Balm of hurt minds

The main character of Haruki Murakami's brilliant and terrifying short story "Sleep" is a perfectly normal middle-class woman living in Tokyo.  Her husband is a dentist, and they've got a lively, cheerful five-year-old son.  Everything about her life is so ordinary that it's hard even to describe.

Then, in one instant, all that changes.

One night, she awakens -- or thinks she has -- to a terrifying vision that even afterward, she's not certain was real or a hallucination during sleep paralysis.  A dark shape is huddled by the foot of her bed, and unfolds itself to reveal the figure of an elderly man, dressed in black, staring at her with an undisguised malevolence.  She attempts to scream, and can't.  After a moment, she forces herself to close her eyes, and when she opens them, the man is gone.  She's drenched with sweat, so she gets up, showers, pours herself a brandy, and waits for morning.

But after that moment, she is completely unable to go to sleep.  Ever.

The remainder of the story could be a teaching text in a fiction writing course lesson about how to create a believable Unreliable Narrator.  She returns to her ordinary life, but everything starts seeming... off.  Some senses are amplified, others dulled into nonexistence.  Everyday objects appear surreal, as if they've changed subtly, but she can't quite tell how.  One evening, she watches her husband as he's sleeping, and realizes that his face suddenly looks ugly to her.  She takes to going out driving at night (once her husband and son are asleep) and meets people who may or may not be real.  Her progressive slide into insanity reaches its apogee in the wee hours of one night, after seventeen days with no sleep, when she drives farther than she has ever driven, and ends up in an empty parking lot overlooking the ocean.  Dark figures raise themselves on either side of her little car, grab it by the handles, and begin to rock it back and forth, harder and harder.  She's thrown around by the motion, slamming against the door and steering wheel, and her last panicked thought is, "It's going to flip over, and there's nothing I can do to stop it."

An apt, if disturbing, summation of what is happening to her mind.

Sleep is an absolutely critical part of human health, but even after decades of research, it is unclear why.  Just about every animal studied sleeps, and many of them seem to dream -- or at least undergo REM sleep -- the same as we do.  (I know my dogs do; both of them bark and twitch in their sleep, and our sweet, gentle little dog Rosie sometimes growls as if she was the biggest meanest Rottweiler on the planet.)

Now, a team at the Binzhou Medical University's Shandong Technology Innovation Center has found one reason why sleep is so critical.  Sleep-deprived mice stop producing a protein called pleiotrophin, which apparently has a protective effect on the cells of the hippocampus.  Reduced pleiotrophin levels lead to cell death -- impairing both memory and spatial awareness.  Pleiotrophin decline has also been implicated in neurodegenerative diseases like Alzheimer's.

[Image licensed under the Creative Commons Sasha Kargaltsev, Sleeping (10765632993), CC BY 2.0]

What's unclear, though, is what direction the causation points.  Does the decline in pleiotrophin from sleeplessness cause the neurodegeneration, or does the neurodegeneration lead to insomnia and a drop in pleiotrophin levels?  The current research suggests the former, as the mice in the study had been genetically engineered to experience sleep disturbances, and the pleiotrophin loss seems to have followed as a consequence of the sleep deprivation.  Then, the question is, if pleiotrophin decline does trigger neurodegeneration, could the damage from Alzheimer's be prevented by increasing the production of the protein?

Uncertain at this point, but it's intriguing to find one piece of a puzzle that has intrigued us for centuries.  It seems fitting to end this musing on the power of sleep with the famous quote from Macbeth:

Methought I heard a voice cry ‘Sleep no more!
Macbeth does murder sleep,’ the innocent sleep,
Sleep that knits up the ravell’d sleave of care,
The death of each day’s life, sore labour’s bath,
Balm of hurt minds, great nature’s second course,
Chief nourisher in life’s feast.

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The scent of memory

When I was about nine years old, I went to live with my paternal grandmother for a year.

Ostensibly the reason was that my parents were in the process of building a house, and where they were living -- a room in my maternal grandfather's house -- there wasn't space for a kid.  My grandmother, on the other hand, lived in a rambling old house with tons of space.  Plus, I idolized my grandma, and had a rather fractious relationship with my parents, so the move resolved several problems simultaneously.

