Introduction to Neuroscience Dr Claire Gibson School of Psychology, University of Leicester PS1000

2 1.Functional Neuroanatomy – The Nervous System and Behaviour 2.Development and Plasticity of the Nervous System

3 Development of the NS 4 main stages 1.Cell proliferation 2.Migration 3.Differentiation 4.Synaptogenesis 5.Neuronal cell death 6.Synapse rearrangement 7.Myelination ….more detailed 7 stages = PS2014/8

4 1. Cell Proliferation 250,000 new cells per minute Neurogenesis = production of new nerve cells Proliferation occurs in the ventricular zone (cells then migrate to final destination) Nerve cells themselves do not divide The cells that produce neurons divide (via mitosis) and = layer of cells within the ventricular zone Eventually some cells migrate away from ventricular zone and begin differentiating into either a neuron or glia cell.

5 Historical opinion - at birth. But, the human brain weight increases following birth –simply due to growth in neuronal size, dendrite branching, increased myelin ??? NO - Neurogenesis occurs even in adulthood Neurogenesis is sensitive to experience –Learning enhances neurogenesis –Social isolation reduces neurogenesis 1. Cell Proliferation – when is it complete?

6 Newly formed neurones migrate from ventricular zone to their final destination Radial glial cells Failure in mechanisms of migration = behavioural disorders Cell adhesion molecules (CAMs) –Promote the adhesion of developing elements of the NS –Guide migrating cells and growing axons 2. Migration

7 3. Differentiation Cells reach their final destination – begin to express particular genes These enable cells to take on characteristics of a particular neuronal type PS2014/8

8 4. Synaptogenesis Cells undergo extensive growth of axons and dendrites = process outgrowth and proliferation of synapses (i.e. synaptogenesis) Growth cones Filapodia and lamellipodia – respond to the environment and pull the growth cone in a particular direction Chemoattractants Chemorepellants Synaptogenesis occurs rapidly on dendrites and dendritic spines

9 5. Neuronal cell death Normal part of development PS2014/8

10 6. Synapse rearrangement Not simply elimination Involves loss of some and formation of others Human cerebral cortex = net loss of synapses from late childhood until mid-adolescence What determines which synapses are kept and which ones are lost? –Neural activity –Neurotrophic factor = a target-derived chemical that acts to ‘feed’ neurones

11 Development of the NS Due to the interaction of intrinsic and extrinsic factors Intrinsic (i.e. genes) – originate from within the cell itself Extrinsic – originate from outside the developing cell e.g. nutrients, experience

12 Genes are the intrinsic factors that influence NS development Genome (genotype) The sum of all the intrinsic genetic information that an individual possesses Determined at the moment of fertilisation Remains constant throughout our lives Phenotype The sum of all the physical characteristics that make up an individual Changes constantly as we mature and age Determined by the interaction of genotype and extrinsic factors (including experience)

13 So, will two identical twins with identical genotypes a)Have the same phenotype? YES/NO b)Behave exactly the same? YES/NO

14 How does experience modify the NS? An individual’s experience during development alters many aspects of behaviour, brain anatomy and neurochemistry Much of the change resulting from experience involves reorganisation Reorganisation = a shift in connections that changes the function of an area of the brain E.g. blind people who read Braille, space in the brain devoted to the index finger increases E.g blind people who excel at sound localisation have recruited the unused visual area of their brain to aid in sound localisation

15 The ‘plastic’ brain So, if experience can ‘reorganise’ the brain = the brain is described as being plastic Plasticity = the lifelong ability of the brain to reorganise neural pathways based on new experiences Why is this important? To enable us to learn As an adaptive mechanism to compensate for lost function and/or to maximize remaining functions in the event of brain injury.

16 Damage and recovery to the CNS Scientists are interested in the development of the NS –Hope to find clues about how to repair the NS when it is damaged by injury, disease or developmental error –PS2014/8

17 Summary Neurogenesis, migration, differentiation, synaptogenesis, neuronal death, synapse rearrangement, myelination Intrinsic and extrinsic factors Role of experience