Smells connect to memories more than other senses
"The smell of fresh chopped parsley may evoke a grandmother's cooking, or a whiff of a cigar may evoke a grandfather's presence," says author.
12 March, 2021
Credit: myboys.me / Adobe Stock
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<p>It's called the <a href="https://journals.sagepub.com/doi/pdf/10.1068/p4312rvw" target="_blank" rel="noopener noreferrer">Proust effect</a> after a story in the author's "Remembrance of Things Past: Swann's Way." When a character dipped a madeleine, a sweet, buttery French cake, into some lime-blossom tea, the scent suddenly transported him back in time to the moment his aunt had served him that same combination:</p><p style="margin-left: 20px;"><em>"Immediately the old grey house upon the street, where her room was, rose up like the scenery of a theatre to attach itself to the little pavilion, opening on to the garden, which had been built out behind it for my parents… and with the house the town, from morning to night and in all weathers, the Square where I was sent before luncheon, the streets along which I used to run errands, the country roads we took when it was fine."</em></p><p>Nothing conjures up a memory so viscerally as the scent with which you associate it. While it's been understood for some time that our olfactory system has a unique ability to vividly summon memories, the mechanism behind the phenomenon has net been well-understood. Now a study by researchers from Northwestern University's Feinberg School of Medicine may have solved the puzzle. The olfactory system has an unusually direct connection to the brain's <a href="https://en.wikipedia.org/wiki/Hippocampus" target="_blank">hippocampus</a>, believed to play an important role in memory.</p><p>The study's published in the journal <a href="https://www.sciencedirect.com/science/article/pii/S0301008221000411" target="_blank">Progress in Neurobiology</a>.</p>
A lasting connection
<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTgxOTUyNi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDM4MjgyMn0.Mj4AjOLAgz5CnCwNejmtWlDpoQTcVggpqu8W6c7aLU4/img.jpg?width=980" id="79e03" width="1440" height="926" data-rm-shortcode-id="ec3296400089e111af312d17ec346b68" data-rm-shortcode-name="rebelmouse-image" />Credit: schankz/Adobe Stock
<p>Previous neuroimaging and intracranial electrophysiology investigations have revealed that our senses are functionally connected to the hippocampus, if not directly. However, the new research, for which the principle investigator is <a href="https://www.feinberg.northwestern.edu/faculty-profiles/az/profile.html?xid=32110" target="_blank">Christina Zelano</a>, is the first rigorous comparison of the strength of those connections.</p><p>It turns out that our primary olfactory cortex is a sense that's still directly connected to the hippocampus.</p><p>"This has been an enduring mystery of human experience," Zelano tells <a href="https://medicalxpress.com/news/2021-03-odors-trigger-powerful-memories.html?fbclid=IwAR2HPSJ3dfzmuNU0KGRJZNMVmodnWxvTcJ0Au-Ty0NlY-lqberm6fMF9YkM" target="_blank">Medical Xpress</a>. "Nearly everyone has been transported by a whiff of an odor to another time and place, an experience that sights or sounds rarely evoke. Yet, we haven't known why. The study found the olfactory parts of the brain connect more strongly to the memory parts than other senses. This is a major piece of the puzzle, a striking finding in humans. We believe our results will help future research solve this mystery."</p><p>It's believed that during evolution, the hippocampus' role shifted away from its original strong relationship to the sensory cortexes and toward connections with higher association cortexes. (In rodents, for example, the hippocampus maintains a powerful connection to all sensory cortexes.) It now appears that as this occurred, the olfactory cortex alone continued to be directly wired to the hippocampus.</p><p>"Humans experienced a profound expansion of the neocortex that re-organized access to memory networks," explains Zelano. "Vision, hearing and touch all re-routed in the brain as the neocortex expanded, connecting with the hippocampus through an intermediary-association cortex-rather than directly. Our data suggests olfaction did not undergo this re-routing, and instead retained direct access to the hippocampus."</p>The importance of smell
