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How human memories are formed
Memory is the retention and ability to recall information “stored” in the brain. It is a concept that relates to the process of remembering rather than a physical object. Despite our scientific and technological advances, we still know very little about how memory works exactly, but the model generally accepted in cognitive psychology is the one that compares the brain to a computer (Figure 1). 4 major steps can be identified in the formation and access of memory: Encoding, consolidation, storage and recall/retrieval. Figure 1. Stage Model based on the work of Atkinson and Shiffrin (1968) Encoding Encoding is the first and most important step in the creation of new memories. The environment sends multiple messages in many forms including light, heat, smell and sound, but our brain can only understand ​
electrical energy​
. The body has special sensory receptor cells that convert the external stimuli to something that the brain is capable of understanding. We can identify four main types of encoding: Acoustic encoding Sound, words and other kinds of auditory input Visual encoding Tactile encoding Semantic encoding Images and visual The feeling of an sensory information object through the sense of touch Sensory input with a particular meaning or context Attention ​
increases neuronal activity, making the experience more intense and increasing the likelihood that the encoding of memory will be successful. Neurons are the cells in the brain that act as a method of transporting the pattern of signals that conform memory. The attention is regulated by the thalamus and the frontal lobe (Figure 2), and this is increased when the stimulus is interesting or it activates a known pattern. ​
Figure 2. Thalamus and frontal lobe Example: When reading a book, the eyes capture the information, which is then transformed into an electrical pulse. Since reading requires attention, most of the information will be encoded. Consolidation Consolidation is the process of stabilizing a memory trace after the initial acquisition. This process utilizes a phenomenon called long-term potentiation, which allows a synapse (Figure 3), a complex membrane junction used to transmit signals between cells, to increase in strength as the number of signals between neurons increases. Potentiation is the process by which synchronous firing of neurons makes them more likely to fire again in the future. Long-term potentiation occurs when a group of neurons fire together so often that they become “permanently wired together”, and the brain manages the organization of these connections. Figure 3. Synapse connection between cells As the connections forming a neural network are traversed over and over again, a pattern is created and neural messages are more likely to flow along those pathways. This process is achieved through the production of new proteins that rebuild synapses that would otherwise erode with time. The ​
repetition​
within ​
short-term memory​
allows information to be properly consolidated within memory, which can then be “stored” within ​
long-term memory​
. Example: The electrical pulse created from reading the book traverses a set of neurons, forming a pattern. This pattern can later be accessed to remember the contents of the book. Storage Storage refers to the passive process of retaining information within the ​
sensory​
, short-term​
, and ​
long-term memories​
. In order to keep us sane, these memories filter encoded information and ​
forget ​
whatever is not necessary. It should be noted that memories can be encoded and stored multiple times, so that if one of the memory patterns (remember that memories are not physically stored information, but rather a pattern that has to be reconstructed to access that information) is damaged, the information may be retrieved through an alternative pattern (Figure 4). Figure 4. Electric pulses can traverse many different neurons, forming many patterns and potentially creating unlimited memories. Memories previously stored may be ​
forgotten​
. There are many causes for ​
forgotten memories, like an incorrect retrieval cue that causes a certain memory to not be able to be accessed at a given time, or the natural ageing process that leads to neurons dying, destroying their associated memory patterns in the process, which results in a permanent inability to ​
retrieve​
those memories. Example: Particularly interesting parts of the book will be stored in long-term memory, whereas the rest will be temporarily stored in short-term memory before becoming a blurry memory. Recall/Retrieval Recalling or retrieving memories means re-accessing information that previously went through the steps of encoding, consolidation and storage. In this step, the brain replays the pattern of neural activity associated with the particular data, recreating the experience. However, this information is not identical to the original experience: a sense of awareness of the current situation is mixed in to distinguish the actual experience from the memory recall. A corollary of this is that memories can be manipulated by adding new information. When memories are ​
retrieved​
from ​
long-term memory​
, they are first sent to the short-term memory​
where the desired information may be manipulated before generating the final ​
response​
. A benefit of this is that the information may be reconsolidated before being sent back to the ​
long-term memory​
, making that particular memory stronger. It can be inferred from this that ​
short-term memory​
acts as a working table for memories/information, much like a computer’s RAM. We usually employ an organized mental structure of pre-conceived ideas of how the world functions, allowing us to obtain details from a vague memory. However, this may lead to memory errors as we associate events that did not happen. We identify three main types of recall: Free recall Cued recall Process in which a person is given a list of items to remember and recall in any order. Process in which a person is given a list of items to remember and is then tested with the use of cues or guides. Serial recall Ability to recall items or events in the order in which they occur in order to make sense of them. Example: After some time, when the reader wants to remember the contents of the book, the patterns stored in long-term memory will be retrieved and moved to short-term memory for access. Conclusion The human brain is still a mysterious organism that has yet to be fully explored. By developing these models of memory formation that explain how they are created and accessed, we come closer to understanding the function and limits of the brain. This in turn could allow us to comprehend and cure memory disorders such as Alzheimer’s disease. References Mastin, Luke. "Memory Processes - The Human Memory." ​
Memory Processes ­ The Human Memory​
. N.p., n.d. Web. 25 Mar. 2016. <http://www.human-memory.net/processes.html>. Huitt, W. "Educational Psychology Interactive: The Information Processing Approach." Educational Psychology Interactive: The Information Processing Approach.​
N.p., n.d. Web. 25 Mar. 2016. <http://www.edpsycinteractive.org/topics/cognition/infoproc.html>. Mohs, Richard C. "How Human Memory Works." ​
HowStuffWorks​
. HowStuffWorks.com, n.d. Web. 25 Mar. 2016. <http://science.howstuffworks.com/life/inside-the-mind/human-brain/human-memory.htm
>. Carroll, Robert Todd. "Memory." ​
­ The Skeptic's Dictionary.​
N.p., n.d. Web. 25 Mar. 2016. <http://www.skepdic.com/memory.html>. Images http://www.edpsycinteractive.org/topics/cognition/info.jpg https://scifeeds.com/wp-content/uploads/2015/12/4ccc2ecfFrontal-lobe-basal-ganglia-thala
mus-of-the-brain-by-Wikimedia-Commons-702x336.jpg http://study.com/cimages/multimages/16/Neuronal_Synapse.jpg http://www.ifc.unam.mx/Brain/gifs/neur5.jpg