Researcher: Rebecca Saxe

A hunger for social contact

Anne Trafton |

Since the coronavirus pandemic began in the spring, many people have only seen their close friends and loved ones during video calls, if at all. A new study from MIT finds that the longings we feel during this kind of social isolation share a neural basis with the food cravings we feel when hungry.

The researchers found that after one day of total isolation, the sight of people having fun together activates the same brain region that lights up when someone who hasn’t eaten all day sees a picture of a plate of cheesy pasta.

“People who are forced to be isolated crave social interactions similarly to the way a hungry person craves food.”

“Our finding fits the intuitive idea that positive social interactions are a basic human need, and acute loneliness is an aversive state that motivates people to repair what is lacking, similar to hunger,” says Rebecca Saxe, the John W. Jarve Professor of Brain and Cognitive Sciences at MIT, a member of MIT’s McGovern Institute for Brain Research, and the senior author of the study.

The research team collected the data for this study in 2018 and 2019, long before the coronavirus pandemic and resulting lockdowns. Their new findings, described today in Nature Neuroscience, are part of a larger research program focusing on how social stress affects people’s behavior and motivation.

Former MIT postdoc Livia Tomova, who is now a research associate at Cambridge University, is the lead author of the paper. Other authors include Kimberly Wang, a McGovern Institute research associate; Todd Thompson, a McGovern Institute scientist; Atsushi Takahashi, assistant director of the Martinos Imaging Center; Gillian Matthews, a research scientist at the Salk Institute for Biological Studies; and Kay Tye, a professor at the Salk Institute.

Social craving

The new study was partly inspired by a recent paper from Tye, a former member of MIT’s Picower Institute for Learning and Memory. In that 2016 study, she and Matthews, then an MIT postdoc, identified a cluster of neurons in the brains of mice that represent feelings of loneliness and generate a drive for social interaction following isolation. Studies in humans have shown that being deprived of social contact can lead to emotional distress, but the neurological basis of these feelings is not well-known.

“We wanted to see if we could experimentally induce a certain kind of social stress, where we would have control over what the social stress was,” Saxe says. “It’s a stronger intervention of social isolation than anyone had tried before.”

To create that isolation environment, the researchers enlisted healthy volunteers, who were mainly college students, and confined them to a windowless room on MIT’s campus for 10 hours. They were not allowed to use their phones, but the room did have a computer that they could use to contact the researchers if necessary.

“There were a whole bunch of interventions we used to make sure that it would really feel strange and different and isolated,” Saxe says. “They had to let us know when they were going to the bathroom so we could make sure it was empty. We delivered food to the door and then texted them when it was there so they could go get it. They really were not allowed to see people.”

After the 10-hour isolation ended, each participant was scanned in an MRI machine. This posed additional challenges, as the researchers wanted to avoid any social contact during the scanning. Before the isolation period began, each subject was trained on how to get into the machine, so that they could do it by themselves, without any help from the researcher.

“Normally, getting somebody into an MRI machine is actually a really social process. We engage in all kinds of social interactions to make sure people understand what we’re asking them, that they feel safe, that they know we’re there,” Saxe says. “In this case, the subjects had to do it all by themselves, while the researcher, who was gowned and masked, just stood silently by and watched.”

Each of the 40 participants also underwent 10 hours of fasting, on a different day. After the 10-hour period of isolation or fasting, the participants were scanned while looking at images of food, images of people interacting, and neutral images such as flowers. The researchers focused on a part of the brain called the substantia nigra, a tiny structure located in the midbrain, which has previously been linked with hunger cravings and drug cravings. The substantia nigra is also believed to share evolutionary origins with a brain region in mice called the dorsal raphe nucleus, which is the area that Tye’s lab showed was active following social isolation in their 2016 study.

The researchers hypothesized that when socially isolated subjects saw photos of people enjoying social interactions, the “craving signal” in their substantia nigra would be similar to the signal produced when they saw pictures of food after fasting. This was indeed the case. Furthermore, the amount of activation in the substantia nigra was correlated with how strongly the patients rated their feelings of craving either food or social interaction.

Degrees of loneliness

The researchers also found that people’s responses to isolation varied depending on their normal levels of loneliness. People who reported feeling chronically isolated months before the study was done showed weaker cravings for social interaction after the 10-hour isolation period than people who reported a richer social life.

“For people who reported that their lives were really full of satisfying social interactions, this intervention had a bigger effect on their brains and on their self-reports,” Saxe says.

