Wayfinding
Page 27
Indeed, Disney was already undertaking merchandising partnerships with LEGO, Subway, and other toy companies. The company released a Halloween costume for the film’s character Maui: a brown-colored shirt, pants, and wig that turned wearers into a dark-skinned, tattoo-covered Polynesian demigod with long hair. The outrage over this “Polyface” costume was so swift that Disney made a public apology and took it off the shelves, assuring the public that the company had taken great care to respect the cultures of the Pacific Islands that inspired the film. When the movie was released in 2016, it grossed over $56 million in two days. Over the next nine months it grossed $638 million. Yet the community at Korova waited years for any compensation; eventually Disney made a donation to a trust managed by a foundation for the construction of a boat. During that period Nuttall’s oldest son used a small inheritance he received after the death of his grandmother to fund the effort of building a drua.
I was curious: why had the community decided to share their knowledge with the Disney producers in the first place? Jim, Bera’s nephew, was sitting next to me and explained, “Some people want to keep it secret. We don’t love that. We believe that to live by the sea, you must not tell lies, and [in return] the ocean will protect you. It’s against what we believe. All that’s why the ocean is protecting us,” he said. “It’s the ocean that is the boss and love. The ocean is clean, powerful, friendly. The ocean can be dangerous if you go against it. That is what the elders, our father, taught us.” Knowledge itself cannot be sold. “It is free to be given,” Bera added.
The conversation turned from Disney to the Paris Climate Accords taking place in a couple of weeks. It was now night and my son was fast asleep in my lap; a few electric lightbulbs illuminated everyone’s faces as they spoke about the meeting. A delegation representing indigenous communities would be in Paris, including a representative from Korova. Nuttall pointed to a young man in the circle who was visiting Korova to learn about canoe-building. He was from Tuvalu, a small island country north of Fiji that is extremely vulnerable to sea level rise, with some predicting it will become uninhabitable in the next century. “Even if the world stopped all the emissions tomorrow, Tuvalu will still be underwater,” said Nuttall. “If he has to migrate, will he do it under his own sail? His ancestors could leave and go anywhere they wanted. But today we leave on a 747.” He paused. “How do we maintain dignity in this crisis?”
The kava drenched my synapses, and the question seemed to hang in the air, essential and daunting. Perhaps it’s hyperbolic to present navigation practices as a response to climate change; the practice itself can’t reduce CO2 emissions, and humans won’t all turn in their cars or airplane tickets for sailboats. But, I thought, what if we took a more critical view of how we move through space? Considered how technology influences our choices and impacts the global environment? What if we paid more attention to the landscape around us, became witnesses to its patterns and changes, and shared that information with others? What if we nourished our attachment and concern for the places we live and travel to? Those things seemed to matter very much.
As the night drew on and the children disappeared to sleep, we gave our thanks and goodbyes, walked back to the car in the dark, and then drove on a winding highway along the southern end of Viti Levu. I sat in the backseat and my thoughts wandered. I was shaken by the tenuous survival of cultural practice and tradition, and the urgent reminder of anthropogenic climate change, the consequences of which were impossible to ignore in Fiji. But I also felt incredibly happy, warmed to the core by the hospitality and testimony of Bera and Samiti (and no doubt the free-flowing kava), who once again shared their thoughts and experiences with strangers. They wanted to give what they knew to others, and their dignity and vulnerability felt like a corrective to all the cynicism of the world. I looked out the window and saw the stars in the sky and remembered a passage in a book I had read by the neuroscientist Oliver Sacks. In the 1990s Sacks had traveled to the Micronesian atoll of Pingelap, some two thousand miles northeast from where we were now driving. He wanted to find out why the island had a disproportionate number of people with achromatopsia, the inability to see color. One night he partook in drinking sakau, as kava is called in that part of Micronesia, an experience Sacks recounts in his book The Island of the Colorblind:
Knut, next to me, was looking upward as well, and pointed out the polestar, Vega, Arcturus, overhead. “These are the stars the Polynesians used,” said Bob, “when they sailed in their proas across the firmament of space.” A sense of their voyages, five thousand years of voyaging, rose up like a vision as he talked. I felt a sense of their history, all history, converging on us now, as we sat facing the ocean under the night sky.… Only then did I realize that we were all stoned; but sweetly, mildly, so that one felt, so to speak, more nearly oneself.
THIS IS YOUR BRAIN ON GPS
In the 1960s, the psychologist Julian Stanley became interested in understanding what makes child geniuses different from other children. What was the nature of their intelligence that made them so intellectually gifted? Stanley launched an investigation he called the “Study of Mathematically Precocious Youth,” and half a century later, it has shown that the best way to raise a smart kid may be to nourish their ability to think spatially. This could mean engaging them in exercises that require them to imagine objects from different perspectives, or mentally manipulate images, and perceive patterns between them.
