Understanding our brain and the sensory system

Your toddler begins to learn through his senses from the day he is born. In fact, from shortly after conception, his senses are already developing. His sensory system is the very special part of his nervous system that receives and processes information in the brain. It is through this process that his brain will grown and develop, although it does not really follow a single master plan. His brain is constantly growing and changing and also, importantly, develops an amazing ability to organise itself.

Your toddlers sensory system is the door to his learning and knowledge, because how he learns, feels and thinks is dependant on his sensory system, through which all his experiences of the world are processed. Isn’t it amazing to think that his memory base patterns are forming and developing as he grows and experiences his sensory environment in greater and greater detail?

His sensory system and how he interprets it, shapes his experience of his world, whilst similarly, his sensory system is shaped by his experiences of the world.

As you are reading these words, your brain is constantly monitoring the sounds, smells, temperature and light around you. It knows which muscles are tense, which are relaxed and where they all are. Your brain is monitoring all your bodily organs’ function, as well as every touch and pressure on your body, whilst at the same time making constant muscle adjustments to keep your eyes and your body aligned to the book in front of you. It enables you to read the words on the page, then integrate and understand each word and meaning , in its context, so that you may benefit from the experience – wow, isn’t that simply amazing ?

What your toddler knows, what he feels, what he thinks and what he learns; is moulded by how he knows, how he feels, how he thinks and how he learns. In other words, all of what he experiences in his life, will help him to develop his brain.

The Brain – the brain is made up of nerves. Most of us are born with a full complement of nerve cells (neurons). These neurons are specialised cells to specifically transmit electrical messages throughout the body. This process of nerve cells connecting and networking is the very basis of learning and thought. For those of you that have read Baby Sense you will know that when your baby was a newborn, his brain was very immature and he was very limited as to what he could do. As he continued to grow, develop and learn from his world, the cells of his nervous system (neurons) began to connect in complex patterns of neural pathways. These amazing patterns are constantly being organized and reorganized throughout his life, allowing him to grow and develop. The brains main function is to be in continuous communication with the rest of our body, and most importantly, to receive information from the environment (via our sensory system), to then decide whether this is important or relevant information, and then to interpret that information so that an appropriate response can occur.
 
The Sensory System – We all live in a sensory rich world. We take in information from the world through our senses, and then, once our brain has integrated, or processed this information, we are then able to act on it (for example removing our hand from a hot surface). The sensory neurons (or nerve cells) deliver sensory information from the body to the brain and spinal cord (Central Nervous System). Did you know that there are five times as many nerves in the brain that are there to receive and organize this sensory information than there are nerves responsible for movement? (Baby Sense pg 12). Your toddlers sensory input will be delivered to his body externally via his skin (touch), his tongue (taste), his ears (hearing), his eyes (visual) and his nose (smell). He also has some internal input from his body senses – these give him information about his internal world these are called proprioceptors and are found throughout tendons, joints and muscles. Interoception is information from all the organs of the body ( such as having a full tummy), and the other internal sense is that of the vestibular sense which is the sense of movement – this sense organ is located in the mechanism of the inner ear.

 

Follow us on a journey of the senses to see how your toddler is interpreting his world via his sensory system.
Sight: The eyes see light, colour and objects. When his sense of sight matured at around 8 months of age, he became capable of being able to see from near to far, as well as to perceive dimension and depth. His eyes are in constant motion gathering sensory information to build up images necessary for learning. When he stops moving his eyes, they will no longer take in any sensory information – the only processing happening then is actually inside his brain (this is why when a child fixates and stares at something hard, he is missing what is happening in his environment!). His eyes will become the trusted window to his world.

Smell: The sense of smell is controlled by receptors in the nose. Billions of tiny hair cells inside the bridge of the nose (which sit right under the frontal lobe of the brain) stimulate nerves to perceive any smells in the environment. Sensations from the nose are the only ones that go directly to the emotional centre of our brain – that is why smell is strongly linked to memory and why it plays an important role in learning. Think of a situation when a smell in the air immediately brings back a flood of memories. Smell is also used to alert us to danger. Pheromones (a type of hormone) is released when one is afraid – these release a scent which can be picked up by animals and children.

Taste: The sense of taste is closely linked to smell. A foetus’ sense of smell and taste is functional from 28 weeks of gestation. Your toddler’s taste buds (or taste receptors) are situated all over his tongue, and they are there to monitor all substances that come into contact with his tongue. Different receptors are sensitive to sweet, sour, bitter and salty tastes.

