OCCTH 583 Neurology Foundations 2 Lecture Notes PDF

OCCTH 583 NEUROLOGY FOUNDATIONS 2 Jennifer Krysa, MSc Registered Occupational Therapist (AB) Outline Brain Development A Spider’s Tale Neuro Games 2 Brain Development Two Phases in which neurocircuitry is built : 1. In utero: genetically determined sequence of events...

OCCTH 583 NEUROLOGY FOUNDATIONS 2 Jennifer Krysa, MSc Registered Occupational Therapist (AB) Outline Brain Development A Spider’s Tale Neuro Games 2 Brain Development Two Phases in which neurocircuitry is built : 1. In utero: genetically determined sequence of events that is influenced by maternal environment 2. Prenatal and postnatal: Emerging connections are responsive to environment and to experiences 3 Brain Development Stages Neurogenesis Cell Migration Cell Differentiation Cell Maturation Synaptic Formation Synaptic Pruning Myelin Formation 4 Neurogenesis Genesis=the origin or formation of something Neurogenesis=the formation of neurons In utero timeline: Week 3 neurons begin to form. They will produce the neural tube Week 6 the cells that become the cerebrum begin to divide 14 weeks cerebrum grossly formed 7 months sulci & gyri appear 5 Neurogenesis Neurons continue to form in the hippocampus thru at least middle age New Learning Exercise 6 Cell Migration & Differentiation Newly formed neurons migrate along glial cells to the outer surface of the cerebral cortex The cerebral cortex forms it 6 layers inside out The neurons appear to migrate to specific regions of the cortex The neurons then begin to differentiate into different cell types Form axons & dendrites Form synapses Synthesize NTs 7 Cell Maturation Cells mature at their final destination Dendrite formation begins in utero and continues post-natal Dendritic growth is slow, and axon growth is fast (~1000x faster) The abundance of axons allows them to influence dendritic differentiation We initially produce more axons & dendrites than we need 8 Synapse Formation Starts ~ week 23 prenatal and continues post-natal Prime time is first two years after birth Up to 700 synapses per second (hence the overproduction) Basic brain processes wire first More complex functions wire later Most neural connections develop and locate on cortex in response to experiences & environment 9 Synaptic Pruning Unused neurons die & neural circuits are pruned away Ergo the most used synapses remain → which is why experiences & env’t is a key factor on brain devel’t The timing for this pruning is variable Visual cortex prunes in early childhood until ~ 6 y.o. Prefrontal cortex prunes in late adolescence 10 Myelin Formation Glial cells develop allowing for formation of myelin Starts prenatally and mostly ends in young adulthood Occurs in waves After age 18 Prefrontal cortex Posterior parietal cortex Anterior temporal cortex 11 Prefrontal Cortex Decision-making Reasoning Social appropriateness Personality expression Complex cognitive behaviours 12 Posterior Parietal Cortex Spatial reasoning Attention Planned movement 13 Anterior Temporal Cortex Semantic memory Knowledge of facts, words, people, objects 14 Pattern Pattern of brain development is hierarchical: bottom up Prenatal & at birth: low level interpretation of sensory stimuli Higher level: e.g. interpretation of facial expression, development of language Heavily contingent on exposure to environments and experiences at critical periods of development Skill development naturally follows this pattern 15  Sensitive Periods Occur at different ages for different parts of the brain Age-appropriate stimulation Stimulating environments and experiences enhance brain architecture These stimulating early experiences are necessary to build the foundation for later learning Lower-level circuitry needs to send precise & high-quality information to the higher-level circuitry to carry out complex tasks. Adding & pruning of neural circuits Vision, hearing, motor skills, behavioural control, emotional development, responses to social cues, language 16 Sensitive Periods - Continued As higher-level circuitry is maturing need to have more diverse and sophisticated experiences Early impoverishment can have lifelong consequences Primary relationships have a significant impact on the architecture of the brain Serve & return interactions with a caregiver 17 Neuroplasticity The ability of the brain to form and reorganize synaptic connections in response to positive stimuli (learning) or negative stimli (injury) e.g. Novel, complex, effortful, sustained, attention 18 A Spider’s Tale – Draw It A spider named Willis lives on the pons He has a nose, angry eyebrows, two suckers for a mouth and two eyes that look outward Willis has crew cut and a fuzzy beard [no moustache, no goatee] He is proud of the 2 pairs of antenna that seem to jut out from his eyes One pair goes straight up, and the second pair goes off at about a 45- degree angle 19 Willis - Continued He has 8 legs coming off his skinny body: 2 pairs right under his head and 2 pairs at the end of his body He has two short feelers coming off the top of his last pair of legs Willis is male 20 21 Significance of Circle of Willis Collateral blood flow between anterior and posterior circulations of the brain Protection against ischemia or damage in one or more areas 22 Launch Neuro Games 23