While living with my grandma, my bedroom was in the attic.  Don't think of a cramped, dark space; it was wide open, with dormer windows and lots of separate "rooms" with various nooks and crannies and alcoves and places to explore.  Got a little hot in the summer -- this was southern Louisiana, and there were lots of fans but no air conditioning except a single window-mounted unit down in the living room -- but it was a splendid retreat for a kid who was already a bit of a loner.

Because of the heat, I often slept with the windows open, and one of the two things that will always bring back memories of that year is the sound of church bells in the distance.  My grandma's house was a couple of blocks from Sacred Heart Catholic Church, and the bells ringing in the evening reminds me of those quiet nights in the attic room.

The other, and stronger, association is the smell of old books.

My grandma loved books.  The attic walls were lined with shelves, and filled with what looked to my young eyes like thousands of books, from old cloth-bound textbooks to paperback novels, and everything in between.  The dusty, dry smell of old books brings me back instantaneously; I can almost see the book sitting in my lap as I sat cross-legged on the attic floor, feel texture of the brittle, yellowed pages and the worn cover.  The memories are vivid, detailed, and immediate.

[Image licensed under the Creative Commons Tom Murphy VII, Old book bindings, CC BY-SA 3.0]

I've always wondered why smells can evoke such powerful memories.  It's a common response, but despite this, the underlying mechanism has remained elusive.  But now a study out of Northwestern University, published this week in Progress in Neurobiology, has shed some light on the relationship between olfaction and memory -- and found that it results from an underlying structural feature of the human brain.

The team, led by neuroscientist Guangyu Zhou, studied the connections between the olfactory centers and other parts of the brain, and also looked at activity levels using fMRI technology.  They found something fascinating -- that the olfactory centers have a higher degree of connectivity with the hippocampus (one of our main memory centers) than any other sense, and the activity level in those connections oscillates to match the rate of our breathing.

"During evolution, humans experienced a profound expansion of the neocortex that re-organized access to memory networks," said study co-author Christina Zelano, in an interview with Science Daily.  "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."

It does make me wonder a bit about my own case, though, because after decades of sinus problems, my sense of smell is pretty lousy.  It's not gone completely, but I certainly don't have the sensitive nose that many have.  (Which has a variety of downsides, including explaining why I was assigned to clean up when our septic tank backed up, and also give our dogs baths the time they got skunked at five AM.)  Now, there's the additional complication of COVID-19 infection wiping out people's senses of smell entirely.  "Loss of the sense of smell is underestimated in its impact," Zelano said.  "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...  Most people who lose their smell to COVID regain it, 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."

I'm a little dubious that my poor sense of smell has anything to do with my tendency toward depression, but that they correlate in my case is at least interesting.  It's reassuring that I still do have memories triggered by smells, so even if I might not be having the full experience of the sense of smell, that part of the system still seems to be working just fine.

Especially the smell of old books and memories of living with my grandmother.  That one is intact and fresh, and (fortunately) a very positive association.  Add it to some sounds -- church bells, the rhythmic drone of an oscillating fan, the song of whippoorwills at night -- and I can close my eyes and for a moment, be nine years old again.

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I've always been in awe of cryptographers.  I love puzzles, but code decipherment has seemed to me to be a little like magic.  I've read about such feats as the breaking of the "Enigma" code during World War II by a team led by British computer scientist Alan Turing, and the stunning decipherment of Linear B -- a writing system for which (at first) we knew neither the sound-to-symbol correspondence nor even the language it represented -- by Alice Kober and Michael Ventris.

My reaction each time has been, "I am not nearly smart enough to figure something like this out."

Possibly because it's so unfathomable to me, I've been fascinated with tales of codebreaking ever since I can remember.  This is why I was thrilled to read Simon Singh's The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography, which describes some of the most amazing examples of people's attempts to design codes that were uncrackable -- and the ones who were able to crack them.

If you're at all interested in the science of covert communications, or just like to read about fascinating achievements by incredibly talented people, you definitely need to read The Code Book.  Even after I finished it, I still know I'm not smart enough to decipher complex codes, but it sure is fun to read about how others have accomplished it.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Mental maps

Picture a place you know well.  Your house, your apartment, a park, a church, a school.  You can probably imagine it, remember what it's like to wander around in it, maybe even visualize it to a high level of detail.

