9.6 Successive phases in a developing function; a potential is actualised.
Map 9.6.1 Two phases in development, from potential to actualisation
A potential function which has not been actualised by a series of priming experiences, is lost when the sensitive period for its development has passed. Thus, a lack of priming causes a developmental defect. The symptoms of such a defect can be similar to the function disorders which are due to brain-damage acquired later in life. In order to distinguish them the former are indicated as 'developmental' and the latter as 'acquired' agnosia, apraxia or dysphasia.
In short: it is important from the point of view of prevention to recognise that partial defects of brain function may arise during growth and maturation of the brain, as well as during the learning phase. One should be aware what consequences lack of adequate challenges and lack of key-experiences in the sensitive period of neuronal organization may have. Early warning signs that emotional or sensory deprivation is taking place should be heeded.