Is cannabis bad for teens? What the data say

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Hello Nature readers, Today we discover a hybrid computer that combines lab-grown brain tissue with electronic hardware. Plus, we explore the risks of cannabis to young people and catch up with the COP28 climate conference as it overruns its deadline today.

Part of a brain organoid, in which stem cells (pink) are differentiating into neurons (purple). (Steve Gschmeissner/Science Photo Library)

Biocomputer recognizes voices A computer that combines laboratory-grown human brain cells with conventional circuits can complete tasks such as voice recognition. Researchers trained the system on 240 recordings of eight people speaking. A machine-learning algorithm decoded the mini brain's neural activity pattern to identify voices, with 78% accuracy. The technology could one day be integrated into artificial-intelligence systems or used to study neurological disorders. Nature | 4 min read Reference: Nature Electronics paper

Critics question 'self-driving lab' Last month, scientists demonstrated the A-Lab, an autonomous chemistry system that can synthesize new materials without human intervention. Critics have now raised concerns about its ability to analyse the results and have questioned whether it really made 41 new compounds. "To me, this doesn't invalidate the A-Lab concept, but it shows that there is considerable work still to do on the autonomy aspects," says chemist Andy Cooper. Two critics' teams are now collaborating to check the paper's claims in more detail. Nature | 5 min read

How CRISPR could help treat Alzheimer's CRISPR gene editing could one day treat Alzheimer's disease caused by genetic mutations. "CRISPR therapies could potentially be a one-and-done cure, which no other drug can match," says neuroscientist Subhojit Roy. In a proof-of-concept experiment, cultured human cells were edited to cut out a faulty version of a gene that produces a toxic protein. For now, gene editing in the brain remains difficult and potentially risky. "Gene editing is not always perfect," says neuroscientist Tara Spires-Jones. "There could be off-target effects including mutations in healthy genes or damage to entire chromosomes." Nature | 6 min read Reference: Nature Neuroscience paper

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Features & opinion

Is cannabis bad for teens? Ten years after cannabis was first legalized for recreational use by adults, there's still little concrete guidance about the drug's risks to young people. "I am concerned that this will hit us like tobacco hit us," says Nora Volkow, director of the National Institute on Drug Abuse. Research has uncovered links between cannabis use and schizophrenia, but it's unclear whether the association is causal. There are now large-scale efforts to understand how prolonged cannabis use, especially of high-potency products, can affect mental health or cognitive function. "I would just like to have information for the teens and for the adults to make better decisions for themselves," says Krista Lisdahl, co-leader of a project investigating the cognitive development of some 10,000 young people that began in 2015. Nature | 10 min read

The unsung pioneers of sleep and dreaming For a long time, we understood little about sleep and dreaming — until a tight-knit band of researchers changed things. In Mapping the Darkness, journalist Kenneth Miller recounts how the field started with a seemingly simple question: why do humans need to sleep, at the expense of other, more obviously productive activities? Trying to answer this and other questions, sometimes against considerable odds, eventually led to treatments for sleep apnoea, narcolepsy and insomnia. "Although this book is about sleep science, it also pays tribute to the pioneers who were first unafraid to ask what lies in the darkness," says reviewer and sleep researcher Jennifer Martin. Nature | 6 min read

'I thought, what the heck is this?' For chemist Louis Brus, a winner of this year's Nobel Prize in Chemistry, the path to the award started with an unexpected signal in the absorption spectra of cadmium sulfide crystals. "There was this bump on the edge of the band gap that was not present in the large crystal, in the bulk material. And I thought, what the heck is this?" Eventually, the theory was the easy part, says Brus — but synthesizing nanoparticles was fiendishly difficult. "We didn't quite understand why it worked some days and not others," he says. Nature Nanotechnology | 11 min read

Where I work

"When I was 12, I became intrigued by the mystery of black holes," says astronomer Sthabile Kolwa. "I wondered whether one day I could develop theories or make observations with powerful telescopes that would help to explain what black holes are and what happens inside them." They have come some way towards fulfilling their childhood dream: Kolwa is now researching black holes and star formation using South Africa's MeerKAT radio telescope. (Nature | 3 min read) (Chris de Beer-Procter for Nature)

COP climate conference poised on the brink Today is the last official day of the United Nations climate conference, COP28, in Dubai. As I write, the official mid-morning closing time has already come and gone. But it's not unusual for COPs to go late and feel fraught as time — and food — runs out at the mega-summit. The event started two weeks ago with events of startling contrast: on the one hand, a historic moment occurred when countries came together to adopt a draft resolution for a 'loss and damage' fund — money for low- and middle-income regions that are facing irreversible climate-related destruction that they had little part in causing. The initial agreement for such a fund was seen as a silver lining of last year's meeting. On the other hand, leaked documents seemed to confirm climate campaigners' worst fears: the United Arab Emirates (UAE) was more interested in chasing fossil-fuel deals with participants than it was in its duties as the host. COP president Sultan al-Jaber rigorously denied the allegations. But al-Jaber's other role as the head of the UAE's state-run energy companies, along with the UAE's standing as a major fossil-fuel producer, continue to raise concerns about conflicts of interest. A draft of the final text — which usually hints at areas of agreement and disagreement — was greeted with dismay by some observers. A key sticking point: a commitment to 'phase out' — rather than somehow mitigate the emissions of — fossil fuels. Climate leader and former US vice-president Al Gore did not mince words: "this obsequious draft reads as if [oil cartel] OPEC dictated it word for word", he wrote. For the Alliance of Small Island States, the issue is survival. "We will not sign our death certificate," says its chair, Samoan lawmaker Cedric Schuster. Brinkmanship is not necessarily unusual at this point in a COP. And ultimately, the real action must occur outside its walls. But observers agree: what happens at COP28 matters deeply. Delegates have a long night ahead as negotiators will work without sleep to deliver the final texts that must be agreed on by all parties. Flora Graham, Senior Editor, Nature Briefing Keep up-to-date with the outcomes with a special breaking-news edition of Nature Briefing: Anthropocene. Update your preferences to sign up for free.

Quote of the day "Phasing out fossil fuels is not negotiable. World leaders will fail their people and the planet unless they accept this reality." Turning away from fossil fuels will be neither easy nor painless, notes a Nature editorial. But it must happen, and it is a question of when, not if.

Did you spot it? I was snug in my bed when asteroid 319 Leona passed in front of the star Betelgeuse, but luckily in Sardinia, amateur astronomer Antonio Piras was awake and caught the occultation on video. Help this newsletter to keep coming back brighter. Send your feedback to briefing@nature.com. Thanks for reading, Flora Graham, senior editor, Nature Briefing With contributions by Gemma Conroy and Katrina Krämer

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