Early-life exposure to dogs may lessen risk of developing schizophrenia

Dog and chalkboard addition (stock image).

Dogs spontaneously process basic numerical quantities, using a distinct part of their brains that corresponds closely to number-responsive neural regions in humans, finds a study at Emory University.

Biology Letters published the results, which suggest that a common neural mechanism has been deeply conserved across mammalian evolution.

"Our work not only shows that dogs use a similar part of their brain to process numbers of objects as humans do -- it shows that they don't need to be trained to do it," says Gregory Berns, Emory professor of psychology and senior author of the study.

"Understanding neural mechanisms -- both in humans and across species -- gives us insights into both how our brains evolved over time and how they function now," says co-author Stella Lourenco, an associate professor of psychology at Emory.

Such insights, Lourenco adds, may one day lead to practical applications such as treating brain abnormalities and improving artificial intelligence systems.

Lauren Aulet, a PhD candidate in Lourenco's lab, is first author of the study.

The study used functional magnetic resonance imaging (fMRI) to scan dogs' brains as they viewed varying numbers of dots flashed on a screen. The results showed that the dogs' parietotemporal cortex responded to differences in the number of the dots. The researchers held the total area of the dots constant, demonstrating that it was the number of the dots, not the size, that generated the response.

The approximate number system supports the ability to rapidly estimate a quantity of objects in a scene, such as the number of predators approaching or the amount of food available for foraging. Evidence suggests that humans primarily draw on their parietal cortex for this ability, which is present even in infancy.

This basic sensitivity to numerical information, known as numerosity, does not rely on symbolic thought or training and appears to be widespread throughout the animal kingdom. Much of the research in non-humans, however, has involved intensive training of the subjects.

Previous research, for example, has found that particular neurons in the parietal cortex of monkeys are attuned to numerical values. Such studies had not clarified whether numerosity is a spontaneous system in non-human primates, because the subjects underwent many trials and received rewards for selecting scenes with greater numbers of dots in preparation for the experiments.

Behavioral studies in dogs that were trained in the task of discriminating between different quantities of objects have also indicated that dogs are sensitive to numerosity.

The Emory researchers wanted to delve further into the neural underpinnings of canine number perception using fMRI.

Berns is founder of the Dog Project, which is researching evolutionary questions surrounding man's best, and oldest friend. The project was the first to train dogs to voluntarily enter an fMRI scanner and remain motionless during scanning, without restraint or sedation.

Lourenco primarily researches human visual perception, cognition and development.

Eleven dogs of varying breeds were involved in the current fMRI experiments. The dogs did not receive advance training in numerosity. After entering the fMRI, they passively viewed dot arrays that varied in numerical value. Eight of the 11 dogs showed greater activation in the parietotemporal cortex when the ratio between alternating dot arrays was more dissimilar than when the numerical values were constant.

"We went right to the source, observing the dogs' brains, to get a direct understanding of what their neurons were doing when the dogs viewed varying quantities of dots," Aulet says. "That allowed us to bypass the weaknesses of previous behavioral studies of dogs and some other species."

Humans and dogs are separated by 80 million years of evolution, Berns notes. "Our results provide some of the strongest evidence yet that numerosity is a shared neural mechanism that goes back at least that far," he says.

Unlike dogs and other animals, humans are able to build on basic numerosity in order to do more complex math, drawing primarily on the prefrontal cortex. "Part of the reason that we are able to do calculus and algebra is because we have this fundamental ability for numerosity that we share with other animals," Aulet says. "I'm interested in learning how we evolved that higher math ability and how these skills develop over time in individuals, starting with basic numerosity in infancy."

Additional authors of the study include Veronica Chiu and Ashley Prichard, Emory graduate students in psychology, and Mark Spivak, CEO of Comprehensive Pet Therapy. Spivak and Berns co-founded Dog Star Technologies to develop techniques to study how dogs perceive the world.

The work was supported by the National Institutes of Health, the John Merck Fund and the Office of Naval Research.

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Materials provided by Emory Health Sciences. Original written by Carol Clark. Note: Content may be edited for style and length.

Early-life exposure to dogs may lessen risk of developing schizophrenia

Child with dog (stock image).