<p>It's known that people who experience a loss of smell, or "anosmia," often develop depression. "Loss of the sense of smell is underestimated in its impact," says Zelano. "It has profound negative effects of quality of life, and many people underestimate that until they experience it. Smell loss is highly correlated with depression and poor quality of life."</p><p>Anosmia is also associated with COVID-19. "The COVID-19 epidemic," says Zelano, "has brought a renewed focus and urgency to olfactory research." Lead author <a href="https://scholar.google.com/citations?user=Kf-ramYAAAAJ&hl=en" target="_blank">Guangyu Zhou</a> agrees: "There is an urgent need to better understand the olfactory system in order to better understand the reason for COVID-related smell loss, diagnose the severity of the loss and to develop treatments."</p><p>"Most people who lose their smell to COVID regain it," notes Zelano, "but the time frame varies widely, and some have had what appears to be permanent loss. Understanding smell loss, in turn, requires research into the basic neural operations of this under-studied sensory system."</p><p>She notes that, "While our study doesn't address COVID smell loss directly, it does speak to an important aspect of why olfaction is important to our lives: Smells are a profound part of memory, and odors connect us to especially important memories in our lives, often connected to loved ones."</p>
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What can Avicenna teach us about the mind-body problem?
The Persian polymath and philosopher of the Islamic Golden Age teaches us about self-awareness.
15 January, 2021
Photo by Andrew Spencer on Unsplash
Philosophers of the Islamic world enjoyed thought experiments.
<p>If the heavens vanished, they wondered, would time continue to pass? If existence were distinct from essence, would that mean that existence itself must exist? Can God turn your household servant into a horse, so that you come back home to find it has urinated all over your books?</p><p>But the most famous is the so-called 'flying man' thought experiment, devised by the most influential philosopher of the Islamic world, Avicenna (in Arabic, <em>Ibn Sīnā</em>, who lived from 980 to 1037 CE). Imagine, he says, that a person is created by God in mid-air, in good condition but with his sight veiled and his limbs outstretched so that he is touching nothing, not even his own body. This person has no memories, having only just been created. Will his mind be a blank, devoid as it is of past or present sensory experience? No, says Avicenna. He will be aware of his own existence.</p><p>Three questions immediately arise. First, when Douglas Adams, the author of <em>The Hitchhiker's Guide to the Galaxy</em> (1978), imagined a whale popping into existence in mid-air above an alien planet, had he been reading Avicenna? I have no idea, but I like to think so.</p><p>Second, is Avicenna right that the 'flying man' would be self-aware? Well, it's important to realise that Avicenna does not attempt to <em>argue</em> that the flying man would know that he exists. Rather, he takes it as obvious. In one version, he even tells readers that we should imagine ourselves being so created. If we put ourselves in the flying man's dangling shoes, we should just see that we would be self-aware. Indeed, this turns out to be a fundamental idea in Avicenna's philosophy. He thinks that we are all always self-aware, even when we're asleep or focusing hard on something other than ourselves. Paradoxically, we're often not <em>aware</em> of being self-aware: it is the non-interruptive background music of human psychology, something we notice only when our attention is called to it, a pre-reflective awareness of self. The flying man thought experiment is itself one way to call attention to this self-awareness: Avicenna calls it a <em>tanbīh</em>, meaning a 'pointer' to something.</p>
<p>Our self-awareness is a foundation for our first-person perspective on things. It's a sign of this that when I see, imagine or think something, I can immediately apprehend that I am seeing, imagining or thinking about that thing. Any other form of cognition – any awareness of other things – presupposes awareness of oneself.</p><p>Incidentally, you might object that the flying man would have certain forms of bodily awareness despite his lack of vision, hearing and so on. Wouldn't he at least sense the location of his limbs by another form of sensation, namely proprioception? Imagine you are in total darkness and your arm is not resting on anything: proprioception is the sense that tells you where it is. This is indeed a problem for the thought experiment as Avicenna sets it up, but it isn't really philosophically decisive. One can just modify the scenario by adding that God blocks the man's ability to use proprioception, or that the flying man's proprioceptive faculty happens to be defective. Avicenna's claim will then be that, even under these circumstances, the flying man would be aware of himself.