Wednesday, August 28, 2013

An Article to Read About Learning.

Dr Laura Markham writes at Aha Parenting about positive parenting. Read this article, note the quote at the end and learn about learning.

Sunday, August 25, 2013

The Special Senses, part 1- the Chemosenses, gustatory and olfactory, aka taste and smell

Smell may be the least neurologically complex system of the sense as the information from the smell sensors in the nose have a direct link to the processor in the brain. Taste is considered one sense but in fact there are 5 specific receptors (located on the tongue in areas) for salty, sweet, tart, sour and what is being called “meat” flavors. These five flavors are given more variety by the sense of smell which distinguishes variations within these five flavors of foods. Often, in high school biology class, teachers do an experiment where they stop the sense of smell and offer a bite of an apple and of an onion to a student. Without smell the student cannot tell which is which as the texture is similar and both are sweet.  Smell is one of the senses that disappears in the aging process and older people often lose interest in most foods, except sweets, because the food becomes bland to them without smell.  Smell is an important first indicator of some dangers as it can detect more remote sensation than taste. To taste something it must touch the tongue but smells waft through the air to your nose.    
The system for smell develops between 16 and 24 weeks of gestation and is in place and ready to function by about 24 weeks gestation. The first taste buds appear at 8-9 weeks gestation with most being present by about 16 weeks gestation. Some refinement continues but most full term babies have a fully developed taste system at birth.
The system of smell is perhaps the strongest sense in infants and babies are able to recognize the smell of their mother’s breast milk from that of another person (the study was done using breast pads) almost from birth. They also respond to strong smells with avoidant movements from an early age. I would avoid strong perfumes and air fresheners around very young infants as these might be unpleasant to their sensitive system. In a study (titled “Natural odour preferences of newborn infants change over time.” by [My paper]H Varendi, R H Porter, J Winberg) it was shown that babies preferred their mother’s unwashed natural breast over the washed and soapy smelling other breast during the first week to 10 days of life.  It has been proposed that smell is the first sense used in socializing as newborns begin to recognize different people by their smell, which allows them to respond socially to those they know and those they do not know from a very early age.

These systems rely on experience after birth to become completely developed. The brain records tastes and smells so that a child can recognize what they mean. Infants can register likes and dislikes from the start. Due to their limited experience, infants are happy with relatively bland food and do not need salt or sugar added to foods to want them. However, they recognize variations in their food and may reject food that tastes
“funny”. Many breast feeding mothers report that their baby is not interested in the breast after they have eaten a certain type of food. Which foods trigger that response are different for each baby but all are strong flavored foods. In my case, it was pickled foods that I had to avoid. This is learned by the baby through experience with foods and by the mother in watching her baby’s reaction to feeding.
On the other hand, older people who have lost some of their sense of smell are best able to taste the flavors that are tasted by the tongue. Sweet is the strongest, being at the front of the tongue, followed by salt. Older adults will often only express interest in sweet foods and will often over salt foods in order to experience variation in tastes. Many older adults will say that food these days doesn’t taste like it used to. For them, it is probably true.
It is thought that these two systems have some protective functions as most really bad smells and bitter tastes are not good for people so your own body can offer some protection against certain poisons. However the system is not foolproof and some unpleasant tasting things are not harmful while some harmful things are not unpleasant. It has been noted that during pregnancy, many women are exceptionally sensitive to smells, which may be a primitive form of guiding them towards the particular foods they need.

In any case, the sense of smell is one of the least studies and most underrated the special senses. Below are some links to references on the sense of smell:

Sunday, August 18, 2013

Repost, link on language development,

Click this link for an article on language development.

The sensory system part one, Introduction.

Your child’s sensory motor system is a very important part of his development. In fact, almost all human activity is based in the sensory motor system. Basically, we take in information through our senses and then we react to it, usually with a motor response of some sort.  The system is very complex and there is coordination (it is a pre internet type of web) among all the senses and the motor systems of the body but I will try to keep it simple here. Something happens in the environment and the sense organs pick it up. The “sensation” is transmitted to the brain where it is processed (and coordinated with other information from other senses) interpreted and a response is formulated. This information goes to the motor cortex of the brain where instructions to your body are transmitted and you react. All this takes place in nanoseconds so your response may seem immediate, certainly much faster than it took to read about. Let’s use a hot iron as an example. Your finger touches the iron and the pain and thermal sensors in your finger recognize the sensation. It is sent to the brain which registers “HOT” and dangerous. The information is sent to the motor areas of the brain which determines that your muscles in your arm must activate to move your finger away from the danger. This information is sent to your finger and you pull your finger away from the iron. Most of us have had this experience so you know how fast this system works.
In looking at the sensory part of this system we need to understand what the senses are. Firstly, the system consists of three basic parts, the sensory receptor, the nerve transmitter and the part of the brain that processes the sensation. The receptors are the organs that come in contact with the sensation, the nerve endings throughout the body and especially around the head that receive the sensation.  The nerves are the transport system, much like telephone cables that transmit the sensation to the brain. All of the understanding of what was sensed takes place in the brain. Each sense is processed in its own part of the brain separately, although there are connections so that this information can be coordinated to form a whole picture. This interconnection also helps when there is an impairment in one of the senses, such as blindness, which allows information from other senses to help “cover” for the impaired sense in gaining a better picture of the environment.
Most of us have heard of the five senses. Many of us have heard the term the sixth sense used to refer to unexplained abilities.  Well, the truth is that we have more than 5 senses so that expression is going to have to change to the 10th sense or something like that.
The first 4 senses are special senses, so called because they have a single sense organ and detect a single type of sensation.  These are sight, hearing, smell and taste.  Each of these has a specific sensory receptor located around the head.  For sight it is the eyes, for hearing it is the ears. Smell and taste are quite related and are often called the chemosenses. 
The remaining senses are called the somatosenses because they affect the body as a whole. These include touch, which is really several senses combined under one name, the proprioceptive sense and the vestibular sense. The first two have sense receptors spread throughout the body while the vestibular sense uses some of the same structures in the ears that are used for hearing.

In the next few articles, I will look at the development of each sense both in terms of the development of the structures and of the sense itself. Most of the sense organs develop in the absence of stimulation but processing continues to develop with experience and, in later years , many of the senses become weaker due to changes in the structures. After looking at each sense in depth I would like to discuss sensory processing and the area of sensory processing dysfunction, which is in the process of becoming a diagnosis as well as being a symptom in several other disorders, including autism.