Now, let's change the perspective to one you probably have never taken.  Would you be able to draw a map of the layout -- as seen from above?  An aerial view?

Here's a harder task.  In a large room, there are various obstacles, all fairly big and obvious.  Tables, chairs, sofas, the usual things you might find in a living room or den.  You're standing in one corner, and from that perspective are allowed to study it for as long as you like.

Once you were done, could you walk from that corner to the diagonally opposite one without running into anything -- while blindfolded?

Both of these tasks require the use of a part of your brain called the hippocampus.  The name of the structure comes from the Greek word ἱππόκαμπος -- literally, "seahorse" -- because of its shape.  The hippocampus has a role in memory formation, conflict avoidance... and spatial navigation.

Like the other structures in the brain, the hippocampus seems to be better developed in some people than others.  My wife, for example, has something I can only describe as an internal GPS.  To my knowledge, she has never been lost.  When we took a trip to Spain and Portugal a few years ago, we rented a car in Madrid and she studied a map -- once.  After that, she navigated us all over the Iberian Peninsula with only very infrequent checks to make sure we were taking the correct turns, which because of her navigational skills, we always were.

I, on the other hand, get lost walking around a tree.

[Image licensed under the Creative Commons Edward Betts, Bloomsbury - map 1, CC BY-SA 2.0]

The topic comes up because of a paper last week in Cell that showed something absolutely fascinating.  It's called "Targeted Activation of Hippocampal Place Cells Drives Memory-Guided Spatial Behavior," and was written by a team led by Nick T. M. Robinson of University College London.  But to understand what they did, you have to know about something called optogenetics.

Back in 2002, a pair of geneticists, Boris Zemelman and Gero Miesenböck, developed an amazing technique.  They genetically modified mammalian nerve tissue to express a protein called rhodopsin, which is one of the light-sensitive chemicals in the retina of your eye.  By hitching the rhodopsin to ion-sensitive gateway channels in the neural membrane, they created neurons that literally could be turned on and off using a beam of light.

Because the brain is encased in bone, animals that express this gene don't respond any time the lights are on; you have to shine light directly on the neurons that contain rhodopsin.  This involves inserting fiber optics into the brain of the animal -- but once you do that, you have a set of neurons that fire when you shine a light down the fibers.  Result: remote-control mice.

Okay, if you think that's cool, wait till you hear what Robinson et al. did.

So you create some transgenic mice that express rhodopsin in the hippocampus.  Fit them out with fiber optics.  Then let the mice learn how to run a maze for a reward, in this case sugar water in a feeder bottle.  Watch through an fMRI and note which hippocampal neurons are firing when they learn -- and especially when they recall -- the layout of the maze.

Then take the same mice, put them in a different maze.  But switch the lights on in their brain to activate the neurons you saw firing when they were recalling the map of the first maze.

The result is that the mice picture the first maze, and try to run that pattern even though they can see that they are now in a different maze.  The light activation has switched on a memory of the layout of the maze they'd learned that then overrode all the other sensory information they had access to.

It's as if you moved from Tokyo to London, and then tried to use your knowledge of the roads of Tokyo to find your way from St. Paul's Cathedral to the Victoria & Albert Museum.

This is pretty astonishing from a number of standpoints.  First, the idea that you can switch a memory on and off like that is somewhere between fascinating and freaky.  Second, that the neural firing pattern is so specific -- that pattern corresponds to that map, and no other.  And third, that the activation of the map made the mice doubt the information coming from their own eyes.  

So once again, we have evidence of how plastic our brains are, and how easy they are to fool.  What you're experiencing right now is being expressed in your brain as a series of neural firings; in a way, the neural firing pattern is the experience.  If you change the pattern artificially, you experience something different.

More disturbing still is that our sense of self is also deeply tied to our neural links (some would say that our sense of self is nothing more than neural links; to me, the jury's still out on where consciousness comes from, so I'm hesitant to go that far).  So not only what you perceive, but who you are can change if you alter the pattern of neural activation.

We're remarkable, complex, amazing, and fragile beasts, aren't we?

So that's today's contribution from the Not Science Fiction department.  I'm wondering if I might be able to get one of those fiber optics things to activate my hippocampus.  Sounds pretty extreme, but I am really tired of getting lost all the time.  There are trees everywhere around here.

