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Forgetting Mechanism: Neurogenesis as a Neurobiological Explanation

Abdulwahab F. Alahmari
Radiology Department, Al-Namas General Hospital, Ministry of Health, Al-Namas City, Saudi Arabia.

Article Info

Received Date: 21 June 2024, Accepted Date: 29 June 2024, Published Date: 02 July 2024

*Corresponding author: Abdulwahab F. Alahmari, Radiology Department, Al-Namas General Hospital, Ministry of Health, Al-Namas City, Saudi Arabia.

Citation:  Abdulwahab F. Alahmari (2024). “Forgetting mechanism: Neurogenesis as a neurobiological explanation”. International Journal of Case Reports and Case Research, 1(1); DOI: http;//

Copyright: © 2024 Abdulwahab F. Alahmari. This is an open-access article distributed under the terms of the Creative Commons Attribution 4. 0 international License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


In the Arabic language, a human called (ٳنسان) pronounced “Ensaan” which means the creature who forgets. This word comes from the verb (نسي) pronounced “Naseaa” which means forgetting. Humans are forgetting creatures by nature for a reason. This paper will highlight the forgetting mechanism and the memory capacity of the human brain.

There are three stages in memory as highlighted below;

Encoding Storage Retrieval

Any issue in the encoding stage called “poor attention”, any issue in the storage stage called “forgetting”, and any issue in the retrieval called “availability or accessibility”.

Forgetting in the memory was explained in two ways; fading away or decay of memories, but there is no biological mechanism were used to explain how these memories, get forgotten. The only biological explanation is the documented change that occurs in the hippocampus knew as neurogenesis. Neurogenesis occurs in different parts of the brain, but mainly in the hippocampus.

Hippocampus has the dentate gyrus which generates neurons in mammals, not only humans. This dentate gyrus has a granule cell layer which generates these newborn neurons. The hippocampus is made by many layers folded on each other (i.e. dentate gyrus, cornu ammonis called “CA 1, 2, and 3”, subiculum, and entorinal cortex). Also, furthermore, the dentate gyrus has three layers: 1) sub granular zone (i.e. other call it “the hilus or polymorphic layer); 2) granular layer (i.e. with two limbs internal and external); and 3) molecular layer. The new neurons are generated in the granular layer then the neurons axon will extend to the hilus, and their dendrites will reach to the molecular layer. It takes 2 months for a newborn neuron to become an adult neuron. Sometimes these cells die with apoptosis in order to control the number of generated cells.

When a proper stimulus has been received the granular neurons will divide then break off and the new cell will migrate on the dentate gyrus and branch out to the CA3. The new neuron sends signals to other neurons in order to receive signals from them. it is suggested that these new neurons improve human’s memory, but that is wrong for many reasons.

When these neurons get destroyed in the process known as neurogenesis, the memories get destroyed as well. The new formed neurons generated without any memories (i.e. clean). With time passing, older neurons get destroyed and a brand-new neuron get formed to take their places. This mechanism of forgetting is an adaptation mechanism to allow humans to let go of bad old memories and get back again to live their lives. The idea of neurogenesis is part of the forgetting mechanism is easy to prove. When patient of Alzheimer's disease has a damage in the hippocampus then the hippocampus get shrinkage, they forget which indicates that these neurons in the hippocampus contains the human memory and when they get damaged the memories get lost. Similarly, in neurogenesis the old painful memories in the hippocampus get deleted with time passing in order to allow the human to function properly. Some claim when two similar memories get mixed up is another mechanism of forgetting or a group of people incorrectly remember the same memory which both are correct, but both are external reasons. But the biological reasons will be internal only.

Donald Thompson argues against eyewitness testimony to incriminates individuals and he present a model;

Leading Question Source Amnesia Misinformation Effect

Donald Thompson was a victim of eyewitness testimony when he was brought by the police -for no reason- then he was in line with criminals and a woman picked him. The woman accused him of rape, but Thompson had a good alibi to be on a TV show speaking about the weakness of eyewitness testimony in the same time that woman was raped and there was a TV showing the show where Thompson was speaking about a relevant topic “eyewitness testimony in crimes”. This story is ironic, but it shows how forgetting mechanism can be seen in certain conditions.  

Dan Schacter describe the memory’s malfunctions as “the seven sins” which are: 1) absent-mindedness; 2) transience; 3) blocking; 4) misattributing; 5) suggestibility; 6) bias; and 7) persistence.

Calcium waves in the brain start when remembering let say a phone number. Neural signal when repeating the number to memorize it, stimulate astrocyte calcium waves which increase the frequency due repetition of the earlier neural firing (Koob, 2009).


Diagram 1. Tulving’s model of long-term memory.

Diagram 2. Squire’s model of the explicit memory.

Diagram 3. Warrington and Weiskrantz (1974) who described the implicit memory and Endel Tulving (1972) who described the explicit memory. Both described parts of the long-term memory.

 Diagram 4. Warrington and Weiskrantz (1974) who described the implicit memory.

Diagram 5. Endel Tulving (1972) who described the explicit memory.


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