How do connections in the brain become strengthened?

In this post, we are going to answer the question ‘’How do connections in the brain become strengthened?’’ We explain the brain processes involved in this process and how they interact with each other to lead to learning.

How do connections in the brain become strengthened?

Connections in the brain are strengthened through practice. Every time an action is repeated, the specific neural network is activated.

Neuroplasticity, also known as brain or neuronal plasticity, is the concept that refers to the way in which our nervous system changes from its interaction with the environment.

Not even in the case of monozygotic twins this interaction is identical, which means that each person perceives the world and acts on it in a different way, depending on the sequence of contexts in which they live.

In addition, neural plasticity is not something that takes a long time to occur: it happens constantly, in real time, and even while we sleep. We are constantly receiving a torrent of stimuli and we are emitting a constant flow of actions that modify the environment, and all these processes cause our brain to change.

To understand it in a simple way, we can think of what the term “plasticity” refers to. The brain, like plastic, can adapt to almost any mold. However, in this comparison, two things must be qualified.

The first is that neuroplasticity depends on the intervention of an external intelligence that directs the fora modeling process towards a specific purpose (in the case of the example, the manufacturer of figures or plastic pieces), and the second is that, Unlike plastic, the structure and shape of the components of our brain can change a lot constantly: not just in a “manufacturing phase”.

How does brain plasticity occur?

Neuroplasticity is based on the way in which neurons in our nervous system connect to each other.

As the Spanish doctor Santiago Ramon y Cajal discovered, the brain is not made up of a tangle of compacted cells that form a single structure, but are microscopic bodies with autonomy and physically separated from each other that, are sending information without getting to join each other in a definitive way. They are, in short, morphological individualities.

When a group of neurons fire at the same time, they tend to send information to each other.

If this activation pattern is repeated with a certain frequency, these neurons not only send information to each other, but also tend to seek a more intense union with the others that are activated at the same time, becoming more predisposed to send information to each other.

This increased probability of firing together is physically expressed in the creation of more stable neuronal branches that unite these nerve cells and make them physically closer together, which modifies the microstructure of the nervous system.

For example, if the neurons that are activated when we recognize the visual patterns of a chocolate bar are “turned on” at the same time as those that are activated when we experience the taste of candy, both groups of nerve cells will connect a little more between yes, which will make our brain change even a little.

The same happens with any other experience: even if we do not notice it, we are constantly experiencing experiences (or, rather, small portions of experiences) that occur practically at the same time and that make some neurons strengthen their bonds more and others weaken them more.

This occurs both with sensations and with the evocation of memories and abstract ideas; the Halo Effect can be considered as an example of the latter.

Long-term potentiation: physiological bases of learning

Long-term potentiation is a process that occurs in the membrane of the neuron that explains how it is possible to establish learning and what its physiological bases are.

The process occurs when information is reviewed several times, causing the neuron to become sensitized and to become more reactive to lower action potentials, allowing it to more easily remember what has been learned.

How is long-term potentiation given?

The human brain has the ability to store information, both for short periods of time, in short-term memory, or for life, in long-term memory.

This can be verified, in a practical way, when we study for an exam. While we are studying, we activate various pathways inside our brain, pathways with which we manage to store, through repetition, the information we have reviewed. The more the information is reviewed, the more it will be retained.

Long-term memory has been mainly associated with a structure, whose shape resembles that of a seahorse: the hippocampus.

This brain structure is located in the medial temporal lobe of both hemispheres, and is responsible for coordinating the storage of information and the retrieval of memories. Research has focused on this part of the brain, when they have tried to study the learning process, especially its various structures: the dentate gyrus, the CA1 and the CA3.

The memorization process begins when information reaches the dentate gyrus from the entorhinal cortex. 

The axons of the granular neurons project their axons to the cells of the CA3 area, which in turn project the information through the so-called Schaffer collaterals to the cells of the CA1 field and, from there, the information returns to the subiculum. the entorhinal cortex.

This whole process is long-term empowerment, which is about the cellular and molecular process of memory. This long-term enhancement involves the lasting improvement of signal transmission between two neurons after repeated stimulation. This process has been mostly studied at the synapses between Schaffer’s collaterals and CA1 field neurons.

 Observing the synapses between CA3 and CA1 cells reveals multiple structures that are related to long-term potentiation. NMDA and AMPA receptors can be found in the postsynaptic neuron and are normally found together. 

These receptors are activated after the neurotransmitter fuses with the cell membrane and is released into the space between neurons.

The AMPA receptor is permeable to sodium ions, that is, it allows them to enter the interior of the neuron. The NMDA receptor is also permeable to sodium ions, but it is also permeable to calcium ions. NMDA receptors are blocked by a magnesium ion, which prevents the entry of sodium and calcium ions into the cell.

When an action potential travels along the presynaptic axon of Schaffer’s collaterals, glutamate is released, a neurotransmitter which fuses with AMPA and NMDA receptors. When that electrochemical stimulus is of low power, the amount of glutamate that is released is low.

The AMPA receptors open and a small amount of sodium enters the neuron, causing a small depolarization to occur, that is, increasing the electrical charge of the neuron. Glutamate also binds to NMDA receptors, but no ions will be able to cross it because the magnesium ion continues to block it.

When the received signal is small, the postsynaptic response is not sufficient to achieve the exit of the magnesium ion, so long-term potentiation does not occur.

