Heavy metals and the brain | Integrated Learning Therapy

Neurodevelopment starts in the early prenatal stage that begins with rapid growth of spreading brain cells, forming synapses especially during the last trimester. Further synaptic growth during the first 2 years of life is particularly critical to ongoing functioning and development.

Myelination begins in the second half of pregnancy and continues until the mid-twenties, with different systems myelinating at different times. As we have learned, the brain’s centre of reasoning and problem solving is among the last to mature, during young adulthood.

The first areas of the brain to mature are those with the most basic functions, such as processing the senses and movement. Areas involved in spatial orientation and language (parietal lobes) follow. Areas with more advanced functions – integrating information from the senses, reasoning and other ‘executive’ functions – mature last.

Tremendous rate of growth in areas of vision and sensation occur in the early school years. During the middle school years (Grades 5-8) areas responsible for language development show rapid growth.

Because infancy and childhood are characterized by the development of different systems, children have unique susceptibilities not seen in adults – and critical time windows for these susceptibilities. The critical times include preconception, gestation and the postnatal period.

It might be hard to imagine that it was only a few decades back that the discovery was made that the foetus is vulnerable to exposures. You’ll remember the terrible wake-up call that came from the use of thalidomide by pregnant women. This was a tragic lesson of the ability of chemicals to traverse the placenta and damage the foetus.

Now we know that during gestation, the foetus may be susceptible to various chemicals, ionizing radiation, alcohol, methylmercury and lead. During the postnatal period, infants are susceptible to second-hand tobacco smoke and lead, amongst other offenders.

Let’s have a brief look at some of these heavy metal offenders.

Lead

Preventing lead exposure continues to be a major challenge in many countries, especially developing countries. Poverty, a large informal sector, limited public health challenges and low levels of awareness of lead hazards and weak capacity to enforce legislation contribute to the intensity of the challenge. Despite progress in this area, a wide range of sources of lead exist in South Africa and certain settings and groups continue to be at high risk of lead exposure. Exposure comes from paint, mining, lead melting in subsistence fishing communities (making of sinkers) and food production.

When lead poisoning begins in the womb, it can affect the most critical system, being the central nervous system of the foetus. The effects of lead exposure can be seen in various areas. Firstly, high levels cause loss of intellectual capacity and changes in behaviour. It has been identified as adversely affecting speech and language, attention, cognitive flexibility and visual-motor integration. These may come about because of low lead concentrations that don’t necessarily produce physical signs. High levels of lead exposure results in disruption of semantic language function in young adulthood.

Mercury

Children who are exposed to mercury (often by mothers who consume a high fish diet contaminated with mercury) may develop reduced IQ, learning and behaviour problems. Mercury is known to have neurotoxic properties and is identified as a significant risk factor for neurodevelopmental behavioural disorders in children.

Acceptance of this now recognised fact has been slow in coming and only recently have dentists acknowledge that teeth fillings containing mercury are a risk factor.

Tobacco

There is now strong evidence that prenatal tobacco exposure is linked with the development of attention difficulties associated with ‘ADHD’. Such exposure can be due to mothers who smoke or who were exposed to second-hand smoke in the home.

We know that there are other heavy metals and environmental offenders that can be contributing to a child’s learning and behaviour challenges. This serves as a reminder that we have to be aware of the many aspects that can impact on neurodevelopment. Don’t overlook anything and if you suspect heavy metals, have a hair analysis done at one of the pathological laboratories

Image supplied by Freepik.

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Martin Doherty, writing for The Conversation, says that at the age of about four, children reach important milestones in brain development.

One of these is a huge improvement in understanding others’ thoughts and feelings. This is the start of empathy. Another is in spatial thinking—understanding how objects are positioned and related. This is the beginning of the ability to read maps.

Martin and his colleague, Catherine Sayer, conducted a study with 175 two to five-year-olds to explore how children are able to use scale models to figure out where something is in the real world. At about four, children are able to use a scale model of a room to work out where something is. We thought that this might result from children’s understanding of how one thing can represent something else. But we actually found that four-year-olds’ ability to use scale models came from their spatial abilities.

At the same age, children start to understand that someone’s behaviour is due to what that person believes, not necessarily what is really the case. This has interesting consequences.

If you’ve played hide-and-seek with young children, you may have noticed that they aren’t always very good at it. They love the ritual of looking in all the wrong places first, but beforehand they may tell you where they are going to hide, hide in the same place every time, or not be especially hidden.

After their fourth birthday, they get much better at hide and seek. They understand that the seeker looks in the wrong places because they don’t know where the hider is.

At about three to four children also start to tell lies. They realize they can make someone believe something that isn’t true.

Understanding symbols

Martin’s earlier research with fellow psychologist Josef Perner suggests that four-year-olds don’t just start to understand how others’ minds work. Figuring this out is part of the development of an understanding of “representation”—that symbols, like thoughts, words, or pictures, can be used to stand for something else.

Children start to think about how words relate to objects. This means, for instance, knowing that “animal” can refer to something you already have a name for, such as “rabbit”. This might help children learn the new word.

Their ability to use a understand the components of pictures also improves around this age. Very young children use a lot of trial and error to complete a jigsaw, picking up random pieces to see if they fit. By the time they are about four years old, they start to use the picture as a guide, trying to connect lines and match bits of colour, while checking the guide picture on the box lid.

Developmental experiments

Another ability children develop at around four is using scale models. A classic set of developmental experiments involved a model of a regular household room. The real room had typical furniture—sofa, table, cupboard and so on—and the model had miniature versions laid out in the same way.

Children were shown where something was hidden in the model and told to find an object hidden in “the same place” in the room. Children of around four can find the object using the identical layouts. If shown a sticker under a particular chair in the model room, for example, they can go straight to the “same” chair in the other room. This is the fundamental understanding required to read maps.

Adults see scale models and maps as representations. Maps represent a town or a country. A scale model of, say, the Eiffel Tower represents the real thing. At first, Martin suspected children’s ability to use scale models is more evidence of understanding representation at this age.

He was wrong. Instead, the researchers found that this ability is based on a development in children’s spatial abilities that also occurs at about four. This is the ability to think about spaces and where objects are within them. Spatial abilities help with maths skills, and good spatial ability is linked to an interest in science, technology, engineering and mathematics.

Their experiment was simple. They compared the model room task with a test of understanding how representation works. The two abilities develop around the same age, but they found they were not related. Children who could do one task couldn’t necessarily do the other.

They also had a test of purely spatial ability. Children who passed the model room task also passed the spatial task. So it looks like the model room task relied on children‘s spatial thinking.

They don’t yet know why two important but apparently unrelated abilities arise at the same time. Perhaps it’s related to changes in the growing brain at this interesting age.

Provided by The Conversation.

Image supplied by Freepik.