Bhargavi Bhattacharyya
Kolkata, India

How are the mind and brain related?

The brain is a ball of nerve cells, or neurons. The mind, the functional unit of the brain, includes imagination, perception, thinking, intelligence, judgment, language, memory, and emotions. How do these basic units, neurons, translate to mental faculty? Scientists wanted to look at the function of individual neurons, so they looked at how a cat’s neurons fire when looking at a flicker of light.¹ By doing this, they mapped the visual cortex, the part of the brain that sees.

But perception and sensation are not the same thing. The eyes, ears, nose, tongue, and skin are sense organs. They take in information from the world and send the raw information to the brain. That is sensation. The brain makes sense of it, which is called perception.

Two terms are important in understanding perception: top-down processing and bottom-up processing. Bottom-up processing is the way in which a child learns to perceive the world. He does not know what a table is because he has never seen a table. He looks at a structure with four pillars, a flat top, and a certain height. He learns that this is a table and then has a picture of a table in his head. Adults look at things with top-down processing. When they look at a table, they do not look at its individual features but rather immediately understand it is a table. They have seen tables before and they have the image stored in the head. Quickly, when they see a match, they recognize it as a table.

One of the first concepts that a child develops is object permanence. A four-month-old baby loses interest in a toy that is out of sight, but a nine-month-old baby does not. She knows that it is hidden somewhere and enjoys peekaboo games.

A child’s understanding of the world comes in stages.² The first stage is the sensorimotor stage, in which a child is making basic associations. If you shake a rattle, it makes noise. If you bite chocolate, it tastes sweet. If you touch the floor, it is cold and smooth. You use your fingers to pick up objects from the floor and put them in your mouth.

The next stage is the preoperational stage. Operation is a basic logical process. Children can now think about symbols and images, but their thinking is still magical, not logical. They feel everything has life. Children’s storybooks are full of talking animals like Winnie the Pooh or Tom and Jerry. Nothing is an accident. If they fall on the floor and hurt themselves, then the floor is intentionally trying to hurt them. And they are the center of the world. The moon follows them home at night.

Then comes the stage of concrete operations. Now they know that if two plus two is four, then four minus two is two. If you take dough and make six balls, it does not become more if you use the same dough to make ten balls.

The last milestone is the formal operational stage. If A implies B and B implies C, then C implies A. If all boys are pink, and Paula is a boy, then Paula is pink. A younger child would have argued vehemently that pink is the color of girls, and Paula is a girl’s name. At this stage they can think like adults and make logical connections that may be divorced from reality.

Scientists have done experiments in animals to see how vision develops.³ If a kitten’s eye is sutured shut for six months, there is an abnormally low number of reactive neurons in the eye that was shut and an abnormally high number of reactive neurons in the other eye. If the eyes of an adult cat were sutured shut for one year, it would have no effect on the brain of the cat that perceives vision.

Monkeys kept in darkness for the first six months of their lives⁴ when introduced into a normal environment cannot distinguish between squares and circles. Normal monkeys learn this within days. If you keep adult monkeys in darkness for prolonged periods, it has virtually no effect on the brain.

All this tells us that there is a critical period for the development of vision. If you are not exposed to objects during this time, you do not develop normal vision.

An unfortunate girl named Genie⁵ was a captive for thirteen years. She was not exposed to sound, so she did not have language. Later, she developed rudimentary language, but was never a fluent speaker.

Scientists have looked into the adult brains of people speaking different languages.⁶ The basic building blocks are the same, but there is a difference in how the dorsal and ventral tracts are organized. The former is stronger in Germans, the latter in English speakers. The Chinese language has many homophones and is heavily reliant on contextual information. The parietal cortex, which integrates visual inputs, is well-developed in Chinese speakers.

Another faculty of the mind is learning. We learn by forming associations. At the neural level, this means connections between nerve cells, or synapses. The strength of the association depends on prediction error. Prediction error⁷ is the mismatch between our expectations and observed reality. When the prediction error is greater, we learn more. The equation is: 𝛥V = 𝛂𝛃 (𝛌-𝚺V), where 𝚫V = change in associative strength, (𝛌-𝚺V) = prediction error or mismatch between expectancy and experience, and 𝛂𝛃 = learning rate parameters associated with cue and outcome respectively.

