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Neurophysiology 10- (Synaptic Strength (Importance (if size of synaptic…

- - - - -individual EPSP from same axon occur during preceding one
      - freq divider - most neurons cant fire that fast so they add during decay, refractory period slows down response, brain uses reduction in freq to produce other info
    - - EPSP from different axons occur within same time window - ANDgate associates inputs
- - - - neurexins- bind to neuroligins on post synaptic side, have esterase homology domain - neuroligins bind to b form of neureins and hold synapse together -C terminal of neuroligins bind to post synaptic apparatus that creates post synaptic element
      - structure goes across synaptic cleft which holds elements that make post synaptic specialisation at one end and on other side holds elements that brings Ca channels and release proteins on pre synaptic side -mutations in neurexins 1,3,4 associated with autism
- - - - using glass capillary microelectrode
      - detects AP firing (currents) in individual neurons
      - only detects activity once neuron activated - cant tell you about mechanisms before signal
      - Strengths: used in any part of NS, multiple recordings at different sites, can be used in vivo)
      - Weaknesses: doesnt identify membrane potential changes that cause firing - doesnt detect neurons that dont fire AP
    - - microelectrode tip inserted into individual neuron , filled w conducting solution,
      - records membrane poten, can measure AP synaptic potentials, passive membrane properties - used in vitro but can be used in vivo
      - injection of markers to identify morphology/neurochem
      - Advan: long term recordin of changes, identifies some membrane mechanisms, suitable for pharm studies w drugs that last minutes
      - Weaknesses: doesnt measure underlying currents or idntify where signal generated
    - - record membrane pot w one electrode and passes curretn w the other - measures current needed to keep potential constant
      - Strength: time res, measures underlying currents, strong data for construction of models
      - Weaknesses: only works in large cells, low control of dendrites, only done in vitro
    - - electrode forms tight seal w membrane, record potential across patch (current clamp) or membrane current through patch (voltage clamp)
      - whole cell patch recording: measure membrane currents,
      - Advan: can sample cytoplasm/mRNA, can inject w Ca indicator , powerful when used to record interconnected membrane , seal gives stable recordings
      - Weaknesses: needs clean cell, not good w connective tissue
  - - - all cells can be made to express one - they are in all neural crest derived cells
      - allows you to stimulate system and look at activity
      - high spatial width of field - moderate time res
    - - output as indvidual reproting what they are thinking/feeling/detecting eg. illusion - to study visual pathway via brain imaging - testing needs to be rigorous and well controlled
    - - MRI -vary magnetic field, can detect changes in molecule spin, put together image - can view brain activity
      - fMRI- where oxygenated venous blood/brain activity is - activity precedes oxygenation (not great time res) and blood flow increases in a range (spatial res not great) - better spatial res than PET
      - PET - radiolabel w positron - emitts gamma rays, low spatial res,
      - (fMRI and PET): cannot be used on freely moving animal, poor spatial res,
      - MEG- measure magnetic fields, high time res, low spatial res, has to be in magnetically shielded rooms
      - TMS- stimulate specific regions to alter behaviour via magnetic currents
      - EEG - electrode recording from scalp, can be used on moving sujects, excellent temporal res, poor spatial res