The researchers also looked at activation patterns in other parts of the brain, including the striatum and the cortex, and found that hunger and isolation each activated distinct areas of those regions. That suggests that those areas are more specialized to respond to different types of longings, while the substantia nigra produces a more general signal representing a variety of cravings.

Now that the researchers have established that they can observe the effects of social isolation on brain activity, Saxe says they can now try to answer many additional questions. Those questions include how social isolation affect people’s behavior, whether virtual social contacts such as video calls help to alleviate cravings for social interaction, and how isolation affects different age groups.

The researchers also hope to study whether the brain responses that they saw in this study could be used to predict how the same participants responded to being isolated during the lockdowns imposed during the early stages of the coronavirus pandemic.

The research was funded by a SFARI Explorer Grant from the Simons Foundation, a MINT grant from the McGovern Institute, the National Institutes of Health, including an NIH Pioneer Award, a Max Kade Foundation Fellowship, and an Erwin Schroedinger Fellowship from the Austrian Science Fund.

Saxe Lab examines social impact of COVID-19

by Julie Pryor |

After being forced to relocate from their MIT dorms during the COVID19 crisis, two members of the Saxe lab are now applying their psychology skills to study the impact of mandatory relocation and social isolation on mental health.

“When ‘social distancing’ measures hit MIT, we tried to process how the implementation of these policies would impact the landscape of our social lives,” explains graduate student Heather Kosakowski, who conceived of the study late one evening with undergraduate Michelle Hung.  This landscape is broad, examining the effects of being uprooted and physically relocated from a place, but also changes in social connections, including friendships and even dating life.

MIT undergrad Michelle Hung in the Saxe lab. Photo: Michelle Hung

“I started speculating about how my life and the lives of other MIT students would change,” says Hung. “I was overwhelmed, sad, and scared. But then we realized that we were actually equipped to find the answers to our questions by conducting a study.”

Together, Kosakowski and Hung developed a survey to measure how the social behavior of MIT students, postdocs, and staff is changing over the course of the pandemic. Survey questions were designed to measure loneliness and other aspects of mental health. The survey was sent to members of the MIT community and shared on social media in mid-March, when the pandemic hit the US, and MIT made the unprecedented decision to send students home, shift to online instruction, and dramatically ramp down operations on campus.

More than 500 people responded to the initial survey, ranging in age from 18 to 60, living in cities and countries around the world. Many but not all of those who responded were affiliated with MIT. Kosakowski and Hung are sending follow-up surveys to participants every two weeks and the team plans to collect data for the duration of the pandemic.

“Throwing myself into creating the survey was a way to cope with feeling sad about leaving a community I love,” explains Hung, who flew home to California in March and admits that she struggles with feelings of loneliness now that she’s off campus.

Although it is too soon to form any conclusions about their research, Hung predicts that feelings of loneliness may actually diminish over the course of the pandemic.

“Humans have an impressive ability to adapt to change,” she says. “And I think in this virtual world, people will find novel ways to stay connected that we couldn’t have predicted.”

Whether we find ourselves feeling more or less lonely as this COVID-19 crisis comes to an end, both Kosakowski and Hung agree that it will fundamentally change life as we know it.

The Saxe lab is looking for more survey participants. To learn more about this study or to participate in the survey, click here.

 

Learning from social isolation

by Heather Kosakowski |

“Livia Tomova, a postdoc in the Saxe Lab, recently completed a study about social isolation and its impact on the brain. Michelle Hung and I had a lot of exposure to her research in the lab. When “social distancing” measures hit MIT, we tried to process how the implementation of these policies would impact the landscape of our social lives.

We came up with some hypotheses and agreed that the coronavirus pandemic would fundamentally change life as we know it.

So we developed a survey to measure how the social behavior of MIT students, postdocs, and staff changes over the course of the pandemic. Our study is still in its very early stages, but it has been an incredibly fulfilling experience to be a part of Michelle’s development as a scientist.

Heather Kosakowski’s daughter in Woods Hole, Massachusetts. Photo: Heather Kosakowski

After the undergraduates left, graduate students were also strongly urged to leave graduate student housing. My daughter (age 11) and I live in a 28th-floor apartment and her school was canceled. One of my advisors, Nancy Kanwisher, had a vacant apartment in Woods Hole that she offered to let lab members stay in. As more and more resources for children were being closed or shut down, I decided to take her up on the offer. Wood’s Hole is my daughter’s absolute favorite place and I feel extremely lucky to have such a generous option. My daughter has been coping really well with all of these changes.

