Neuroplasticity : A Science behind Learning

To understand how Mr Nishant Kashibhatla able to achieve this extraordinary feat we need to understand the basics and structure of brain and how it works.

Neuroplasticity is made up of two words: Neuro and plasticity. Neuro is a greek word related to nervous system where as plasticity means something which can change its shape very easily. Neuroplasticity means the ability of the brain to change itself throughout life. To understand it we need to understand the basic structure of nervous system.

Our Nervous system is divided into two parts: Central Nervous system and Peripheral Nervous system. We can correlate Nervous system with a circle which consists of a center and periphery. The Central Nervous system contains brain and spinal cord which are known as the command and control center of Nervous system. The Peripheral Nervous system carries the electric signal from sensory receptors to spinal cord and then to brain where it processes the signal move back to spinal cord then to the corresponding muscles and glands of sensory receptors. Our Central Nervous system is not known to be plastic initially unlike Peripheral Nervous system. If Peripheral nerve is cut it can heal itself with time.

Our brain is made up of neurons. These neurons are densely interconnected to each other. Let's draw an analogy to understand what it means. Suppose you were standing in the middle of Cricket ground and by extending yourself you can communicate with everyone present in that stadium. Substitute yourself with neurons and spectators with neighboring neurons.

A neuron is made up of three parts: Dendrite, Axon and cell body. Dendrite receives an electric signal from neighboring neurons. A cell body sustains the life of a cell and contains its DNA. Axons are usually compared with electric wires as they carry electric signal in them at a very high speed.

Dendrite receives two kinds of signals: Excitatory and Inhibitory. If a dendrite receives enough excitatory signal then it also fire itself by releasing its own electric signal. If dendrite receives inhibitory signal then it is less likely to fire. The Axon of a particular neuron is not directly connected to the dendrite of a neighboring neuron. There is a microscopic gap between the axon and the dendrite of a neighboring neuron known as synapse. When an electric signal reaches at the end of Axon it releases a chemical signal called neurotransmitter which moves through the synapse and reaches at the dendrite of the neighboring neuron. When we say neuron rewire itself it means strengthening and weakening of connection occur at synapse.

Dr. Wilder Penfield Neurosurgeon at Montreal Neurological Institute in 1930 made few remarks on Brain map. Brain map means where are the different parts of our body located in brain and how does our brain respond when an input is given to various parts of our body. Our frontal lobe is the main seat of sensory system. The three lobes behind it are occipital lobe, parietal lobe and temporal lobe. These lobes comprises the brain sensory system which processes the input coming from our sensory receptors.

A newly born baby's brain map is undifferentiated. As he gets stimulation from environment changes occur in his brain to make it differentiated. Time period in which brain map changes from undifferentiated state to differentiated brain is known as Critical period.

To test above hypothesis David Hubel and Torsten Wiesel did an experiment in John Hopkins on newly born kitten. During its Critical period they close its one eye so that it doesn't receive any stimulation from environment while the other eye remains open. They found that visual area of brain which doesn't receive any stimulation from environment has failed to develop itself leaving the kitten blind in that eye for its entire life. They also made an another remarkable discovery that brain map of closed eye doesn't sit idle and starts using the input from the open eye as if it doesn't want to waste its cortical real estate. They also got Noble prize for this experiment.

Competitive Plasticity

Merzenich(Neuroscientist) with his friend John Kass of Vanderbilt University in Nashville performed an experiment on adult monkeys which leads to the discovery of Competitive Plasticity.

A Monkey's hand consists of three nerves: Radial, Median and Ulnar nerve. They cut out its median nerve to prevent its brain map to get any input from middle part. After two months they observed to their surprise that as they touched its radial nerve its median nerve brain map also lit up leading to the discovery of Competitive Plasticity. It mean our brain works on the principle of use it or lose it.

If brain map is not used for long enough period of time then its brain map should be taken up by other brain maps. That is why if calculus(any skill) is not practiced for a long time we are more likely to forget it.

Competitive Plasticity also explains why bad habits are difficult to break? We think that brain is likely an empty vessel and acquiring new skills is like putting new things into an empty vessel which is a wrong concept. As we acquire any habit our brain maps gets stronger with every repetition. Changing old brain map with new one is very arduous and require lots of effort. That is why it's difficult to break or unlearn a habit. Hence, Childhood education is very important. It's better to start early before bad habit gets competitive advantage.