</p><p>Now for the third, and hardest, question: what does the flying man thought experiment prove? Avicenna draws a surprising conclusion: it shows that we are not identical with our bodies. Just consider. The flying man is aware of himself; he knows that he exists. But he is not aware of his body; he doesn't know that his body exists, nor indeed that any body exists. And if I am aware of one thing but not another, how can those two things be identical?</p>
<p>This sounds pretty persuasive, until you reflect that one can be conscious of a thing without being conscious of everything about it. You, for example, have been aware of reading this article for the past few minutes, but you haven't been aware of reading something written while Dixieland jazz was playing. It would be a mistake to conclude from this that the article is not something written with Dixieland jazz playing. In fact, that is exactly what it is. To put it another way, the flying man could be aware of his self without realising that his self is a body. Contemporary philosophers would say that Avicenna is mistakenly moving from a 'transparent' to an 'opaque' context, which is basically a fancy way of saying what I just said.</p><p><a href="http://philpapers.org/rec/MARAFM" target="_blank">Efforts</a> have been made to spare Avicenna from this mistake. One possible way to rescue the argument would go like this. Avicenna is trying to criticise another way of thinking about the soul, one that goes back to Aristotle. According to the theory he rejects, the soul is so closely associated with the body that it can only be understood as an aspect or organising principle of the body, which Aristotle called the body's 'form'. The thought experiment is designed to show that this is wrong. It does so by calling to our attention that we have a means of access to our souls apart from bodily sensation, namely self-awareness.</p><p>How would this refute Aristotle? Well, consider again just why it is that the flying man is not aware of his body. It is because he is not currently using his senses and has never done so (he only just started existing, remember), and sense perception is, Avicenna assumes, the <em>only</em> way to become aware of any body. If this is right, then anything that the flying man grasps without using sense perception is not a body, not material. Since he does grasp his soul without using sense perception, his soul is therefore not a body.</p><p>On this reading, Avicenna would be helping himself to a pretty big assumption, which is that bodies can be discovered only by the senses. You can see, hear, touch, taste or smell them, but otherwise you can never so much as know that they exist. Since for Aristotle the soul was a form of the body, if you couldn't experience the body, you would not, on his account, have access to the soul; and yet, Avicenna claims, the falling man <em>would</em> have access to his soul.</p><p>I suspect this is (at least in part) what he had in mind in creating this thought experiment. But that's not to say that I'm convinced. All Avicenna has really done is to throw down a challenge to his materialist opponents: show me how a body could be aware of itself without using sensation to do so.</p><p><a href="https://global.oup.com/academic/product/philosophy-in-the-islamic-world-9780199577491?cc=au&lang=en&" rel="noopener noreferrer" target="_blank"><em>Philosophy in the Islamic World</em></a><em> by Peter Adamson is out now through Oxford University Press.</em><img src="https://metrics.aeon.co/count/99e82cab-61e0-4404-a510-3e190ab2802e.gif" alt="Aeon counter – do not remove"></p><p>Peter Adamson</p><p>This article was originally published at <a href="https://aeon.co/?utm_campaign=republished-article" target="_blank">Aeon</a> and has been republished under Creative Commons. Read the <a href="https://aeon.co/ideas/what-can-avicenna-teach-us-about-the-mind-body-problem" target="_blank">original article</a>.</p>
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Aphantasia: the rare brain condition that darkens the mind’s eye
A new study provides validation for the recently identified phenomenon.
08 January, 2021
Credit: agsandrew/ Adobe Stock
- Aphantasia, a recently identified psychological phenomenon, describes when people can't conjure visualizations in their mind's eye.