Over the decades, Stanley and his colleagues tracked the achievements of five thousand children who had scored unusually high on the SAT, some in the top 0.01 percent. From the start Stanley was interested in how the ability to understand and remember spatial relationships between objects might predict achievement and intelligence better than other tests such as verbal acuity. He regularly tested the study’s participants on spatial aptitude, and, as the journal Nature reported in 2017, researchers decided to look at the scores on those tests and compare them to the number of patents and peer-reviewed journal articles the participants, many of them highly successful, had generated over the course of their careers. What they found was that the two data points were strongly correlated, so much so that David Lubinski, a director of the study, told a reporter, “I think [spatial ability] may be the largest unknown, untapped source of human potential.” Raw intelligence, it seems, is intertwined with our brain’s spatial cognition aptitude.
This insight has come at a time when young people in general are experiencing less and less demand to exercise their spatial navigation skills. As the neuroscientist Véronique Bohbot told me, she has begun to suspect that the sedentary, habitual, and technology-dependent conditions of modern living are changing how children and even adults use their brains. Bohbot, a researcher at the Douglas Mental Health University Institute and associate professor in the Department of Psychiatry at McGill University, has studied spatial cognition for two decades and believes that we are, in general, flexing our hippocampus less and less, with potentially damaging consequences. “People who have shrunk hippocampus are more at risk for PTSD, Alzheimer’s, schizophrenia, and depression,” she told me. “For a long time we thought the disease causes shrinkage in the hippocampus. But studies show that the shrunk hippocampus can be there before the disease.”
Bohbot did her doctoral research with Lynn Nadel, coauthor of The Hippocampus as a Cognitive Map. “Back then the hippocampus was a fascinating brain structure to study, and it was the only structure known to be involved in spatial memory. But it was hypothesized that there were other brain structures involved in different ways to navigate in the environment,” she said. In the mid-1990s at McGill University, where Bohbot was training rats in memory tasks, fellow researchers Norman White and Mark Packard discovered one other brain circuit was the caudate nucleus. Bohbot became fascinated by the implications of this discovery. Was it possible that people use very different brain structures for different strategies of navigation? If so, why? She began to conduct experiments in humans designed to disting
uish which strategies were dependent on the hippocampus and which involved the caudate nucleus. What she found was that not only were the circuits different, but the strategies they corresponded to were hugely different too.
“The hippocampus is involved in spatial learning, i.e., learning to navigate using the relationships between landmarks,” she explained. “Once you have learned the relationship between landmarks, you can derive a novel route to any destination from any starting position in the environment. Spatial memory is allocentric, it’s independent of your starting position. You use spatial memory when you can picture the environment in your mind’s eye. That’s when you are using your internal map to find your way.” Meanwhile, the caudate nucleus isn’t involved in creating cognitive maps, it’s a structure that builds habits. Using it, the brain can learn a series of directional cues such as “turn right at the corner with the grocery store” and “turn left at the tall white building,” creating what are called stimulus-response memories. To understand what the caudate nucleus does, she told me to imagine how to get to the local bakery. “Every day you use the same route, and at some point it becomes automatic,” Bohbot said. “You don’t think about it anymore. You don’t ask, where do I have to turn? Autopilot takes over. You see the white building, it acts as a stimulus and triggers a response to turn left to get to the bakery.”
Although this strategy might seem similar to the egocentric strategy used in route navigation, it can actually be quite different. There are three types of stimulus-response strategies, according to Bohbot, and an egocentric strategy is just one of them. “An egocentric strategy involves a series of right and left turns that begin with your starting position: when you leave your home (the stimulus), you will turn right (the response). Then there’s a beacon strategy where you could reach a target location from many different starting positions: the tall white building is your beacon (stimulus), and you head toward it, turning at every corner in its direction (response). And then there is the most common form of stimulus-response: a series of turns in response to various landmarks in the environment.” Even though the caudate nucleus uses repetition to navigate successfully, it’s actually not a spatial strategy. The key difference is that the response strategy doesn’t involve learning the relationship between landmarks, so it becomes impossible to generate a novel trajectory in the environment. All the caudate does is signal—left or right—in response to a cue without engaging your active attention.
There is a persuasive evolutionary explanation for why nature invented this other (seemingly lazier) circuit: it means you don’t have to retrieve a memory of a route or make spatial inferences every time you need to go home. It gives us the advantage of not needing to make calculations or decisions—or pay very much attention—to where we are going and how we are getting there. Autopilot is fast and efficient. “I don’t have to think, that’s great!” said Bohbot. But Bohbot also discovered a negative correlation between the two strategies: the human brain is using either the hippocampus or the caudate nucleus to get somewhere, but it never engages these two brain areas at the same time. This means that the more we use one, the less we use the other, and like a muscle that grows in strength and compensates for weaker muscles, a specific circuit can become preferred over time.
