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Midterm

Second midterm notes

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Department
Psychology
Course
PSY100H1
Professor
Mark Schmuckler
Semester
Fall

Description
PSYB20 Midterm Notes Chapter 6 – The Child’s Growth: Brain, Body, Motor Skills, and Sexual Maturation Brain Development in Infancy  In the prenatal period, the brain grows very rapidly, and it continues to grow at an amazing pace  At birth, an infant’s brain weighs only about 25% as much as a mature brain, but by the time the baby is about 6 months old, his brain weighs half of what an adult brain weighs, and the brain of a 2 year old child weighs 75% as much as an adult brain\  The largest portion of the human brain consists of the two connected hemispheres that make up the cerebrum, a mass of tissue that embodies not only attributes particular to humans – such as speech and self-awareness – but also those that we human beings share with other vertebrate animals – such as sensory perception, motor abilities and memory o The covering layer of the human cerebrum, the cerebral cortex, is highly convoluted and contains about 90% of the brain’s cell bodies o Specific functions such as seeing, hearing, moving, feeling emotions, thinking, and speaking, can be traced to specific regions of the cerebral cortex  The left hemisphere is generally associated with the processing of language, whereas the right hemisphere plays a greater role in visual and spatial processing o Functions lost because of damage to a hemisphere, lobe or area may be compensated for by another brain region, due to plasticity  Neurons and synapses o A baby’s brain has most of its neurons, or nerve cells (100-200 billion) o Most neurons are present in the brain by the seventh month of gestation o During the embryonic period, neurons multiply at a very rapid pace in a process called neuron proliferation, and 250 000 new neurons are born every minute  Neuron proliferation: the rapid proliferation of neurons in the developing organism’s brain o Brain growth also reflects the growth of glial cells, which surround and protect neurons, providing them with structural support, regulating their nutrient concentrations and repairing neural tissue  Some glial cells are responsible for the important task of myelination o Neural migration: the movement of neurons within the brain that ensures that all brain areas have a sufficient number of neural connections  The absence of an appropriate number of neurons in their proper locations may be associated with various forms of mental retardation and with such disorders as dyslexia, schizophrenia or epileptic seizures o Synapses are crucial to survival and learning, for as the brain’s neurons receive input from the environment, they continue to create new synapses, allowing for increasingly complex communications o Synaptogenesis, or the forming of synapses, begins early in prenatal life, as soon as neurons begin to evolve o The brain forms synapses even more rapidly than it forms neurons  At birth in the brain’s visual cortex alone, there are 2500 synapses for every neuron  Peak: at 2 years old when there are 15000 synapses for every neuron o When new synapses are formed, some surrounding neurons die in what is called neuronal death, apparently to provide more space for these crucial loci of information transmission o Synaptic pruning: the brain’s disposal of the axon and dendrites of a neuron that is not often stimulated o This also frees up space for new synaptic connections  both neuronal death and synaptic pruning increase the speed, efficiency and complexity of transmissions between neurons and allow room for new connections that develop as the child encounters new experiences  loss in this case leads to a gain for the developing organism o by adulthood, each of the brain’s approximately one trillion neurons makes 100- 1000 connections with other neurons  = one quadrillion synapses in the adult human brain  Sequential development of the brain o Huttenlocher (1994) found that the processes of forming and pruning synapses occur at different times for various parts of the brain  As baby moves from mostly reflexive behaviour in the early months of life to voluntary control over movements, the motor area of the brain develops most rapidly  When the infant is about 2 months old, motor reflexes such as rooting and the startle response, drop out, and the motor cortex begins to oversee voluntary movement such as reaching, crawling and walking  Gradually, the infant begins to master purposeful movements, such as the effort to make contact with an object  Within the first four to 12 months, the number of connections in the visual cortex rises to about 150% of those present in the adult brain  Because of this, visual capacities are greatly enhanced; child becomes more skilled at focusing on objects at different distances  A similar sequence of synaptic and behavioural development characterizes the evolution of the auditory cortex as well as other areas of the brain o The hippocampus, which aids in memory processes, becomes fully functional at about 8 or9 months  In the prefrontal cortex, which is involved in forethought and logic, synaptic density develops more slowly and does not reach its peak until after the first year  Hemisphere specialization o Brain hemisphere: the two, left and right, halves of the brain’s cerebrum  Corpus callosum: the band of nerve fibres that connects the two hemispheres of the brain o There is a great amount of cross-wiring between the hemispheres, even though both halves are anatomically and functionally different  If one side of brain suffers damage, the other half may take over some functions  Brain has plasticity that helps it adapt to adverse circumstances o Left and right brain functions  Hemisphereic specialization: differential functioning of the two cerebral hemispheres; for example, the control of speech and language by the left hemisphere and of visual-spatial processing by the right  This begins early in life  Left hemisphere of the motor cortex controls the right side of the body, andt eh right hemisphere controls the left side  (Molfese and Molfese) in babes, spoken syllables evoke electrical potentials that indicate that these infants’ brains process speech syllables faster in the left hemisphere than in the right one  Each side of the brain tends to specialize in certain perceptual and cognitive tasks o The right hemisphere is involved in the processing of visual-spatial information, nonspeech sounds, such as music and the perception of faces  When damage occurs to the right side o
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