The Hardest Problem in Neuroscience is the Skull!
Notes on the first Third Thursday Salon meeting of 2018. Topic of discussion: Brain Computer Interfaces. Co-organized with Ben Reinhardt.
See the Economist BCI summary: https://www.dropbox.com/sh/rndus3rewaq2yri/AADw2Bu9x52JAYUKO1ayeYNMa?dl=0
https://www.economist.com/technology-quarterly/2018-01-06/thought-experiments
Assertion: We’re interface limited:
We don’t have enough resolution to do X
If X is manipulation:
You can do XY control with 50 electrodes <Source>
Biomimetic — go all the way to the brain
Co-Adaptaton
Utah Array
Brain has 85 Billion Neurons and 85 Billion Glia
Glia in the central nervous system are divided into four kinds:
- Astrocytes (20–40%) — Gradient Following Badasses, star shaped, envelop synapses, wrap foreign bodies, are the bane of implant designers but ignore things less than 10–15 microns (neuron body size, perhaps a coincidence but likely not)
- Microglia — Basically white blood cells (the brain has its own freaking immune system)
- Oligodendrocytes — wrap neurons to help with electrical tranmission
- Ependyma — important for neuroregeneration and creating cerebrospinal fluid. Lines the walls of the ventricals
¾ of all neurons are in the cerebellum.… but people can get by without it. Cerebellum neurons are tiny.
Ben Barres: brough scientific attention to the important role of Gilia in the brain. Incidentally, also an incredibly valuable perspective on sexism since Ben was a academic before and after sex change.
Brain has its own immune system
You can trick the brain immune system with things that are <10–15 microns which is ~one neuron body
Dura Fibroblasts
Measuring brain activity and strucutre.
One way to do things is to project signals into a 400 dimensional space and then back down into your few-dof control
Neurons are a many->one->many mapping. Many things activate voltage spikes which then
cause many effects.
Other Tools Besides Voltage Sensors
- Optical Tools — interact with calcium ions via two photon control
- These image deep inside the brain with lasers fired for 50 fempto (10–15) seconds. A gaussian times another gaussian is a sharper gaussian.
- Need special genes that fluoresce with the laser.
- Glutamate Detectors
Phil Kennedy -> Data
Attention Paradox?
Eyes as a BCI
What is attention?
Argument for natural Stimulus
Bengio — Boltzman machine
-Bengio gave a definition of how backprop is equivalent to some biological stuff. My sense was that it was regarded as not too true…
-Hinton thinks otherwise
Will we have more Neuroshaming? People with funny shaped brains.
Where does physical intuition come from?
Visual-semantic boundary.
“The ways of Nature” — good term
Other input methods:
Transcranial Magnetic Stimulation
Cochlear implant — bright light near the ear to bounce around into the brain. 800nm light
Somatosensory Stimulation
Hardest Problem in Neuroscience is the skull (ha!)
Lorentz-force imager
Neural Dust
Need more non polar things to get through the blood brain barrier
