approached to studying NS

• ELECTROPHYSIOLOGY:

  Extracellular electrophysiology – compound action potential

  Sum of all action potentials firing simultaneously
• Extracellular single unit recordings

  microelectrode placed close to neurone

  record action potential discharge activity = spikes

  in vitro or in vivo

  single or multi array electrodes
• Intracellular electrophysiology 

  -          Neurone into the actual neurone

  Intracellular sharp microelectrodes – for smaller neurones – tip smaller than 1 micro meter

  Can record:

  • Resting membrane potentials
  • Synaptic and receptor potentials
  • Action potentials
• voltage clamp

  whole cell changes in current

  
• Patch clamp

  records activity of individual ion channels

  • seal a small pipette tip to cell membrane
  • such up small amount of membranes
• Extracellular - EEG

  • electrodes on scalp
  • measures synaptic potentials from populations of neurones from small areas of cerebral cortex
  • waves of electrical activity in brain
• voltage sensitive dyes

  -          Molecules that fluoresce in response to membrane potential changes

  -          Dye taken up by cells – changes amount of fluorescence depending on voltage potential
• Ca2+ sensitive dyes

  -          Fluoresce in response to Ca2+ binding

  -          Helps us understand synaptic events
• optogenetics

  uses light to inhibit or stimulate activity

  • genetically engineering neurones so they express light sensitive channels
  • -          Depending on channel you can turn neurone on or off

  -          On – channel rhodopsin – depolarised

  -          Off – halorhodopsin – hyper polarising
• tracers

  MAP PATHWAYS

  • injected into brain tissue
  • move intracellularly through neurones
  • fluorescent
• anterograde tracer

  cell body to terminal

  Fluorescent adeno-associated virus (AAV)

  
• retrograde

  Terminal to cell body

  Horse radish peroxidase (HRP) enzyme

  
• brainbow

  • Genetic cell labelling technique
  • DNA inserted into neurones that express slightly modified versions of green fluorescent protein (GFP): green, red and blue
  • Modify neurones to express colour protein