Ever since humans domesticated the dog, the faithful, obedient and protective animal has provided its owner with companionship and emotional well-being. Now, a study from Johns Hopkins Medicine suggests that being around "man's best friend" from an early age may have a health benefit as well -- lessening the chance of developing schizophrenia as an adult.

And while Fido may help prevent that condition, the jury is still out on whether or not there's any link, positive or negative, between being raised with Fluffy the cat and later developing either schizophrenia or bipolar disorder.

"Serious psychiatric disorders have been associated with alterations in the immune system linked to environmental exposures in early life, and since household pets are often among the first things with which children have close contact, it was logical for us to explore the possibilities of a connection between the two," says Robert Yolken, M.D., chair of the Stanley Division of Pediatric Neurovirology and professor of neurovirology in pediatrics at the Johns Hopkins Children's Center, and lead author of a research paper recently posted online in the journal PLOS One.

In the study, Yolken and colleagues at Sheppard Pratt Health System in Baltimore investigated the relationship between exposure to a household pet cat or dog during the first 12 years of life and a later diagnosis of schizophrenia or bipolar disorder. For schizophrenia, the researchers were surprised to see a statistically significant decrease in the risk of a person developing the disorder if exposed to a dog early in life. Across the entire age range studied, there was no significant link between dogs and bipolar disorder, or between cats and either psychiatric disorder.

The researchers caution that more studies are needed to confirm these findings, to search for the factors behind any strongly supported links, and to more precisely define the actual risks of developing psychiatric disorders from exposing infants and children under age 13 to pet cats and dogs.

According to the American Pet Products Association's most recent National Pet Owners Survey, there are 94 million pet cats and 90 million pet dogs in the United States. Previous studies have identified early life exposures to pet cats and dogs as environmental factors that may alter the immune system through various means, including allergic responses, contact with zoonotic (animal) bacteria and viruses, changes in a home's microbiome, and pet-induced stress reduction effects on human brain chemistry.

Some investigators, Yolken notes, suspect that this "immune modulation" may alter the risk of developing psychiatric disorders to which a person is genetically or otherwise predisposed.

In their current study, Yolken and colleagues looked at a population of 1,371 men and women between the ages of 18 and 65 that consisted of 396 people with schizophrenia, 381 with bipolar disorder and 594 controls. Information documented about each person included age, gender, race/ethnicity, place of birth and highest level of parental education (as a measure of socioeconomic status). Patients with schizophrenia and bipolar disorder were recruited from inpatient, day hospital and rehabilitation programs of Sheppard Pratt Health System. Control group members were recruited from the Baltimore area and were screened to rule out any current or past psychiatric disorders.

All study participants were asked if they had a household pet cat or dog or both during their first 12 years of life. Those who reported that a pet cat or dog was in their house when they were born were considered to be exposed to that animal since birth.

The relationship between the age of first household pet exposure and psychiatric diagnosis was defined using a statistical model that produces a hazard ratio -- a measure over time of how often specific events (in this case, exposure to a household pet and development of a psychiatric disorder) happen in a study group compared to their frequency in a control group. A hazard ratio of 1 suggests no difference between groups, while a ratio greater than 1 indicates an increased likelihood of developing schizophrenia or bipolar disorder. Likewise, a ratio less than 1 shows a decreased chance.

Analyses were conducted for four age ranges: birth to 3, 4 to 5, 6 to 8 and 9 to 12.

Surprisingly, Yolken says, the findings suggests that people who are exposed to a pet dog before their 13th birthday are significantly less likely -- as much as 24% -- to be diagnosed later with schizophrenia.

"The largest apparent protective effect was found for children who had a household pet dog at birth or were first exposed after birth but before age 3," he says.

Yolken adds that if it is assumed that the hazard ratio is an accurate reflection of relative risk, then some 840,000 cases of schizophrenia (24% of the 3.5 million people diagnosed with the disorder in the United States) might be prevented by pet dog exposure or other factors associated with pet dog exposure.

"There are several plausible explanations for this possible 'protective' effect from contact with dogs -- perhaps something in the canine microbiome that gets passed to humans and bolsters the immune system against or subdues a genetic predisposition to schizophrenia," Yolken says.

