What is happening in the brain?

What is happening in the brain?

Developmental dyscalculia is assumed to be caused by a difference in brain function, and/or structure, in areas of the brain involved in mathematics. But what are these differences, and how much evidence is there for them?

This research is very much in its infancy compared to the research on dyslexia, because very little was known about how the brain represents mathematics until the last 15 or so years.

To date, most of the research has been in special populations associated with dyscalculia such as individuals with Turner's syndrome, Foetal Alcohol Syndrome, or born with a low birth weight [1-3]. All of these studies show either less grey matter (brain cells), or less brain activity in a specific area of the brain known to process mathematics (the intra-parietal sulcus).

Research on children with dyscalculia which is not due to a known medical syndrome is starting to emerge, with the same sort of findings. A recent brain imaging study showed less brain activity in parietal and frontal areas of the brain associated with mathematical cognition [4]. In addition children with dyscalculia also show difficulties on basic cognitive tasks known to involve these areas [5].

Research on acquired dyscalculia (dyscalculia acquired as a result of brain injury) fits with these findings; damage to the parietal lobes of the brain results in similar symptoms to developmental dyscalculia.

I thought the brain couldn't be changed?

This is a common misconception which is completely untrue. Every time you learn a new piece of information or a new skill, your brain changes. If you practice a new skill considerably your brain can show quite large changes. We call this ability to change "plasticity". The brain is at its most plastic during childhood, but it shows much plasticity in adulthood as well.

So even though dyscalculia is related to brain function, there is no reason why that function cannot be changed. It could be changed by experiences in the home (an environment which encourages attention to number), by teaching in school, and by intervention programmes.

Intervention programmes show particular promise for severe learning disabilities. We know from research on dyslexia that auditory training programs can result in significant improvement in reading which is associated with changes in brain function [6, 7].

But what is the root cause?

Why is the brain functioning differently in dyscalculia individuals? There are many possible causes, including both genetic and environmental, and an interaction of the two. The cause for one individual may not be the same as for another, and in many cases it may not be obvious.

Genetic causes include known genetic disorders such as Turner's syndrome, Fragile X syndrome, Velocardiofacial syndrome, Williams’s syndrome. In addition studies suggest that there are genes present in the general population which increase the risk of dyscalculia [8, 9].

Known environmental causes include alcohol consumption during pregnancy, and pre-term birth. Both of these can result in underdevelopment of the brain.

Dyscalculia often co-occurs with other learning difficulties such as dyslexia, dyspraxia, attention deficit and hyperactivity disorder (ADHD), and specific language impairment (SLI). This is probably because both environmental and genetic factors which affect brain development are likely to act on several areas of the brain at once.

 Brain damage occurring at birth or from infections in early childhood can also cause a learning disability.

How often do epilepsy and learning disability happen together?

Epilepsy is more common in people with a learning disability than in the general population.

·        About 30% of people (nearly 1 in 3) who have a mild to moderate learning disability also have epilepsy.

·        The more severe the learning disability, the more likely that the person will also have epilepsy.

·        Around 20% of people (1 in 5) with epilepsy also have a learning disability.

Emotional and behavioural problems [edit]

TBI may cause emotional or behavioural problems and changes in personality.^[15] Emotional symptoms that can follow TBI include emotional instability, depression, anxiety, hypomania, mania, apathy, irritability, and anger.^[9] TBI appears to predispose a person to psychiatric disorders including obsessive compulsive disorder, alcohol or substance abuse or substance dependence, dysthymia,clinical depression, bipolar disorder, phobias, panic disorder, and schizophrenia.^[16] About one quarter of people with TBI suffer from clinical depression, and about 9% suffer mania.^[17] The prevalence of all psychiatric illnesses is 49% in moderate to severe TBI and 34% in mild TBI within a year of injury, compared with 18% of controls.^[18] People with TBI continue to be at greater risk for psychiatric problems than others even years after an injury.^[18] Problems that may persist for up to two years after the injury include irritability, suicidal, insomnia, and loss of the ability to experience pleasure from previously enjoyable experiences.^[17]

Behavioural symptoms that can follow TBI include disinhibition, inability to control anger, impulsiveness, and lack of initiative, inappropriate sexual activity, and changes in personality.^[9] Different behavioural problems are characteristic of the location of injury; for instance, frontal injuries often result in disinhibition and inappropriate or childish behaviour, and temporal lobe injuries often cause irritability and aggression.^[19]

The risk of post-traumatic seizures increases with severity of trauma (image at right) and is particularly elevated with certain types of brain trauma such as cerebral contusions or hematomas.^[22] As many as 50% of people with penetrating head injuries will develop seizures.^[20] People with early seizures, those occurring within a week of injury, have an increased risk of post-traumatic epilepsy (recurrent seizures occurring more than a week after the initial trauma).^[23] Generally, medical professionals use anticonvulsant medications to treat seizures in TBI patients within the first week of injury only ^[24] and after that only if the seizures persist.