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This week's Skeptophilia book-of-the-week is one that has raised a controversy in the scientific world: Ancient Bones: Unearthing the Astonishing New Story of How We Became Human, by Madeleine Böhme, Rüdiger Braun, and Florian Breier.

It tells the story of a stupendous discovery -- twelve-million-year-old hominin fossils, of a new species christened Danuvius guggenmosi.  The astonishing thing about these fossils is where they were found.  Not in Africa, where previous models had confined all early hominins, but in Germany.

The discovery of Danuvius complicated our own ancestry, and raised a deep and difficult-to-answer question; when and how did we become human?  It's clear that the answer isn't as simple as we thought when the first hominin fossils were uncovered in Olduvai Gorge, and it was believed that if you took all of our millennia of migrations all over the globe and ran them backwards, they all converged on the East African Rift Valley.  That neat solution has come into serious question, and the truth seems to be that like most evolutionary lineages, hominins included multiple branches that moved around, interbred for a while, then went their separate ways, either to thrive or to die out.  The real story is considerably more complicated and fascinating than we'd thought at first, and Danuvius has added another layer to that complexity, bringing up as many questions as it answers.

Ancient Bones is a fascinating read for anyone interested in anthropology, paleontology, or evolutionary biology.  It is sure to be the basis of scientific discussion for the foreseeable future, and to spur more searches for our relatives -- including in places where we didn't think they'd gone.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

The persistence of memory

One of the many amazing things about the brain is its ability to form connections between associated events.

These links can have amazing staying power.  The smell of old books will forever remind me of my grandmother's attic, which was my bedroom for a year when I was about ten years old.  Dan Fogelberg's songs always bring back painful memories of my ex-wife (a shame to have that association, because I actually like Dan Fogelberg).  The pretty little flowers called "sweet williams" call to mind the small plot of garden I had in my parents' back yard -- they were the first flowers I had real success with, and I still remember the pure, unalloyed joy of watching them flower for the first time.

[Image licensed under the Creative Commons Jim Evans, Sweet William -- Dianthus barbatus, CC BY-SA 4.0]

That we form these kinds of associations is common knowledge; how we do it is another matter entirely.  But some new research at Columbia University's Zuckerman Mind-Brain Behavior Institute has shed some light on this innate and ubiquitous capacity of the human mind.

In "Hippocampal Network Reorganization Underlies the Formation of a Temporal Association Memory," by Mohsen S. Ahmed et al., which appeared a couple of weeks ago in the journal Neuron, we find out that memories are as persistent as they are not because of a change in the neural firing pattern -- but because they actually cause a reorganization of synaptic connections in the hippocampus, a part of the brain long known to be crucial in memory consolidation.

The researchers taught mice to associate a neutral sound with a short, startling puff of air.  They were quick to learn to link the two; which, after all, was no different than Pavlov's dog connecting a bell with being fed dinner.  Because the two events being linked in the brain occurred with a significant separation in time, the researchers didn't think it could be that the parts of the hippocampus responsible for storing the memory of each were engaging in some kind of continuing cross-talk.  "We expected to see repetitive, continuous neural activity that persisted during the fifteen-second gap, an indication of the hippocampus at work linking the auditory tone and the air puff," said Stefano Fusi, professor of neuroscience at Columbia's Vagelos College of Physicians and Surgeons and co-author of the study, in an interview with Science Daily.  "But when we began to analyze the data, we saw no such activity...  We were happy to see that the brain doesn't maintain ongoing activity over all these seconds because, metabolically, that's not the most efficient way to store information.  The brain seems to have a more efficient way to build this bridge, which we suspect may involve changing the strength of the synapses."

Understanding the way memories of different events become linked in the brain isn't just of academic interest, explaining the kinds of ordinary associations I described from my own life; it could be of real help in treating people with severe anxiety and/or post-traumatic stress syndrome, where traumatic events are linked to common stimuli (such as survivors of wartime who are triggered to panic by loud noises).  "While our study does not explicitly model the clinical syndromes of either of these disorders, it can be immensely informative," said study lead author Mohsin Ahmed.  "For example, it can help us to model some aspects of what may be happening in the brain when patients experience a fearful association between two events that would, to someone else, not elicit fright or panic."

