* Changes in Body Proportions
* Cephalocaudal trend: “head to tail” – during prenatal period, the head develops more rapidly than the lower part of the body. * Proximodistal trend:growth proceeds, literally, from “near to far” – from the center of the body outward. In the prenatal period, the head, chest, and trunk grow first, then the arms and legs, and finally the hands and feet. * Brain Development
* Development of Neurons (nerve cells that store and transmit information) * Synapses: between neurons, are tiny gaps where fibers from different neurons come close together but do not touch. * Neurotransmitters: neurons send messages to one another by releasing chemicals called neurotransmitters, which cross the synapse. * In the prenatal period, neurons are produced in the embryo’s primitive neural tube. Then they migrate to from the major parts of the brain. Once neurons are in place, they differentiate and establish their unique functions by extending their fibers to form synaptic connections w/in neighboring cells. * Synaptic Pruning: returns neurons not needed at the moment to an uncommitted state so they can support future development. Neurons that are seldom stimulated soon lose their synapses. * Glial cells: consists about half the brain’s volume and are responsible for myelination. * Myelination: coating of neural fibers with an insulating fatty sheath (called myelin) that improves the efficiency of message transfer. * Neurophysiological Methods
* Electroencaphalogram (EEG): electrodes, usually embedded in a head cap, are attached to the scalp with conductive gel to record electrical brain-wave activity in the brain’s outer layers - the cerebral cortex. * Event-related potentials (ERPs): using EEG, the frequency and aplitude of brain waves in response to particular stimuli (ex: picture, music, speech) are recorded in the cerebral cortex, Enables identification of general regions of stimulus-induced activity. * Functional Magnetic Resonance Imaging (fMRI): doesn’t depend on x-ray which requires radioactive injection. While person lies inside a tunnel-shaped apparatus that creates a magnetic field, a scanner magnetically detects increased blood flow and oxygen metabolism in areas of the brain as the individual processes particular stimuli. Result is a computerized moving picture of activity anywhere in the brain. * Positron Emission Tomography (PET): after injection or inhalation of a radioactive substance, the person lies inside an apparatus with a scanner that emits fine streams of x-rays, which detect increased blood flow and oxygen metabolism in areas of the brain as the person processes particular stimuli. As with fMRI, the result is a computerized image of activity anywhere in the brain. PET and fMRI are not suitable for infants and young children because motionless laying is required. * Near-Infrared Optical Topography (NIROT): using thin, flexible optical fibers, attached to the scalp through a head cap, infrared light is beamed at the brain; its absorption by areas of the cerebral cortex varies with changes in blood flow and oxygen metabolism as the individual processes particular stimuli. The result is a computerized moving picture of active areas in the cerebral cortex. Unlike fMRI and PET, NIROT is appropriate for infants and young children, who can move with limited range during testing. * Development of the Cerebral Cortex:
* Cerebral cortex: surrounds the rest of the brain, resembling half of a shelled walnut. It is the largest, most complex brain structure – accounting for 85% of the brain’s weight and containing the greatest number of neurons and synapses. * Regions of the Cortex:
* Frontal Lobe: body movement and coordination. Cortical...