When Andrea Gilmore-Bykovskyi, an associate professor in emergency medicine at the University of Wisconsin-Madison, saw that the N.I.A. was interested in video research on lucid episodes, she knew one way to approach the problem. Her past work had involved filming people with dementia during interactions with nursing staff and then meticulously analyzing the videos, second by second, to assess which types of care affected patients’ behavioral symptoms. She proposed retooling those video methods to study lucidity.

Gilmore-Bykovskyi knew that people with dementia showed modest fluctuations in cognition frequently enough, particularly at the mild and moderate stages; she had also seen firsthand how, in the right environment and the presence of good caregivers, the behavioral symptoms of dementia could sometimes lessen. But the turnarounds described by the N.I.A. were said to be more pronounced and especially likely to occur in the final days or hours of life, a deeply sensitive time for cameras to be rolling at a patient’s bedside. Knowing she would need to closely partner with a medical facility and its staff to have any chance of success, Gilmore-Bykovskyi reached out to a hospice nearby, Agrace, which had a 12-bed memory care unit. The hospice agreed to work with her team, and in 2020 the N.I.A. awarded her a grant.

Lucid episodes were thought to be quite rare; Gilmore-Bykovskyi suspected her odds of documenting the phenomenon in such a small study were low. The cameras were set up in December 2021, and to the U.W. team’s surprise, the first episodes occurred not long after. By then, Alison Coulson, a nurse who served as the team’s data collector, had worked with Joan Stephen, an 89-year-old resident, for a few months “and not gotten a lot of back-and-forth,” she told me. Stephen had largely stopped speaking and had appeared not to recognize her family members for several months. Suddenly, while looking at old photos of her children one day, she named them. Cameras were running not long after when she recalled her late husband, John, and shared, in full sentences, specific details about his job (“He worked for Comstock Tire”). She also recognized a picture of the award-winning rose bushes she tended for decades, before Alzheimer’s took away her focus and made them wither. When Coulson showed the videos to Stephen’s daughter, she said she was amazed. “It was extremely exciting,” Coulson told me. (The U.W. team protects the anonymity of its study’s participants; some of the subjects’ family members permitted the team to share details with The Times.)

Sometime later, another participant, an elderly man with Alzheimer’s whose verbal output the researchers assessed to be “minimally coherent,” showed an even starker change. The man had been mobile throughout the full 10 years of his illness, but over a two-week period, his energy notably declined and he began spending more time sleeping in bed. Seeing this, nurses made the decision to tell his family to gather — the end seemed to be near. By the time his family members arrived, however, the man had gotten out of bed and begun speaking. During his decline, he had reverted, as many bilingual patients with Alzheimer’s do, to his native language. Now he spoke clearly in English again, reminiscing about his childhood and his father. The nurses and his family were stunned. He stayed alert like this for two days, at one point telling his family, “I’m leaving soon.” Nine days after the episode ended, he died.

Along with the U.W. team, the N.I.A. sent funding to five other research groups. One of those teams, based at the Mayo Clinic, focused its efforts on surveying caregivers about their experiences with lucid episodes. As the data came back, they found that there appeared to be different types. Some episodes resembled the prototypical cases of terminal lucidity like those that Nahm and Batthyany reported, with heightened recoveries occurring close to death. But many more were subtle instances — a flash in the eyes, a few meaningful words — that occurred weeks or even months before death. Many caregivers were deeply moved, but the events were not always positive on balance. “Sometimes they’re totally negative,” Joan Griffin, the lead researcher on the Mayo Clinic team, told me. “We had one caregiver who was like: ‘My dad was an [expletive] when I was young, and he had a lucid episode — and he was an [expletive] when he came back. He was a terrible father, and it reminded me about why he was so bad.’”