5 ms·

Cadaver studies have shown that this is almost certainly placebo. Not enough current actually reaches the brain: https://buzsakilab.com/wp/wp-content/uploads/20

by tbenst 3y ago

Cadaver studies have shown that this is almost certainly placebo. Not enough current actually reaches the brain: https://buzsakilab.com/wp/wp-content/uploads/2017/07/Underwoood-Cadaver-Science-16.pdf https://buzsakilab.com/wp/wp-content/uploads/2017/07/Underwo...

agucova 3y ago
The article mentions this explicitly.
petesergeant 3y ago
Is it possible to blind test this? Like can people feel whether or not the current is passing through their brain? Feels like it should be easy enough to do a study on
- swader999 3y ago
  Yes, you can feel the current at times. It is pretty mild though.
- mattkrause 3y ago
  Yes! I ran an experiment where we blocked the skin sensations with topical anesthesia and then recorded the responses of individual neurons to tES. Nothing changed, so the sensation is not necessary for its effects. https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000834 https://journals.plos.org/plosbiology/article?id=10.1371/jou... We also created the same sensations elsewhere on the scalp, and this was not sufficient to cause neural entrainment either. https://www.pnas.org/doi/10.1073/pnas.1815958116 https://www.pnas.org/doi/10.1073/pnas.1815958116 Placebo/skin effects can certainly mess up a readout based on performance or behavior but they aren’t the full story either.
superbiome 3y ago
“Other people tried to put tDCS on a cadaver and said that there wasn’t enough electricity that was penetrating the skull to make any difference in terms of action potentials. But the next meta-analysis found some effectiveness for depression and anxiety. The study[1], published in 2017, was one of the best out there.” 1. https://www.sciencedirect.com/science/article/abs/pii/S1388245716306344 https://www.sciencedirect.com/science/article/abs/pii/S13882... Article also mentions living bone is conductive.
hackernewds 3y ago
this seems easy to refute based on (my personal reproducible) observation of physical phenomenon, such as tasting coins in the back of my throat.
- PcChip 3y ago
  Can you expand on this? If I get a sharp scare I suddenly taste metal for a second
mattkrause 3y ago
That study is misleading/wrong and has done a huge amount of damage to this field. What they actually showed is that 1) much of the current does not reach the brain, and 2) the current that does is not sufficient to directly “force” neurons to fire. However, that doesn’t mean the remaining current does nothing at all, as it could still modulate brain activity. Using direct recordings of individual neurons, I showed that various forms of tES shift spike timing. Simulation causes them to fire sooner or later than they otherwise would. This matters because information is carried in both by overall rate of spiking and the timing of those spikes. Moreover, it’s not just a placebo, because knocking out the sensations with topical anesthetic doesn’t block the neural effects, nor is recreating them sufficient to cause them. I just wrote a little think-piece about this for PLOS Biology that summarizes what we know—-and don’t—-about it https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001973 https://journals.plos.org/plosbiology/article?id=10.1371/jou...
- tbenst 3y ago
  Thanks! That is interesting and well reasoned. If one wants to change neural computation via a global oscillator, it would seem that a flashing light, auditory tone, or tactile vibration might be a more potent alternative. These stimuli indisputably drive substantial brain wide activity, including many action potentials. I suppose I’m reluctantly team Firing Rate when it comes to mammals—there’s beautiful work on spike ordering in cold blooded animals for example but I’m less aware of computational work where precise spike time matters and not the relative time ie hebbiwn plasticity. I’m also somewhat influenced by my first hand difficulty when doing in vitro patch clamp to induce sub threshold voltage changes on a neuron with a second probe even just 100um away. Color me skeptical, in part as it’s really hard to do a double-blinded control and the effect sizes seem small.
luxuryballs 3y ago
perhaps the current does not need to actually reach the brain in the way these studies are setup to measure? it’s possible the brain is more sensitive and/or there’s some low powered emf naturally at play in your brain/body, for example

by tbenst 3y ago

agucova 3y ago

The article mentions this explicitly.

petesergeant 3y ago

Is it possible to blind test this? Like can people feel whether or not the current is passing through their brain? Feels like it should be easy enough to do a study on

swader999 3y ago
Yes, you can feel the current at times. It is pretty mild though.
mattkrause 3y ago
Yes! I ran an experiment where we blocked the skin sensations with topical anesthesia and then recorded the responses of individual neurons to tES. Nothing changed, so the sensation is not necessary for its effects. https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000834 https://journals.plos.org/plosbiology/article?id=10.1371/jou... We also created the same sensations elsewhere on the scalp, and this was not sufficient to cause neural entrainment either. https://www.pnas.org/doi/10.1073/pnas.1815958116 https://www.pnas.org/doi/10.1073/pnas.1815958116 Placebo/skin effects can certainly mess up a readout based on performance or behavior but they aren’t the full story either.

superbiome 3y ago

“Other people tried to put tDCS on a cadaver and said that there wasn’t enough electricity that was penetrating the skull to make any difference in terms of action potentials. But the next meta-analysis found some effectiveness for depression and anxiety. The study[1], published in 2017, was one of the best out there.” 1. https://www.sciencedirect.com/science/article/abs/pii/S1388245716306344 https://www.sciencedirect.com/science/article/abs/pii/S13882... Article also mentions living bone is conductive.

hackernewds 3y ago

this seems easy to refute based on (my personal reproducible) observation of physical phenomenon, such as tasting coins in the back of my throat.

PcChip 3y ago
Can you expand on this? If I get a sharp scare I suddenly taste metal for a second

mattkrause 3y ago

That study is misleading/wrong and has done a huge amount of damage to this field. What they actually showed is that 1) much of the current does not reach the brain, and 2) the current that does is not sufficient to directly “force” neurons to fire. However, that doesn’t mean the remaining current does nothing at all, as it could still modulate brain activity. Using direct recordings of individual neurons, I showed that various forms of tES shift spike timing. Simulation causes them to fire sooner or later than they otherwise would. This matters because information is carried in both by overall rate of spiking and the timing of those spikes. Moreover, it’s not just a placebo, because knocking out the sensations with topical anesthetic doesn’t block the neural effects, nor is recreating them sufficient to cause them. I just wrote a little think-piece about this for PLOS Biology that summarizes what we know—-and don’t—-about it https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001973 https://journals.plos.org/plosbiology/article?id=10.1371/jou...

tbenst 3y ago
Thanks! That is interesting and well reasoned. If one wants to change neural computation via a global oscillator, it would seem that a flashing light, auditory tone, or tactile vibration might be a more potent alternative. These stimuli indisputably drive substantial brain wide activity, including many action potentials. I suppose I’m reluctantly team Firing Rate when it comes to mammals—there’s beautiful work on spike ordering in cold blooded animals for example but I’m less aware of computational work where precise spike time matters and not the relative time ie hebbiwn plasticity. I’m also somewhat influenced by my first hand difficulty when doing in vitro patch clamp to induce sub threshold voltage changes on a neuron with a second probe even just 100um away. Color me skeptical, in part as it’s really hard to do a double-blinded control and the effect sizes seem small.

luxuryballs 3y ago

perhaps the current does not need to actually reach the brain in the way these studies are setup to measure? it’s possible the brain is more sensitive and/or there’s some low powered emf naturally at play in your brain/body, for example