Published online by Cambridge University Press: 22 September 2009
Connection: The brain and cognition both develop in systematic patterns of cycles and gradients, which are evident from the very beginnings in prenatal development and continue for later developments of brain activity and behavior in childhood and adolescence. One of the most powerful tools for examining brain activity and relating it to cognitive development is the electroencephalogram (EEG), a measure of the electrical waves generated by the cortex of the brain. A valuable property of the EEG is coherence, the similarity between waves in different brain regions, which is measured by correlating wave forms through Fourier analysis. Coherence shows clear developmental cycles and gradients, which seem to relate to general patterns of cognitive development as well as individual differences.
The EditorsGradients and cycles in prenatal development
From the moment of conception embryological development is organized in terms of spatial gradients and growth cycles. Brain development reflects these processes from its earliest origins.
Spatial gradients of prenatal development
Spatial gradients shape development from the beginning prenatally (Diamond, Scheibel, & Elson, 1985; Rakic, 1988). Shortly after conception, a ball of cells grows symmetrically without a clear left or right or an anterior or posterior plane. At the first differentiation, spatial polarization occurs in which a disk with an anterior and posterior end and a medial and lateral plane appears. The inner layer (i.e. the endoderm) differentiates to form the skeleton and gut, while the outer layer of the disk (i.e. the ectoderm) differentiates to form the neural plate from which the entire nervous system develops.
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