The neurological contribution to understanding problems of intellect, learning and behaviour in children:
1 Organically based psychological sequelae of brain damage can occur in the absence of neurological physical signs.
2 Behaviour and psychiatric disorders are more commonly seen in children with brain pathology than in those without, and this is in part a function of the pathology itself, rather than any functional disability which it may have caused.
3 There is no distinctive pattern of behavioural or psychiatric disorder which can be attributed to brain pathology. All patterns of disturbance can be found in children with and in those without brain pathology. The exception is the syndrome of gross social disinhibition, which may be associated with frontal lobe damage
4 Primate experiments suggest that the functions of damaged areas of the brain (excluding motor areas and vital centres) are not immutable and the intact areas can often make up for any deficiencies, although at the cost of a slight reduction in overall intellectual capacity. Head injury studies support the idea that, in children, brain injury is more likely to result in a global intellectual deficit than in a specific developmental or learning disability. Nevertheless, although the young child's brain shows considerable plasticity of function, some hemisphere specialization is present very early in life.
5 Disturbances in psychological functioning are probably more likely to result from abnormal brain activity (e.g. epilepsy) than from loss of brain substance.
6 A threshold phenomenon appears to govern the relationship between the severity of brain damage and the sequelae; the damage must reach a certain degree of severity before sequelae become detectable.
7 Severe intrauterine malnutrition is associated with mild reduction in ail parameters of intelligence and particularly motor function; possibly this is due to reduction of neuronal numbers and connections, notably in the cerebellum. Similar effects may result from prolonged postnatal malnutrition. There is an association between early growth faltering (first 6 months) and fine motor and speech impairment.
8 Whatever the nature of the biological insult to the brain, psychosocial factors strongly affect the outcome by interacting with the child's intrinsic problems and become an increasingly important influence as the child grows older. An adverse environment greatly exaggerates the effects of brain damage, whereas a good one minimizes them.
9 Severe asphyxial brain damage in the neonate can cause cerebral palsy and learning disability but rarely causes severe learning disability without cerebral palsy. However, impaired concentration, learning and motor co-ordination, without cerebral palsy, may be associated with other forms of brain injury, such as may occur in association with extreme prematurity or hypoglycaemia.
10 If one excludes cases of identifiable perinatal brain damage associated with obvious neurological abnormality in the neonatal period, some relationship still exists between perinatal disorder and intellectual and learning deficits, but the correlations are weak and it is far from certain that the relationship is causal. In studying such relationships it is vital to control for the numerous psychosocial factors which contribute both to the occurrence of perinatal disorder (e.g. prematurity) and to the outcome.
11 Many developmental disorders are probably due not to focal brain lesions but to other types of dysfunction. For example, in attention deficit disorder there may be an abnormality in the handling of neurotransmitters. New imaging methods such as positron emission tomography (PET) scans and echo-planar imaging, developed from magnetic resonance techniques, suggest that in this condition and in obsessive compulsive disorder there are atypical patterns of brain activity, which can be corrected by medication.
12 Some learning problems, for example dyslexia, may occasionally be associated with abnormal neuronal migration (the process by which neurons align themselves into columns and layers during early brain development). These abnormalities may be under genetic control. Similarly, there are structural asymmetries between the left and right hemisphere which have some relationship to the development of language and reading skills
13 Brain function can be considered in terms of circuits and systems which share and exchange information at so-called 'convergence zones'. It seems likely that differences in the structure and function of these circuits and zones may ultimately explain the genetic influences.
14 Children with brain damage may receive drugs (e.g. anticonvulsants) which may adversely affect behaviour.