Merzenich with his friend Bill Jenkins performed various ingenious experiment which leads to following observations:

1. With training our brain maps become bigger. As time passes by individual neurons become more and more efficient and only few neurons are required to perform a given task. For example as we learn a new skill(Algebra). In the beginning we experience lot of strain while solving problems because our brain map is increasing its size. With enough practice we solve problems with much ease because brain map becomes more efficient with time.

2. Individual neurons got more selective with training.

3. As neurons are trained and become more selective then they can process faster. If you are practicing Algebra from a long time you can answer any question merely by looking at it.

4. When neurons fire faster then they give clear signal to our brain. In 1949 Canadian behavioral psychologist proposed a model which says if two neurons fire at the same time repeatedly (or firing of one neuron causes the other to fire) then they are more strongly connected to each other. If neurons fire faster then it's more likely to connect with neighboring neurons and their tendency to become better team player increases. Powerful signals have very great impact on our brain.

5. Paying close attention to something will bring lasting change in the brain.

In "Brain that Changes itself" Norman Doidge wrote, The difference between critical period plasticity and adult plasticity is that in the critical period the brain maps can be changed just by being exposed to the world because the learning machinery is continuously on. It makes biological sense for the machinery to be on because babies can't possibly know what will be important in life, so that they pay attention to everything. Only a brain that is somewhat organized can sort out what is worth paying attention to [...] Levi-Montalcini and Stanley Cohen isolated the protein responsible for nerve growth and called it Nerve Growth factor for which they receive Nobel Prize in 1986.

Brain-derived neurotrophic factor (BDNF) a one of the nerve growth factor plays a crucial role in reinforcing plastic changes in the brain in the critical period. According to Merzenich it did in four different ways.

When we perform an activity that requires specific neurons to fire together, they release BDNF. This growth factor consolidates the connection between those neurons and helps to wire them together so that they can fire together reliably in the future. BDNF also promotes the growth of the thin fatty coat around every neuron that speeds up the transmission of electric signal.

During the critical period BDNF turns on the nuclear basalis, the part of our brain that allow us to focus our attention- and keeps it on throughout the entire critical period. Once turned on, the nucleus basalis help us not only pay attention but remember what we are experiencing. It allows map differentiation and change to take place effortlessly. Merzenich told me, " It's like a teacher in the brain saying 'Now this is really important -this you have to know for the exam of life." Merzenich calls the nucleus basalis and the attention system the "modulatory control of plasticity" the neurochemical system that, when turned on, puts the brain in extremely plastic state.

The fourth and the final service that BDNF performs- when it has completed strengthening key connections- is to help close down the critical period. Once the main neural connections are laid down, there is a need for stability and hence less plasticity in the system. When BDNF is released in sufficient quantities, it turns off the nucleus basalis and end that magical epoch of effortless learning. Henceforth the nucleus can be activated only when something imporatnt, surprising or novel occurs or if we make the effort of close attention."

In "Peak", Anders Ericsson wrote "The years spent mastering the knowledge had enlarged precisely that part of the brain responsible for it.[...] The human body is incredibly adaptable. It is not just the skeletal muscles, but also the heart, lungs, circulatory system, the body energy stores and more-everything that goes into physical strength and stamina. There may be limits but there is no indication that we have reached them yet.[...] Homeostasis refers to the system of the body that acts in a way which preserves its own stability. When a body system - certain muscles, the cardiovascular system or something else is stressed to the point that homeostasis can no longer be maintained, the body respond with changes that are intended to reestablish homeostasis.

This is how the body's desire for homeostasis can be harnessed to drive changes: push it hard enough and for long enough, and it will respond by changing in a ways that make that push easier to do. You have gotten a little stronger, built a little more endurance, developed a little more coordination. But there is a catch: once the compensatory changes have occurred - new muscle fibers have grown and become more efficient, new capillaries have grown and so on-the body can handle that physical activity that had previously stressed it. It is comfortable again. The changes stop. So to keep the changes happening, you have to keep upping the ante: run faster, run faster, run uphill. If you don't keep pushing and pushing some more, the body will settle into homeostasis, albeit at a different level than before, and you will stop improving."

Spend each day trying to become a little wiser than you were when you woke up. Day by day and at the end of the day if you live long enough like most people, you will get out of life what you will deserve. Charlie Munger

Conclusion: Our traits are not fixed but keeps on changing throughout our life. During childhood we go through the period of intense learning. In middle age we don't push ourselves instead replaying our already mastered skills. We think we are improving but we aren't. So, challenge yourself, disrupt your homeostasis and become better an inch smarter everyday.

Happy Learning!!!