- A new study published in Cortex compared the visual memories of aphantasic participants with a group of controls.
- Its results found experimental validation for the condition.
<p>Escapism is one of the imagination's great joys. Through fantastic literature, we can explore the vast stretches Arrakis's deserts or the forests of Middle Earth alongside Gandalf the Grey. We can embark on vacations weeks in advance and enjoy a sunny beach while at our desks. We can relive a cherished memory with a favorite relative in an instant, and, of course, always rely on our flock of trusty sheep to lull us to sleep.</p><p>We manage this through what is colloquially called "the mind's eye," our ability to generate psychological images without sensory input. However, such escapism is not possible for people with the rare, and only recently identified, condition aphantasia. People with aphantasia cannot conjure mental images—original or from memory. Instead, their minds' eyes produce dark, blank canvases that cannot be painted in. As Wilma Bainbridge, an assistant professor of psychology at the University of Chicago, <a href="https://news.uchicago.edu/story/cant-draw-mental-picture-aphantasia-causes-blind-spots-minds-eye" target="_blank">told UChicago News</a>:</p><p style="margin-left: 20px;">"Some individuals with aphantasia have reported that they don't understand what it means to '<a href="https://www.bbc.com/news/health-34039054" target="_blank" rel="noopener noreferrer">count sheep'</a> before going to bed. They thought it was merely an expression, and had never realized until adulthood that other people could actually visualize sheep without seeing them."</p><p>For such individuals, literature may produce facts but not visual representations. Arrakis isn't a planet of vast deserts but vast emptiness, Gandalf the Grey a colorless, featureless blob. Sunny beaches can't be visited in their imaginations but must remain on the office calendar until summer vacation. And while memories exist, they cannot be visually recalled except between scrapbook cellophane.</p><p>Scientists don't yet know what causes aphantasia, whether it's a distinct psychological condition, or, indeed, if we are simply jarring against language's limited ability to accurately describe our internal realities. But a burgeoning body of research—among it a new study led by Bainbridge and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0010945220304317?via%3Dihub" target="_blank" rel="noopener noreferrer">published in Cortex</a> last month—suggests the condition is more than misfiring expressions.</p>
Changing our understanding of the mind's eye
<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTI2NjM0Mi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0ODM2ODE5NX0.SWkNBfgO1uLsAMsetcmmwOHvJqzK1UsPMxc6tL6Je9k/img.jpg?width=1245&coordinates=0%2C228%2C0%2C873&height=700" id="2092d" width="1245" height="700" data-rm-shortcode-id="b0ee9078541b6ecdda2dab654bf1131b" data-rm-shortcode-name="rebelmouse-image" />Francis Galton was the first to describe a condition that would today be recognized as aphantasia.
<p>Though no long-term studies have focused on aphantasia, <a href="https://www.scientificamerican.com/article/when-the-minds-eye-is-blind1/" target="_blank">its history</a> stretches back more than a century. Francis Galton first described people with "no power of visualising" in 1880, an observation made during his breakfast-table survey. At that time, however, the science of psychology was still in its infancy, and Galton's observation was shelved like so many other early-day curios—brought down and dusted off by the occasional psychologist but given little attention before being shelved again.</p><p>That changed in 2003 when neurologist Adam Zeman was contacted by a 65-year-old man who claimed his mind's eye went blind. During a coronary angioplasty, the man suffered a small stroke that damaged his brain. Afterward, he lost his ability to render psychological imagery.</p><p>"He had vivid imagery previously," Zeman told <a href="https://www.sciencefocus.com/the-human-body/aphantasia-life-with-no-minds-eye/" target="_blank">Science Focus</a>. "He used to get himself to sleep by imagining friends and family. Following the cardiac procedure, he couldn't visualise anything, his dreams became avisual, [and] he said that reading was different because previously he used to enter a visual world and that no longer happened. We were intrigued."</p><p>Zeman and his colleagues began a case study into the man's condition. Tests found he could describe objects and their color but could not visualize them. (He claimed he simply knew the answer.) He could rotate three-dimensional images in his mind, but it took him longer to manage than controls. And brain imaging showed brain regions associated with visualization to be dark when he tried to imagine images.