Brain Development PDF

The brain has over 100 billion neurons Each neuron has up to 15000 connections to other cells Neurons produced at a rate of 250000/min Cerebrum has 2 hemispheres & is largest part of the brain 4 lobes – Frontal, temporal, parietal and occipital 2 Association areas – anterior and posterior (link up i...

The brain has over 100 billion neurons Each neuron has up to 15000 connections to other cells Neurons produced at a rate of 250000/min Cerebrum has 2 hemispheres & is largest part of the brain 4 lobes – Frontal, temporal, parietal and occipital 2 Association areas – anterior and posterior (link up information from different parts of the brain Cerebellum Brain stem Corpus callosum connects 2 hemispheres 3 further classification olf the brain Reptilian brain – brain stem & cerebellum (most developed in reptiles) Paleomammalian brain - limbic system Mammalian brain - cerebrum The nerves structure and function Neuron = nerve cell Glial cells – supportive roles Dendrites Cell body Axon Terminal buttons Synapse Neurotransmitters Sensory/motor Development of the nerve Starts in the embryonic period Most neurons present by 7th month (imagine all our nerves present before we are even born) Process is NEURON PROLIFERATION – 250000 neurons generated per min Neurons produced in one part of brain often travel to other parts following neurochemical trails. This is NEURAL MIGRATION Initial axons find their own way, but subsequent axons follow trails left by initial axons Initial axons guided by chemical signals and proteins to the connect with the correct neuron Once in final destination , starts creating synapses and building the brain’s communication channels Myelination of neurons mostly complete by 2 years old but changes occur into aduthood Brain over produces neurons and synaptic connections Why? 1. Allows experience to mold which neurons and synapses are kept and which are lost. The more a pathway is used through experience the more likely it will be permanent and the child will have optimal development. 2. It allows PLASTICITY. Brain can compensate for early damage by replacing connections that are lost or rerouting to another part of the brain. Thus, there is some possibility of recovery following injury. BUT Recovery is dependent on Age at time of injury Severity of injury Quality of environment child is raised in Control of over production of neurons Neuronal death – some of the cells are programmed to die in order to give room for the future cell clusters Synaptic Pruning – brain disposes of neuron’s connection with neurons. 20-80% of neurons die as synapses form These processes increase the efficiency of transmissions between neurons. Those that are used survive, those that aren’t die Development of the Brain Main development is Increase in size: At birth brain = 400g, 25% of adult brain (~1400g); 6 months old = 50% of adult brain; 2 years old brain = 75% of adult brain weight. Areas of the brain Reptilian = cerebellum & brainstem – basic survival. Controls e.g. breathing, digestion, excretion, reflex behaviours. Paleomammalian = limbic system – emotions & memory. Mammalian = cerebrum Cerebrum 90% brain’s cells are located in the outer cerebral cortex Most advanced part of the brain Frontal lobe associated with planning, organizing and higher mental functions Left & Right hemispheres anatomically distinct with differing functions Parietal lobe is associated with processing bodily sensations Temporal lobe, larger on left than right, associated with language, hearing & smell Occipital lobe is associated with vision Hemispheric specialisation Left and right hemispheres functions Begins at birth remains throughout life – INVARIENCE HYPOTHESIS, functions of each hemisphere remain unchanged throughout life The changes are what the child can do, as they develop, with the information processed by the 2 hemispheres Both hemispheres mature at different rates, the right maturing faster Hemispheric specialisation the differences Right Controls movement and sensation of left side of body Spatial awareness Music Facial recognition Emotions that withdraw from external environment e.g. fear, distress, disgust Shyness and fear – right frontal lobe Left Controls movement and sensation of right side of body Language processing Emotions that approach external environment e.g. Anger, interest, joy EXCEPTIONS Eyes send input to both sides of the brain Separation of functions between left and right is not set in stone. Brain damage to right side affects interpreting nonliteral language such as sarcasm yet it is the left side that is predominantly associated with language. Right side associated with the pragmatics of language. LATERISATION The process by which each hemisphere develops specialist functions This is complex Learning languages as an adult may be the right hemisphere rather than the left. Young children with brain injury can recover a great deal of the loss partly because brain is still developing and lateralisation is not complete e.g if damage to the left hemisphere, the child can still develop normal language skills. Older adults can also regain skills after brain damage BUT But Compensation due to brain injury has a cost Child may recover