Memory is a function that allows you to keep and return something that you have learned before consciously. It is better to talk about accumulative memories. According to Tulving's model, humans present five memory systems. These different types of memory interact in them but depend on distinct brain regions. Thus some patients may have some forms of memories preserved and others altered. There are three temporal categories of memories i.e., sensory memory, working memory, and long-term memory.
The sensory memory is the ability to keep an element in memory between 200 milliseconds to three seconds through visual perception and auditory perception. Sense organs transmit information to certain brain areas where they are analyzed very briefly. This is how you can remember what you saw, touched, and said.
Working memory or short-term memory is the second category that will allow the mind to retain information during tasks. They are processed for storage by long-term memory. The central administrator controls the operations when we use elements from other regions of the brain. The two neural loops, visual and phonological, temporarily store the data before the next task erases it.
The most classic example of working memory is the search for an object that has been lost while avoiding places where it is well known that it will not be! It includes the structure of the prefrontal cortex and the parietal cortex.
Long-term memory is the third category of temporal memory that results from lasting storage within certain areas of the brain. It can be subdivided into declarative and non-declarative memory.
1. Declarative memory or explicit memory is based on a record of cultural or general knowledge that an individual can consciously emerge with semantic memory. Thus the mere fact that a man walked on the moon may have been related to our own lives but is stored as an element of knowledge. The semantic memory concerns the temporal and frontal lobe:
At the same time, explicit memory deals with personal memories dated and localized with episodic memory. The regions of the brain involved in episodic memory depend on the content of the original experience. Thus the rather visual experiences activate the visual areas of the brain, whereas to remember the voice of a person asks the auditory cortex rather. Episodic memory involves the structure of the hippocampus, frontal lobe, and cortical regions:
2. Non-declarative memory, called procedural or implicit memory, is not accessible to consciousness contrary to declarative memory. These are memories that concern associations and know-how such as cycling. These gestures are learned through their repetition and then stored in long-term procedural memory. It does not require a conscious reminder of learning gestures.
It envelops the cerebellum, the caudate nucleus, and the putamen.
We have all these different forms of memory, but we are not equal to memory.
To understand how memory works, we must already understand the functioning of the brain, a fascinating but extremely complicated organ, since inside a cranial box, we find almost 100 billion neurons.
But what does a neuron look like?
A neuron is a nerve cell: a nucleus, surrounded by numerous small extensions (dendrites) that receive nerve impulses, and a long extension (the axon) through which the nerve impulse flows, to other cells. The length of the axon can vary from a few millimeters to more than one meter.
To explain the relationship between neurons and memory, let's take an example. When a human learns a new word, there is somewhere in the brain, a group of neurons that activates. An electric current then passes from one neuron to another.
And when it comes to finding the word learned, we automatically activate the same network of neurons, which will connect with each other in the same way as the first day the word was learned.
Thus, the more one makes his neurons work, the faster the connections will be made.
There is no "one" center of memory in the brain. The different memory systems involve separate neural networks distributed in different areas of the brain. Functional Imaging (CT by positron emission, functional magnetic resonance imaging) now allows brain function to be observed as normal involved in cognitive processes.
Thus, the role of the hippocampus and frontal lobe appears to be particularly important in episodic memory, with preponderant roles of the left and right prefrontal cortex in its encoding and recovery, respectively. Perceptual memory recruits networks in different cortical regions, near sensory areas. Semantic memory involves extensive regions, particularly the temporal and parietal lobes. Finally, procedural memory recruits subcortical and cerebellar neural networks.
The storage phase of the information requires repeated consolidation steps. The hippocampus appears to be an important element in the process. Finally, the restitution of memory, whatever its age, would also rest on this brain structure, interacting with different neocortical regions. However, it would be less solicited when the recall comes from semantic memory rather than episodic memory.
The ability to maintain memory and cope with lesions seems variable from one individual to another. Indeed, it has been described that equivalent brain damage in imaging; all do not present the same cognitive impairment. These abilities would depend on the cerebral reserve, relative to brain tissue, and the cognitive reserve, which is based on its functionality.
According to different studies, an increased brain volume, or a high number of neurons or synapses is associated with a later onset of dementia. At equivalent lesions, those with greater brain reserve would have less severe disorders. This brain reserve is under the influence of genetic and probably environmental parameters.
The cognitive reserve corresponds to the efficiency of the neural networks involved in the realization of a task and that of the brain to mobilize or set up compensatory networks. It also results in variability, from one subject to another, in the tolerance of identical brain lesions. Indeed, the available data suggest that the richness of the interactions and the level of education are associated with a later onset of cognitive disorders or Alzheimer's.
The constitution of the cognitive reserve could depend on:
- the importance of learning
- level of education
- intellectual stimulation throughout life
- the quality of social relations
- of food
- some sleep
- genetic parameters would also likely be involved
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Dec 26, 2019