While my research is at an exciting stage, I miss being on campus with the students from my cohort and my lab mates and my weekly in-person meetings with my advisors. One way I’ve been coping with this reality is by listening to stories of other people’s experiences. We are all human and we are all in the midst of a pandemic but, we are all experiencing the pandemic in different ways. I find the diversity of our experience intriguing. I have been fortunate to have friends write stories about their experiences, so that I can post them on my blog. I only have a handful of stories right now but, it has been really fun for me to listen, and humbling for me to share each individual’s unique experience.”

Heather Kosakowski is a graduate student in the labs of Rebecca Saxe and Nancy Kanwisher where she studies the infant brain and the developmental origins of object recognition, language, and music. Heather is also a Marine Corps veteran and single mom who manages a blog that “ties together different aspects of my experience, past and present, with the hopes that it might make someone else out there feel less alone.”

#WeAreMcGovern

Three from MIT awarded 2020 Guggenheim Fellowships

by Julie Pryor |

MIT faculty members Sabine Iatridou, Jonathan Gruber, and Rebecca Saxe are among 175 scientists, artists, and scholars awarded 2020 fellowships from the John Simon Guggenheim Foundation. Appointed on the basis of prior achievement and exceptional promise, the 2020 Guggenheim Fellows were selected from almost 3,000 applicants.

“It’s exceptionally encouraging to be able to share such positive news at this terribly challenging time” says Edward Hirsch, president of the foundation. “A Guggenheim Fellowship has always offered practical assistance, helping fellows do their work, but for many of the new fellows, it may be a lifeline at a time of hardship, a survival tool as well as a creative one.”

Since 1925, the foundation has granted more the $375 million in fellowships to over 18,000 individuals, including Nobel laureates, Fields medalists, poets laureate, and winners of the Pulitzer Prize, among other internationally recognized honors. This year’s MIT recipients include a linguist, an economist, and a cognitive neuroscientist.

Rebecca Saxe is an associate investigator of the McGovern Institute and the John W. Jarve (1978) Professor in Brain and Cognitive Sciences. She studies human social cognition, using a combination of behavioral testing and brain imaging technologies. She is best known for her work on brain regions specialized for abstract concepts such as “theory of mind” tasks that involve understanding the mental states of other people. She also studies the development of the human brain during early infancy. She obtained her PhD from MIT and was a Harvard University junior fellow before joining the MIT faculty in 2006. Saxe was chosen in 2012 as a Young Global Leader by the World Economic Forum, and she received the 2014 Troland Award from the National Academy of Sciences. Her TED Talk, “How we read each other’s minds” has been viewed over 3 million times.

Jonathan Gruber is the Ford Professor of Economics at MIT, the director of the Health Care Program at the National Bureau of Economic Research, and the former president of the American Society of Health Economists. He has published more than 175 research articles, has edited six research volumes, and is the author of “Public Finance and Public Policy,” a leading undergraduate text; “Health Care Reform,” a graphic novel; and “Jump-Starting America: How Breakthrough Science Can Revive Economic Growth and the American Dream.” In 2006 he received the American Society of Health Economists Inaugural Medal for the best health economist in the nation aged 40 and under. He served as deputy sssistant secretary for economic policy at the U.S. Department of the Treasury. He was a key architect of Massachusetts’ ambitious health reform effort, and became an inaugural member of the Health Connector Board, the main implementing body for that effort. He served as a technical consultant to the Obama administration and worked with both the administration and Congress to help craft the Affordable Care Act. In 2011, he was named “One of the Top 25 Most Innovative and Practical Thinkers of Our Time” by Slate magazine.

Sabine Iatridou is professor of linguistics in MIT’s Department of Linguistics and Philosophy. Her work focuses on syntax and the syntax-semantics interface, as well as comparative linguistics. She is the author and coauthor of a series of innovative papers about tense and modality that opened up whole new domains of research for the field. Since those publications, she has made foundational contributions to many branches of linguistics that connect form with meaning. She is the recipient of the National Young Investigator Award (USA), of an honorary doctorate from the University of Crete in Greece, and of an award from the Royal Dutch Academy of Sciences. She was elected fellow of the Linguistic Society of America. She is co-founder and co-director of the CreteLing Summer School of Linguistics.

