Variability in infant motor behavior: A hallmark of the healthy nervous system

Application of the concepts of the Neuronal Group Selection Theory (NGST) may shed a new light on motor development. According to NGST, normal motor development is characterized by two phases of variability. Variation is not random, but determined by criteria set by genetic information. Development starts with the phase of primary variability, during which variation in motor behavior is not geared to external conditions. At function-specific ages secondary variability starts, during which motor performance can be adapted to specific situations. In both forms of variability selection on the basis of afferent information plays a significant role. From the NGST point of view, children with pre- or perinatally acquired brain damage suffer from stereotyped motor behavior produced by a limited repertoire of primary (sub)cortical neuronal networks. These children also have problems in selecting the most efficient neuronal activity due to deficits in the processing of sensory information.