21: Mental Structure

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Epilepsy? I’d never heard the word. I shook my head.

“That’s not surprising. It’s been incredibly rare for a long time, as we identify more of the genetic risk factors involved, and we cure it whenever we do find it, because it’s so dangerous. Epilepsy is a neurological condition – it’s a disease in the brain – that causes patches of brain cells to communicate wrong. When they get triggered by the wrong sort of information, they talk to each other when they shouldn’t, which can cause all kinds of fits, from people losing attention to violently convulsing. It used to be a lot more common on Earth, and back then,, people didn’t know how to cure it.

“There’s a story in one of Aspen Greaves’ books. Aspen’s your favourite colonist, right? You’ll have to read the books when you’re older. Now, I don’t know if this story’s completely real, because most of Aspen’s stories are allegories about how we should try to live, they’re not all completely true. But I can tell you that whether this specific thing happened exactly like this or not, the science is real – it’s been redone, to similar results.

“A long time ago, before we knew how to cure epilepsy, people tried lots of different ways of treating it. One way to treat severe epilepsy in one half of the brain was to cut a bundle of nerves between the halves, to stop the halves from talking to each other. This way, hopefully, the epilepsy in one half of the brain wouldn’t spread to the other. Now, these original experiments were of course done on Earth, and any repeat experiments were concluded generations ago so everybody involved died before either of use were born, so we can’t exactly interview these people. But by all records, they went on to live relatively normal lives. There’d be occasional issues where they might try to put on two sashes at once, one with each hand; there were some minor memory and information processing problems, and of course the ones on Earth presumably still had epilepsy. But on the whole, they functioned fairly normally.

“The experiments done with the epilepsy victims taught us a lot about the structure of the brain. See, your brain is mostly bilaterally symmetrical, just like the rest of you.” He bunched his hands into fists and held them against each other to make a brain shape. “A left half, that controls the right half of your body and your right senses; a right half, that controls the left half of your body and your left senses.”

“Why are they reversed like that?”

“I have no idea. But this was discovered by showing imaged to one eye and not the other, and having the subject indicate what they saw. If you show an image to their right eye, and then give them cards with different images on them, they could point to the matching card with their right arm. Same with their left eye and left arm. But their left arm can’t “know” what their right eye saw, or vice versa, if the two halves of the brain can’t talk to each other.

“Interestingly, if you showed an image or word to the left eye, the subject couldn’t name what they saw. But if you showed it to their right eye, they could. This is because most of the language processing is in a specialised area on the left side of the brain; only the left side of the brain, and therefore the right side of the body, can “talk”. But if you showed their left eye, their left hand could copy down what they’d seen, and if the right eye could see that drawing or word then they could name it.”

“And my grandmother has a different brain structure?” I asked.

“Oh, no. Preliminary testing when she applied to join the treegrave would’ve revealed something like that. No, the brain structure isn’t important; we have far more specialised ways of reading and mapping that now. What matters is not the structure of the brain; we have better ways to learn about that sort of thing now. What matters here is the part where I said that the subjects went on to live relatively normal lives. Despite the ‘conscious’ parts of their brain having no communication between the two sides, despite each half controlling different sides of the body, they didn’t conceive of themselves as two people fighting over a single body. They might try to put on two sashes and see that as a slightly frustrating lapse in focus the same as you might go into a room and forget why you went in there. That’s what matters here, and that’s what the retests were about, not affirming ancient knowledge of brain structure. The fact that two independent entities piloting parts of one body, receiving near-identical but separate information, act as one without any internal communication, by seeing what the other does and back-rationalising identical intents and behaviours.

“One test done involved showing a subject’s eyes two different pictures and then getting them to select something related to the picture with their left hand. So, they might show the left eye a puddle of spilled water, and the right eye a birthday egg. Then the left hand – controlled by a brain unable to see the egg – would skip over birthday-related images and select, say, a mop, obviously to clean up the water. Then the experimenter would ask, ‘Why that one?’ Remember, the left eye and arm can’t talk, only the right eye and arm can, so the honest answer is ‘I don’t know’. But the subjects would say something like ‘to clean up after the party!’ The side of the brain that can see the birthday egg doesn’t conceive of the other arm as pointing to something unrelated out of their control, but as pointing to a related image as they were instructed to do, and they back-rationalise a relationship for it.

“This is what matters when it comes to discussing the nature of the treegrave. Because this is something that can be tested when you cut off communication between different parts of the brain, but the fact of the matter is that it’s true for everyone all the time. ‘You’ aren’t real; you’re not a specific person who makes decisions and acts on them. What ‘you’ are is a whole lot of semi-independent calculations and reactions that see ‘you’ doings something and immediately back-rationalise a single, unified reason behind the decision that you hallucinate as being made by a single, unified entity. But that’s only an illusion. The difference between you and me isn’t our age, or experience, or gender, or families. The difference between you and me is two skulls and an impassible gap of air.”