</p><p>Zeman published his case study, and it was subsequently <a href="https://www.discovermagazine.com/mind/the-brain-look-deep-into-the-minds-eye" target="_blank" rel="noopener noreferrer">featured in Discover magazine</a>. After the story's publication, more people reached out to Zeman. They too claimed their minds' eyes were blind, but unlike Zeman's original subject, many of these people had lived with the condition their entire lives. They only became aware of their condition later in life when, as Bainbridge mentions above, they realized that the mental worlds described by friends and family were based on more than fanciful expressions. </p><p>While some managed to live normal, even thriving, lives without visual memory, others found the condition distressing. <a href="https://www.sciencedaily.com/releases/2015/08/150826101648.htm" target="_blank" rel="noopener noreferrer">As one subject told Zeman</a> and his coauthors: "After the passing of my mother, I was extremely distraught in that I could not reminisce on the memories we had together. I can remember factually the things we did together, but never an image. After seven years, I hardly remember her."</p><p>Zeman published another case study focusing on <a href="https://ore.exeter.ac.uk/repository/bitstream/handle/10871/17613/Lives%20without%20imagery%20Letter%20version%20FINAL%2017.5.15%20.pdf?sequence=7&isAllowed=y" target="_blank" rel="noopener noreferrer">21 of these individuals in 2015</a>. It was here that he coined the phrase* "aphantasia," from the Greek <em>phantasia</em> meaning "imagination." Since then, <a href="http://sites.exeter.ac.uk/eyesmind/" target="_blank" rel="noopener noreferrer">Zemen has connected with thousands of people</a> claiming to have the condition, and his studies have raised intriguing questions for researchers interested in memory and the mind. </p>Visualizing the difference
<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTI2NjMzNS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzMjAyMDk3M30.EYfZH3v5DRhu4ImOjpuuXdHiXbPkgTUCOxJsTQmDYA8/img.png?width=980" id="fed74" width="598" height="245" data-rm-shortcode-id="411ff90d5a21d04c844ece17c627fd3b" data-rm-shortcode-name="rebelmouse-image" />On the left, an aphantastic participant's recreation of a photo from memory. On the right, the participant's recreation when the photo was available for reference.
<p>Bainbridge is one such researcher. <a href="https://www.nature.com/articles/s41467-018-07830-6#Sec10" target="_blank">Her previous work</a> has focused on perception and memory, both their underlying mechanics and how this content is stored. In her latest study, she and her co-authors aimed to not only tease out the distinctions between object and spatial memory but also deepen our understanding of aphantasia.</p><p>To do this, they invited 61 people with aphantasia and a group of controls to participate in their experiment. They showed each participant a photo of a room and then asked them to draw it in as much detail as possible. For one test, the participants were allowed to keep the photo for reference. For the next test, however, they had to draw the room from memory. Bainbridge and her coauthors then put the drawings online to be quantified by nearly 3,000 online assessors, who were asked to score both sets of test images for object and spatial details.</p><p>The results showed the aphantastic participants had difficulty with the memory experiment. They produced reproductions with fewer objects, less color, and fewer details than their control peers. Many leaned on verbal scaffolding in lieu of visual details—for example, one participant drew a rudimentary box with the word "window" rather than a window with a frame and panes of glass.</p><p>Although the aphantastic patients drew rooms with fewer objects, they were very accurate in their placement of those objects. They also made fewer errors than the controls and avoided incorporating features and furniture absent in the original images. The researchers write that this suggests high spatial accuracy despite a lack of visualization.</p><p>"One possible explanation could be that because aphantasics have trouble with this task, they rely on other strategies like verbal-coding of the space," Bainbridge told UChicago News. "Their verbal representations and other compensatory strategies might actually make them better at avoiding false memories."</p><p>The online assessors found no significant differences between the aphantastic participants and the controls when the original photo was available for reference. In fact, some of the aphantastic participants produced stunningly accurate and artistic recreations during this test.</p><p>Bainbridge and her coauthors suggest that these results not only support the idea that object and spatial information is store in separate neural networks. They also provide "experimental validation" for aphantasia as a valid psychological phenomenon.</p>Discovering a new reality in aphantasia?