The strength and persistence of memories can be a lifelong reminder of something joyful, or of something tragic, shocking, angering, or outright painful.  This experiment represents the first step on the road to understanding how our brain forms one memory and links it to another, and -- possibly -- gives us a direction to pursue in searching for how to disconnect that link, and allow people with severe anxiety and PTSD to live more normal lives.

And anything we can do to alleviate that suffering is a most laudable goal.

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This week's Skeptophilia book-of-the-week is one that should be a must-read for everyone -- not only for the New Yorkers suggested by the title.  Unusual, though, in that this one isn't our usual non-fiction selection.  New York 2140, by Kim Stanley Robinson, is novel that takes a chilling look at what New York City might look like 120 years from now if climate change is left unchecked.

Its predictions are not alarmism.  Robinson made them using the latest climate models, which (if anything) have proven to be conservative.  She then fits into that setting -- a city where the streets are Venice-like canals, where the subways are underground rivers, where low-lying areas have disappeared completely under the rising tides of the Atlantic Ocean -- a society that is trying its best to cope.

New York 2140 isn't just a gripping read, it's a frighteningly clear-eyed vision of where we're heading.  Read it, and find out why The Guardian called it "a towering novel about a genuinely grave threat to civilisation."

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Choosing the right path

We're all so familiar with our own mental internal state that it's interesting to consider (1) that not everyone has the same sort of thing going on in their brains, and (2) what's really going on in there is not at all obvious.

I was just discussing the first bit last night with a friend.  She told me that she has entire, back-and-forth conversations in her mind, pretty much constantly.  Asking herself things, musing over answers, as if she was on both sides of a discussion over what to do and how to do it.  Me?  I have a crazy, trippy, disjointed monologue, jumping from topic to topic, as if my skull was occupied by Daffy Duck on speed.  And generally there's a soundtrack, too, usually of whichever song I heard on the radio over the past 48 hours was the most annoying.

It's no wonder I have such difficulty focusing.

Some people are highly visual, and rather than words, they think in pictures.  No internal chatter at all, which is hard for me to imagine.  And I guess it's no surprise I don't think in images much, especially not images of people; being face-blind, I can't picture anyone's face, including my own.  Nada.  I know I have blond-ish hair and blue eyes and short facial hair and a big nose, but I can't put it all together into a composite image the way some people (apparently) do with ease.

Of course, in most ways I get by just fine.  I was asked one time, "If you can't picture your own face at all, how do you know it's you when you look into the bathroom mirror in the morning?"  I stared at the person for a moment, and said, "Because I know there's no one else in the bathroom but me."

I mean, I may be face-blind, but fer cryin' in the sink, I'm not stupid.

But I digress.

Anyway, there seems to be a huge variety of internal experience, which I suppose is what we should expect given the huge variety of outward expressions of that experience.  But that brings us to the second question: what's happening inside our skulls that creates that internal experience in the first place?

Neuroscientists are just beginning to piece together an answer to that question.  We have a pretty good idea of where in the brain certain activity occurs; higher-order processing in the prefrontal cortex, motor coordination in the motor cortex and cerebellum, spatial navigation in the hippocampus, speech production in the Wernicke's and Broca's areas of the cerebrum, and so on.  Even my own particular difficulty, which goes by the medical name prosopagnosia, has been localized to a place called the fusiform gyrus, which in the face-blind simply doesn't respond when confronted with an image of a face.  So we can see it just fine, but we don't recognize who it is.  (It manifests in me as everyone looking vaguely familiar -- so when someone starts talking to me, I can usually slip right into acting like I know who I'm talking to, when in fact I very rarely do until I recognize the voice or pick up context clues.  But I'm good at faking recognition, at least until I get fed up fishing around and say, "I'm sorry, but I have no idea who you are.")

But other than the general locations in the brain where certain functions occur, we're still largely in the dark.  Think about something really simple that isn't in your mind before the question was asked -- for example, what did you have for dinner last night?

Now, where was that information before I asked the question?  How was it encoded?  How did you retrieve it?  Even weirder are those moments when you know you know a piece of information, and it's in there, but you can't get at it -- the "tip of the tongue" phenomenon.  And why, when you stop worrying at it and start thinking about other things, does the answer spontaneously pop out?  (In the days before Google, when finding out factual information usually required a trip to the library, I was driving myself nuts trying to remember the names of the Three Musketeers.  Athos, Porthos, and...?  It was a full two days later, while I was out for a run and completely thinking about other things, that suddenly my brain went "... Aramis!")

