Let us assume that Science has discovered how to keep a brain alive outside the body, that mind-machine interfaces are advanced enough to connect the CNS to electronic hardware and communicate meaningfully and that, in this carefully controlled environment it is possible to keep the brain eternally* young by injecting younger cells manufactured in a machine nearby and that these cells are vetted for cancer (so no brain cancer).

This technology will be used by future humans to build cybernetic bodies (not powered by nuclear energy as I discovered in an earlier question I asked) that, as long they are powered and fed with organic matter, will last a long time and, with such immortality they will be free to plan long term, like STL expansion, improved science and technology with scientists and technicians living dozens of thousands of years, etc.

But they are humans, they want to stay humans and that means feelings like humans. That means hormones like Testosterone, Estrogen, or the ones produced by the adrenal glands.

So, the question is: what are the best ways to deal with the hormones when your brain is connected to a robotic body and you still want to have human feelings? My first idea is to pack the glands together with the brain, but surely there are better ways.

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    $\begingroup$ Your "brain in a jar" is connected to blood supply, right? And this blood supply contains oxygen, glucose and other nutrients, right? Why not adrenaline and testosterone? $\endgroup$ – Alexander Dec 13 '19 at 18:15
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    $\begingroup$ You have the weirdest idea of what human feelings are. $\endgroup$ – Starfish Prime Dec 13 '19 at 18:48
  • $\begingroup$ @Alexander, they are immersed in a fluid, that's for sure, but probably won't be blood. $\endgroup$ – Geronimo Dec 13 '19 at 20:13
  • $\begingroup$ Then you need to solve the issue with circulation. $\endgroup$ – Alexander Dec 13 '19 at 20:16
  • $\begingroup$ You could use an RTG. See my answer to another question here: worldbuilding.stackexchange.com/a/162916/43560 $\endgroup$ – Richard Smith Dec 13 '19 at 23:36

Your question seems more focused on the biochemical responses such as an adrenaline rush or "feeling horny" rather than on the more esoteric definitions of emotion which might include love, hate, envy, etc.
With this understanding, the administration of hormones into the brain's blood supply would be governed by the AI of the cybernetic body.

  • When the body detects danger or has been harmed, the AI might decide that it needs the brain to be hyper alert. It would then administer adrenaline (and maybe a little cocaine).
  • When the body detects no danger but need time to recharge its batteries, the AI might offer the brain a chemical sleep aid.

More advanced bodies would be able to synthesize a larger range of compounds, allowing the host brain to customize their own state of consciousness. Focus enhancing, creativity enhancing, mood elevating... the catalog would be ever expanding as the technology of the body and it's integral AI increases.

There is nothing dehumanizing about having more control of one's biochemical responses. Meditation and life experience both provide such control and the mature, sane humans which benefit from them are arguably more human than the young brutes who don't.

  • $\begingroup$ I don't see that a separate AI would need to determine danger. The brain in an ordinary body transmits signals to the glands to release hormones that in turn loop back and affect the brain (as well as other systems). The cybernetic body could obey the same neurochemical instructions, no AI interpretation of outside phenomena necessary. (If biological bodies do release emotion-affecting chemicals into the bloodstream outside in direct response to damage outside of the neural nociception route, artificial bodies could too, but I don't see that that would require something I'd describe as AI.) $\endgroup$ – Jacob C. Dec 13 '19 at 22:09
  • $\begingroup$ @JacobC.supportsGoFundMonica, including AI in the body allows the neurochemical catalog to be enhanced without requiring that the biological brain learn the necessary chemistry. $\endgroup$ – Henry Taylor Dec 13 '19 at 22:24
  • $\begingroup$ "The neurochemical catalog to be enhanced" in what regard? Neurons have a certain set of receptors and ion channels, and the artificial body would need the ability to send the appropriate cues to begin with. Our adult nervous systems don't currently have to "learn" novel chemistry (beyond learning to associate smells -- and olfaction should be wired up analogously). Ideally, a humanoid artificial body should require no intelligence that our present bodies don't possess, unless it must handle some senses we don't normally have.) $\endgroup$ – Jacob C. Dec 13 '19 at 22:44
  • $\begingroup$ My thought was that as science advances we might find chemical compounds that have new effects on the host brain. Building an AI into the body would also allow the body to learn how to maintain its brain's unique needs in ways that a generic off the shelf cybernetic body would never do. $\endgroup$ – Henry Taylor Dec 14 '19 at 2:53
  • $\begingroup$ In further defense of the inclusion of an AI in the cybernetic body, this is all future tech and very soon AI's are going to become ubiquitous in every device that we use. Your toaster is going to recognize you and the bread you are putting in it to realize that you prefer whole wheat lightly brown as opposed to your child who prefers it blackened. It will also know how you like all the different bread types you have ever let it cook for you and will learn (relearn) your preferences every time you use it. If toasters are about to become that smart, how smart will your next body be? $\endgroup$ – Henry Taylor Dec 16 '19 at 3:23

The hormones are at base the result of emotions, not the cause. (Though of course there's a feedback cycle.) For example, if you've ever had skin tests for allergies, when the test is finished you get an injection of epinephrine/adrenaline to forestall any delayed allergic reactions. That, of course, is the hormone involved in the "fight or flight" response to fear/anger. But while you feel the bodily reactions of the fight or flight state, you don't feel the emotion at all.

So your brain in a jar will still feel the emotions, just not the body's reaction to those emotions.


Skip the glands and just synthesize the molecules

I mean, the brain does a decent job (fine, an okay job) of regulating emotions on its own, but if you want the complete chemical cocktail produced by the rest of the body, skip the rest of the organs and just have a a synthesizer make the molecules for you and regulate them.

This would also let you do cool stuff, like control the hormones with a little toggle bar and let you regulate your emotions.


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