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Chapter 5

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` Chapter notes Chapter 5- The child’s growth: Brain, Body, Motor skills, and sexual maturation Brain Development in Infancy Cerebrum: a mass of tissue that embodies not only attributes particular to humans—such as speech and self –awareness—attributes shared with other vertebrate animals—such as sensory perception, motor abilities, and memory. It is the connected hemisphere of the brain. Cerebral Cortex: The covering layer of the cerebrum that contains the cells that control specific functions, such as seeing, hearing, moving, and thinking. Contains about 90% of the brain’s cell bodies. Figure 5-1: Fetal brain development Figure 5-3: The Brain’s cortex Neurons and Synapses th  Most neurons are present in the brain b the 7 month of gestation  During the embryonic period, neurons multiply at a very rapid pace in a process called neuron proliferation o About 250,000 new neurons born every minute  Adult brain has the capacity to regenerate nerve cells  Glial cell: Provide neurons with structural support, regulate their nutrient, and repair neural tissue. o Some glial cells are responsible for the important task of myelination (in which parts of neurons are covered with layers of a fatty membranous wrapping called myelin) o Myelination occurs during the first two years of life, but some continues into adulthood. Figure 5-4: Myelinated Neuron  Neural Migration ensures that all parts of the brain are served by a sufficient number of neurons.  Absence of sufficient neurons associated with mental disabilities 9ex: dyslexia, schizophrenia)  Connections between neurons are known as synapses  Synapses allow for increasingly complex communications  Synaptogenesis: forming of synapses, begins early in prenatal life  When new synapses are formed, some surrounding neurons die in what is called a neuronal death  In Synaptic pruning the brain disposes of a neuron’s axons and dendrites if that particular neuron is not often stimulated. (use it or lose it)  Neuronal death and synaptic pruning are to increase the speed efficiency and complexity of transmission between neurons and to allow room for new connections that develop as the child encounters new experiences Figure 5-5: Synaptic connection between two neurons ` Chapter notes Turning points chart (pg. 160-161) Sequential Development of the Brain  Orderly sequence to brain development during infancy present  Moves from reflexive behaviour to voluntary control of movements  Motor area develops rapidly Hemispheric Specialization  The left and right hemispheres are connected by a set of nerve fibres called the corpus callosum  They are anatomically different and control different functions  When one side of the brain suffers damage, the other half may take over some functions Left and Right Brain Functions  The left hemisphere of the motor cortex controls simple movement in the right side of the body  Right hemisphere controls the body’s left side  Lateralization describes the specialization of each hemisphere in specific perceptual and cognitive tasks.  The right hemisphere processes visual-spatial information, non=speech sounds like music and the perception of faces  Damage to the right side of the brain = difficulty attending to a task requiring visual-spatial perception  Right hemisphere = processing emotional information  Right-brain damage can have difficulty interpreting facial expressions  Left-hemisphere is activated in the expression of emotions associated with approach to the external environment such as joy, interest, and anger  Right region activated in emotional expressions that cause the person to turn away or withdraw from that environment (distress, disgust, fear)  Left hemisphere associated with language processing (trouble understanding and or speaking clearly themselves)  Language that involves motor movement of hands (sign language) = right side of the brain which takes over  Brain injury at a young age can recover their losses b/c brain isn’t fully developed and hemispheric specialization is not yet complete Consequences of Brain Lateralization  Infants whose left hemisphere differentiates among speech sounds and whose right hemisphere differentiates among non-speech sounds exhibit better language skills at age 3 than infants who do not show such strong lateralization  Dyslexia: the difficulties some children experience in learning to read o have difficulty integrating visual and auditory information ` Chapter notes o ex: matching written letters or words to the sounds of those letters and words o children w/ dyslexia do not show the normal lateralization pattern o they process spatial info on both sides of the brain rather than primarily on the right and thus, their left hemispheres may b/cm overloaded leading to deficits in language skills such as reading  Handedness is a/o function that is lateralized  Some left-handed people are ambidextrous (able to use both hands) for some tasks o Suggests that their brains may be less clearly lateralized than the brains of right-handed people The Brain’s Plasticity: Experience and Brain Development  Stimulation from the environment plays a role in brain development  Brain’s plasticity is the capacity of the brain (particularly in its developmental stages) to respond and adapt to input from the external environment  2 types of experiences influence the brain development: 1) Experiences such as touch, patterned visual input, sounds of language, affectionate expressions from caregivers, and nutrition a. Triggers synaptic development and pruning and are critical for normal brain development 2) Experiences that are unique to individuals a. Experiences encountered in particular families, communities, and cultures b. Brain respond to different environments by developing synaptic connections