BioBasesSup 2

BioBasesSup 2

1. Neurophysiological principles

   • Volume condution
     • the closer we are to the electrode
     • we can assume that the activity are not activited together because they are relevant at different stages of processing
     • Dipole
       • the electric field quickly falls off
       • electrodes farther away have a weaker strength in measurement
     • lack of localisation
       • You may encouter statements like "we found activity in such and such area" because there is an intractable inverse solution
       • If we know where the activity sits, with a fairly good estimate, use the forward solution. The inverse solution however, estimating the surface potentials in the brain, there is no solution to this.
       • Skull and Sculp projection
   • EEG
     • Sophisticated stats can untangle the locations, since not all activity is at the same time (synchronous)
     • It is instant
     • Forward solution is possible
     • 64 channels over the entire sculp is a good standard; 100 or so does nothing to improve the spatial resolution
     • Practical aspects
       • At least three electrodes.
         • Reference electrode
         • Ground
         • Recording

2. Basic brain areas

   • Thalamus
     • Gate to the cortex
   • Occipital Lobe
   • Parts of our brain are working together at the same time and as such, superimposed

3. fMRI

   • Preciesly find the location but metabolic to the activity

4. biophysics

   • intrectable inverse solution
   • It is not such a problem, but be careful of claims in localisation

5. Two dimensions

   • EEG and MEG
     • The BOLD response - showing the metabolic response of the brain to the neural activity is milliseconds
   • fMRI
     • finer spatial resolution
   • 1) Spatial resolution - grain of where it could be measured
     • Temporal resolution is poor
   • 2)Temporal resolution - fractions of a second in measurement milliseconds
     • Spatial resolution is poor; 6 secs later

6. CogNeuroMethods