This is a situation that can occur, for example, when you have been studying for a very short time. A high frequency of action potentials have not been activated as so little has been studied, which has not induced this process of knowledge retention.

On the other hand, when there is a high frequency of action potentials, traveling through the collateral axons of Schaffer, a greater amount of glutamate is released into the synaptic space.

This can be achieved if you study more, since it encourages a greater frequency in the action potentials. Glutamate will bind to AMPA receptors, causing a greater amount of sodium to enter the interior of the neuron because the channel remains open for longer.

Strengthening of synapses

Long-term potentiation is a process that involves strengthening the connection between two neurons. The introduction of calcium into the postsynaptic neuron acts as a second messenger, activating multiple intracellular processes.

The increase in calcium leads to two processes involved in long-term potentiation: the early phase and the late phase.

Early phase

During the early phase, calcium fuses with its fusion proteins, causing the insertion of new AMPA channels in the cell membrane of the synapse between the cells of the CA1 and CA3 field.

These new AMPA receptors were stored inside the neuron, and are only released thanks to the influx of calcium from the NMDA receptor. Thanks to this, AMPA channels will be available in future synaptic connections. The changes induced during the early phase only last a few hours.

Late phase

During the late phase, there is a greater influx of calcium, which causes the activation of genetic transcription factors that cause new proteins to be synthesized. Some of these proteins will end up being new AMPA receptors, which will be inserted into the neuronal membrane.

In addition, there is an increase in the synthesis of growth factor proteins, which lead to the growth of new synapses and are the basis of synaptic plasticity. Thus, in this way, the brain changes as it turns on.

These synapses form between the CA1 and CA3 neurons, allowing for a stronger connection. The late phase changes are more durable, ranging from 24 hours to a lifetime.

It should be noted that long-term potentiation is not a mechanism, but rather an increase in the activity between two neurons, which results in an increase in the AMPA channels of the neurons that will allow, even with low frequencies of action potentials, to create a cellular depolarization when, before, a high frequency of potentials was necessary to achieve such a goal.

This whole process is the foundation of memory. However, it should be noted that the hippocampus is not the only region where long-term potentiation occurs. 

Memory processing occurs in many other brain regions, including the cerebral cortex. Be that as it may, it must be clear that the more one studies, the more pathways are activated throughout the brain, making learning become more consolidated.

That between more sodium inside the cell causes the depolarization of it, managing to repel the magnesium ion from the NMDA receptor thanks to a process called electrostatic repulsion. 

At this point, the glutamate-activated NMDA receptor allows sodium and calcium to enter its pore. 

NMDA receptors are called voltage and ligand-dependent receptors because they require presynaptic and postsynaptic excitation for channel opening: fusion of released presynaptic glutamate and postsynaptic cell depolarization.

Hebb’s Law

Hebb’s proposal had a strong impact on neuropsychology, becoming the core of many approaches developed in subsequent decades, and it remains a very important reference in this field today.

In the early 1970s, the existence of a very relevant mechanism for learning was discovered: long-term enhancement, which consists of the consolidation of memories through repeated experience. Thus, short-term memory is based on structural changes (gene expression, protein synthesis, and changes in synapses).

The validation of this model supported Hebb’s fundamental thesis, determining the concrete biological bases that explain his law. Today we also know with certainty that long-term potentiation is limited exclusively to neurons that are active at the same time, and that if several synapses converge on the same neuron, they are strengthened even more.

One of the most recent applications of Hebb’s rule is related to mirror neurons, which are activated both when we perform a behavior and when we see another living being doing the same and are understood as the basis of empathy and the theory of the mind. Relevant synapses have been found to be strengthened following Hebb’s law.

FAQS: How do connections in the brain become strengthened?

How do you increase neural connections in the brain?

9 keys to exercising neurons

Practice neurobics. …

Don’t stand still. …

Eat with your head. …

Learn languages or music. …

Open yourself to others. …

Sleep like a baby …

Relieves tensions. …

Have a laugh.

How do you strengthen synaptic connections?

Reduce stress.

Stimulate your brain.

Exercise.

Challenge your mind.

How does the brain make new connections?

When engaged in new learning or experience, the brain establishes a series of neural connections.

What are connections in the brain called?

The synapse is the junction between a neuron and another cell (neuron or not). A very active place where things continually happen. There are two different types of synapse, the electrical synapse and the chemical synapse.

Can intelligence be improved?

Regardless of what is considered the standard for intelligence, it is undeniable that the brain is the key. Fortunately, the human brain has a great capacity for adaptation. Neural networks are expanded and strengthened through learning experiences.

In this post we answered the question ‘’How do connections in the brain become strengthened?’’ We explained the brain processes involved in this process and how they interact with each other to lead to learning.

If you have any questions or comments please let us know!

References

Abraham WC, Bear MF (1996): Metaplasticity, the plasticity of synaptic plasticity. Trends in Neuroscience,19,126-130

Agranoff BW, Uhler M (1994): Learning and memory. In: Basic Neurochemistry, Molecular, Cellular and Medical aspects, 5th Ed., ed. By GJ Siegel. Raven Press, N. York, 1025-1045.

Paradiso, Michael A.; Bear, Mark F.; Connors, Barry W. (2007). Neuroscience: Exploring the Brain. Hagerstwon, MD: Lippincott Williams & Wilkins.

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