Brain and nerves develop structures and functions {brain, development} {nervous system, development}. Neurons move by amoeboid motion to final locations, guided by glia. At final locations, special molecules bind neurons together in layers or masses. Neurons send out dendrites and axons, which grow toward targets marked by chemicals, mostly to same-type neurons. Brain makes more dendrites and axons than it can use, so it eliminates many after growth finishes.
multisensory to unimodal development
During maturation, brain transforms multisensory regions to unimodal regions.
topological maps
During development, brain coordinates sense-organ movements and perceptions using attention mechanisms, to align sensory maps in superior colliculus and to maximize sensitivity.
consciousness
During human development, consciousness increases gradually as brain develops structures and functions [Aoki and Siekevitz, 1988] [Borrell and Callaway, 2002] [Carey, 1987] [Schaeffer-Simmern, 1948]. Embryos before three weeks old are unlikely to have sensations, because neurons are just forming. Children older than three can remember sensations.
Head evolved {cephalization} to hold sensors and integrate sense and muscle ganglia.
During development, invertebrates can change actions to opposite actions {reactive inhibition}.
Children develop ideas about their and other minds {theory of mind, development}. Knowing what relation moving or stationary objects have to oneself {intentionality, mind} begins at nine months old. Following another's eye direction toward distant objects begins at nine months old. At age 12 to 24 months, infants realize that people are pointing at or looking at something. Knowing that another person is looking at same object {attention sharing}, so two people attend to same thing, begins at 18 months old.
At age 24 to 36 months, toddlers start talking about goals, feelings, and thoughts. Later, they learn that perceptions from their viewpoint differ from perceptions from other viewpoints. Later, they learn that beliefs can be false and that people can deceive.
By four years old, children know that they and other people have beliefs and goals and that these guide behavior {belief-desire reasoning}.
autism
Autistic children appear to have no theory of mind.
animals
Animals seem to have no theory of mind.
test
False-belief tests can check if people have theories of mind. People can see someone place something at a location and see someone else move it while the first one is not looking. Tests ask people to name place where the first one will look for something.
People with theories of mind realize that the first one does not know that something moved, so the first one will look at the original place. People with no theory of mind will think only that something is now in new position and that everyone knows where it is, so the first one will look in the new place. If people do not know where the first one will look, they are still developing theories of mind.
From neural tube, glial processes extend into outlying regions {glial trail}. Developing neurons move along glial trails to final locations. Neurons that develop near each other in neural tube are near each other in outlying regions.
Axon tips {growth cone} have filopodia that guide axons to correct regions and synapses. Proteoglycans cover dendrites and cell bodies afterward. chABC enzyme cuts proteoglycans and allows more axon connections.
Axon-tip growth cones have cilia-like projections {filopodia} that guide axons to correct regions and synapses.
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Date Modified: 2022.0225