Scientists already knew that as we age, the strategies we use to move change. As children and young adults, we navigate and explore new spaces. Over time we increasingly rely on familiar routes and return to places that barely strain our cognition—we underuse our hippocampus. Each of our life histories likely traces this trajectory: we go from utilizing hippocampal spatial strategies to increased automatization. Bohbot discovered this when she undertook a study of 599 children and adults and compared the spatial strategies they preferred to solve tasks with. She and her coauthors found that children rely on hippocampal spatial strategies some 85 percent of the time, but adults over the age of sixty complete a virtual maze test using this strategy just under 40 percent of the time. The question remained, however, whether the preference for one strategy over another led to physiological differences in gray matter density and volume in the hippocampus.
In 2003 and 2007 in the Journal of Neuroscience, Bohbot and several researchers published two studies focused on measuring activity and gray matter in both the hippocampus and the caudate nucleus. They mimicked the classic spatial test for rats and applied it to humans by creating a radial maze in a virtual setting and asking participants to navigate it while they tracked their brain activity with fMRI. As expected, the individuals who used spatial memory strategies showed increased activity in the hippocampus, and those who used signal response had increased activity in the caudate nucleus. But then they went a step further and measured the morphological differences in these two brain regions for each individual. The researchers found a high probability that people who used a spatial strategy had more gray matter density in the hippocampus, and the inverse was also true: those who used a response strategy had more gray matter in the caudate nucleus. In and of themselves, these results might not be alarming. Successful navigators likely have an ability to deploy flexibility when it comes to these strategies: they can go on autopilot for speed and efficiency and engage cognitive mapping to solve new questions and challenges that they encounter. But what if we persistently prioritize the caudate nucleus over a hippocampal strategy? And what if this prioritization was not just occurring in some individuals in the population but was happening at a more endemic scale?
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Bohbot told me she thinks it’s possible that the conditions of modern life are leading us to flex the hippocampus less while spurring us to rely on the caudate nucleus. “Maybe in the past we never had to go on autopilot. Having jobs in one location and lives being more habitual is new. Industrialization learned to capitalize on the habit-memory-learning system,” she said.
Compounding these societal changes is the fact that chronic stress, untreated depression, insomnia, and alcohol abuse can all shrink hippocampal volume. Anxiety alone has been shown to impact the spatial learning and memory of rats. Stress and depression seem to affect neurogenesis in the hippocampus, whereas exercise seems to improve learning and memory and resistance to depression, spurring a proliferation of new neurons. Patients with PTSD have been shown to have lower hippocampal volume, and one of the consequences of effective treatment for the disorder, such as the use of antidepressants and changes in environment, is increased hippocampal volume.
The widespread prevalence of these conditions has led Bohbot to be concerned that by the time children enter young adulthood, they might already have relatively shrunken hippocampal volume that makes them susceptible to cognitive and emotional impairments and behavioral issues. Indeed, an overreliance on stimulus-response navigation strategies does seem connected to a host of destructive yet seemingly unrelated behaviors. Because the circuit is located in the striatum, a brain area involved in addiction, Bohbot began to wonder: Would people who rely on a response strategy to navigate show any difference in substance abuse from those who relied on spatial strategies? In 2013 she published a study of fifty-five young adults that showed those who relied on response strategies in navigating had double the amount of lifetime alcohol consumption, as well as more use of cigarettes and marijuana. In a separate study of 255 children, she found that those with ADHD symptoms primarily rely on caudate nucleus stimulus strategies. More recently, Bohbot and her colleague Greg West showed that ninety hours of in-lab action video games will shrink the hippocampus of young adults who use their caudate nucleus, providing the first clear evidence that the activities we engage in can have a negative impact on the hippocampus.
Worst of all is the relationship between Alzheimer’s and the hippocampus, which has been documented since the late 1980s. Hippocampal atrophy is associated with memory impairments in the elderly, and neuroimaging studies reveal that in patients with clinically diagnosed Alzheimer’s, the presence of atrophy is nearly universal. Moreover, shrinkage of the h
ippocampus and neighboring entorhinal cortex predicts future diagnosis of Alzheimer’s disease years later. This isn’t surprising in light of the established links between hippocampal damage in amnesiac patients and their loss of spatial memory. Individuals with Alzheimer’s undergo a painful process of losing both memory and identity. But one of the first symptoms is that they often lose their way, misplace things, and forget where they are and how they got there.
There may be genetic factors at work when it comes to the hippocampus and its relationship to Alzheimer’s. As early as 1993, researchers had documented a risk gene for Alzheimer’s called Apoipoprotein E or APOE. A year later, an allele of the gene (ApoE2) was found to be associated with reduced risk and delayed onset of Alzheimer’s, slowing hippocampal atrophy. On the other hand, a different allele of the gene (ApoE4) indicated a greater risk for the disease. Young adults with the good allele seem to have more cortical thickness in the entorhinal cortex, which delivers inputs to the hippocampus, as well as a larger hippocampus itself. In her recent research, Bohbot has studied the cognitive correlates to the presence of these genetic traits in young adults. She genotyped 124 young people and tested them on a virtual radial maze: those with the good allele were more likely to use a hippocampal spatial strategy and possess more gray matter in that part of their brains.