Most female mammals give birth and care for their offspring, while the males often breed with multiple partners and play little role in parenting once the mating is over. Yet researchers have had a hard time pinpointing exactly where in the brain these gender differences are located and how they translate into behavior. The extent of “hardwired parental behavior” is hotly disputed.
In new research published in Nature, Weizmann Institute of Science neurobiologists Dr. Tali Kimchi and her graduate student Niv Scott, in collaboration with Dr. Ofer Yizhar and postdoctoral fellow Dr. Matthias Prigge, offer new insight into this issue. This research shows that same network of brain cells operates differently in male and female mice.
Female mice, even those that have never had pups, act in ways that can be defined as maternal. They will carry a pup left in the corner of the cage back to the nest, for example, and spend time grooming a newborn.
This tendency becomes amplified once they become mothers. Males, in contrast, are generally aggressive and territorial. They may ignore strange pups or else attack them. However, males will become parental for a short period after mating with a female, starting around the birth of their pups.
To investigate how the brain manages parental behavior, the researchers zeroed in on a small structure the brain’s hypothalamus gland called the anteroventral preventricular nucleus (AVPV), which is larger in female mice than in males. The team was particularly interested in certain neurons that express a protein known as tyrosine hydroxylase (TH), which is required for the production of dopamine – a chemical messenger in the brain. They observed that specific TH-containing neurons are more numerous in mothers than in either virgin females or any males.
This hinted that these neurons – even though they are shared by both sexes – could drive parental care in females while serving a different function in males.
Using advance genetic and neuro-biochemical tools, the team first increased and then decreased the amount of TH in both adult male and female mice, just in neurons of this particular brain region. Then the researchers recorded how these changes affected the parenting styles of the mice.
The team also employed optogenetic technology, in which neurons are activated by light, to precisely manipulate the activity of TH-containing neurons – literally, at the flip of a light switch.
The researchers found they were especially able to trigger maternal actions in female mice – both virgins and mothers – by elevating the TH levels in these neurons. Also, brief optogenetic activation, even a few minutes, was all that was required to get a female to hurry to the corner of the cage to carry a pup back to her nest. Further tests revealed that these manipulations enhanced blood levels of oxytocin – a hormone associated, among other things, with lactation and female reproductive behavior in general. Decreasing the number of TH-containing neurons in females lowered their levels of oxytocin and severely impaired their maternal instincts.
When the scientists used optogenetics to activate TH-containing neurons in male mice, there was no effect on oxytocin levels or pup-caring. However, surprisingly, there was a significant drop in aggressive behavior toward unfamiliar pups and adult males.
Decreasing the number of TH-containing neurons, on the other hand, led to a profound increase in the males’ aggression toward both.
“By controlling the amount and activities of these unique neurons, we were able to manipulate the maternal behavior of the females and the aggression of the males, said Kimchi. “Our results hint that maternal behavior arises from neuronal networks that are largely hard-wired. These are different from those of males, and they are at least partly regulated by the hormone oxytocin.”
These findings may in the future provide insight into the ways that male and female brains function when it comes to such conventional gender-related activities as tending to infants, and other innate reproductive and social behaviors. Kimchi hoped that this discovery may ultimately advance our understanding of the biological factors that contribute to mental disorders, which have a social aspect, as well as gender differences. These include postpartum depression, aggression and autism spectrum disorders.NURSING SIMULATION LAB FOR JCT
A $245,000 grant for nursing-student simulation laboratories at the Jerusalem College of Technology- Lev Academic Center (JCT) has been made by the Leona and Harry Helmsley Charitable Trust. Offering one of the only academic programs especially designed for the haredi (ultra-Orthodox) community, JCT provides modern Orthodox and haredi men (and separately, women) with excellent academic education, which will enable them to integrate into the Israeli workforce. This improves the overall economic situation of the haredi community in Israel and reducing their dependence on government and social support. An additional goal of the program is to create successful role models for this community, who successfully combine their haredi lifestyle with modern society.
The nursing program is a program of excellence in nursing education, research and practice, preparing dedicated and committed nursing professionals to treat, heal and comfort those in their care.
Today, JCT’s nursing classes are conducted in three locations, with 530 women studying at Tal Campus in the capital’s Givat Shaul quarter; 187 studying in the Mivhar program for haredi women and an additional 50 men participating in the pilot program at Lev Campus in Jerusalem’s Givat Mordechai section.
Graduates of the program attain the highest national averages in the national board examinations each year.
Hi-tech, advanced simulation labs give nursing students hands-on experience, allowing them to practice and perfect skills, while eliminating potential risks to patients in the event of errors. Students will receive professional training in areas such as anatomy, physiology and communications and will use all applicable disciplines and best practices and receive reliable feedback using the digital resources in the lab, which will also generate self-confidence among students and safer care as students go into their clinical stage of study.
“The Helmsley Charitable Trust is one of the largest and most important philanthropic institutions supporting Israel today,” said JCT president Prof. Chaim Sukenik. “We are honored that they have chosen to support our nursing program which is one of the largest and most successful in Israel.”