humans and other vertebrates.

Major component of the brain of humans and other vertebrates.

Humans have two hippocampi, one in each hemisphere of the brain. They are located in the medial temporal lobes of the cerebrum. In this lateral view of the human brain, the frontal lobe is at the left, the occipital lobe at the right, and the temporal and parietal lobes have largely been removed to reveal one of the hippocampi underneath.
Image 1: The human hippocampus and fornix (left) compared with a seahorse (right)
Image 2: Cross-section of cerebral hemisphere showing structure and location of hippocampus
Image 3: Coronal section of the brain of a macaque monkey, showing hippocampus (circled)
Image 4: Basic circuit of the hippocampus, as drawn by Cajal DG: dentate gyrus. Sub: subiculum. EC: entorhinal cortex
Image 5: Hippocampal location and regions
Rats and cognitive maps
Image 6: Spatial firing patterns of 8 place cells recorded from the CA1 layer of a rat. The rat ran back and forth along an elevated track, stopping at each end to eat a small food reward. Dots indicate positions where action potentials were recorded, with color indicating which neuron emitted that action potential.
Image 7: Examples of rat hippocampal EEG and CA1 neural activity in the theta (awake/behaving) and LIA (slow-wave sleep) modes. Each plot shows 20 seconds of data, with a hippocampal EEG trace at the top, spike rasters from 40 simultaneously recorded CA1 pyramidal cells in the middle (each raster line represents a different cell), and a plot of running speed at the bottom. The top plot represents a time period during which the rat was actively searching for scattered food pellets. For the bottom plot the rat was asleep.
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Image 9: An EEG showing epilepsy right-hippocampal seizure onset
Image 10: An EEG showing epilepsy left-hippocampal seizure onset
Image 11: Drawing by Italian pathologist Camillo Golgi of a hippocampus stained using the silver nitrate method
thumb|Hippocampus highlighted in green on coronal T1 MRI images
thumb|Hippocampus highlighted in green on sagittal T1 MRI images
thumb|Hippocampus highlighted in green on transversal T1 MRI images

It is apparent that complete amnesia occurs only when both the hippocampus and the parahippocampus are damaged.

Short-term memory

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Capacity for holding a small amount of information in an active, readily available state for a short interval.

Capacity for holding a small amount of information in an active, readily available state for a short interval.

Patients with this form of amnesia have an intact ability to retain small amounts of information over short time scales (up to 30 seconds) but have little ability to form longer-term memories (illustrated by patient HM).

Thiamine

Korsakoff syndrome

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Thiamine

Korsakoff syndrome (KS) is a disorder of the central nervous system characterized by amnesia, deficits in explicit memory, and confabulation.

Episodic memory

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Memory of everyday events that can be explicitly stated or conjured.

Memory of everyday events that can be explicitly stated or conjured.

The label "amnesia" is most often given to patients with deficits in episodic memory.

Psychogenic amnesia

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Memory disorder characterized by sudden retrograde episodic memory loss, said to occur for a period of time ranging from hours to years to decades.

Memory disorder characterized by sudden retrograde episodic memory loss, said to occur for a period of time ranging from hours to years to decades.

Psychogenic amnesia is distinguished from organic amnesia in that it is supposed to result from a nonorganic cause: no structural brain damage or brain lesion should be evident but some form of psychological stress should precipitate the amnesia, however psychogenic amnesia as a memory disorder is controversial.

A common symptom of PTA is confusion.

Post-traumatic amnesia

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State of confusion that occurs immediately following a traumatic brain injury (TBI) in which the injured person is disoriented and unable to remember events that occur after the injury.

State of confusion that occurs immediately following a traumatic brain injury (TBI) in which the injured person is disoriented and unable to remember events that occur after the injury.

A common symptom of PTA is confusion.
Hippocampus (animation)
A Vasopressin molecule
Image from WWI, taken in an Australian dressing station near Ypres in 1917. The wounded soldier in the lower left of the photo has a dazed stare, a frequent symptom of "shell shock".
An elderly woman

There are two types of amnesia: retrograde amnesia (loss of memories that were formed shortly before the injury) and anterograde amnesia (problems with creating new memories after the injury has taken place).