How Do You Learn the Human Brain?

Our brain learns From the experiences: confronting our environment alters our behavior through the modification of our nervous system (Carlson, 2010).

Although we are still far from knowing exactly and at each level each of the neurochemical and physical mechanisms involved in this process, the different experimental evidences have accumulated a very broad knowledge about the mechanisms involved in the learning process.

How the brain learns

Brain Changes throughout our lives. The neurons that compose it can be modified as a consequence of different causes: the development; The suffering of some kind of brain injury ; Exposure to environmental stimulation and, fundamentally, as a consequence of learning (BNA, 2003).

Basic Characteristics of Brain Learning

Learning is an essential process which, together with the memory , Supposes the main means that the living beings have to adapt to the recurrent modifications of our environment.

We use the term learning to refer to the fact that experience produces changes in our nervous system (SN), which can be long lasting and involve a behavioral modification (Morgado, 2005).

Experiences in themselves change the way our organism perceives, acts, thinks, or plans through the modification of the SN, altering the circuits involved in these processes (Carlson, 2010).

Thus, at the same time that our organism interacts with the medium, the synaptic connections of our brain will undergo changes, new connections can be established, those that are useful in our behavioral repertoire will be strengthened or others that are not useful or efficient will disappear (BNA, 2003).

Therefore, if learning has to do with the changes that occur in our nervous system as a result of our experiences, when these changes are consolidated we can talk about memories. (Carlson, 2010). The memory is a Phenomenon inferred from those changes that occur in the SN and gives a sense of continuity to our lives (Morgado, 2005).

Due to the multiple forms of learning and memory systems, it is currently thought that the learning process and the formation of new memories depends on the synaptic plasticity, a phenomenon through which the neurons alter their communication capacity between them (BNA, 2003 ).

Types of Brain Learning

Before describing the brain mechanisms involved in the learning process , It will be necessary to characterize the different forms of learning, within which we can differentiate at least two basic types of learning: non-associative learning and associative learning.

Non-associative learning

Non-associative learning refers to the change in the functional response that occurs in response to the presentation of a single stimulus. Non-associative learning in turn can be of two types: Habituation Or sensitization (Bear et al., 2008).

  • Habituation : The repeated presentation of a stimulus produces a decrease in the intensity of the response to it (Bear et al., 2008).

Example: If I lived in a house with a single telephone. When it rings, it runs to answer the call, however, every time it does, the call is for another person. As this occurs repeatedly, you will stop reacting to the phone and you may even stop hearing it (Bear et al., 2008).

  • Sensitization : The presentation of a new or intense stimulus produces a response with an increased magnitude to all the following stimuli.

Example: Suppose you are walking down a sidewalk from a well-lit street at night, and suddenly a blackout occurs. Any new or strange stimuli that appear, such as hearing footsteps or seeing the headlights of a car approaching, will alter it. Sensory stimulation (blackout) led to sensitization, which intensifies its response to all of the following stimuli (Bear et al., 2008).

Associative learning

This type of learning is based on the establishment of associations between different stimuli or events. Within associative learning we can distinguish two subtypes: classical conditioning Y Instrumental conditioning (Bear et al., 2008).

  • Classical conditioning : In this type of learning the association between a stimulus that causes a response (unconditioned response or unconditioned response, RNC / RI), unconditioned or unconditioned stimulus (ENC / EI) and another stimulus that normally does not provoke the response, Conditioned stimulus (EC), and will require training. The matched presentation of the EC and the IE, will involve the presentation of the learned response (conditioned response, RC) to the trained stimulus. Conditioning will only occur if the stimuli are presented in a way Simultaneous or if the EC precedes the ENC in a very short time interval (Bear et al., 2008).

Example: An ENC / EC stimulus, in the case of dogs, may be a piece of meat. Upon visualization of the meat the dogs will emit a salivation response (RNC / RI). However, if a dog is presented as a stimulus the sound of a bell will not present any particular response. If we present both stimuli simultaneously or first the sound of the bell (EC) and then the meat, after a repeated training. The sound will be able to provoke the response of salivation, without being present the meat. There has been an association between food and meat. Sound (EC) is capable of causing a conditioned response (RC), salivation.

  • Instrumental conditioning : In this type of learning, one learns to associate an answer (motor act) with a meaningful stimulus (a reward). For instrumental conditioning to occur, it is necessary for the stimulus or reward to occur after the individual's response. In addition, motivation will also be an important factor. On the other hand, there will also be an instrumental type of conditioning if instead of a reward, the individual obtains a disappearance of a aversive valence stimulus (Bear et al., 2008).

Example: If we introduce a hungry rat into a box with a lever that will provide food, when exploring the box the rat will press the lever (motor act) and notice that food appears (reward). After performing this action more times, the rat will associate the lever pressure with obtaining food. Therefore, you will press the lever until it is satiated (Bear et al., 2008).

Neurochemistry of brain learning

Empowerment and depression

As we have previously mentioned, it is thought that learning and memory depend on processes of Synaptic plasticity .

Thus, different studies have shown that learning processes (among which are described above) and memory, lead to changes in synaptic connectivity that alter the strength and ability of communication between neurons.

These changes in connectivity would be the result of molecular and cellular mechanisms that regulate this activity as a consequence of excitation and neuronal inhibition that regulates structural plasticity. Thus, one of the main characteristics of Synapses Excitatory and inhibitory factors is the high level of variability in its morphology and stability that occurs as a consequence of its activity and the passage of time (Caroni et al., 2012).

