-proliferation
-rate of growth of neurons-begins at 5 weeks GA
- migration
- integration
- neurons moving to final location (brain stem, cerebellum, etc)
- neurons reach final destination
synaptogenisis
neurons spin out axons that connect to each other via dendrites
- anywhere from 1000-100000 connections/neuron
- at the end of the prenatal period, some connections die (if they are inactive) and some strengthen
differentiation
occurs AFTER synaptogenesis-separation of function of neurons
- efferent=motor neurons
- afferent=sensory neurons
myelination
insulation of neural pathway-occurs at about 20 weeks and continues to age 30 in some areas
-enhanced by physical activity
Post-Natal Brain Growth Spurt
- occurs starting at the third trimester and continues to age 4
- at birth, brain 25% of adult weight, at age 3, brain 90% of adult weight-example of cephalo-caudal principle
- attributed to increase in neuron size, branching, and increase in glia and myelin, but highly susceptible to nutrition and extrinsic factors
- allows mother to carry child more easily and may be due to evolutionary explanation-brain too big for pelvic structure at birth
activity-independent
activity-dependent
- hardwired processes determined by genetic processes played out in individual neurons (migration, differentiation) [NATURE]
- influence things after axons reach final location and require neural activity (myelination, syaptogenesis) [NURTURE]
pruning
connections not made or not stimulated are eliminated (40-70% of original)-keeps system from becoming too confusing
-epilepsy related to this
Critical peroids
period of maximum sensitivity to environmental stimuli-a child who misses an opportunity may not develop brain’s circuitry to full potential for that aspect of development
- organism must be in state of readiness
- if stimulation does not occur in this window, optimal development is lost forever
- stimulation affects things permanently
- critical periods exist for all aspects of behavior
Electroencephalography (EEG)
- measures electrical activity with electrodes
- measures an average of event-related potentials (ERP)
Computed Technology (CT)
- uses x-ray beams to collect cross sectional images of the brain and develops them onto film
- shows structure of brain
Positron Emission Tomography (PET Scan)
- detects radioactive material that is injected/inhaled
- shows brain function
Magnetic Resonance Imaging
- detects frequency signals produced by displaced radio waves in a magnetic field
- shows anatomical view
Functional MRI
- detects change in blood flow to brain
- provides anatomical and functional view
Magnetoencephalography
- measures magnetic fields produced by brains electrical activity
- shows function (how brain responds to stimuli)
