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.
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>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.
Aphantasia: the rare brain condition that darkens the mind’s eye
A new study provides validation for the recently identified phenomenon.
- 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.
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>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.
- 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.
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>Crazy dreams help us make sense of our memories
A new theory suggests that dreams' illogical logic has an important purpose.
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>