Fred Crittenden, 73 years old, sits in front of his TV in his tiny apartment one hour north of Toronto every baseball season.
“Oh, I love my sports — I love my Blue Jays,” says Crittenden. “They need me as a coach — they’d win, I’ll tell you.” He listens in his apartment to the games. He can’t see them so he doesn’t keep an eye on them.
Crittenden recalls that “I went blind” when he was 35 years old.
He says, looking back, “The last thing that I saw clearly” and then he recalls, “It was my daughter Sarah.” She was five years old at the time. I used to sneak in at night to look at her in her crib. I couldn’t make out her tiny eyes, her nose, lips, chin or nose. It’s still hard to see her even today.
Crittenden claims it took him around a year to accept his blindness. He still doesn’t see any light, 35 years later. He reports that it is total darkness. He manages to do just fine. He can do most things himself, including sync up with the 24-hour night/day cycle.
Crittenden is a night owl who listens to music or talks on his talk-back machine. He falls asleep at 11 o’clock in the morning and rises every morning at 6:30 – no alarm required. This may seem odd, but our circadian clocks are profoundly influenced by light.
MarlaFeller is a neurobiologist from the University of California, Berkeley. She says that if you didn’t see any light, your sleep cycle would shift so that you fall asleep later and later. What happens is that every day you look at the sun, it entrains your circadian clock to follow the 24-hour cycle.
Crittenden is a bit of a mystery. His internal clock is accurate to the 24-hour rhythm of a sunlit day, even though he’s blind. However, this is not true for everyone who is blind. What’s the deal?
This brings us to Iggy PROvencio a University of Virginia biologist who studied the African clawed Frog in graduate school in the 1990s. He chuckles, “The frog looks really disgusting.” It has extremely slimy skin.”
The skin is made up of cells that absorb light and darken with pigment. This helps the frogs blend in to the streambed below. Provencio found the light-detecting molecule melanopsin. It wasn’t only in the skin of the frogs. It was also found in the retinas of mice and frogs by Provencio and his team.
Provencio recalls that they were looking at the microscope and Provencio said, “And I told my colleague, ‘We’re the first people to actually see a completely new sensory system in mammals'” — which includes humans.
Melanopsin doesn’t reside in rods or cones. It’s in large neurons called melanopsin cell which are stored in a different layer on the retina. Michael Do is a neurobiologist at Boston Children’s Hospital. “The melanopsin cell — their arms extend out and overlap with other melanopsin cell arms to form a net over the retina.”
The whole mesh is sensitive to bright blue light. The sun emits a lot of light. Our phones, tablets, screens, and other indoor lights, streetlights, and headlights also contribute to that light. These melanopsin cells’ tentacles radiate throughout our brains.
Do says that about 30 brain regions are directly contacted by these cells. Do says that one place is the structure at base of the brain, which is our master circadian clock. It’s called the suprachiasmatic nuclear nucleus and uses light information from melanopsin cells as a signal to the rest of the body to know when it’s bedtime and when it is time to get up. Melanopsin cells can also influence our mood, how we learn, and temperature control.
Satchin Pan, a Salk Institute chronobiologist, said that there have been laboratory experiments in which mice had their melanopsin turned off. He says that these mice can sense light to a certain extent, but the results are not consistent.
Panda states that if you give them a lab mouse version of jetlag, where the lights suddenly turn on, and the mice shift, it will take them seven days to adjust to the new time zone. (There is variability in the system which is why some people are more difficult to adjust to daylight saving or changes in time zones.
That’s the end of the mystery. Fred Crittenden doesn’t have functioning rods or cones. However, he does possess melanopsin cells.
Crittenden’s experiences offer insight into a system in the brain, retina, and rods and cones that is preserved in blind people. This special system of melanopsin cells may be what allows Crittenden to use light to synchronize his internal clock.
These cells tell his body to begin a new day each morning, to ensure he is awake when Sarah (his daughter who’s now 42) calls him.
Crittenden fondly recalls, “She usually calls me every two days to see how my doing and that stuff.” “She’s a great girl.”
Crittenden had a picture of Sarah in his apartment when we spoke. It shows her smiling. It was hanging in his bedroom next to the window. On a clear day, the sunlight would shine through the window and illuminate Sarah’s face.
This story is part our periodic science series “Finding Time” — a journey through four dimensions to discover what makes us tick.
A second version was premiered in a live performance at the Charles Hayden Planetarium, Museum of Science, Boston.
Copyright 2022 NPR. Visit https://www.npr.org to see more.
Transcript:
SCOTT SIMON, HOST
Our days are marked by the sun. Our eyes use light to tune our bodies and our clocks, so we naturally rise in the morning and fall asleep at night. Ari Daniel speaks next in our science series Finding Time to a man who is in tune with the sun even though he has been blind for many years.
