It can make a parent’s heart race – finding out your infant must undergo extensive surgery that requires general anesthesia. According to the U.S. Food and Drug Administration (FDA), approximately one million children under the age of four annually undergo surgery with general anesthesia, making understanding effects of early life exposure to anesthesia critical.

Yerkes National Primate Research Center researchers and their colleagues at Mt. Sinai’s Icahn School of Medicine set out to determine just that. Through animal research, the team discovered infant monkeys repeatedly exposed to a common anesthetic, sevoflurane, suffered impairment in visual recognition memory after the first year of life. Furthermore, results indicated the impairment may persist long term.

Dr. Maria Alvarado, first author and leader of the Yerkes team, noted, “Animal studies have shown exposure to general anesthesia in infancy can cause loss of cells in the central nervous system and long-term impairments in neurocognitive function.” This finding is consistent with previous human epidemiological studies, which have shown children with multiple exposures to general anesthesia before the age of four are at greater risk of learning disabilities and other cognitive impairments. Impairments may not become apparent until the child begins formal schooling.

The research team published these results in the British Journal of Anaesthesia, marking a significant advancement in anesthesia-related studies. Whereas past studies included variables for surgical procedures, the NPRC and Mt. Sinai teams eliminated these variables, allowing the team to focus specifically on the side effects of anesthesia. With this knowledge, the team is now conducting research to further clarify the extent and duration of these anesthesia-induced impairments.

“Our studies with rhesus monkeys are fundamental to making anesthesia exposure in infancy and childhood as safe as possible,” Dr. Alvarado explains.

Reviewed August 2019

Familiarity makes the heart grow fonder, at least when it comes to the prairie vole. This rodent species is monogamous, with partners forming lifelong bonds. Until recently, no one knew why. That “why” is exactly what researchers at the Yerkes National Primate Research Center at Emory University want to understand.

“Prairie voles were critical to our team’s findings because studying pair bonding in humans has been traditionally difficult,” said Dr. Elizabeth Amadei, a co-lead author on the research. “As humans, we know the feelings we get when we view images of our romantic partners, but until now, we haven’t known how the brain’s reward system works to lead to those feelings and to the voles’ pair bonding.”

The existing research suggests an interaction between chemicals, such as oxytocin and dopamine, and brain regions, including the prefrontal cortex, leads to these lifelong bonds. That, however, wasn’t enough information for this team that wants to understand the specific neural process and neural networks.

So why do prairie voles mate for life? When a male and female vole interact for extended periods of time, the prefrontal cortex increases the activity of the nucleus accumbens, the brain’s reward system. The decision to engage in affiliative behaviors, such as cuddling and mating, strengthens the animals’ bond and increases overall pleasure for both voles.

While this research has led to additional questions about how the brain impacts the sensational and emotional components of love, it also has longer-term implications. According to Dr. Larry Young, co-author, director of the Emory Conte Center and chief of the Behavioral Neuroscience and Psychiatric Disorders Division at Yerkes, “this discovery is just part of the larger effort to understand how brain circuits works during natural social behaviors. The more we understand, the easier it is to tackle disorders, such as autism, which impair social functioning.”

Reviewed August 2019

Menopause isn’t always accompanied by physical symptoms. In fact, for many women, the side effects of this hormonal change aren’t quite as tangible as hot flashes and stiff joints. A decline in mental faculties such as reasoning and perception can often occur. However, a study from the Oregon National Primate Research Center suggests that hormone therapy may mitigate such cognitive changes.

For the nonhuman primates treated with estradiol implants, both spatial working memory and visuospatial attention improved throughout the course of the one-year testing period compared to those receiving a placebo. While post-menopausal hormone therapy has been a frequent topic of debate, the research supported the hypothesis that estradiol treatment is a sustainable solution for managing symptoms.

“There have been several previous studies published on the effect of hormone therapy on cognition in the nonhuman primate, with equivocal results,” said lead author Dr. Steven G. Kohama, a neuroscientist at the Oregon NPRC. “However, in comparison to these earlier reports, our study was much longer, and it suggests a sustained benefit from early intervention after menopause with hormone treatment.”

As the pro-hormone therapy argument grows stronger, the list of research questions grows longer. Researchers are already considering whether treatment earlier in menopause slows cognitive decline more than therapy introduced later.