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="4ce66da461c82a0293b5bf1227c94c69"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/zNHDTvqbUm4?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>And Bainbridge's study has joined an ever-growing panoply. A <a href="https://www.sciencedirect.com/science/article/abs/pii/S0010945217303581" target="_blank">2018 study, also published in Cortex</a>, measured the binocular rivalry—the visual phenomenon in which awareness fluctuates when different images are presented to each eye—of participants with and without aphantasia. When primed beforehand, control participants choose the primed stimuli more often than not. Meanwhile, aphantastic participants showed no such favoritism, whether primed or not. Like Bainbridge's study, these results suggest a physiological underpinning for aphantasia.</p><p>Another critical factor is growing awareness. As more studies and stories are published, more and more people are realizing they aren't alone. Such a realization can empower others to come forward and share their experiences, which in turn spurs researchers with new questions and experiences to study and hypothesize over.</p><p>Yet, there's still much work to be done. Because this psychological phenomenon has only recently been identified—Galton's observation notwithstanding—there has been sparingly little research on the condition and what research has been done has relied on participants who self-report as having aphantasia. While researchers have used the <a href="https://en.wikipedia.org/wiki/Vividness_of_Visual_Imagery_Questionnaire" target="_blank">Vividness of Visual Imagery Quiz</a> to test for aphantasia, there is currently no universal method for diagnosing the condition. And, of course, there is the ever-vexing question of how one can assess one mind's experiences from another.</p><p>"Skeptics could claim that aphantasia is itself a mere fantasy: describing our inner lives is difficult and undoubtedly liable to error," Zeman and his co-authors wrote in <a href="https://ore.exeter.ac.uk/repository/bitstream/handle/10871/17613/Lives%20without%20imagery%20Letter%20version%20FINAL%2017.5.15%20.pdf?sequence=7&isAllowed=y" target="_blank" rel="noopener noreferrer">their 2015 case study</a>. "We suspect, however, that aphantasia will prove to be a variant of neuropsychological functioning akin to synesthesia [a neurological condition in which one sense is experienced as another] and to congenital prosopagnosia [the inability to recognize faces or learn new ones]."</p><p>Time and further research will tell. But scientists need phenomenon to test and questions to experiment on. Thanks to researchers like Zeman and Bainbridge, alongside the many people who came forward to discuss their experiences, they now have both when it comes to aphantasia.</p><p>* Zeman also coined the term "<a href="https://www.sciencedirect.com/science/article/abs/pii/S0010945220301404" target="_blank">hyperphantasia</a>" to describe the condition in which people's psychological imagery is incredibly vivid and well-defined.</p>
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Loneliness is wired into the human brain. Here's what it looks like.
A large study shows changes in the brain scans of lonely people in the area involved in imagination, memory, and daydreaming.
17 December, 2020
Credit: Adobe Stock
- A study of 40,000 participants shows specific signatures in the brain scans of lonely people.
- Loneliness is linked to variations in grey matter volume and connections in the brain default network.
- This area of the brain is connected to the use of imagination, memory, future planning, and daydreaming.