“As we grapple with the difficulties of the moment, it is also important to look to the future,” says Hirsch. “The artists, writers, scholars, and scientific researchers supported by the fellowship will help us understand and learn from what we are enduring individually and collectively, and it is an honor for the foundation to help them do their essential work.”

Can I rewire my brain?

by Halie Olson |

As part of our Ask the Brain series, Halie Olson, a graduate student in the labs of John Gabrieli and Rebecca Saxe, pens her answer to the question,”Can I rewire my brain?”

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Yes, kind of, sometimes – it all depends on what you mean by “rewiring” the brain.

Halie Olson, a graduate student in the Gabrieli and Saxe labs.

If you’re asking whether you can remove all memories of your ex from your head, then no. (That’s probably for the best – just watch Eternal Sunshine of the Spotless Mind.) However, if you’re asking whether you can teach a dog new tricks – that have a physical implementation in the brain – then yes.

To embrace the analogy that “rewiring” alludes to, let’s imagine you live in an old house with outlets in less-than-optimal locations. You really want your brand-new TV to be plugged in on the far side of the living room, but there is no outlet to be found. So you call up your electrician, she pops over, and moves some wires around in the living room wall to give you a new outlet. No sweat!

Local changes in neural connectivity happen throughout the lifespan. With over 100 billion neurons and 100 trillion connections – or synapses – between these neurons in the adult human brain, it is unsurprising that some pathways end up being more important than others. When we learn something new, the connections between relevant neurons communicating with each other are strengthened. To paraphrase Donald Hebb, one of the most influential psychologists of the twentieth century, “neurons that fire together, wire together” – by forming new synapses or more efficiently connecting the ones that are already there. This ability to rewire neural connections at a local level is a key feature of the brain, enabling us to tailor our neural infrastructure to our needs.

Plasticity in our brain allows us to learn, adjust, and thrive in our environments.

We can also see this plasticity in the brain at a larger scale. My favorite example of “rewiring” in the brain is when children learn to read. Our brains did not evolve to enable us to read – there is no built-in “reading region” that magically comes online when a child enters school. However, if you stick a proficient reader in an MRI scanner, you will see a region in the left lateral occipitotemporal sulcus (that is, the back bottom left of your cortex) that is particularly active when you read written text. Before children learn to read, this region – known as the visual word form area – is not exceptionally interested in words, but as children get acquainted with written language and start connecting letters with sounds, it becomes selective for familiar written language – no matter the font, CaPItaLIZation, or size.

Now, let’s say that you wake up in the middle of the night with a desire to move your oven and stovetop from the kitchen into your swanky new living room with the TV. You call up your electrician – she tells you this is impossible, and to stop calling her in the middle of the night.

Similarly, your brain comes with a particular infrastructure – a floorplan, let’s call it – that cannot be easily adjusted when you are an adult. Large lesions tend to have large consequences. For instance, an adult who suffers a serious stroke in their left hemisphere will likely struggle with language, a condition called aphasia. Young children’s brains, on the other hand, can sometimes rewire in profound ways. An entire half of the brain can be damaged early on with minimal functional consequences. So if you’re going for a remodel? Better do it really early.

Plasticity in our brain allows us to learn, adjust, and thrive in our environments. It also gives neuroscientists like me something to study – since clearly I would fail as an electrician.

Halie Olson earned her bachelor’s degree in neurobiology from Harvard College in 2017. She is currently a graduate student in MIT’s Department of Brain and Cognitive Sciences working with John Gabrieli and Rebecca Saxe. She studies how early life experiences and environments impact brain development, particularly in the context of reading and language, and what this means for children’s educational outcomes.

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Do you have a question for The Brain? Ask it here.

How our gray matter tackles gray areas

by Gina Vitale | MIT News correspondent |

When Katie O’Nell’s high school biology teacher showed a NOVA video on epigenetics after the AP exam, he was mostly trying to fill time. But for O’Nell, the video sparked a whole new area of curiosity.

She was fascinated by the idea that certain genes could be turned on and off, controlling what traits or processes were expressed without actually editing the genetic code itself. She was further excited about what this process could mean for the human mind.

But upon starting at MIT, she realized that she was less interested in the cellular level of neuroscience and more fascinated by bigger questions, such as, what makes certain people generous toward certain others? What’s the neuroscience behind morality?

