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Biopsychology - Brain Development (Y1) - Coggle Diagram

- - - - Cells migrate in an orderly fashion from deep to superficial layers - cortical cells migrate through already formed lower levels of cortex before reaching the destination, known as the inside-out pattern
        
        However, new research has shown many cells actually use tangenital migrations and that patterns of proliferation and migration depend on the area of the cortex developing
        
        Neural crest - dorsal to neural tube - cells that break off as tube forms, develop into neurons and glial cells of peripheral nervous system (tube becomes CNS)
        
        Aggregation - alignment of developing neurons with other neurons that have migrated to the same area to form structures of the nervous system
        -> mediated by CAMs, cell adhesion molecules located on the surface of neurons, recognise molecules on other cells and adhere to them - eliminating one CAM in a knockout mouse had a devastating effect on brain development
        -> Gap junctions also have a role - connexins, communication with adjacent cells
        -> Achieved through interactions of microglia and neurons
    - - Similar in regeneration after a part is destroyed - regrow to fill available space e.g. lesion half of retina, tectum fills half left, lesion half of tectum, retina projects all to that half
        
        Topographic gradient hypothesis - axons growing from one topogaphic surface to another are guided to specific targets arranged on terminal surface in the same way they are arranged to original surface - guided through intersecting signal gradients of anterior-posterior and medial-lateral
        
        Spontaneous neural activity and neuron-astrocyte interactions contribute to accurate topographic mapping (one area mirrors adjacent area)
      - Synapse formation -
        
        takes coordinated activity of two axons to create one - spontaneous neurotransmitter release has been linked to synapse formation
        
        some of the chemical signals that play a role in location and formation of synapses have been identified and cell surfaces interact before synapse formation
        
        Synaptogenesis - dependent on astrocytes and microglia, developing synapses requires high cholesterol levels, which can be provided by astrocytes - they also process, transfer and store information supplied by neurons
        
        Neurons can form synapses with any other neuron types, but once established, synapses that do not function appropriately tend to be eliminated
    - - Triggers
        -> some neurons are genetically programmed for early death - once function is fulfilled, groups of neurons die together in the absence of stimuli
        -> Also fail to obtain the life preserving chemicals that are supplied to developing neurons by their postsynaptic targets - evidence that these chemicals come from here is the grafting of an extra target structure to an embryo before the period of synaptogenesis reducing neuron death in the area, and destroying some of the neurons growing in an area increases the survival rate of others
        -> life-preserving chemicals - neurotrophins - NGF and brain dervied neurotrophic factor (BDNF) - promote growth and survival of neurons, function as axon guidance and stimulate synaptogenesis
      - Synapse rearrangement - neurons that have incorrect connections are likely to die, and as they die the vacant space is filled by sprouting axon terminals of surviving neurons; cell death results in a massive rearrangement of synaptic connections
        
        This phase also results in a number of postsynaptic cells, thus increasing the selectivity of transmission - microglia have a role
- - - - Learning dependent plasticity in adults -
        Gaser and Schlaug, 2003:
        
        how much plasticity can happen - found a bigger volume in musicians, especially in areas related to playing and perceiving the piano
        
        Cannot be sure if music training leads to bigger brain volume, or these people have bigger brains initially making it easier to learn music
        
        Draganski et al, 2004:
        
        In this study, volunteers were trained who had no prior experience to juggle 3 balls at the same time - after training, they found an increase in the motor cortex volume
        
        McGuire's taxi drivers (2000) - enlarged hippocampal areas for spatial navigation