Overview of the forms and functions of memory.
Hippocampus (brain)

For example, anterograde amnesia, from damage of the medial temporal lobe, is an impairment of declarative memory that affects both episodic and semantic memory operations.

- Episodic memory

Furthermore, the data do not explain the dichotomy that exists in the MTL memory system between episodic memory and semantic memory (described below).

- Anterograde amnesia
Overview of the forms and functions of memory.

7 related topics

Alpha

Multi-store model: Atkinson and Shiffrin's (1968) original model of memory, consisting of the sensory register, short-term store, and long-term store.

Long-term memory

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.

Multi-store model: Atkinson and Shiffrin's (1968) original model of memory, consisting of the sensory register, short-term store, and long-term store.

Long-term memory is commonly labelled as explicit memory (declarative), as well as episodic memory, semantic memory, autobiographical memory, and implicit memory (procedural memory).

His subsequent total anterograde amnesia and partial retrograde amnesia provided the first evidence for the localization of memory function, and further clarified the differences between declarative and procedural memory.

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

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

People with extensive, bilateral hippocampal damage may experience anterograde amnesia: the inability to form and retain new memories.

Over the years, three main ideas of hippocampal function have dominated the literature: response inhibition, episodic memory, and spatial cognition.

Lobes of the human brain (temporal lobe is shown in green)

Temporal lobe

One of the four major lobes of the cerebral cortex in the brain of mammals.

One of the four major lobes of the cerebral cortex in the brain of mammals.

Lobes of the human brain (temporal lobe is shown in green)
Animation showing the position of the human left temporal lobe

Declarative (denotative) or explicit memory is conscious memory divided into semantic memory (facts) and episodic memory (events).

The medial temporal lobes include the hippocampi, which are essential for memory storage, therefore damage to this area can result in impairment in new memory formation leading to permanent or temporary anterograde amnesia.

Hippocampus as seen in red

Explicit memory

One of the two main types of long-term human memory, the other of which is implicit memory.

One of the two main types of long-term human memory, the other of which is implicit memory.

Hippocampus as seen in red
Amygdala as seen in red
The Morris water maze

Explicit memory can be divided into two categories: episodic memory, which stores specific personal experiences, and semantic memory, which stores factual information.

Guy Pearce plays an ex-insurance investigator suffering from severe anterograde amnesia caused by a head injury.

The line processes to make information memory

Memory consolidation

Category of processes that stabilize a memory trace after its initial acquisition.

Category of processes that stabilize a memory trace after its initial acquisition.

The line processes to make information memory
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Systematic studies of anterograde amnesia started to emerge in the 1960s and 1970s.

Multiple trace theory (MTT) builds on the distinction between semantic memory and episodic memory and addresses perceived shortcomings of the standard model with respect to the dependency of the hippocampus.

Amnesie

Amnesia

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.

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.

Amnesie

There are two main types of amnesia: retrograde amnesia and anterograde amnesia.

Retrograde amnesia is inability to recall memories before onset of amnesia. One may be able to encode new memories after the incident. Retrograde is usually caused by head trauma or brain damage to parts of the brain besides the hippocampus. The hippocampus is responsible for encoding new memory. Episodic memory is more likely to be affected than semantic memory. The damage is usually caused by head trauma, cerebrovascular accident, stroke, tumor, hypoxia, encephalitis, or chronic alcoholism. People with retrograde amnesia are more likely to remember general knowledge rather than specifics. Recent memories are less likely to be recovered, but older memories will be easier to recall due to strengthening over time. Retrograde amnesia is usually temporary and can be treated by exposing them to memories from the loss. Another type of consolidation (process by which memories become stable in the brain) occurs over much longer periods of time/days, weeks, months and years and likely involves transfer of information from the hippocampus to more permanent storage site in the cortex. The operation of this longer-term consolidation process is seen in the retrograde amnesia of patients with hippocampal damage who can recall memories from childhood relatively normally, but are impaired when recalling experiences that occurred just a few years prior to the time they became amnesic. (Kirwan et al.,2008)In the case of LSJ, her case shows that retrograde amnesia can affect many different parts of knowledge. LSJ was not able to remember things from her child or adult life. She was not able to remember things that most people pick up in everyday life such as logos or the names of common songs.

A representative column of neocortex. Cell body layers are labeled on the left, and fiber layers are labeled on the right.

Neocortex

Set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language.

Set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language.

A representative column of neocortex. Cell body layers are labeled on the left, and fiber layers are labeled on the right.

If damage is sustained to this area, patients do not develop anterograde amnesia and are able to recall episodic information.