Last night, I headed down to the beautiful Bell House, in the Gowanus section of Brooklyn, for this month's Secret Science Club lecture featuring neuroscientist Dr Nim Tottenham of Columbia University. This lecture was presented in collaboration with the Dana Foundation.
Dr Tottenham's lecture concerned early experience and the subsequent emotional development of individuals. The effects of early experiences endure throughout one's lifetime. Her studies in particular explored the interactions of the amygdala and the prefrontal cortex. The amygdala helps us pay attention to emotionally important events. Connections to the prefrontal cortex help to quiet over-arousal of the amygdala. While the whole brain is involved in the processing of emotions, Dr Tottenham takes a narrow view to study emotions- this allows her to look at the system as it is unfolding. She likened it to 'looking at a pie as it is baking'.
Early experience plays a role in emotional brain development- there are sensitive periods in early brain development when the brain is amenable to influence. During these sensitive periods, the phenotype of the central nervous system emerges. Phenotypic expression is affected by environment, and the ability to regulate emotions takes a long time to develop. Mental disorders such as schizophrenia, mood disorders, and substance abuse often emerge during adolescence.
Dr Tottenham went on to describe an experiment to test functional amygdala responses. Forty-five participants ages 4-22 were observed during passive viewing of faces displaying fear expressions. Neuroimages were obtained using magnetic resonance imaging. The participants were allowed to view movies or television shows of their choice, but were intermittently shown, with advance notice, the fear faces. Their amygdala responses were then imaged. Younger participants showed high amygdala responses, and the researchers looked for changes in amygdala activity as a function of age. Dr Tottenham noted that there is a negative correlation between amygdala activity and the age of the subjects- younger participants have stronger responses with more activity. The main role of the amygdala is to allow learning about the relative safety and danger of the environment.
Using imaging, Dr Tottenham was able to 'pull out' the activity of different regions of the brain and compare their activity. The amygdala and the prefrontal cortex are in communication, with the prefrontal cortex having an inhibitory relationship with the amygdala. As the amygdala is 'quieted', there is lower autonomic arousal. Younger individuals have lower amygdala/prefrontal cortex connectivity, and the maturation of connectivity occurs slowly. Children have positive correlation between the amygdala and the prefrontal cortex, a switch from positive to negative correlation is accompanied by behavioral change. Specifically, normal separation anxiety decreases with age- positive prefrontal cortex/amygdala correlation is connected with higher separation anxiety. The regulation of emotions can be inhibited by early stress (particularly institutional care of children separated from their parents). Early adversity or neglect can result in amygdala hyperactivity.
Dr Tottenham informed us that the brain develops hierarchically, from back to front. The prefrontal cortex matures around twenty-five years of age (she joked that the insurance companies knew this before the scientists did). The amygdala develops in childhood, Dr Tottenham poetically described it as 'the older sister who informs the rest of the brain'. She invoked Wordsworth: "The Child is father of the Man".
One of the contrasts measured in Dr Tottenham's experiment was the contrast between stimulus related amygdala/prefrontal cortex connectivity and resting state connectivity. When the brain is in a resting state, the connectivity is lower- a sort of 'functional skeleton' of the brain takes over, and this connectivity ramps up when fear stimuli are presented.
Dr Tottenham quipped: 'Cells that fire together wire together'. The youngest participants in the study exhibited more brain plasticity than the older participants. The connections 'settle down' as aging occurs. There are Juvenile Sensitive Periods, and stimuli from an individual's youth can help reduce anxiety in adults. Mice in an 'open field', a box without shelter, run to the corners of the enclosure (Dr Tottenham joked, 'like middle schoolers at their first dance'). If the mouse pups are exposed to music, playing the music that they are habituated to will cause them to be less anxious about exploring the center of the enclosure.
It is difficult to identify the Juvenile Sensitive Periods among humans, due to our long lifespans and slow development. In one experiment, Billboard charts were used to date particular stimuli (for instance, the Backstreet Boys were popular in 1997). Subjects were exposed to stress in the form of difficult math problems from the SAT exams. Students were told they were below average, and instructed to speed up their problem solving. Given a choice of music to listen to, US born subjects prefered listening to the Backstreet Boys rather than Justin Bieber, while non-US born subjects had no such preference. The preference among US born subjects was not correlated with liking the Backstreet Boys. Exposure to childhood music led to less autonomic stress, less anxiety.
Dr Tottenham noted that being supported by our parents allows long childhood development... our parents are the scaffolding that allows us to mature and figure out how the world works. Rat pups prefer odors associated with their mothers. If a rat pup is raised to associate a peppermint smell with its mother, that rat will even tolerate a shock associated with the peppermint smell. This preference is regardless of violence versus reward. Parental buffering occurs- the presence of the mother decreases corticosteroidal production and amygdala activity. Having mom around frees the pups to learn about the world around them. Among altricial animals, fight and flight strategies are not reliable, and attachment to parents is a better survival strategy. Human brains are Among altricial animals, fight and flight strategies are not reliable, and attachment to parents is a better survival strategy. Humans being altricial, our brains are neotenous, there is a long period of plasticity. Among precocial animals, such as sea turtles, there is little plasticity, and infants know what to do immediately after birth. The stretched-out period of plasticity among humans gives our parents time to provide the scaffolding which aids in brain development.
In one experiment, subjects were stressed by making them speak publicly- among younger subjects, parental buffering resulted in lower cortisol production, while it had no effect with adolescent subjects. Parents may help their offspring to guide attention to what is important, to allow exploration of scary subjects. Notably, parents are good at buffering if they are calm, but not when they are anxious. During adolescence, the parents lose effectiveness in suppressing amygdala function. The sensitive period of neurohormonal activity ends, but what was learned is reflected throughout life. Dr Tottenham noted that there is value in 'slow cooking', the transition to adult emotional regulation is largely dependent on the environmental scaffolding we receive through adolescence.
The lecture was followed by a Q&A session. One sobering question regarded the role of attachment in cases of abusive parents- the shock paired with a smell associated with a parent is a model for abuse. To understand how attachment works, the sources of plasticity must be understood, a development which might have implications for family court proceedings. Another question involved the case of institutional care (e.g. orphanages)- 'growing up fast' can trunctate development and result in less coordination between amygdala and prefrontal cortex... on average, of course. Another question regarding promoting plasticity- therapy works on plasticity, and there are pharmacological boosters, such as Prozac, in experiments on rats. Still another question involved the need to support families in order to protect children's mental health. Dr Tottenham noted that a child doesn't struggle alone- we need to address a child's mental health AND what is wrong with society. Regarding 'helicopter parenting', good parenting allows a child to fall, the rupture and repair is needed, and good parents should help a child to mend.
Some bastard in the audience, unable to get a question in during the formal Q&A, asked the good doctor if any of her subjects had received a traumatic brain injury in the course of the study, which would affect results. Fortunately, none of them did, but there are studies at the University of Nebraska to gauge the role of concussions in brain plasticity, and the use of physical exercise to increase plasticity.
Once again, the Secret Science Club served up a fantastic lecture. Kudos to Dr Tottenham, Margaret and Dorian, the DANA Foundation, and the staff of the beautiful Bell House. While the lecture was wonderful, I could not escape the societal implications of the family separation policy at the border. The US government is doing untold harm to thousands of children, and the mental health effects will be felt for a generation. I had a good amount of time to reflect on this on the subway ride home, so my prefrontal cortex had a lot of regulating to do.
Here's a video of Dr Tottenham discussing emotional regulation to take your mind off of that downer ending:
Pour yourself a nice beverage and soak in that SCIENCE!