ARI DANIEL BYLINE: We will start in a tiny one-bedroom apartment located about an hour north of Toronto.
FRED CRITTENDEN : I love sports. My Blue Jays are my favourite team. They need me as their coach. They would be winning, I will tell you.
DANIEL: Fred Crittenden, 73, sits in front of his TV every season and listens to the baseball games. Because he cannot see, he doesn’t view them.
CRITTENDEN: I went blind. I was 35 years old.
DANIEL: Crittenden has Retinitis Pigmentosa. This is an inheritable condition that causes the retinas to deteriorate. All his rods, which are cells that allow us to see in dim lighting, were lost, as well as all his cones. These cells let us see color in brighter lights. Crittenden claims that he went from having perfect vision to being completely blind in 1985.
CRITTENDEN – Sarah, my daughter was the last thing I could see clearly. She was five years old at the time. I used to sneak in at night to look at her in her crib. I couldn’t make out her tiny eyes, nose, lips, or chin. It’s still hard to do it even today.
DANIEL: How long did it take you to come to terms?
CRITTENDEN: Took me about a year.
DANIEL: Now you have no light perception.
CRITTENDEN: My light perception is completely absent. It is total darkness.
DANIEL: Crittenden is doing just fine, more than 35 years after his first day. He doesn’t need any help with many things, such as the 24-hour night-day cycle.
CRITTENDEN: Oh, yes. I eat almost the same thing every day. In the mornings, it’s 8 and 12, then 5 at dinner. I love my food.
DANIEL: Crittenden is a night owl who listens to music or talks on his talk-back machine. He falls asleep at 11 and wakes up every morning at 6:30. This may seem odd, but our circadian clocks are profoundly influenced by light.
MARLA FELLER – If you didn’t see any light, your sleep cycle would shift slowly so you fell asleep later and more often.
DANIEL: MarlaFeller is a neurobiologist from UC Berkeley.
FELLER: What happens is that every day, you look out at the sun and this entrains the circadian clock to be on a 24-hour cycle.
DANIEL: So we are faced with a mystery. Crittenden is blind.
CRITTENDEN: Yup, total darkness.
DANIEL: His internal clock still beats to the sunlit 24-hour rhythm, minus a few seconds. Crittenden and others like it offer insight into a system within our brains that allows some people who are blind to still make use of the sun to keep their internal clocks running. This brings us to Iggy Provencio at the University of Virginia. He was studying the African clawed Frog in graduate school in the 1990s.
IGGY PROVENCIO – The frog is a very disgusting looking animal. It has very slimy skin.
DANIEL: Skin contains pigment-producing cells that darken when they see light. Provencio identified the melanopsin molecule that is responsible for light detection. It was also found in the retinas of mice and frogs.
PROVENCIO – We were looking through the microscope and I told my colleague, who was also there, that we were the first to see a completely new sensory system in mammals.
DANIEL: Including humans. Melanopsin is not in our rods and cones. It’s actually inside melanopsin cells, which are large neurons. They are located in a different part of the retina. Here’s Michael Do from Boston Children’s Hospital, and Harvard Medical School.
MICHAEL DO: Picture an octopus reaching out with its tentacles. The melanopsin cell’s arms extend outward and overlap with other melanopsin cell arms to create a mesh around the retina.
DANIEL: All of the mesh is sensitive to light. The melanopsin cells’ tentacles radiate throughout our brains.
DO: It’s believed that about 30 brain regions are directly contacted by these cells. One of these is the structure located at the base, which is our master circadian timer.
DANIEL Satchin Panda, a chronobiologist at Salk Institute is saying that there have been laboratory experiments in which mice had their melanopsin turned off.
SATCHIN PANDA – These mice can sense light to a certain extent. They take a long time.
DANIEL: Give them a lab mouse jetlag version where you suddenly shift from one position to another when the lights are turned on.
PANDA: Instead of seven days, these mice will reset to the new time zone in a month.
DANIEL: That’s the mystery solved. Fred Crittenden is our man near Toronto. He doesn’t have functioning rods or cones. However, he does possess melanopsin cells which allow him to use light subconsciously to help synchronize the circadian rhythms. This allows his body to begin a new day each morning to ensure he’s awake when Sarah (his daughter) calls him.
CRITTENDEN: She calls me almost every other day to check on my health and ask how I am doing. She is a wonderful girl.
DANIEL It shows her smiling. It was displayed in his bedroom, right next to the window. On a clear day, the sunlight would shine through the window, lighting Sarah’s face.
Ari Daniel, NPR News
SIMON: This story was also presented live at the Charles Hayden Planetarium, Museum of Science in Boston. NPR provided the transcript, copyright NPR.