“College is a time you can learn about anything you want, and what I want to know is why humans are really, really wacky,” she says. “We’re dumb, we make super irrational decisions, it makes no sense. Sometimes it’s beautiful, sometimes it’s awful.”

O’Nell, a senior majoring in brain and cognitive sciences, is one of five MIT students to have received a Marshall Scholarship this year. Her quest to understand the intricacies of the wacky human brain will not be limited to any one continent. She will be using the funding to earn her master’s in experimental psychology at Oxford University.

Chocolate milk and the mouse brain

O’Nell’s first neuroscience-related research experience at MIT took place during her sophomore and junior year, in the lab of Institute Professor Ann Graybiel at the McGovern Institute.

The research studied the neurological components of risk-vs-reward decision making, using a key ingredient: chocolate milk. In the experiments, mice were given two options — they could go toward the richer, sweeter chocolate milk, but they would also have to endure a brighter light. Or, they could go toward a more watered-down chocolate milk, with the benefit of a softer light. All the while, a fluorescence microscope tracked when certain cell types were being activated.

“I think that’s probably the closest thing I’ve ever had to a spiritual experience … watching this mouse in this maze deciding what to do, and watching the cells light up on the screen. You can see single-cell evidence of cognition going on. That’s just the coolest thing.”

In her junior spring, O’Nell delved even deeper into questions of morality in the lab of Professor Rebecca Saxe. Her research there centers on how the human brain parses people’s identities and emotional states from their faces alone, and how those computations are related to each other. Part of what interests O’Nell is the fact that we are constantly making decisions, about ourselves and others, with limited information.

“We’re always solving under uncertainty,” she says. “And our brain does it so well, in so many ways.”

International intrigue

Outside of class, O’Nell has no shortage of things to do. For starters, she has been serving as an associate advisor for a first-year seminar since the fall of her sophomore year.

“Basically it’s my job to sit in on a seminar and bully them into not taking seven classes at a time, and reminding them that yes, your first 8.01 exam is tomorrow,” she says with a laugh.

She has also continued an activity she was passionate about in high school — Model United Nations. One of the most fun parts for her is serving on the Historical Crisis Committee, in which delegates must try to figure out a way to solve a real historical problem, like the Cuban Missile Crisis or the French and Indian War.

“This year they failed and the world was a nuclear wasteland,” she says. “Last year, I don’t entirely know how this happened, but France decided that they wanted to abandon the North American theater entirely and just took over all of Britain’s holdings in India.”

She’s also part of an MIT program called the Addir Interfaith Fellowship, in which a small group of people meet each week and discuss a topic related to religion and spirituality. Before joining, she didn’t think it was something she’d be interested in — but after being placed in a first-year class about science and spirituality, she has found discussing religion to be really stimulating. She’s been a part of the group ever since.

O’Nell has also been heavily involved in writing and producing a Mystery Dinner Theater for Campus Preview Weekend, on behalf of her living group J Entry, in MacGregor House. The plot, generally, is MIT-themed — a physics professor might get killed by a swarm of CRISPR nanobots, for instance. When she’s not cooking up murder mysteries, she might be running SAT classes for high school students, playing piano, reading, or spending time with friends. Or, when she needs to go grocery shopping, she’ll be stopping by the Trader Joe’s on Boylston Avenue, as an excuse to visit the Boston Public Library across the street.

Quite excited for the future

O’Nell is excited that the Marshall Scholarship will enable her to live in the country that produced so many of the books she cherished as a kid, like “The Hobbit.” She’s also thrilled to further her research there. However, she jokes that she still needs to get some of the lingo down.

“I need to learn how to use the word ‘quite’ correctly. Because I overuse it in the American way,” she says.

Her master’s research will largely expand on the principles she’s been examining in the Saxe lab. Questions of morality, processing, and social interaction are where she aims to focus her attention.

“My master’s project is going to be basically taking a look at whether how difficult it is for you to determine someone else’s facial expression changes how generous you are with people,” she explains.

After that, she hopes to follow the standard research track of earning a PhD, doing postdoctoral research, and then entering academia as a professor and researcher. Teaching and researching, she says, are two of her favorite things — she’s excited to have the chance to do both at the same time. But that’s a few years ahead. Right now, she hopes to use her time in England to learn all she can about the deeper functions of the brain, with or without chocolate milk.

