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Ever wish you could just swap your brain out with a spare one? If so, sorry.

We definitely can't grow backup brains in jars. But you may have heard about a study in which researchers at the University of California,. San Diego were able to grow lumps of neural tissue that showed measurable activity -- a little bit like an actual brain.

This kind of research raises some ethical questions. But the good news is that at this point, it's unlikely the activity in these so-called cortical organoids means they're awake and having experiences. And in this case, they weren't meant to be -- instead they're just a new and uncommon way to study neural tissue, which could help model the progression of diseases, test medication, or just understand how humans came to be the way we are.

In a study reported in the journal Cell Stem Cell in 2019, researchers grew small clusters of neural tissue, like neurons and glial cells, in culture. And the neurons connected and started firing, apparently syncing up with their neighbors. This was exciting, because before this type of research, we'd had to base our knowledge of how human brains develop on the brains of rodents.

And based on those kinds of studies, we had thought that human neural tissue needed feedback from other parts of the developing nervous system -- as well as the uterus -- to develop and start sending signals. What's more, the organoids were firing in some patterns that looked like patterns we see in actual brains -- a pattern called a delta wave. Basically, they had brainwaves. ...

Of a sort. They even found those waves bore some resemblance to existing data on the brains of infants who were born prematurely. So does that mean these tiny cell clusters were... conscious?

Or, at least as conscious as a very young infant? The short answer is probably not. And to explain why it helps to know what a "brain wave" even is.

Like the rest of your organs, your brain is a cluster of cells -- in this case, neurons and glial cells. And those neurons generate an electrical signal. A tiny one -- like, your whole brain is probably not enough to power an old-school light bulb.

When a neuron fires, an imbalance of sodium and potassium ions gets pushed down the axon toward another neuron -- thanks to channels and pumps in the cell membrane -- which makes an electrical signal. But individual neurons usually fire kind of randomly. Their activity as a group is how we get brainwaves.

The patterns that look like waves are visualized using a technology called electroencephalography, or EEG, which detects these changes on your scalp through electrodes. Each electrode could be about a centimeter wide, so it picks up the activity of a lot of neurons, not one at a time -- which is how patterns like waves tend to emerge. And those waves can be related to what you're doing.

Like, high frequency waves, called beta waves, appear when you're thinking hard about something. Alpha waves appear when a person is a bit more relaxed. Then come theta waves, which you might see if you're falling asleep.

Then finally there's delta waves, which are the slowest type of waves. People tend to show these if they're in a deep but dreamless sleep -- or if they're a newborn infant. That's the kind of wave these organoids showed.

So if you were hoping to grow your own backup brain anytime soon, the activity isn't the kind we typically associate with being awake and aware of your surroundings, or even dream perception -- in case any of that was part of your backup brain plan. Some people have argued that we can't really objectively decide if another entity is truly sentient or not -- and so we should be careful with organoids like these. In fact, some experts are drawing attention to the need for more rigorous ethical boundaries in this research -- because they believe we are approaching a point where those boundaries are needed.

Or maybe that we're already there. For example, in this study, the entire sample of all the organoid clusters they grew amounted to 15,600 neurons. That sounds like a lot, but it's roughly what you'd find in the nervous system of a sea slug.

And that wasn't one cluster -- it was the total number in all of them. They compared that data to that of newborn infants, all of whom were born before 28 weeks in the womb. By about halfway through fetal development, they would likely have already developed most of the billions of neurons that babies are born with.

However, even with “only” thousands of neurons, some ethics experts are calling for safeguards. After all, a sea slug is a real animal, so this is a fairly complex issue. In humans, we also know of some specific structures that are involved in waking a brain up, as well as arousing it into consciousness.

One key structure is called the reticular formation. This group of neurons sends signals into the rest of your brain to basically wake it up. Like, if you stimulate this area in anaesthetized rats, they show less of those dreamless-sleep brainwaves, and more of the awake-and-focused waves.

And injury there can result in altered levels of consciousness. So, at least based on what we know about how bigger brains work, these organoids might need more complex structures to be able to arouse them into being aware and having experiences. But making working backup brains was never the point.

These organoids are pretty remarkable for other reasons. For example, the fact that they can sort of model the activity of human brains means we could use them in research -- like the way we start with rats and mice before moving to human subjects. Like, we could see how drugs that could have neurological effects might affect the pattern of activity in a tiny model brain.

Or, they could be an additional model to use when studying the brains of certain populations, like those with Alzheimer's or schizophrenia. If we can develop neural tissue that models these conditions, these organoids could be a stand-in for people's actual brains. So it's possible these organoids could lead to more discoveries in the future.

And best not to assume you'll be issued a backup brain any time soon. Thanks for watching this episode of SciShow Psych, and thanks to all of our patrons for supporting our content. None of this would be possible without you guys.

If you'd like to get involved, head on over to patreon.com/scishow. {♫Outro♫}.