Hearing: We know that a foetus’ sense of hearing is fully developed by 28 weeks of gestation. Since it is one of his earliest senses to develop, hearing is important for him as it alerts his brain to incoming stimulus, whether for protection or understanding – all of which assists in the learning process by identifying where the sound comes from and then attaching a meaning to each sound. Sound is carried on airwaves and picked up and registered by receptors found in the ear. Martie Pieterse in her book “School readiness through play – Metz Press 2001” says that a child who is able to hear and listen well learns faster, makes fewer mistakes, and is less easily frustrated.
 
Touch: Touch is an integral, natural part of life. Our skin contains touch receptors which give us information about pain, pressure (deep and light), and temperature and also tells us what our bodies are up to (via our muscles, tendons and movement). The sense of touch is closely linked to our emotions; it tells us whether we are being threatened or comforted. Touch is a strong anchor in behaviour and learning, so much so that the absence of touch can slow down nerve development leading to dysfunction of development, and even death. (Smart Moves: pages 39 -41). Touch also plays an important role in full understanding of vision – for example, a toddler will always say “let me see that” whilst reaching out to touch an object.

Movement: (vestibular sense) This is the first sensory system to fully develop in-utero (by 5 months of gestation). This sense controls our sense of movement and balance. Receptors in the inner ear sense changes of our position in space, more specifically, movement of our head in space. When this sense is working well, we know which direction we are moving in, how fast, and whether we are speeding up or slowing down. When it functions optimally, we don’t become nauseous or feel threatened by normal movement. (Baby Sense, page 12). The connection between the vestibular system and the brain is crucial – if we do not move to activate and stimulate this system, we will be unable to take in any information from our environment, this is necessary in order to stimulate our brain for learning. The vestibular system is tied to the muscles of the abdomen and back which are the backbone of all motor activity, so obviously any activation of the vestibular system enables a baby to move from primitive reflexive movement at birth, gaining a sense of gravity by learning to sit, stand, and walk by the time they have turned one year of age. From this basic sense of understanding gravity, your toddler will develop his balancing skills as he grows (such as learning to walk on a plank).

Body Position (proprioception):  Proprioception is the sense of body position and equilibrium. It is often referred to as “the sixth or secret sense” Proprioceptors are sense organs that relay information from our joints and muscles – whether they are tense or relaxed, and whether they are busy or still- to give the body a sense of itself in space. It is important to our body to know what position we are in and how our limbs are moving. These proprioceptors are found in all our muscles, joints, tendons and in the inner ear. Proprioception gives your toddler the necessary feedback to his brain to maintain optimal muscle contraction and relaxation for balance in his environment. (Smart Moves pg 43).  Proprioception plays a significant role in his awareness of his world, and in his ability to understand and learn by allowing his proprioceptors to be his learning tools whilst he explores his environment through his “muscle sense”.

Interoception: This is the sense that our internal organs give us when they send out information about our needs and comfort levels. These sensations include hunger, digestion, body temperature and elimination. (Baby Sense pg 12).

Our entire body is designed as a finely tuned sensory receptor for gathering information from our environment. As adults we can control to a large extent what sensory information we take in by simply controlling our environment to the best of our ability. However, before we are even conscious of any sensory information we may have received, our brain will determine whether this information is important to us or not. If it is not important, the brain has an ability to filter out or inhibit this information by recognising that it is familiar input and then deciding to no longer focus on it. This process is called habituation. – an example of habituation is that we do not always feel the label of our clothing resting against our skin – this input has been habituated so that it doesn’t reach our consciousness. Habituation is crucial as it allows us to focus on important information without becoming over-stimulated. So, as you sit reading this, you are able to focus on the words in front of you, and not be distracted by the drone of the traffic outside your window, or the smell of cooking from down the passage.  If this process of habituation is impaired, too much unimportant stimulation floods the nervous system. This leads to sensory overload, or over-stimulation. (Baby Sense pg 13).

In the first year of life, your baby’s’ process of habituation was immature. This is why you had to regulate how much stimulation your child was exposed to. You also had to filter out and monitor certain sensory input into his nervous system. Now that your baby is older, it is still important to filter out excessive sensory input to prevent sensory overload. It will still be necessary to regulate the type of sensory input he receives, as well as how much stimulation he is exposed to.

Understanding how your toddlers sensory system works will help you to know when, why and how to nurture, stimulate or calm him. It will also help you to enhance his physical and mental development with appropriate stimulation, while at the same time keep him happy, calm and content.

For more age-specific information, read Toddler Sense (Metz Press 2011)

 

Written by Sister Ann Richardson, qualified nurse and midwife and co-author of Baby Sense; Sleep Sense and author of the international best seller Toddler Sense

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