Our learning or strength of association depends on prediction errors, environmental factors, and learner factors. We learn better if something is relevant to us. Children’s schoolwork improves if they like the teacher and look forward to the class. If a child is interested in cars, it is likely that he will learn more about cars than about birds.

Learning occurs by classical conditioning⁸ and operant conditioning.⁹ The most famous experiment of classical conditioning is the dogs of Pavlov. Dogs normally salivate at the sight of food. All animals do. These dogs learned to salivate on hearing a bell. The bell was sounded just before food was served. They learned to make the association that the bell signals the arrival of food. Similarly, rats have been taught to press a lever to get food. This is operant conditioning, where you get a reward if you perform an action.

These two learning mechanisms can act together to perpetuate fears. If you are involved in a car accident, the loud bang, the road, the sight of blood on the road, and the car you were traveling in all get encoded in your mind. This is classical conditioning. If you start avoiding the road, the car, or anything that makes a loud noise, the fear will be perpetuated. Avoidance is instrumental conditioning.

Learning and memory are intimately connected. When we learn something, we commit it to memory. The synaptic connections get stronger with time and rehearsal. This is called long-term potentiation. Different parts of the brain store different memories.

Just imagine you are enjoying a meal. There is a part of the brain called amygdala¹⁰ that processes emotions, whether pleasurable or threatening. When enjoying the food, the amygdala sends signals to other parts of the brain that the food is good and enjoyable. Another part of the brain, the hippocampus, remembers information about the context. What is the name of the restaurant? Who am I with? What was the exact meal? It codes all information about the experience. The nucleus accumbens is involved with motor function. It uses the hands to take another helping. The prefrontal cortex is the last part of the loop. It takes all factors into consideration. Should I eat the meal? It will make me put on weight. If I eat too much I may have gastric problems later. It balances these factors and makes the final call.

Similarly, when threatened the amygdala goes into overdrive. The hippocampus encodes all information about the context where the threat occurred. The prefrontal cortex has to make the decision, whether the panic reaction was justified or not. It either calms down the amygdala if the threat is not serious, or tries to recruit other resources if the threat is serious.

Every individual is unique. The brain is an intricate and complex organ. Recent developments in neuroscience and computational approaches have transformed our conceptualization of the brain and helped unravel some of its mysteries. We can now make computational mathematical models and explore new horizons.

Notes and Bibliography

1. Hubel and Wiesel & the Neural Basis of Visual Perception https://knowingneurons.com/2014/10/29/hubel-and-wiesel-the-neural-basis-of-visual-perception/
2. The 4 Stages of Cognitive Development: Background and Key Concepts of Piaget’s Theory https://www.verywellmind.com/piagets-stages-of-cognitive-development-2795457 Piaget
3. David H. Hubel and Torsten N. Wiesel’s Research on Optical Development in Kittens https://embryo.asu.edu/pages/david-h-hubel-and-torsten-n-wiesels-research-optical-development-kittens
4. Visual acuity and visual responsiveness in dark-reared monkeys (Macaca nemestrina) https://www.sciencedirect.com/science/article/abs/pii/0042698976900341
5. Genie (Feral child) https://en.wikipedia.org/wiki/Genie_(feral_child)
6. Big Ideas in Cognitive Neuroscience, CNS 2017: Angela Friederici https://www.youtube.com/watch?v=1dfKX-OvjKs&ab_channel=CognitiveNeuroscienceSociety
7. Neural coding of prediction Errors https://www.cnbc.cmu.edu/~tai/readings/nature/schultz_prediction.pdf
8. Classical Conditioning https://www.simplypsychology.org/classical-conditioning.html
9. Operant conditioning https://www.simplypsychology.org/operant-conditioning.html
10. Neuroscience lab: Reward pathway https://www.nncionline.org/course/neuroscience-lab-reward-pathway/