<p>COVID-19 has exacerbated the worldwide spread of loneliness that had been alarming researchers prior to the pandemic. A new study pinpoints a distinct signature that can be observed in the brains of lonely people and makes the case that social isolation leads to changes in the areas of the brain using memory and imagination.</p><p>The scientists defined loneliness as "the subjective perception of social isolation, or the discrepancy between one's desired and perceived levels of social connection." They based their findings on a large trove of information from about 40,000 participants aged 40 to 69. This was culled from UK's Biobank, an open-access to database for international health scientists. The researchers had access to magnetic resonance imaging (MRI) data, as well as genetics and psychological self-assessments.</p>
<p>The scientists compared the MRI data of the study participants who said they often felt lonely versus those who didn't and discovered key differences. These revolved around the <strong>default network</strong>, an area of the brain responsible for memories, as well as social cognition and imagination. It is employed when we focus on the past or think about the future or daydream about a different present.</p><p>Lonely people's default networks were wired together stronger and unexpectedly had more <strong>grey matter volume</strong>. Lonely people also seemed to show more preservation in the structure of the <strong>fornix</strong>—the nerve fiber bundle that transmits signals from the hippocampus to the default network.</p><p>What is responsible for the brain differences between people who feel lonely and those who don't? The scientists think the answer lies in the function of the default network. Lonely people tend to use their imagination, memories, and hopes more, contend the researchers, in an effort to manage their isolation.</p>
Scientists show what loneliness looks like in the brain
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="426d45d6ed6e79c14050286b188db3a6"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/wkWpqlfA_2Q?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>The study's lead author, Nathan Spreng from The Neuro (Montreal Neurological Institute-Hospital) of McGill University in Canada, linked the use of the inner world by lonely people to their unexpected findings:<br></p><p style="margin-left: 20px;">"In the absence of desired social experiences, lonely individuals may be biased towards internally-directed thoughts such as reminiscing or imagining social experiences," stated Spreng in a <a href="https://www.mcgill.ca/neuro/channels/news/scientists-show-what-loneliness-looks-brain-325504" target="_blank">press release.</a> "We know these cognitive abilities are mediated by the default network brain regions. So this heightened focus on self-reflection, and possibly imagined social experiences, would naturally engage the memory-based functions of the default network."</p>
<p>The scientists think their research can help paint a fuller picture of loneliness and how to treat it, as the amount of people experiencing such feelings grows, affecting their health. <a href="https://pubmed.ncbi.nlm.nih.gov/25956016/" target="_blank" rel="noopener noreferrer">Studies</a> on older people showed loneliness was linked to a stronger risk of dementia and cognitive issues.</p><p style="margin-left: 20px;">"Human evolution has been shaped by selection pressures towards enhanced inter-individual cooperation, write the scientists in their <a href="https://www.nature.com/articles/s41467-020-20039-w" target="_blank">study</a>. "Social interactions are crucial for survival, and fulfillment. Our species' extraordinary reliance on other individuals has led to the characterization of humans as the "ultra-social animal". Consequently, the absence of sufficient social engagement can impose substantial physical and psychological costs."</p><p>Check out the study, published in the journal <a href="https://www.nature.com/articles/s41467-020-20039-w" target="_blank">Nature Communications.</a></p>
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Crazy dreams help us make sense of our memories
A new theory suggests that dreams' illogical logic has an important purpose.