How motion conveys emotion in the face

by Sabbi Lall |

While a static emoji can stand in for emotion, in real life we are constantly reading into the feelings of others through subtle facial movements. The lift of an eyebrow, the flicker around the lips as a smile emerges, a subtle change around the eyes (or the sudden rolling of the eyes), are all changes that feed into our ability to understand the emotional state, and the attitude, of others towards us. Ben Deen and Rebecca Saxe have now monitored changes in brain activity as subjects followed face movements in movies of avatars. Their findings argue that we can generalize across individual face part movements in other people, but that a particular cortical region, the face-responsive superior temporal sulcus (fSTS), is also responding to isolated movements of individual face parts. Indeed, the fSTS seems to be tied to kinematics, individual face part movement, more than the implied emotional cause of that movement.

We know that the brain responds to dynamic changes in facial expression, and that these are associated with activity in the fSTS, but how do calculations of these movements play out in the brain?

Do we understand emotional changes by adding up individual features (lifting of eyebrows + rounding of mouth= surprise), or are we assessing the entire face in a more holistic way that results in more generalized representations? McGovern Investigator Rebecca Saxe and her graduate student Ben Deen set out to answer this question using behavioral analysis and brain imaging, specifically fMRI.

“We had a good sense of what stimuli the fSTS responds strongly to,” explains Ben Deen, “but didn’t really have any sense of how those inputs are processed in the region – what sorts of features are represented, whether the representation is more abstract or more tied to visual features, etc. The hope was to use multivoxel pattern analysis, which has proven to be a remarkably useful method for characterizing representational content, to address these questions and get a better sense of what the region is actually doing.”

Facial movements were conveyed to subjects using animated “avatars.” By presenting avatars that made isolated eye and eyebrow movements (brow raise, eye closing, eye roll, scowl) or mouth movements (smile, frown, mouth opening, snarl), as well as composites of these movements, the researchers were able to assess whether our interpretation of the latter is distinct from the sum of its parts. To do this, Deen and Saxe first took a behavioral approach where people reported on what combinations of eye and mouth movements in a whole avatar face, or one where the top and bottom parts of the face were misaligned. What they found was that movement in the mouth region can influence perception of movement in the eye region, arguably due to some level of holistic processing. The authors then asked whether there were cortical differences upon viewing isolated vs. combined face part movements. They found that changes in fSTS, but not other brain regions, had patterns of activity that seemed to discriminate between different facial movements. Indeed, they could decode which part of the avatar’s face is being perceived as moving from fSTS activity. The researchers could even model the fSTS response to combined features linearly based on the response to individual face parts. In short, though the behavorial data indicate that there is holistic processing of complex facial movement, it is also clear that isolated parts-based representations are also present, a sort of intermediate state.

As part of this work, Deen and Saxe took the important step of pre-registering their experimental parameters, before collecting any data, at the Open Science Framework. This step allows others to more easily reproduce the analysis they conducted, since all parameters (the task that subjects are carrying out, the number of subjects needed, the rationale for this number, and the scripts used to analyze data) are openly available.

“Preregistration had a big impact on our workflow for the study,” explained Deen. “More of the work was done up front, in coming up with all of the analysis details and agonizing over whether we were choosing the right strategy, before seeing any of the data. When you tie your hands by making these decisions up front, you start thinking much more carefully about them.”

Pre-registration does remove post-hoc researcher subjectivity from the analysis. As an example, because Deen and Saxe predicted that the people would be accurately able to discriminate between faces per se, they decided ahead of the experiment to focus on analyzing reaction time, rather than looking at the collected data and deciding to focus on this number after the fact. This adds to the overall objectivity of the experiment and is increasingly seen as a robust way to conduct such experiments.

Rebecca Saxe

Mind Reading

Rebecca Saxe studies human social cognition, using a combination of behavioral testing and brain imaging technologies. She is best known for her work on brain regions specialized for abstract concepts such as “theory of mind” tasks that involve understanding the mental states of other people. While it was previously known that humans and animals have brain regions that are specialized for basic functions such as visual recognition and motor control, this was the first example of a brain region specialized for constructing abstract thoughts. Saxe continues to study this region and has found that it is involved when we make moral judgements about other people. She is also exploring its possible role in autism, where the ability to understand other people’s beliefs and motivations is often impaired. A major area of her work involves looking at how and when these specialized brain regions form in children.

