Neuroscientists at Northeastern University are seeking to learn more about the impact and physical changes in the brain which are caused by severe neglect.
In a recent paper, Northeastern researchers found that female rats, in particular, developed abnormal connections between two areas of the brain in response to neglect. These are the same areas that show abnormal activity in brain scans of children who have suffered from child abuse or other forms of severe maltreatment. Children with this abnormal activity are more likely to develop anxiety later on in childhood or adolescence.
“The early work looking at biological underpinnings of this specific circuitry has been largely in male animals,” Jennifer Honeycutt, a postdoctoral researcher at Northeastern and the lead author on the paper explained.
“We were able to not only expand what we know about generally how the circuitry is developing in both sexes, but now we can pinpoint a possible locus of unique vulnerability for females.”
Ms Honeycutt and her colleagues were specifically examining the connections between the basolateral amygdala, part of an almond-shaped structure tucked in near your temple, and the prefrontal cortex, which is right behind your forehead.
The role of the amygdala will be familiar to many early childhood education and care (ECEC) professionals. Essentially, the amygdala is the zone of the brain which “fires off” signals to several other areas of the brain, indicating that a threat is present.
In response, the prefrontal cortex integrates information from other areas of the brain, like context clues or prior memories , and signals the amygdala to, essentially, calm down.
In children who have lived with ongoing abuse and neglect, this pathway is often compromised.
“The disruption of this circuit is going to lead to maladaptive behaviors,” Ms Honeycutt says. “That’s where you start to see increasing anxiety-like behaviors even in the absence of something that could be anxiety-provoking.”
The connections between the amygdala and the prefrontal cortex develop throughout childhood and adolescence. Research has demonstrated, however, that these connections seemed to develop abnormally in children who had experienced severe neglect and later developed anxiety-like disorders.
“This circuit was showing accelerated maturation,” says Heather Brenhouse, an associate professor of psychology at Northeastern. “It was as if the brain was trying to adapt to the experience of early trauma and maybe predict later threats, and which could translate into being hyper-responsive.”
In order to test the exact mechanism behind this change, researchers needed to be able to examine brains more directly, using rats.
“What a young rat, just like a young human, needs the most for its well-being is proper caretaking and nurturing,” Ms Brenhouse says. “If you disturb the infant-mother relationship somehow, that’s the way to best model early life adversity.”
The researchers removed male and female rat pups from their mothers for three to four hours every day during their infancy. The pups were separated into warm areas with bedding that smelled like their mother and littermates, but without any physical contact or caretaking.
The researchers examined the rats’ brains at different points in development. They found marked differences between males and females.
In female rats that were separated from their mother, an excess of new connections grew rapidly between the amygdala and the prefrontal cortex early on in development. Males saw some of this same nerve growth (known as innervation), but not until much later on.
“These excess neural connections were disturbing the efficiency of that circuit,” Ms Brenhouse outlined. “Basically, the circuit didn’t work as well, and it didn’t mature as well.”
The animals whose brains developed abnormally also behaved differently. Rats with excess connections between the amygdala and the prefrontal cortex spent more time in safer areas of a maze, while rats with fewer connections were more exploratory.
The early development of this circuit seemed to be creating a sense of hyper-vigilance in these animals.
“It’s the first time we’ve really seen a sex-specific circuitry change over development after early life stress,” Ms Brenhouse said. “Early life trauma is actually setting up the circuit to develop differently.”
The important thing, researchers said, is that these changes don’t have to be permanent. Understanding the differences in how male and female brains develop, and the impact of neglect on this process, could help improve treatments and interventions for children before mental illnesses begin to manifest themselves.
“I’m always worried when we talk about early life trauma that it sounds like once you experience it, then you’re broken,” Ms Brenhouse said, adding “the truth is, our brain continues to be plastic throughout our lives. Maladaptive circuitry can certainly be molded by later enrichment, interventions, and treatments.”