BIOMEDSCIE Lecture 17 neuroscienze

• Motor cortex


  Control of skeletal muscles
• Frontal lobe


  Prefrontal cortex (decision making, planning)
• Broca's area


  Forming speech
• Temporal lobe


  Auditory cortex (hearing), Wernicke's area (comprehending language)
• Somatosensory cortex


  Sense of touch
• Parietal lobe


  Sensory association cortex (integration of sensory information), Visual association cortex (combining images and object recognition)
• Occipital lobe


  Visual cortex (processing visual stimuli and pattern recognition)
• Cerebellum


  Processing visual stimuli and pattern recognition
• The nerve fibres of the brain were traced by diffusion spectrum imaging, and coloured to represent their direction
• Changes in synaptic connections underlie memory and learning
• Embryonic development of the nervous system

  1. Neurons compete for growth-supporting factors in order to survive

  2. Only half the synapses that form during embryo development survive into adulthood
• Neural plasticity


  The ability of the nervous system to be modified after birth
• Neural plasticity


  • Changes can strengthen or weaken signaling at a synapse
  • Can take the form of Long-Term potentiation (LTP) (enhancing synaptic transmission)
• Short-term memory


  Accessed via the hippocampus
• Long-term memory


  Stored in the cerebral cortex
• Some consolidation of memory is thought to occur during sleep
• H.M.


  • Suffered severe, uncontrolled epilepsy as a result of a childhood accident
  • Underwent a bilateral medial temporal lobe resection in 1953
  • Lost some memory of previous events (retrograde amnesia) and was unable to form new memories (anterograde amnesia)
  • No loss of intellect
• H.M. provided first evidence of a role for the hippocampus in memory formation
• Hippocampus


  Hippo=horse, kampos = sea monster
• HM had both hippocampi removed
• Declarative (Explicit) memory


  Hippocampal dependent, Fast Learning, Facts, Figures, Spatial learning: Route to work, home
• Procedural (Implicit) memory


  Motor learning: Cerebellar dependent, Slow accumulation of skills, Previous experience e.g. riding a bike
• Long-term potentiation (LTP)


  A form of learning involving an increase in the strength of synaptic transmission, requires NMDA and AMPA type glutamate receptors
• Induction of LTP


  1. High frequency stimulation removes Mg2+ block from NMDA receptor, allowing Ca2+ influx which increases number of surface AMPA receptors

  2. Low frequency stimulation now induces a larger EPSP
• Newly formed neurons in the hippocampal dentate gyrus play an essential role in learning and memory
• Newly formed neurons


  • Labelled with green fluorescent protein, other older neurons labelled red
• Mg2+


  Can be activated again with sufficient depolarisation of the post synaptic neuron caused by activation of AMPA receptors
• Fred Gage (California) and Peter Erickson (Sweden) identified neural progenitor cells 'stem cells' in post-mortem tissue from adult hippocampus


  1998
• Subsequent discoveries showed that, under experimental conditions, these cells can give rise to neurons that mature and integrate into existing neural networks
• Historically it was thought that humans were born with the exact number of neurons that they will have for a lifetime, incapable of cell division –with no new neurons produced throughout life
• Neurons lost, e.g. as a result of neurodegenerative disease, could never be replaced (NOT TRUE)
• Newly formed neurons in Hippocampal Dentate Gyrus – labelled with green fluorescent protein. Other older neurones are labelled red
• Thousands of new hippocampal neurons are born each day
• Positive regulators of new neuron survival


  • Hippocampal-dependent learning
  • Physical exercise
  • Environmental enrichment
  • LTP
• Negative regulators of new neuron survival


  • Stress
  • Social isolation
  • Alcohol/drug abuse
  • Ageing
• Neurogenesis can be manipulated for therapeutic advantage
• Potential therapeutic applications of manipulating neurogenesis


  • Upregulation of neurogenesis by genetic, environmental and other factors to promote cognition
  • Boost neurogenesis to reduce age-related cognitive decline
  • Modulate neurogenesis to facilitate CNS repair
  • Stem cell therapies to promote neurogenesis
• Nervous system disorders can be explained in molecular terms
• Examples of nervous system disorders


  • Schizophrenia
  • Depression
  • Bi-polar disorder
  • Drug addiction
  • Alzheimer's disease
  • Parkinson's disease
• Genetic and environmental factors contribute to diseases of the nervous system