For bipolar disorder, the study results suggest there is no risk association, either positive or negative, with being around dogs as an infant or young child.

Overall for all ages examined, early exposure to pet cats was neutral as the study could not link felines with either an increased or decreased risk of developing schizophrenia or bipolar disorder.

"However, we did find a slightly increased risk of developing both disorders for those who were first in contact with cats between the ages of 9 and 12," Yolken says. "This indicates that the time of exposure may be critical to whether or not it alters the risk."

One example of a suspected pet-borne trigger for schizophrenia is the disease toxoplasmosis, a condition in which cats are the primary hosts of a parasite transmitted to humans via the animals' feces. Pregnant women have been advised for years not to change cat litter boxes to eliminate the risk of the illness passing through the placenta to their fetuses and causing a miscarriage, stillbirth, or potentially, psychiatric disorders in a child born with the infection.

In a 2003 review paper, Yolken and colleague E. Fuller Torrey, M.D., associate director of research at the Stanley Medical Research Institute in Bethesda, Maryland, provided evidence from multiple epidemiological studies conducted since 1953 that showed there also is a statistical connection between a person exposed to the parasite that causes toxoplasmosis and an increased risk of developing schizophrenia. The researchers found that a large number of people in those studies who were diagnosed with serious psychiatric disorders, including schizophrenia, also had high levels of antibodies to the toxoplasmosis parasite.

Because of this finding and others like it, most research has focused on investigating a potential link between early exposure to cats and psychiatric disorder development. Yolken says the most recent study is among the first to consider contact with dogs as well.

"A better understanding of the mechanisms underlying the associations between pet exposure and psychiatric disorders would allow us to develop appropriate prevention and treatment strategies," Yolken says.

Working with Yolken on the research team are the following members from Sheppard Pratt Health System: Cassie Stallings, Andrea Origoni, Emily Katsafanas, Kevin Sweeney, Amalia Squire, and Faith Dickerson, Ph.D., M.P.H.

The study was largely supported by grants from the Stanley Medical Research Institute.

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Story Source:

Materials provided by Johns Hopkins Medicine. Note: Content may be edited for style and length.

Early-life exposure to dogs may lessen risk of developing schizophrenia

Child with dog (stock image).

Credit: © melounix / Adobe Stock

Ever since humans domesticated the dog, the faithful, obedient and protective animal has provided its owner with companionship and emotional well-being. Now, a study from Johns Hopkins Medicine suggests that being around "man's best friend" from an early age may have a health benefit as well -- lessening the chance of developing schizophrenia as an adult.

And while Fido may help prevent that condition, the jury is still out on whether or not there's any link, positive or negative, between being raised with Fluffy the cat and later developing either schizophrenia or bipolar disorder.

"Serious psychiatric disorders have been associated with alterations in the immune system linked to environmental exposures in early life, and since household pets are often among the first things with which children have close contact, it was logical for us to explore the possibilities of a connection between the two," says Robert Yolken, M.D., chair of the Stanley Division of Pediatric Neurovirology and professor of neurovirology in pediatrics at the Johns Hopkins Children's Center, and lead author of a research paper recently posted online in the journal PLOS One.

In the study, Yolken and colleagues at Sheppard Pratt Health System in Baltimore investigated the relationship between exposure to a household pet cat or dog during the first 12 years of life and a later diagnosis of schizophrenia or bipolar disorder. For schizophrenia, the researchers were surprised to see a statistically significant decrease in the risk of a person developing the disorder if exposed to a dog early in life. Across the entire age range studied, there was no significant link between dogs and bipolar disorder, or between cats and either psychiatric disorder.

The researchers caution that more studies are needed to confirm these findings, to search for the factors behind any strongly supported links, and to more precisely define the actual risks of developing psychiatric disorders from exposing infants and children under age 13 to pet cats and dogs.

According to the American Pet Products Association's most recent National Pet Owners Survey, there are 94 million pet cats and 90 million pet dogs in the United States. Previous studies have identified early life exposures to pet cats and dogs as environmental factors that may alter the immune system through various means, including allergic responses, contact with zoonotic (animal) bacteria and viruses, changes in a home's microbiome, and pet-induced stress reduction effects on human brain chemistry.