that encode specific and unique experiences  Enriched environments tent to increase the complexity of neurons as measured by the number of dendrites they develop (heavier brains)  More dendrites means more synapses formed which means more info can be sent via these synaptic connections o Recall experiment w/ rats in enriched environment vs. impoverished environments which led to the discovery of heavier brains for rats in enriched environments  Infant brains develop “auditory maps” to respond to certain auditory features and not o/s o These maps then guide infants in recognizing their native language  Exposure to music can also enrich brain development  Some research demonstrates that the brain can undergo structural change based on unique experiences even in adulthood  In abused children, both the cortex and the limbic system (centres in the brain that are involved in emotions and infant=parent attachment) are 20-30% smaller and have fewer synapses Table 5-1: Techniques for studying human brain function and structure - EEG (electroencephalograph), PET (positron-emission tomography), SPECT (single-photon emission computed tomography), MRI ( Magnetic Resonance imaging), TMS (Transcranial magnetic stimulation) Motor Development ` Chapter notes Hand Skills  Reaching and grasping obj = 1 of the greatest achievement in the first 2 years of life  Preaching uncoordinated swipes at objects newborn notices  @ 3 months infants initiate more complex pattern directed reaching  @ 5 months they succeed in reaching in for an object o Involves muscle growth, postural control, control over the movement of arms and hands and a variety of o/ perceptual/ motor abilities  1 component of the dynamic system = visual perception o If infant has nothing to look at, there is no incentive to reach out  a/o component = Motor ability to grip an object o grip improves w/ age o type of grip also depends on the size and shape of the object o in the first year of life, can also begin using objects as tools (ex: spoon) Locomotion  Various theories of how walking develops  Maturational theorists: o Believes it depends on the development of the motor cortex  Cognitive theorists: o Suggest that it is a response to cognitive plans or representations that are the consequence of watching other people walk  Dynamic Systems theory (most satisfactory) o Walking skills determined by the interplay of a variety of emotional, perceptual, attentional, motivational, postural, and anatomical factors o Disappearance of stepping response for 10 month period b/c baby’s size and weight b/cm too much of a load on the emerging motor system masking the child’s stepping capability (possible theory) o 12 months should be able to step as long as they are given the stability and postural support necessary to stretch e/ leg forwards and back while in an upright position How Locomotion May affect Other Aspects of Development  Consequence of locomotor development is increased independence 9explore environments more fully and initiate more contact w/ o/ ppl)  Early walking is related to increased parent-child interaction and more “testing” of wills between mothers and their children  Many researchers have adopted a “perception-action coupling” approach to understanding the growth of such independent mobility  Motor or action systems are functionally interrelated to sensory or perceptual systems such that changes in one aspect influence the development of the other aspect. ` Chapter notes  Researchers have suggested that the onset of locomotion can change the way babies understand their perceptual world  Locomotion helps infants deal better with changes in spatial orientation  a/o link = “moving room” o moving room= walls and ceiling moved back and forth while floor stays immobile  demonstrated infants and young children use the visual input produced by a moving room to control their balance (despite lack of vestibular info) The Role of Experience and Culture  timing of the onset of various skills may be affected by societal and o/ factors  cross-cultural studies have provided us with information about how specific ways of caring for infants can alter their motor development  when caretakers give babies special physical attention, infants achieve motor milestones somewhat earlier than children not given such care and opportunities  experiment: asked moms to give their infants practice in stepping reflex for a few mins/ day o these babies made more walking responses @ 2-8 weeks and they walked earlier than a control group of babies who were given no practice o applicable to sitting practices as well  infants with more walking experience= most skilled walkers  there are limits though as to how far infant motor development can be pushed  Infants born in the summer or fall months acquired motor skills later than infants born in the winter or spring months because the former group would begin to develop locomotor skills in the winter to early spring, a time when motor skills might be constrained due to more restrictive clothing, activity-reducing illnesses, and less time for free movement b/c of shorter days. Box 5.1: Risk and Resilience  Being blind puts infants at a risk for many difficulties  Slower development of motor abilities  Lessens ability to explore independently and to discover objective rules that govern things in the external world  Technology can play a role in building motor capabilities for blind infants o Device that provides “echoes” help children “see” o ETA (electronic travel aids) = useful to avoid contact w/ other ppl and detecting presence of nearby objs Physical Growth  Study of growth guided by 2 principles:  Cephalocaudal development: growth that occurs from the head downwards o The brain and neck develop earlier than the legs and trunk  Proximal- distal pattern: developmen
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