Amat part 2

• What are the 4 elements of EEG ?

  • Synchronization of neurons = increase in voltage
  • Spontaneous cortical activation = baseline distribution.
  • Can record different arousal level
  • Can record ERP = time locked to the onset of a specific stimulus
• At what level does EEG work ?

  Global
• What is LFP ?

  • Called Local field potential
  • Reflects the summed electrical activity of neurons in one given region
• At what level does LFP work ?

  Global (but less global than EEG)
• What is extracellular multi-unit activity recording ?

  • It is an invasive technique
  • Captures signle unit and multi unit neuronal activity
• What can variation in spikes in MUA can be atributed to ?

  Spike amplitude can be attributed to differences in their distance from electrode. Or simply the presence of non-conductive materials
• What does the amplitude differences facilitate ?

  Spike sorting : separation of spikes from different neurons thanks to the amplitude differences
• What are the advantages of using multiple measurements techniques ?

  • Have a broader insight (with global techniques like EEG & LFP)
  • Have a detailed info on neuronal activity (MUA)
  • Combining can show neural dynamics at different levels : MUA & LFP
• What are the 4 types of neural codes ?

  • Rate coding
  • Temporal coding
  • Convergence coding
  • Population coding
• What is rate coding ?

  • a quantative coding
  • discharge rate depends on intensity of response
  • intensity of stimulation is encoded by spike frequency
• What are the issues of rate coding ?

  • does not show the quality of a stimulus
  • only provides info on intensity and duration of stimulus
• What is the bar code theory ?

  • a qualitative coding mechanism
  • based on distinctive patterns of neuronal discharges rather than calculating mean frequency of AP
  • you want to see distribution of spike
• What are the issues with bar code theory ?

  • representation of stimulus
  • not consistent : distribution of spikes may be identical across different stim
  • difference between central and peripheral levels
  • only first spikes integrated into excitatory post synaptic potentials
  • Issue of time
  • dispersion of information = binding problem
• What is convergence coding ?

  • different levels of neuronal hierarchy
  • based on discharge rate of neurons
  • see how brain integrates distributed neural activity representing different attributes
• What are the issues of convergence coding ?

  • unrealiable
  • not robust
  • too large nb required to actually represent every asepct
  • acquisition of new infos impossible
• What is population coding ?

  • object not represented by individual activity but by simultaneous activtion of population
  • collective activity
• What are the issues with population coding ?

  • slow processing to integrate all of the discharges
  • activation and desactivation hard to separate assemblies
  • representation hard when objects overlap
• Which one of the coding theories is the best ?

  It's the population coding because it is spatio temporal coding and has different advantages : economic, robust and flexible
• What is an oscillation ?

  It is rhyhtmical variation of an electrical signal
• What does an oscillation represents in neural network ?

  A rhythmical variation of electrical activity in the population !