Some investigators, Yolken notes, suspect that this "immune modulation" may alter the risk of developing psychiatric disorders to which a person is genetically or otherwise predisposed.

In their current study, Yolken and colleagues looked at a population of 1,371 men and women between the ages of 18 and 65 that consisted of 396 people with schizophrenia, 381 with bipolar disorder and 594 controls. Information documented about each person included age, gender, race/ethnicity, place of birth and highest level of parental education (as a measure of socioeconomic status). Patients with schizophrenia and bipolar disorder were recruited from inpatient, day hospital and rehabilitation programs of Sheppard Pratt Health System. Control group members were recruited from the Baltimore area and were screened to rule out any current or past psychiatric disorders.

All study participants were asked if they had a household pet cat or dog or both during their first 12 years of life. Those who reported that a pet cat or dog was in their house when they were born were considered to be exposed to that animal since birth.

The relationship between the age of first household pet exposure and psychiatric diagnosis was defined using a statistical model that produces a hazard ratio -- a measure over time of how often specific events (in this case, exposure to a household pet and development of a psychiatric disorder) happen in a study group compared to their frequency in a control group. A hazard ratio of 1 suggests no difference between groups, while a ratio greater than 1 indicates an increased likelihood of developing schizophrenia or bipolar disorder. Likewise, a ratio less than 1 shows a decreased chance.

Analyses were conducted for four age ranges: birth to 3, 4 to 5, 6 to 8 and 9 to 12.

Surprisingly, Yolken says, the findings suggests that people who are exposed to a pet dog before their 13th birthday are significantly less likely -- as much as 24% -- to be diagnosed later with schizophrenia.

"The largest apparent protective effect was found for children who had a household pet dog at birth or were first exposed after birth but before age 3," he says.

Yolken adds that if it is assumed that the hazard ratio is an accurate reflection of relative risk, then some 840,000 cases of schizophrenia (24% of the 3.5 million people diagnosed with the disorder in the United States) might be prevented by pet dog exposure or other factors associated with pet dog exposure.

"There are several plausible explanations for this possible 'protective' effect from contact with dogs -- perhaps something in the canine microbiome that gets passed to humans and bolsters the immune system against or subdues a genetic predisposition to schizophrenia," Yolken says.

For bipolar disorder, the study results suggest there is no risk association, either positive or negative, with being around dogs as an infant or young child.

Overall for all ages examined, early exposure to pet cats was neutral as the study could not link felines with either an increased or decreased risk of developing schizophrenia or bipolar disorder.

"However, we did find a slightly increased risk of developing both disorders for those who were first in contact with cats between the ages of 9 and 12," Yolken says. "This indicates that the time of exposure may be critical to whether or not it alters the risk."

One example of a suspected pet-borne trigger for schizophrenia is the disease toxoplasmosis, a condition in which cats are the primary hosts of a parasite transmitted to humans via the animals' feces. Pregnant women have been advised for years not to change cat litter boxes to eliminate the risk of the illness passing through the placenta to their fetuses and causing a miscarriage, stillbirth, or potentially, psychiatric disorders in a child born with the infection.

In a 2003 review paper, Yolken and colleague E. Fuller Torrey, M.D., associate director of research at the Stanley Medical Research Institute in Bethesda, Maryland, provided evidence from multiple epidemiological studies conducted since 1953 that showed there also is a statistical connection between a person exposed to the parasite that causes toxoplasmosis and an increased risk of developing schizophrenia. The researchers found that a large number of people in those studies who were diagnosed with serious psychiatric disorders, including schizophrenia, also had high levels of antibodies to the toxoplasmosis parasite.

Because of this finding and others like it, most research has focused on investigating a potential link between early exposure to cats and psychiatric disorder development. Yolken says the most recent study is among the first to consider contact with dogs as well.

"A better understanding of the mechanisms underlying the associations between pet exposure and psychiatric disorders would allow us to develop appropriate prevention and treatment strategies," Yolken says.

