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- [Narrator] We are the paradoxical ape.
Bipedal, naked, large brained,
long the master of fire, tools, and language,
but still trying to understand ourselves.
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yet filled with optimism.
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We shape the future from our shared understanding
of the past.
CARTA brings together experts
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An exploration made possible
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- So, I've spent my research career
focusing on the phenomenon of mothering.
And I'd like to start with a video
that I think does a good job illustrating
why I find mothering to be so phenomenal.
The maternal instinct is sometimes greater
than the instinct for one's own survival.
And you can see this wild rat was caught chasing
a predator, attacking this predator
so that it would release her baby or pup, as we call it.
And my favorite part is the last part,
where after the snake releases the pup
she actually continues to run after the snake
and continue to attack it, just to make sure
that it gets the point to stay away from her nest.
So, certainly, this behavior is not limited to wild rats,
but we can see these kinds of behaviors
in the laboratory as well.
This is a rat from my lab.
And we were weighing her pups one morning,
she's rearing them in a semi-natural environment,
so this is outdoors, and you can see she wasn't having
any of it, and she retrieved each one
of her pups back into her nest box.
So rats aren't the only ones that care for infants.
Maternal care is a defining characteristic
of mammalian behavior.
And this behavior is really motivated,
and it's also unconditional.
So, as we saw in these videos,
mom's care for infants across multiple contexts,
even when those contexts are quite challenging.
So, it's not escaped my attention
that not all mothers are committed
to the survival of their infants, unfortunately.
And this is quite predominant in humans.
So we've already heard a little bit about this earlier today
but the statistics are really quite staggering.
So three million annual reports
of child abuse in the United States.
Many of these incidents go without report,
so I think this is probably a conservative estimate.
Five children die every single day due
to abuse, maltreatment, or neglect.
And, actually, a large portion of abuse
or maltreatment is neglect, failing to care for infants,
failing to provide basic food, water,
shelter, protection from harm.
As well as, of course, emotional support.
Every 10 seconds is how often abuse gets reported.
So these statistics, for me, were really staggering
when I read them, and I think what I find most outrageous
is that despite the prevalence of neglect
we know almost nothing about dysfunction
in the maternal brain and, to me, this is
a huge gap in our literature that we really need to focus on
So today, I want to propose, first and foremost,
that studying mothers has merit.
If we want to understand how to prevent child neglect
I think it's important to understand
what causes a neglectful parenting style in the first place.
And, with respect to this, I want to talk
about my hypothesis for one of the ways
I think, neglect might emerge.
And that's related to disruption
in experience-dependent plasticity
within the maternal brain.
And, specifically, I'm talking about neural systems
that have been identified in rodent models
that we know are important
for the onset of mothering behavior.
And these systems are changed during this transition
to motherhood, to both increase the likelihood
that positive responses are displayed towards infants,
but also and importantly to reduce the likelihood
that some negative fearful defensive type
of response occurs when moms are interacting with infants.
So my laboratory has addressed
these issues using rodent models.
And I think it's important to take a moment
and talk about why I think that studying rodents
can tell us something about humans.
So, first and foremost, what we know
about the neurobiology of parental care actually comes
from work that was conducted in rats.
So rats have been a really important model organism
for studying caregiving behavior.
They reproduce well in the laboratory,
they have short gestations, but what's really,
I think, most important is that
they don't form selective attachments with their young.
And so, when we talk about selective attachment
I'm talking about this idea that a mother would recognize
its own infants, and distinguish its own infant
from other infants, and provide care and support only
to its own infant while actually actively avoiding,
or rejecting the advances of any other infant.
I'm not really interested in mechanisms
that underlie infant recognition.
And that's why I think it's important that rats allow us
to study questions about motivation to interact
with infants more generally.
And we can therefore use foster infants
when we conduct studies with rats and with mice
to ask questions about the capacity an animal might have
to show caregiving behavior regardless of whether
or not it's actually appropriate for
that animal to show caregiving behavior at all.
