Hello Nature readers,
Today we hear good news about an eye implant for age-related macular degeneration, learn that breastfeeding boosts immune cells that protect against breast cancer and explore how AI tools are changing universities.

Retinal implant restores vision lost to AMD

An implant has improved the vision of dozens of people with age-related macular degeneration (AMD), the commonest form of incurable blindness in older people. The device is inserted just under the retina to replace the light-sensitive cells that have been lost to the disease. Camera-glasses capture images and transmit them to the implant, which then electrically stimulates the surviving retinal neurons. “Patients could read letters, they could read words,” says ophthalmologist and trial leader Frank Holz. But the device takes months of intensive training to use.

Nature | 5 min read
Reference: The New England Journal of Medicine paper

Disconnected, but not switched off

When a part of the brain has been surgically disconnected, slow, sleep-like waves persist in that area despite the person being awake — contributing to our understanding of what conscious and unconscious brain states look like. Researchers studied children with severe epilepsy who had undergone a hemispherotomy, in which the part of the brain in which seizures originate is severed from the rest of the organ. The team found that electrical activity in the isolated area slowed to rhythms called delta waves. This activity was similar to that observed in the brains of deeply sleeping children who hadn’t had the surgery.

Nature | 4 min read
Reference: PLOS Biology paper

Breastfeeding boosts anticancer immunity

Pregnancy and breastfeeding induce the accumulation of specialized immune cells that protect against breast cancer. As breast tissue remodels to create a supply of milk, and reverses the process after weaning, new cells are created and older, damaged ones are cleared out. This biological redesign is “a main trigger” for the recruitment of specialized immune cells called CD8⁺ T cells, says oncologist and study co-author Sherene Loi. Researchers found that women with breast cancer who had breastfed after giving birth had more T cells in the breast tumours and better survival rates than did those who hadn’t.

Nature | 4 min read
Reference: Nature paper

The limit of human endurance

Researchers gave 14 volunteer runners, cyclists and triathletes an energy-tracking cocktail of water labelled with deuterium and oxygen-18 to confirm the maximum amount of energy a person can expend for a sustained period of time. It was around 2.4 times the basal metabolic rate (BMR) — the amount of energy the body uses while just chilling out. At their peak — during competitions, for example — some athletes burnt around 9,000 calories a day. But they unconsciously cut back on using energy elsewhere, such as walking or fidgeting, ultimately keeping their output under the 2.4 BMR ‘metabolic ceiling’ over the long term. The limit seems to come down to how much food you can absorb.

Nature | 4 min read
Reference: Current Biology paper

Is AI helping or hindering universities?

The arrival of artificial intelligence (AI) tools onto campuses is sending shockwaves through universities worldwide. Some institutions, such as Ohio State University in Columbus, are weaving AI into their entire curriculum and encouraging students to experiment with AI-powered tools. But concerns that AI will impede learning also loom large. The University of Sydney is mandating in-person tests to ensure that students have learned skills and not outsourced them to AI. Academics are split: some are experimenting with AI in their teaching, whereas critics argue that universities should be cautious about embracing tools dogged by ethical and environmental concerns and with unknown cognitive impacts.

Nature | 14 min read

To slash US drug prices, make fewer new drugs

President Donald Trump’s plan to reduce US drug prices with a direct-to-consumer website is unlikely to deliver on its goals, argues health economist Beth Woods. It won’t be any cheaper for people with health insurance, and for those without, medications sold through the site will still be prohibitively expensive, writes Woods. And Trump’s efforts to harmonize US drug prices with cheaper ones abroad would be more effective if they focused on regulation at home instead of applying diplomatic pressure and tariff threats to other countries. Ultimately, tying drug prices to their health benefits would mean fewer but more-effective new medicines, curbing excessive drug spending.

Nature | 5 min read

Where are PhD students happiest?

Brazil, Australia and Italy have the highest satisfaction scores in Nature’s global 2025 PhD survey. Meanwhile the Nordic countries — which routinely score near the top of global happiness surveys — collectively reported an impressive 85% satisfaction rate, higher even than Brazil’s. Worldwide, the survey identifies some measures that correlate with satisfaction: spending at at least one hour a week with a supervisor and not working excessively long hours, for example.

Nature | 12 min read