Working with Yolken on the research team are the following members from Sheppard Pratt Health System: Cassie Stallings, Andrea Origoni, Emily Katsafanas, Kevin Sweeney, Amalia Squire, and Faith Dickerson, Ph.D., M.P.H.

The study was largely supported by grants from the Stanley Medical Research Institute.

---

Story Source:

Materials provided by Johns Hopkins Medicine. Note: Content may be edited for style and length.

Daily exposure to blue light may accelerate aging, even if it doesn't reach your eyes

Woman looking at blue light from at computer screen 

Prolonged exposure to blue light, such as that which emanates from your phone, computer and household fixtures, could be affecting your longevity, even if it's not shining in your eyes.

New research at Oregon State University suggests that the blue wavelengths produced by light-emitting diodes damage cells in the brain as well as retinas.

The study, published today in Aging and Mechanisms of Disease, involved a widely used organism, Drosophila melanogaster, the common fruit fly, an important model organism because of the cellular and developmental mechanisms it shares with other animals and humans.

Jaga Giebultowicz, a researcher in the OSU College of Science who studies biological clocks, led a research collaboration that examined how flies responded to daily 12-hour exposures to blue LED light -- similar to the prevalent blue wavelength in devices like phones and tablets -- and found that the light accelerated aging.

Flies subjected to daily cycles of 12 hours in light and 12 hours in darkness had shorter lives compared to flies kept in total darkness or those kept in light with the blue wavelengths filtered out. The flies exposed to blue light showed damage to their retinal cells and brain neurons and had impaired locomotion -- the flies' ability to climb the walls of their enclosures, a common behavior, was diminished.

Some of the flies in the experiment were mutants that do not develop eyes, and even those eyeless flies displayed brain damage and locomotion impairments, suggesting flies didn't have to see the light to be harmed by it.

"The fact that the light was accelerating aging in the flies was very surprising to us at first," said Giebultowicz, a professor of integrative biology. "We'd measured expression of some genes in old flies, and found that stress-response, protective genes were expressed if flies were kept in light. We hypothesized that light was regulating those genes. Then we started asking, what is it in the light that is harmful to them, and we looked at the spectrum of light. It was very clear cut that although light without blue slightly shortened their lifespan, just blue light alone shortened their lifespan very dramatically."

Natural light, Giebultowicz notes, is crucial for the body's circadian rhythm -- the 24-hour cycle of physiological processes such as brain wave activity, hormone production and cell regeneration that are important factors in feeding and sleeping patterns.

"But there is evidence suggesting that increased exposure to artificial light is a risk factor for sleep and circadian disorders," she said. "And with the prevalent use of LED lighting and device displays, humans are subjected to increasing amounts of light in the blue spectrum since commonly used LEDs emit a high fraction of blue light. But this technology, LED lighting, even in most developed countries, has not been used long enough to know its effects across the human lifespan."

Giebultowicz says that the flies, if given a choice, avoid blue light.

"We're going to test if the same signaling that causes them to escape blue light is involved in longevity," she said.

Eileen Chow, faculty research assistant in Giebultowicz's lab and co-first author of the study, notes that advances in technology and medicine could work together to address the damaging effects of light if this research eventually proves applicable to humans.

"Human lifespan has increased dramatically over the past century as we've found ways to treat diseases, and at the same time we have been spending more and more time with artificial light," she said. "As science looks for ways to help people be healthier as they live longer, designing a healthier spectrum of light might be a possibility, not just in terms of sleeping better but in terms of overall health."

In the meantime, there are a few things people can do to help themselves that don't involve sitting for hours in darkness, the researchers say. Eyeglasses with amber lenses will filter out the blue light and protect your retinas. And phones, laptops and other devices can be set to block blue emissions.

"In the future, there may be phones that auto-adjust their display based on the length of usage the phone perceives," said lead author Trevor Nash, a 2019 OSU Honors College graduate who was a first-year undergraduate when the research began. "That kind of phone might be difficult to make, but it would probably have a big impact on health."

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Story Source:

Materials provided by Oregon State University. Original written by Steve Lundeberg. Note: Content may be edited for style and length.