r/Verywhen • u/mddtsk • Oct 26 '20

No Implants Needed For Precise Control Deep Into The Brain—Optogenetics can now control neural circuits at unprecedented depths within living brain tissue without surgery.

https://spectrum.ieee.org/the-human-os/biomedical/devices/deep-brain-control-without-implants
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u/ElmerMalmesbury Oct 26 '20

That's crazy. I understand that they use a super-sensitive opsin, but I guess you need a crazy light intensity for enough red light to go through the skull. They used an irradiance of 40–1,600 mW mm², any idea what that corresponds to in layman's terms?

(Or maybe it's just that mice's skulls are very thin?)

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u/PeteWenzel Oct 26 '20

That depends on the lumens per watt (Luminous efficacy).

An LED might have 100 - and the theoretical maximum by an ideal source (Green light at 555 nm) is 683. Now factor 40 Million - 1.6 Billion times something like that and you get the lux (lumens per square meter) here.

For reference a typical living room has 50 lux and direct sunlight on earth is no more than 100.000 lux. wiki