17 November, 2020
Credit: Paul Fleet/Adobe Stock
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<p>For a while now, the leading theory about what we're doing when we dream is that we're sorting through our experiences of the last day or so, consolidating some stuff into memories for long-term storage, and discarding the rest. That doesn't explain, though, why our dreams are so often so exquisitely weird.</p><p>A new theory proposes our brains toss in all that crazy as a way of helping us process our daily experiences, much in the way that programmers add unrelated, random-ish nonsense, or "noise," into machine learning data sets to help computers discern useful, predictive patterns in the data they're fed.</p>
Overfitting
<p>The goal of machine learning is to supply an algorithm with a data set, a "training set," in which patterns can be recognized and from which predictions that apply to other unseen data sets can be derived.</p><p>If machine learning learns its training set too well, it merely spits out a prediction that precisely — and uselessly — matches that data instead of underlying patterns within it that could serve as predictions likely to be true of other thus-far unseen data. In such a case, the algorithm describes what the data set <em>is</em> rather than what it <em>means</em>. This is called "overfitting."</p><img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDc4NTQ4Ni9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2NDM4NDk1Mn0.bMHbBbt7Nz0vmmQ8fdBKaO-Ycpme5eOCxbjPLEHq9XQ/img.jpg?width=980" id="5049a" width="1440" height="585" data-rm-shortcode-id="10fc10e636fcb55325a1f4f1f8bf9db3" data-rm-shortcode-name="rebelmouse-image" />Big Think
The value of noise
<p>To keep machine learning from becoming too fixated on the specific data points in the set being analyzed, programmers may introduce extra, unrelated data as noise or corrupted inputs that are less self-similar than the real data being analyzed.</p><p>This noise typically has nothing to do with the project at hand. It's there, metaphorically speaking, to "distract" and even confuse the algorithm, forcing it to step back a bit to a vantage point at which patterns in the data may be more readily perceived and not drawn from the specific details within the data set.</p><p>Unfortunately, overfitting also occurs a lot in the real world as people race to draw conclusions from insufficient data points — xkcd has a fun example of how this can happen with <a href="https://xkcd.com/1122/" target="_blank">election "facts."</a></p><p>(In machine learning, there's also "underfitting," where an algorithm is too simple to track enough aspects of the data set to glean its patterns.)</p><img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDc4NTQ5My9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMDE5NjY1M30.iS2bq7WEQLeS34zNFPnXwzAZZn9blCyI-KVuXmcHI6o/img.jpg?width=980" id="cd486" width="1440" height="810" data-rm-shortcode-id="debb36da6eff5a4f368914f6bac5054d" data-rm-shortcode-name="rebelmouse-image" />Credit: agsandrew/Adobe Stock
Nightly noise
<p>There remains a lot we don't know about how much storage space our noggins contain. However, it's obvious that if the brain remembered absolutely everything we experienced in every detail, that would be an awful lot to remember. So it seems the brain consolidates experiences as we dream. To do this, it must make sense of them. It must have a system for figuring out what's important enough to remember and what's unimportant enough to forget rather than just dumping the whole thing into our long-term memory.</p><p>Performing such a wholesale dump would be an awful lot like overfitting: simply documenting what we've experienced without sorting through it to ascertain its meaning.</p><p>This is where the new theory, the <a href="https://arxiv.org/pdf/2007.09560.pdf" target="_blank">Overfitting Brain Hypothesis</a> (OBH) proposed by Erik Hoel of Tufts University, comes in. Suggesting that perhaps the brain's sleeping analysis of experiences is akin to machine learning, he proposes that the illogical narratives in dreams are the biological equivalent of the noise programmers inject into algorithms to keep them from overfitting their data. He says that this may supply just enough off-pattern nonsense to force our brains to see the forest and not the trees in our daily data, our experiences.</p><p>Our experiences, of course, are delivered to us as sensory input, so Hoel suggests that dreams are sensory-input noise, biologically-realistic noise injection with a narrative twist:</p><p style="margin-left: 20px;">"Specifically, there is good evidence that dreams are based on the stochastic percolation of signals through the hierarchical structure of the cortex, activating the default-mode network. Note that there is growing evidence that most of these signals originate in a top-down manner, meaning that the 'corrupted inputs' will bear statistical similarities to the models and representations of the brain. In other words, they are derived from a stochastic exploration of the hierarchical structure of the brain. This leads to the kind structured hallucinations that are common during dreams."</p><p>Put plainly, our dreams are just realistic enough to engross us and carry us along, but are just different enough from our experiences —our "training set" — to effectively serve as noise.</p><p>It's an interesting theory.</p><p>Obviously, we don't know the extent to which our biological mental process actually resemble the comparatively simpler, man-made machine learning. Still, the OBH is worth thinking about, maybe at least more worth thinking about than whatever <em>that</em> was last night.</p>
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