“And in the treegrave…”

“In the treegrave, we take a whole lot of people and hook them into a new body together. They take a while to learn to use the ship’s eyes and ears, to move its pipes and doors and engines, but they learn. And they can contribute to what’s happening and see what’s happening, and not only that, their brains can communicate directly to each other, through a bit of programming. At first, they’re individuals trying to fit into a system and coordinate their own control around others’, but eventually two minds in the treegrave are as two halves of an epileptic subjects’ brain. Once they get good enough at communicating directly, they’re more like parts of a healthy brain. Revisiting and analysing and communicating memories may result in single memories being spread over multiple brains and computer systems; reactions and perceptions and methods of speech come together from different minds like different specialised areas of your brain contributing to a single action. It’s fairly common, though not universal, for brains in the treegrave to specialise, to drop doing things that other brains are better at or enjoy more. This is all normal ways for brain tissue to behave when connected to other brain tissue, or indeed to other things that can do parts of its job well. If you go into piloting and spend a lot of time controlling a ship directly, or into security and spend all day looking at cameras, you’ll notice a similar effect yourself, of seeing your ship as an extension of your body or your cameras as extra eyes. But you’ll go home at the end of the day and recalibrate. The minds in the treegrave don’t.”

“That doesn’t sound right,” I said. “I mean, I’m me. I know I’m me.”

Yamin nodded. “It’s an incredibly strong illusion, fundamental to how we think and act. See, even here I’m describing us as people who think and act. Even when you accept intellectually that this is how it works, you’ll still always be a person, operating in the framework of a person; some people spend decades developing the mental discipline to truly shake the illusion and even then, most of them fail. Frankly, I’ve never seen the point in trying to do that. It’d be like learning that most of what you see is invented by your brain and blinding yourself in retaliation.”

“But how can the treegrave do it? It’s so many different people…”

“You think the different parts of your brain aren’t different? I’m not sure how complete or incomplete the identity of a healthy treegrave is, you’d need to ask a treegrave psychologist about that. But if I had to guess I’d say that there’s probably quite a bit of division in there. It’s hardly an either-or position; it’s possible for people within the treegrave to see themselves as individual and the treegrave itself to see itself as singular and neither of them to be wrong because ‘identity’ is a matter of perspective. If we isolate a long-time participant in the treegrave for medical attention and they’re not particularly responsive but they operate just fine in the treegrave itself, does that mean that we’ve removed a part of the treegrave’s brain for treatment and then grafted it back in, or does it mean we’ve roused a person who’s lost the ability to operate independently and brightens up when reconnected to their assistive devices? Same situation, different perspective.

“Personally, I wouldn’t be surprised if even within a treegrave there were multiple ‘people’ consisting of multiple minds; a treegrave is a large and complex thing. That sort of thing happens even within a single human brain, sometimes. You might act radically different on two different days and chalk it up to behaving differently when you’re in different ‘moods’, both of whom are still you, but some brains will render different behaviours in different circumstances as coming from separate people in the same brain, which may or may not share hobbies or perspectives, and may or may not share memories. So one has to imagine that treegraves probably experience something similar. I’m not sure though, because I’m not a treegrave psychologist and it’s also a little difficult to accurately communicate information unless you can agree on what terms are. It’s possible that what a treegrave conceptualises as a single treegrave might differ from what we conceptualise as a single person, making communication on the matter unreliable.”

“When I talk to the treegrave,” I said, “it usually calls itself ‘I’, but sometimes says ‘we’.”

“Yes, I’ve noticed that too. It picks whatever is easiest to communicate the topic at hand without differentiating much between the concepts. It’ll also change its voice and speech patterns for different topics or moods, have you noticed that?”

“Yeah.”

“And of course, we can’t rely on the treegrave’s ability to tell us everything that’s going on in its mind. Remember the water puddle and the birthday egg? The treegrave’s ability to communicate with humans on the ship is fairly centralised, to avoid chaos and crosstalk. Even if there are multiple ‘identities’ in there, only the biggest and oldest can speak, and if it perceives as the others being part of it, we have no way of knowing what they perceive any more than the test subject’s left eye and arm could explain the connection between the puddle and the mop.”

“So, Grandma…”

“Is certainly fine. You would’ve been told otherwise. She’s just integrating very slowly. It might be because she’s having more difficulty than average adapting, or it might be by choice.” He shrugged. “It’s not unheard of for people to come to the treegrave seeking freedom from their old responsibilities, to spend their countdown years free from pain and watching their loved ones through the cameras while making conversation with the rest of the treegrave on their own terms and at their own distance. If that’s what she’s doing, it could be years before her mind properly merges. Or perhaps she’ll decide to let them in tomorrow and merging will be very rapid from this point. It’s honestly up to her.”

“She wants to,” I said. “She told me that one of the reasons she was merging was because she was tired of feeling useless. She wanted to become part of the treegrave in order to help the ship.”

Yamin nodded. “Perhaps,” he said. “I’ve never met her, and I know you two were close. You’d know better than me.”

But I could see in his eyes that he didn’t believe me. He knew something about my grandma that I didn’t.

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