Virtual Tour of Saxe Lab

A social side to face recognition by infants

Anne Trafton |

When interacting with an infant you have likely noticed that the human face holds a special draw from a very young age. But how does this relate to face recognition by adults, which is known to map to specific cortical regions? Rebecca Saxe, Associate Investigator at MIT’s McGovern Institute and John W. Jarve (1978) Professor in Brain and Cognitive Sciences, and her team have now considered two emerging theories regarding early face recognition, and come up with a third proposition, arguing that when a baby looks at a face, the response is also social, and that the resulting contingent interactions are key to subsequent development of organized face recognition areas in the brain.

By a certain age you are highly skilled at recognizing and responding to faces, and this correlates with activation of a number of face-selective regions of the cortex. This is incredibly important to reading the identities and intentions of other people, and selective categorical representation of faces in cortical areas is a feature shared by our primate cousins. While brain imaging tells us where face-responsive regions are in the adult cortex, how and when they emerge remains unclear.

In 2017, functional magnetic resonance imaging (fMRI) studies of human and macaque infants provided the first glimpse of how the youngest brains respond to faces. The scans showed that in 4-6 month human infants and equivalently aged macaques, regions known to be face-responsive in the adult brain are activated when shown movies of faces, but not in a selective fashion. Essentially fMRI argues that these specific, cortical regions are activated by faces, but a chair will do just as well. Upon further experience of faces over time, the specific cortical regions in macaques became face-selective, no longer responding to other objects.

There are two prevailing ideas in the field of how face preference, and eventually selectivity, arise through experience. These ideas are now considered in turn by Saxe and her team in an opinion piece in the September issue of Trends in Cognitive Sciences, and then a third, new theory proposed. The first idea centers on the way we dote over babies, centering our own faces right in their field of vision. The idea is that such frequent exposures to low level face features (curvilinear shape etc.) will eventually lead to co-activation of neurons that are responsive to all of the different aspects of facial features. If these neurons stimulated by different features are co-activated, and there’s a brain region where these neurons are also found together, this area with be stimulated eventually reinforcing emergence of a face category-specific area.

A second idea is that babies already have an innate “face template,” just as a duckling or chick already knows to follow its mother after hatching. So far there is little evidence for the second proposition, and the first fails to explain why babies seek out a face, rather than passively look upon and eventually “learn” the overlapping features that represent “face.”

Saxe, along with postdoc Lindsey Powell and graduate student Heather Kosakowski, instead now argue that the role a face plays in positive social interactions comes to drive organization of face-selective cortical regions. Taking the next step, the researchers propose that a prime suspect for linking social interactions to the development of face-selective areas is the medial prefrontal cortex (mPFC), a region linked to social cognition and behavior.

“I was asked to give a talk at a conference, and I wanted to talk about both the development of cortical face areas and the social role of the medial prefrontal cortex in young infants,” says Saxe. “I was puzzling over whether these two ideas were related, when I suddenly saw that they could be very fundamentally related.”

The authors argue that this relationship is supported by existing data that has shown that babies prefer dynamic faces and are more interested in faces that engage in a back and forth interaction. Regions of the mPFC are also known to activated during social interactions and known to be activated during exposure to dynamic faces in infants.

Powell is now using functional near infrared spectroscopy (fNIRS), a brain imaging technique that measures changes in blood flow to the brain, to test this hypothesis in infants. “This will allow us to see whether mPFC responses to social cues are linked to the development of face-responsive areas.”

In Daniel Deronda, the novel by George Eliot, the protagonist says “I think my life began with waking up and loving my mother’s face: it was so near to me, and her arms were round me, and she sang to me.” Perhaps this type of positively valenced social interaction, reinforced by the mPFC, is exactly what leads to the particular importance of faces and their selective categorical representation in the human brain. Further testing of the hypothesis proposed by Powell, Kosakowski, and Saxe will tell.

Study finds early signatures of the social brain

Anne Trafton |

Humans use an ability known as theory of mind every time they make inferences about someone else’s mental state — what the other person believes, what they want, or why they are feeling happy, angry, or scared.

Behavioral studies have suggested that children begin succeeding at a key measure of this ability, known as the false-belief task, around age 4. However, a new study from MIT has found that the brain network that controls theory of mind has already formed in children as young as 3.

The MIT study is the first to use functional magnetic resonance imaging (fMRI) to scan the brains of children as young as age 3 as they perform a task requiring theory of mind — in this case, watching a short animated movie involving social interactions between two characters.