We don't have to a lactation, variability in the health
of offspring, any of those things.
We can ask questions about how does
this animal respond to infants?
How can we turn caregiving behavior on?
In this regard, I think, one of the greatest things
about using rodent models is we can ask questions
about turning caregiving behavior on in males.
So rodents are uni-parental, like most mammalian species
it's the mother that provides the sole care,
but because we can use foster pups
we can ask questions about what turns
on mothering like behaviors in males.
And I won't have time to talk about that today,
but I think it's an important point.
So, the first indication, that experience might be
an important regulator came from work
that was done studying the onset
of maternal behavior in rats.
And this work was conducted by Alison Fleming.
And, at the time, people were really interested
in hormonal changes that happened around the time of birth
that function to synchronize birth
with the onset of maternal motivation and the onset of care.
And those hormonal changes are, undoubtedly, important.
But Alison really wanted to ask what happens with ...
What happens in a situation where mom isn't allowed
to interact with her infants anymore?
Will those hormonal events produce a long-term change
in how she perceives infant stimuli?
Or is it the experience of interacting
with infants that's really important?
So to address this, she separated mother
and her offspring right at the time of birth.
And what she found is that this separation, actually,
completely blocked the onset of caregiving behavior,
and produced this state of infant avoidance.
So rats are not particularly keen on interacting
with infants, if they haven't given birth to their own.
And so these animals kind of reverted back
as though they had never given birth to offspring at all.
So this is a graph you can see from her paper.
On the left, you see animals with no experience,
so those that were completely separated
from their infants, literally took days
to show any care giving behaviors at all
when presented with foster infants.
Animals with full experience, that naturally interacted
with their infants at birth,
were immediately responsive to young.
And so, again, what's important about this
is that although hormonal changes that are associated
with pregnancy and birth are important
they, certainly, aren't producing any lasting effect
in of themselves, instead it's interacting
with infants in the context of
those hormonal changes that's so important.
So she concluded experience is necessary for care.
And when I started my own lab at UC Davis
I was actually interested in the opposite question.
So if we can remove experience and completely obliterate
the onset of maternal behavior at birth
can we deliver experience to animals
that have never been pregnant?
And can we get these animals to show a level
of caregiving behavior that's on par
with what a new mother would show?
And I did this work using a mouse model.
And I had to give them a challenging task.
So, rodents are very neophobic, they hate new things.
This is a novel environment, and I was asking whether
they would be willing to rescue infants
in this novel environment rather
than try to find an escape route for themselves?
And what I found is that if they had no experience at all
with infants, they'd never seen an infant before
they where more likely to spend all their time
on the maze trying to find a way out.
However, if they had as little as eight hours of experience,
as you can see, they retrieve pups back to the nest.
And so, this graph actually represents a meta-analysis
from my lab, I've shown this now several times replicated
it on a number of publications
and these are all of the data lumped together.
And you can see, that around 80% of females
with no experience at all avoid infants,
look for an escape route on the maze.
Whereas as little as eight hours of experience,
produces a completely different effect.
And what I found to be most exciting
when I ran these first experiments is
I thought new mothers respond to infants
with high levels of motivation,
and that tends to be consistent for a long period of time.
And so I said, "What happens a month later?"
And what I found is that a month later,
even though these animals had
not had additional interactions with infants
really seems like some plasticity took place
because they responded in exactly the same way.
So I concluded then that experience with infants,
in the absence of pregnancy and birth,
can promote maternal care, it can block avoidance,
and therefore experience is sufficient for care.
So I was excited when I conducted these studies
and it kind of led to me to think,
"Well, if experience is so critical
"for caregiving behavior, what if neglect
"is actually really due to some disruption,
"or dysfunction in experience dependent plasticity?"
And I had to ask myself the obvious question,
is neglect a failure to learn?
But is this relevant at all to humans?
Is there any evidence at all that experience
is involved in human parenting?
