Brain Pickings

Posts Tagged ‘neuroscience’

09 JULY, 2014

Visionary Neurologist Oliver Sacks on What Hallucinations Reveal about How the Mind Works

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“We see with the eyes, but we see with the brain as well.”

While our delusions may keep us sane, hallucinations — defined as perceptions that arise independently of external reality, as when we see, hear, or sense things that aren’t really there — are an entirely different beast, a cognitive phenomenon that mimics mysticism and has no doubt inspired mystical tales over the millennia. In the 18th century, Swiss lawyer-turned-naturalist Charles Bonnet, the first scientist to use the term evolution in a biological context, turned to philosophy after deteriorating vision rendered him unable to perform the necessary observations of science. Blindness eventually gave him a special form of complex visual hallucinations, known today as Charles Bonnet syndrome, but he was otherwise fully lucid and marveled, as a cognitive scientist might, at “how the theater of the mind could be generated by the machinery of the brain.”

Some 250 years later, pioneering neurologist Oliver Sacks (b. July 9, 1933) — who has previously explored the necessary forgettings of creativity and how music impacts the mind — picked up Bonnet’s inquiry in his immeasurably fascinating book Hallucinations (public library). In this TED talk based on the book, Sacks draws on his extensive clinical experience of working with patients, illuminating that astounding “theater of the mind” to shed light on what hallucinations reveal about how the mind works.

We see with the eyes, but we see with the brain as well. And seeing with the brain is often called imagination. And we are familiar with the landscapes of our own imagination, our inscapes. We’ve lived with them all our lives. But there are also hallucinations as well, and hallucinations are completely different. They don’t seem to be of our creation. They don’t seem to be under our control. They seem to come from the outside, and to mimic perception.

In the book, Sacks offers a detailed definition of hallucinations, contrasting them with regular perception and peering into their promise for better understanding the brain and the human mind:

When the word “hallucination” first came into use, in the early sixteenth century, it denoted only “a wandering mind.” It was not until the 1830s that Jean-Étienne Esquirol, a French psychiatrist, gave the term its present meaning — prior to that, what we now call hallucinations were referred to simply as “apparitions.” Precise definitions of the word “hallucination” still vary considerably, considerably, chiefly because it is not always easy to discern where the boundary lies between hallucination, misperception, and illusion. But generally, hallucinations are defined as percepts arising in the absence of any external reality— seeing things or hearing things that are not there.

Perceptions are, to some extent, shareable — you and I can agree that there is a tree; but if I say, “I see a tree there,” and you see nothing of the sort, you will regard my “tree” as a hallucination, something concocted by my brain or mind, and imperceptible to you or anyone else. To the hallucinator, though, hallucinations seem very real; they can mimic perception in every respect, starting with the way they are projected into the external world.

[…]

When you conjure up ordinary images— of a rectangle, or a friend’s face, or the Eiffel Tower —the images stay in your head. They are not projected into external space like a hallucination, and they lack the detailed quality of a percept or a hallucination. You actively create such voluntary images and can revise them as you please. In contrast, you are passive and helpless in the face of hallucinations: they happen to you, autonomously — they appear and disappear when they please, not when you please.

[…]

Hallucinations are “positive” phenomena, as opposed to the negative symptoms, the deficits or losses caused by accident or disease, which neurology is classically based on. The phenomenology of hallucinations often points to the brain structures and mechanisms involved and can therefore, potentially, provide more direct insight into the workings of the brain.

Hallucinations, which goes on to explore how advances in neuroimagining in the last few decades have greatly enhanced our understanding of hallucinations and the brain, is a mind-bending read in its entirety. Complement it with Sacks on the psychology of plagiarism.

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08 APRIL, 2014

The Science of How Memory Works

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What the four “slave” systems of the mind have to do with riding a bicycle.

“Whatever becomes of [old memories], in the long intervals of consciousness?” Henry James wistfully pondered upon turning fifty. “They are like the lines of a letter written in sympathetic ink; hold the letter to the fire for a while and the grateful warmth brings out the invisible words.” James was not alone in seeking to understand the seemingly mysterious workings of human memory — something all the more urgently fascinating in our age of information overload, where we’re evolving a new kind of “transactive memory.” But like other scientific mysteries of how the brain works — including what actually happens while we sleep and why some people are left-handed — memory continues to give scientists more questions than answers.

In The Guardian of All Things: The Epic Story of Human Memory (public library) technology writer Michael S. Malone takes a 10,000-year journey into humanity’s understanding of our great cognitive record-keeper, exploring both its power and its ongoing perplexity.