language skills but may have reduced complex skills in later life As healthy brain compensates for the loss of language there is less room for the development of other tasks Cerebral cortex is limited – some room for compensation but cant be overcrowded Developmental cognitive Neuroscience Brain development is ongoing process Prefrontal cortex matures well into adulthood While the brain is vulnerable and sensitive it is also has high resilience to internal and external threats If there are no major threats the brain will develop in the right way to optimise for learning and adaptation to the environment Brain change and behavioural development 1. Maturation – Brain growth leads to new behaviours, direct effect on developing skills 2. Skill learning – Brain is developed but active learning and teaching is required to acquire skills and behaviours 3. Interactive specialization- Brain has framework for development which are influenced by interaction with the environment and how other brain areas develop and interact with each other e.g. The capacity is built into the brain but development is dependent on the environment, development of other parts of the brain and how they all interact. OR Or SYNAPTIOC PROLIFERATION AND PRUNING The infant cerebral cortexes have twice as many synaptic connections than the adult (30 years old) Pruning results in synapses that are rarely used losing their connection thereby moulding the child’s brain to suit the child’s individual environment If pruning didn’t occur there would be too much activity in the brain for the individual to cope with. It is thought that Autism is linked to a lack of pruning of these excess synapses. Pruning starts at puberty and lasts into early adulthood UNDERSTNADING THE PRUNING PROCESS 1. Knowing how long the process takes to complete can help with the timing of education and the best time to acquire new skills 2. Allows an understanding of when we move from a developmental personality mode to a concrete adult personality 3. Can give an understanding of the development of neuropsychiatric disorders that appear in adolescence and later adulthood e.g. autism; schizophrenia; drug induced psychoses. 4. Since pruning is thought to extend into adulthood it suggests there is scope for cognitive and emotional change into adulthood MYELINATION There is little development of neurons after about week 20 of gestation. However, glial cells continue to be generated throughout life – mainly in the process of myelination which produces the white matter of our CNS and explains the growth of the Brain despite synaptic pruning taking place. Myelin insulates axons and supports the transfer of information through the nervous system Myelin also provides a track for regrowth of some nerve fibres, supporting nerve regeneration Importance of Myelination Neurodegenerative diseases such as Multiple Sclerosis result in demyelination of nerves and can result in speech, balance and cognitive impairment. Myelination continues into adulthood, particularly in the frontal cortex. Grey matter - the neurons decline with age As the brain refines and moulds itself through pruning of neurons it develops the efficiency of transferring information through the nervous system with myelination The frontal cortex is associated with higher order thinking – required as adults for planning, organizing, attention and inhibition NEUROPLASTICITY The brain has a degree of plasticity through development The brain can change as a result of new experiences with time Initially as the brain develops areas are not fully committed to specific functions therefore highly receptive to learning Plasticity can also give hope in cases of brain damage since some of the functions can be recovered But as we age there are limits to regeneration Plasticity is dependent on age, site of brain damage, amount of tissue damaged, the skills area involved. Regeneration may be possible, but information processing may be slower Certain motor functions can be regenerated in adults Individuals born preterm show reduced plasticity GROWTH SPURTS Frontal lobe activity and an increase of synaptic connections during infancy and toddlerhood relate to grasping objects; walking; language. Surges in brain growth can relate to cognitive development BRAIN STIMULATION Under as well as over stimulation can have negative consequences Overstimulation as a result of exposure to educational programmes can lead to 10% lower language tests scores for infants and toddlers Screen time education is fast paced rather than the slow-paced personal interaction between parents and child The brain requires environmental experience in order for some areas to develop ACTIVITY Considering your understanding now of brain and neuron development, consider how this might relate to the developmental theories we explored last week. The brain over produces neurons and prunes these dependent on our environment How does this relate to the nature/nurture argument? The brain develops as a result of our individual environment with time sensitivity – How do these relate to Piaget’s, Erickson’s, Vygotsky’s Freud’s, etc.. Developmental timelines? Make notes for yourself relating brain development to these concepts and theories.