So, I scoured the literature and lo and behold
I found that there is a lot of evidence
that increased contact between mother
and infant just after birth can promote attachment,
can promote maternal care for years
beyond that period of time.
But I found one paper that, I thought,
was particularly compelling.
And this work was done in the '80s.
And, at this time, it wasn't very common
for mothers to actually be able to interact
with their infants after birth.
The infants were typically taken to a nursery,
unless the mothers were financially well-off enough
to afford their own maternity suite.
So, in this paper, the authors looked at mothers
that were considered to be high risk.
So these were very young women, low socioeconomic status,
considered to be high risk for potential abuse and neglect.
And they conducted a really simple manipulation.
Half these women were upgraded to a maternity suite
in which they could spend just a few extra hours
with their infants on the day of birth.
And then the authors followed these women for years.
And what they found is that women who would experience
this rooming in manipulation were significantly less likely
to show any signs, or show any pathology in their parenting.
On the other hand, control women that were subject
to the standard procedures of the time had substantially
more instances of child abuse and neglect.
And I thought this was really compelling evidence.
So, in my laboratory what we've been focusing
on is trying to understand the neurobiological mechanisms
that regulate caregiving behavior
and, importantly, prevent neglect.
And in thinking about this, I've turned to
what we know about the neurobiology of the onset of care.
Again, work that comes from rats.
And this work suggests that not only do
maternal neural systems need to be turned
on for motivation to occur, but also infant access
to defense, fearful circuitry needs
to be limited, needs to be turned off.
And so, there are kind of these two distinct neural systems
that need to be manipulated in order
for the appropriate response to infants to be selected.
So to get a little bit more specific about what I mean
when I refer to infant stimuli and behavioral responses
I'm talking about sensory cues from the infants:
vocalizations, odors, et cetera,
and I'm wondering how these cues lead to these
two distinct behavioral responses: neglect versus care.
We know from rat literature that there's
a defensive neural system that can be activated
before a female becomes maternal, before the onset of care.
In my work recently in mice has shown
that when females are ignoring pups on that novel maze
we see an activation of this same defense system.
On the other hand, caregiving responses are associated
with activation of reward pathways within the brain.
And the idea really is that the medial preoptic area,
which is the central site for maternal care,
it's an important region in the hypothalamus
that we know regulates caregiving behavior
in many studied species, likely plays
a role in coordinating appropriate responses
by simultaneously inhibiting the activation of
this defense system and activating the activation
of this approach system in response to infant cues.
And so the idea is that sensory cues
from infants might reach this defensive system
to induce neglect but once plasticity has occurred
in the MPOA, the MPOA inhibits that activation.
So even if sensory cues are still capable
of reaching this defense system
they don't result in any neglectful behavior.
And then, simultaneously this approach system
is activated to induce care.
So, in my laboratory, what I've been particularly focused on
over the last few years is trying
to understand how this plasticity occurs
within the medial preoptic area.
And specifically, if we think about hypothetical neurons,
which project to these two different systems
I'm interested in how pup cues alter gene expression.
So the idea is that infant cues, which are processed
by receptors at the cell surface,
can induce cascades, which function to alter
the activity of regulatory molecules
that then affect which genes are expressed,
when these genes are expressed to mediate plasticity
or change the way these neurons respond
to infant cues in the future.
And through this plasticity we've hypothesized
that there's a permanent reduction in neglect,
and a permanent up regulation in care.
So, in summary, caregiving behavior
is critically regulated by experience, we've seen that.
Understanding how experience sustains care
and prevents neglect, I think,
has really critical implications for child neglect.
Work from rodent models indicates
that infant neglect occurs when infant cues fail
to activate a neural reward system
and instead activate a neural defense system.
And, I think, the key to understanding the neural basis
of neglect is to uncover the critical events
that happen within these neurons of the medial preoptic area
which then program the appropriate neural system
and hence appropriate response to infant cues.
So I just would like to acknowledge members
of my lab who've contributed to the ideas
and work I've shown here.
And, of course, also my funding from NICHD, thank you.
(applause)
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