Illustration from 'Neurocomic,' a graphic novel about how the brain works. Click image for more.

One of the most astounding facts Malone points out is that memory — that is, the creation of memories — is the result of a biochemical reaction that takes place inside neurons, one particularly common among neurons responsible for our senses. Scientists have recently discovered that our short-term memory — also known as “working memory,” the kind responsible for the “chunking” mechanism that powers our pattern-recognition and creativity — is localized to a few specific areas of the brain. The left hemisphere, for instance, is mostly in charge of verbal and object-oriented tasks. Even so, however, scientists remain mystified by the specific distribution, retrieval, and management of memory. Malone writes:

One popular theory holds that short-term memory consists of four “slave” systems. The first is phonological, for sound and language that (when its contents begin to fade) buys extra time through a second slave system. This second operation is a continuous rehearsal system — as you repeat a phone number you’ve just heard as you run to the other room for your phone. The third system is a visuo-spatial sketch pad that, as the name suggests, stores visual information and mental maps. Finally, the fourth (and most recently discovered) slave is an episodic buffer that gathers all of the diverse information in from the other slaves, and maybe other information from elsewhere, and integrates them together into what might be described as a multimedia memory.

It’s worth noting that memory and creativity have a great deal in common — the combinatorial process of memory-making that Malone describes is remarkably similar to how creativity works: we gather ideas and information just by being alive and awake to the world, record some of those impressions in our mental sketch pad, then integrate the various bits into new combinations that we call our “own” ideas, a kind of “multimedia” assemblage of existing bits.

Malone goes on to explore the inner workings of long-term memory — a substantially different beast, designed to keep our permanent mental record:

Chemically, we have a pretty good idea how memories are encoded and retained in brain neurons. As with short-term memory, the storage of information is made possible by the synthesis of certain proteins in the cell. What differentiates long-term memory in neurons is that frequent repetition of signals causes magnesium to be released — which opens the door for the attachment of calcium, which in turn makes the record stable and permanent. But as we all know from experience, memory can still fade over time. For that, the brain has a chemical process called long-term potentiation that regularly enhances the strength of the connections (synapses) between the neurons and creates an enzyme protein that also strengthens the signal — in other words, the memory — inside the neuron.

From the functional, Malone moves on to the structural organization of memory, where another dichotomy emerges:

Architecturally, the organization of memory in the brain is a lot more slippery to get one’s hands around (so to speak); different perspectives all seem to deliver useful insights. For example, one popular way to look at brain memory is to see it as taking two forms: explicit and implicit. Explicit, or “declarative,” memory is all the information in our brains that we can consciously bring to the surface. Curiously, despite its huge importance in making us human, we don’t really know where this memory is located. Scientists have, however, divided explicit memory into two forms: episodic, or memories that occurred at a specific point in time; and semantic, or understandings (via science, technology, experience, and so on) of how the world works.

Implicit, or “procedural” memory, on the other hand, stores skills and memories of how to physically function in the natural world. Holding a fork, driving a car, getting dressed — and, most famously, riding a bicycle — are all nuanced activities that modern humans do without really giving them much thought; and they are skills, in all their complexity, that we can call up and perform decades after last using them.

One of the most confounding pieces of the cognitive puzzle, however, is a form of memory known as emotional memory — a specialized system for cataloging our memories based on the emotions they evoke. It’s unclear whether it belongs to the explicit or implicit domain, or to both, and scientists are still seeking to understand whether it serves as a special “search function” for the brain. (What we do now know, however, is that sharpening “emotional recall” might be the secret to better memory.)

From all this perplexity emerges Malone’s bigger point, a somewhat assuring testament to the idea that science, at its best, is always driven by “thoroughly conscious ignorance”:

What we do know is that — a quarter-million years after mankind inherited this remarkable organ called the brain — even with all of the tools available to modern science, human memory remains a stunning enigma.

The Guardian of All Things is a fascinating read in its entirety. Complement it with Joshua Foer’s quest to hack memory to superhuman levels and Henry James on aging and memory.

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08 NOVEMBER, 2013

The Science of Why Our Brains Are Wired to Connect

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“The self is more of a superhighway for social influence than it is the impenetrable private fortress we believe it to be.”