“The brain regions involved in theory-of-mind reasoning are behaving like a cohesive network, with similar responses to the movie, by age 3, which is before kids tend to pass explicit false-belief tasks,” says Hilary Richardson, an MIT graduate student and the lead author of the study.

Rebecca Saxe, an MIT professor of brain and cognitive sciences and an associate member of MIT’s McGovern Institute for Brain Research, is the senior author of the paper, which appears in the March 12 issue of Nature Communications. Other authors are Indiana University graduate student Grace Lisandrelli and Wellesley College undergraduate Alexa Riobueno-Naylor.

Thinking about others

In 2003, Saxe first showed that theory of mind is seated in a brain region known as the right temporo-parietal junction (TPJ). The TPJ coordinates with other regions, including several parts of the prefrontal cortex, to form a network that is active when people think about the mental states of others.

The most commonly used test of theory of mind is the false-belief test, which probes whether the subject understands that other people may have beliefs that are not true. A classic example is the Sally-Anne test, in which a child is asked where Sally will look for a marble that she believes is in her own basket, but that Anne has moved to a different spot while Sally wasn’t looking. To pass, the subject must reply that Sally will look where she thinks the marble is (in her basket), not where it actually is.

Until now, neuroscientists had assumed that theory-of-mind studies involving fMRI brain scans could only be done with children at least 5 years of age, because the children need to be able to lie still in a scanner for about 20 minutes, listen to a series of stories, and answer questions about them.

Richardson wanted to study children younger than that, so that she could delve into what happens in the brain’s theory-of-mind network before the age of 5. To do that, she and Saxe came up with a new experimental protocol, which calls for scanning children while they watch a short movie that includes simple social interactions between two characters.

The animated movie they chose, called “Partly Cloudy,” has a plot that lends itself well to the experiment. It features Gus, a cloud who produces baby animals, and Peck, a stork whose job is to deliver the babies. Gus and Peck have some tense moments in their friendship because Gus produces baby alligators and porcupines, which are difficult to deliver, while other clouds create kittens and puppies. Peck is attacked by some of the fierce baby animals, and he isn’t sure if he wants to keep working for Gus.

“It has events that make you think about the characters’ mental states and events that make you think about their bodily states,” Richardson says.

The researchers spent about four years gathering data from 122 children ranging in age from 3 to 12 years. They scanned the entire brain, focusing on two distinct networks that have been well-characterized in adults: the theory-of-mind network and another network known as the pain matrix, which is active when thinking about another person’s physical state.

They also scanned 33 adults as they watched the movie so that they could identify scenes that provoke responses in either of those two networks. These scenes were dubbed theory-of-mind events and pain events. Scans of children revealed that even in 3-year-olds, the theory-of-mind and pain networks responded preferentially to the same events that the adult brains did.

“We see early signatures of this theory-of-mind network being wired up, so the theory-of-mind brain regions which we studied in adults are already really highly correlated with one another in 3-year-olds,” Richardson says.

The researchers also found that the responses in 3-year-olds were not as strong as in adults but gradually became stronger in the older children they scanned.

Patterns of development

The findings offer support for an existing hypothesis that says children develop theory of mind even before they can pass explicit false-belief tests, and that it continues to develop as they get older. Theory of mind encompasses many abilities, including more difficult skills such as understanding irony and assigning blame, which tend to develop later.

Another hypothesis is that children undergo a fairly sudden development of theory of mind around the age of 4 or 5, reflected by their success in the false-belief test. The MIT data, which do not show any dramatic changes in brain activity when children begin to succeed at the false-belief test, do not support that theory.

“Scientists have focused really intensely on the changes in children’s theory of mind that happen around age 4, when children get a better understanding of how people can have wrong or biased or misinformed beliefs,” Saxe says. “But really important changes in how we think about other minds happen long before, and long after, this famous landmark. Even 2-year-olds try to figure out why different people like different things — this might be why they get so interested in talking about everybody’s favorite colors. And even 9-year-olds are still learning about irony and negligence. Theory of mind seems to undergo a very long continuous developmental process, both in kids’ behaviors and in their brains.”

Now that the researchers have data on the typical trajectory of theory of mind development, they hope to scan the brains of autistic children to see whether there are any differences in how their theory-of-mind networks develop. Saxe’s lab is also studying children whose first exposure to language was delayed, to test the effects of early language on the development of theory of mind.

The research was funded by the National Science Foundation, the National Institutes of Health, and the David and Lucile Packard Foundation.