Are New Neural Connections Formed Every Time We Learn? Neuroplasticity & Neurogenesis

Short answer: YES.
Long answer: Probably YES on most occasions as far as we know from laboratory experiments.

(I am saying ‘Probably Yes’ because not enough experiments are done to look for exceptions)
I’ll begin by introducing the idea of neurogenesis and then write about forming new neural connections. This post highlights the transition of cognitive aspects of learning as studied in psychology to the biological aspects of learning as studied in neuroscience.

Before we begin looking at the evidence, we should understand one term:

Plasticity: This is the ability of our biological brain to change over time. Plasticity or neuroplasticity or brain plasticity represents the change in the brain’s structure via new neurons and new neural connections.

The questions we are really addressing are: Is the brain plastic? If yes, is it always plastic? How plastic is the brain and to what degree are new neural connections formed?

Are new neural connections formed every time we learn something? 

Neurogenesis

This is the ability that lets the human body create new cells in the brain that later become neurons. In most of the currently published studies, neurogenesis occurs in the hippocampus regularly. Throughout adult life as well. Which is, surprise surprise, largely implicated in Memory and Learning. Perhaps the most conclusive evidence comes from:

You Can Grow New Brain Cells.

In one of the first studies to highlight the links between aerobics and neurogenesis, Rusty Gage of the Salk Institute examined new brain cell growth in mice. The ‘control’ mice had no running wheel in their cages, while the ‘runners’ were able to run in their cages regularly. In the snapshots below, from Gage’s experiment, the black dots are new neurons-to-be.

Neurogenesis: Are new neurons formed while learning?

Another study has demonstrated evidence for neurogenesis. Here is an excerpt.

Our study demonstrates that cell genesis occurs in human brains and that the human brain retains the potential for self-renewal throughout life. Although earlier studies in adult primates have been unsuccessful in showing neurogenesis in the dentate gyrus, a recent report has demonstrated neurogenesis in three-year-old marmoset monkeys.

So I will conclude that the brain, in fact, does facilitate the growth of new cells. 



But, for what purpose? To use them as back-up cells? Learning new things? 

Let us look at the evidence from a few more studies that suggest learning something new directly translates into biological changes in the form of neural connections.

A review of studies done by Tim Stephans suggests a number of things.

The researchers studied mice as they learned new behaviors, such as reaching through a slot to get a seed. They observed changes in the motor cortex, the brain layer that controls muscle movements, during the learning process. Specifically, they followed the growth of new “dendritic spines,” structures that form the connections (synapses) between nerve cells.

This clearly suggests that new connections are formed to accommodate the learning of said tasks. We are now talking about Synaptogenesis (synaptic plasticity) which is relatively better understood. New synapses are formed all throughout adulthood. One of the more famous aspects of synaptic plasticity is the saying “What fires together, wires together.” This is known as the Hebbian principle. If 2 neural circuits or individual neurons repeatedly fire together in response to some other signal, they are likely to form a connection between each other. This is where a correlation becomes a cause.

Research led by Yi Zuo (associate professor of molecular & developmental biology at the University of California, Santa Cruz) suggests that many new neurons emerge in clusters.

They observed new synapses being formed in the pyramidal neurons of the motor cortex and their growth strengthed as the mice learned their task. These neurons also persisted after the learning was discontinued. Thus, clearly suggesting that a cluster of new neurons were formed as a direct consequence of learning the task at hand.

In their research, they found out that repeating the task was positively correlated to the number of neurons in a cluster. Learning new tasks daily without continued practice led to the growth of new connections as well, but, in a spaced out form.

“We found very quick and robust synapse formation almost immediately, within one hour of the start of training,” said Yi Zuo, assistant professor of molecular, cell and developmental biology at UCSC.

Another study done on cab drivers from London who were extensively trained to learn 25,000 city streets had a very interesting finding. Researchers found out that their hippocampus was larger than untrained people.

These drivers went through with memorizing roads few at a time systematically for a number years and as a result, their hippocampus grew larger than untrained people! 

These research studies show that the brain is plastic and it underpins learning & memory.

The kicker: New research has now confirmed that neurogenesis occurs in the hippocampus of old humans, even in those brains which have Alzheimer’s. This has massive implications for what people can do to defend against cognitive impairment, old-age, and Alzheimer’s. Turns out you can teach an old dog new tricks and the brain is ready for that.


In conclusion, we can say 3 things:
1. New brain cells are constantly formed
2. Learning leads to newer connections in the brain
3. The brain is highly plastic


As for considering all types of different learning tasks, it may be premature to say that there will certainly be new neural connections. It’ll be great to have more experiments conducted on things like learning music, learning how to compute faster, speak multiple languages or even simple things like learning how to say the alphabet in reverse and learning the names of 10 new friends.

I am certainly inclined to subscribe to this conjecture: Learning new things requires brain re-wiring along with the formation and utilization of new neurons in a variety of ways.

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