“Without the sense of fellowship with men of like mind,” Einstein wrote, “life would have seemed to me empty.” It is perhaps unsurprising that the iconic physicist, celebrated as “the quintessential modern genius,” intuited something fundamental about the inner workings of the human mind and soul long before science itself had attempted to concretize it with empirical evidence. Now, it has: In Social: Why Our Brains Are Wired to Connect (public library), neuroscientist Matthew D. Lieberman, director of UCLA’s Social Cognitive Neuroscience lab, sets out to “get clear about ‘who we are’ as social creatures and to reveal how a more accurate understanding of our social nature can improve our lives and our society. Lieberman, who has spent the past two decades using tools like fMRI to study how the human brain responds to its social context, has found over and over again that our brains aren’t merely simplistic mechanisms that only respond to pain and pleasure, as philosopher Jeremy Bentham famously claimed, but are instead wired to connect. At the heart of his inquiry is a simple question: Why do we feel such intense agony when we lose a loved one? He argues that, far from being a design flaw in our neural architecture, our capacity for such overwhelming grief is a vital feature of our evolutionary constitution:

The research my wife and I have done over the past decade shows that this response, far from being an accident, is actually profoundly important to our survival. Our brains evolved to experience threats to our social connections in much the same way they experience physical pain. By activating the same neural circuitry that causes us to feel physical pain, our experience of social pain helps ensure the survival of our children by helping to keep them close to their parents. The neural link between social and physical pain also ensures that staying socially connected will be a lifelong need, like food and warmth. Given the fact that our brains treat social and physical pain similarly, should we as a society treat social pain differently than we do? We don’t expect someone with a broken leg to “just get over it.” And yet when it comes to the pain of social loss, this is a common response. The research that I and others have done using fMRI shows that how we experience social pain is at odds with our perception of ourselves. We intuitively believe social and physical pain are radically different kinds of experiences, yet the way our brains treat them suggests that they are more similar than we imagine.

Citing his research, Lieberman affirms the notion that there is no such thing as a nonconformist, pointing out the social construction of what we call our individual “selves” — empirical evidence for what the novelist William Gibson so eloquently termed one’s “personal micro-culture” — and observes “our socially malleable sense of self”:

The neural basis for our personal beliefs overlaps significantly with one of the regions of the brain primarily responsible for allowing other people’s beliefs to influence our own. The self is more of a superhighway for social influence than it is the impenetrable private fortress we believe it to be.

Contextualizing it in a brief evolutionary history, he argues that this osmosis of sociality and individuality is an essential aid in our evolutionary development rather than an aberrant defect in it:

Our sociality is woven into a series of bets that evolution has laid down again and again throughout mammalian history. These bets come in the form of adaptations that are selected because they promote survival and reproduction. These adaptations intensify the bonds we feel with those around us and increase our capacity to predict what is going on in the minds of others so that we can better coordinate and cooperate with them. The pain of social loss and the ways that an audience’s laughter can influence us are no accidents. To the extent that we can characterize evolution as designing our modern brains, this is what our brains were wired for: reaching out to and interacting with others. These are design features, not flaws. These social adaptations are central to making us the most successful species on earth.

The implications of this span across everything from the intimacy of our personal relationships to the intricacy of organizational management and teamwork. But rather than entrusting a single cognitive “social network” with these vital functions, our brains turn out to host many. Lieberman explains:

Just as there are multiple social networks on the Internet such as Facebook and Twitter, each with its own strengths, there are also multiple social networks in our brains, sets of brain regions that work together to promote our social well-being.

These networks each have their own strengths, and they have emerged at different points in our evolutionary history moving from vertebrates to mammals to primates to us, Homo sapiens. Additionally, these same evolutionary steps are recapitulated in the same order during childhood.

He goes on to explore three major adaptations that have made us so inextricably responsive to the social world:

  • Connection: Long before there were any primates with a neocortex, mammals split off from other vertebrates and evolved the capacity to feel social pains and pleasures, forever linking our well-being to our social connectedness. Infants embody this deep need to stay connected, but it is present through our entire lives.
  • Mindreading: Primates have developed an unparalleled ability to understand the actions and thoughts of those around them, enhancing their ability to stay connected and interact strategically. In the toddler years, forms of social thinking develop that outstrip those seen in the adults of any other species. This capacity allows humans to create groups that can implement nearly any idea and to anticipate the needs and wants of those around us, keeping our groups moving smoothly.
  • Harmonizing: The sense of self is one of the most recent evolutionary gifts we have received. Although the self may appear to be a mechanism for distinguishing us from others and perhaps accentuating our selfishness, the self actually operates as a powerful force for social cohesiveness. During the preteen and teenage years, adolescent refers to the neural adaptations that allow group beliefs and values to influence our own.

The rest of Social: Why Our Brains Are Wired to Connect, which dives deeper into this trifecta of adaptations and their everyday implications, is absolutely fascinating — necessary, even. Get a teaser-taste with Liberman’s TEDxStLouis talk based on his research and the resulting book:

Public domain images via Flickr Commons

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