Scientists specializing in this area are particularly interested in long-term changes in synaptic strength as a result of long-term potentiation (PLP) and long-term depression (DLP).

  • Long-term potentiation : An increase of the synaptic force occurs as a consequence of the stimulation or repeated activation of the synaptic connection. Therefore, a consistent response will appear to the presence of the stimulus, as in the case of sensitization.
  • Long-Term Depression (DLP) : An increase of the synaptic force occurs as a consequence of the absence of the repeated activation of the synaptic connection. Therefore, the magnitude of the response to the stimulus will be less or even zero. We could say that there is a process of habituation.

Habituation and awareness

Early experimental studies interested in identifying the neural changes that underlie learning and memory used simple forms of learning such as habituation, sensitization, or classical conditioning.

In this scenario, the American scientist Eric Kandel Focused his studies on the reflex of gill retraction of the California Aplysia, starting from the premise that the neural structures are analogous between these and the superior systems.

These studies provided first evidence that memory and learning are mediated by the plasticity of synaptic connections between neurons involved in behavior, revealing that learning leads to profound structural changes accompanying memory storage (Mayford et al. Al., 2012).

Kandel, like Ramón y Cajal , Concludes that synaptic connections are not immutable and that structural and / or anatomical changes form the basis of memory storage (Mayford et al., 2012).

In the context of neurochemical learning mechanisms, different events will occur for both habituation and sensitization.

Habituation

As mentioned above, the habituation consists in the decrease of the intensity of the response, consequence of the repeated presentation of a stimulus. When a stimulus is sensed by the sensory neuron, an excitatory potential is generated that allows an effective response.

As the stimulus repeats, the excitatory potential decreases progressively until it finally fails to exceed the minimum discharge threshold needed to generate a potential of Postsynaptic action , Which makes possible the contraction of the muscle.

The reason why this excitatory potential decreases is because, by continually repeating the stimulus, there is an increasing output of potassium ions (K + ), Which in turn leads to the closure of the calcium channels (Ca 2+ ), Which prevents the ingress of calcium ions. Therefore, this process is produced by a decrease in the release of glutamate (Mayford et al, 2012).

Sensitization

Sensitization is a more complex form of learning than habituation, in which an intense stimulus produces an exaggerated response to all the following stimuli, even to those that previously caused little or no response, which can also be seen in the retraction reflex Of the Aplysia gill, caused by an excess of glutamate release in the presence of a new stimulus (Mayford et al, 2012).

Despite being a basic form of learning, it presents different stages, both short and long term. While short-term sensitization would involve rapid and dynamic synaptic changes, long-term sensitization would lead to lasting and stable changes resulting from profound structural changes.

In this sense, in the presence of the sensitizing stimulus (intense or new) will occur a release of glutamate , When the amount released by the presynaptic terminal is excessive, it will activate postsynaptic AMPA receptors.

This fact allows the entry of Na2 + into the postsynaptic neuron allowing its depolarization as well as the release of NMDA receptors, which until now were blocked by Mg2 + ions, both events will allow a massive entry of Ca2 + into the postsynaptic neuron.

If the sensitizing stimulus occurs continuously, it will cause a persistent increase in the Ca2 + input, which will activate different Kinases , Giving rise to the implementation of the early expression of genetic factors and the synthesis of proteins. All this will lead to structural changes in the long term.

Therefore, the fundamental difference between both processes is in the synthesis of proteins. In the first case, in short-term sensitization, its action is not necessary for it to occur, whereas in the long-term sensitization it is essential that a synthesis of proteins is produced to produce lasting and stable changes that have As a goal the training and maintenance of new learning.

Consolidation of learning in the brain

Learning and memory are the result of structural changes that occur as a consequence of synaptic plasticity.

In order for these structural changes to occur, a long-term potentiation or synaptic strength consolidation process must be maintained.

As in the induction of long-term sensitization, both protein synthesis and expression of genetic factors are required which will lead to structural changes. For these events to occur, a number of molecular factors must occur:

  • The persistent increase in Ca 2+ entry in the terminal will activate different kinases, giving rise to the early expression of Genetic factors and protein synthesis that will lead to the induction of new AMPA receptors that will be inserted into the membrane and will maintain PLP.

These molecular events will result in alteration of the size and dendritic form, being able to give increases or decreases in the number of dendritic spines of certain zones.

In addition to these localized changes, current research has shown that changes also occur globally, since the brain acts as a unified system. Therefore, these structural changes are the basis of learning, in addition, when these changes tend to last in time, we will be speaking of memory.

References

  1. (2008). In B. N. association, & BNA, Neuroscience. Science of the brain. An introduction for young students. Liverpool.
  2. Bear, M., Connors, B., & Paradiso, M. (2008). Neuroscience: exploring the brain. Philadelphia: Lippincott Wiliams & Wilkings.
  3. Caroni, P., Donato, F., & Muller, D. (2012). Structural plasticity upon learning: regulation and functions. Nature, 13 , 478-490.
  4. Fundamentals of behavioral physiology. (2010). In N. Carlson. Cambridge: Cambridge University Press.
  5. Mayford, M., Siegelbaum, S.A., & Kandel, E.R. (s.f.). Synapses and Memory Storage.
  6. Morgado, L. (2005). Psychobiology of learning and memory: foundations and recent advances. Rev Neurol, 40 (5), 258-297.


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