3 ms·

Yes, the current spreads regardless, since everything is basically saline (so to speak). So the more distant neurons are activated at a lower level (due to the

by kghose 13y ago

Yes, the current spreads regardless, since everything is basically saline (so to speak). So the more distant neurons are activated at a lower level (due to the r^2 drop in current density)

jlgreco 13y ago
Have there been experiments with implanting numerous electrodes in a sort of shotgun pattern, but only activating the center ones at first so that when they "wear out" the outer electrodes can take over? That might mitigate the need to up the current or perform another surgery, but on the other hand I suppose you want to keep the number of electrodes in there to a minimum.
- kghose 13y ago
  Well, that's a cool thought: current DBS leads do have multiple contacts. However, the main reason for this is that exact placement of the leads is not possible. Even with structural MRI and CT scans and so on, the placement is only approximate. So, surgeons have the patient awake and talking etc. to make sure they are not hitting the internal capsule (which would be bad for movement etc.) and then have access to multiple leads which they activate in turn to see which leads are best at mitigating symptoms (i.e. are activating/deactivating the appropriate structure) What I am very excited about is the concept of neurotrophic chemicals on electrode leads. These chemicals encourage neurons to grow processes towards them, thereby making a better and longer lasting connection with the electrode. If we ever get to a Neuromancer/Matrix like future where we 'jack in' our brains, I think neurotrophic electrodes with very fine spacing will be part of the technology, so that we can activate many neurons in many different patterns in a well controlled manner.
  - jlgreco 13y ago
    Aaah, very interesting. That is a much more elegant solution.
- etrautmann 13y ago
  It's currently understood that it's the presence of the electrode that causes buildup of glial tissue, not the stimulation current, so this approach wouldn't really work. It isn't really necessary though, since you can turn up the current slightly to compensate for the buildup around the electrode. It's a relatively coarse manipulation, but we'll be increasingly using optogenetics as a replacement.

by kghose 13y ago

Yes, the current spreads regardless, since everything is basically saline (so to speak). So the more distant neurons are activated at a lower level (due to the r^2 drop in current density)

jlgreco 13y ago

Have there been experiments with implanting numerous electrodes in a sort of shotgun pattern, but only activating the center ones at first so that when they "wear out" the outer electrodes can take over? That might mitigate the need to up the current or perform another surgery, but on the other hand I suppose you want to keep the number of electrodes in there to a minimum.

kghose 13y ago
Well, that's a cool thought: current DBS leads do have multiple contacts. However, the main reason for this is that exact placement of the leads is not possible. Even with structural MRI and CT scans and so on, the placement is only approximate. So, surgeons have the patient awake and talking etc. to make sure they are not hitting the internal capsule (which would be bad for movement etc.) and then have access to multiple leads which they activate in turn to see which leads are best at mitigating symptoms (i.e. are activating/deactivating the appropriate structure) What I am very excited about is the concept of neurotrophic chemicals on electrode leads. These chemicals encourage neurons to grow processes towards them, thereby making a better and longer lasting connection with the electrode. If we ever get to a Neuromancer/Matrix like future where we 'jack in' our brains, I think neurotrophic electrodes with very fine spacing will be part of the technology, so that we can activate many neurons in many different patterns in a well controlled manner.
- jlgreco 13y ago
  Aaah, very interesting. That is a much more elegant solution.
etrautmann 13y ago
It's currently understood that it's the presence of the electrode that causes buildup of glial tissue, not the stimulation current, so this approach wouldn't really work. It isn't really necessary though, since you can turn up the current slightly to compensate for the buildup around the electrode. It's a relatively coarse manipulation, but we'll be increasingly using optogenetics as a replacement.