What about when we're trying to make a decision between two alternatives?  For me, I'll bat back and forth between them, then -- quite suddenly -- I settle down into one or the other.  And just last month a paper in Cell has suggested that what's going on in the brain might be exactly what it feels like, only much, much faster.

In "Constant Sub-second Cycling between Representations of Possible Futures in the Hippocampus," a team led by neuroscientist Kenneth Kay of Columbia University found that rats confronted with a choice in maze-running shuttle back and forth quickly (about eight times per second) between patterns of neural firing representing the two choices -- as if they were thinking, "Let's see, I wonder what's down the right-hand path?  Hmm, how about the left-hand path?"

The authors write:

Cognitive faculties such as imagination, planning, and decision-making entail the ability to represent hypothetical experience.  Crucially, animal behavior in natural settings implies that the brain can represent hypothetical future experience not only quickly but also constantly over time, as external events continually unfold.  To determine how this is possible, we recorded neural activity in the hippocampus of rats navigating a maze with multiple spatial paths.  We found neural activity encoding two possible future scenarios (two upcoming maze paths) in constant alternation at 8 Hz: one scenario per ∼125-ms cycle...  Notably, cycling occurred across moving behaviors, including during running.  These findings identify a general dynamic process capable of quickly and continually representing hypothetical experience, including that of multiple possible futures.

There are a couple of interesting things about this.  First, there's the role of the hippocampus; higher-order decision-making is traditionally thought to be the provenance of the prefrontal cortex, although the fact that this decision has to do with spatial navigation is probably why it occurs where it does.  Second, why is the cycling so fast -- each flip lasting, on average, an eighth of a second -- when it feels very much like we're considering each possibility slowly and deliberately?  (Of course, that's assuming that our neurology and experience are both comparable to what's happening in rats, which may be a poor assumption.)

I also wonder what's happening with the consideration of imaginary scenarios.  Being a fiction author, I do that a lot, and I know I spend a great deal of time testing out various ideas and plot twists before settling on the one that I want.  It's quite remarkable when you think about it; we're capable of dreaming up highly detailed and completely counterfactual scenes, and interact with them as if they were real -- deciding which path to take, which of the two magical doors to open.

As author and journalist Kathryn Schulz put it, in her phenomenal TED talk "On Being Wrong," "The most wonderful thing about the human mind is not that we can see the world as it is, but that we can see the world as it isn't."

But this is just the first step of solving that most fundamental of questions in neuroscience, which is how we emulate our experience in our brains.  This is one small piece of the puzzle of human consciousness, the origins of creativity, imagination, and memory, the last-mentioned of which hopefully will solve how I can set a tool down and literally thirty seconds later can't remember where I put it.

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One of my favorite people is the indefatigable British science historian James Burke.  First gaining fame from his immensely entertaining book and television series Connections, in which he showed the links between various historical events that (seen as a whole) play out like a centuries-long game of telephone, he went on to wow his fans with The Day the Universe Changed and a terrifyingly prescient analysis of where global climate change was headed, filmed in 1989, called After the Warming.

One of my favorites of his is the brilliant book The Pinball Effect.  It's dedicated to the role of chaos in scientific discovery, and shows the interconnections between twenty different threads of inquiry.  He's posted page-number links at various points in his book that you can jump to, where the different threads cross -- so if you like, you can read this as a scientific Choose Your Own Adventure, leaping from one point in the web to another, in the process truly gaining a sense of how interconnected and complex the history of science has been.

However you choose to approach it -- in a straight line, or following a pinball course through the book -- it's a fantastic read.  So pick up a copy of this week's Skeptophilia book of the week.  You won't be able to put it down.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Last week's episode

One of the enduring mysteries of neuropsychology is how memory is encoded.

As I tell my introductory neuroscience students, think of the simplest thing you can.  Your middle name.  What 2 + 3 is.  What three colors are in the American flag.  Now, where was that information before I asked you?  And how did you retrieve it?  And where does it go when you no longer are thinking about it?

We have some ideas about where memory is stored, given recent studies with fMRI machines.  Scientists can see what parts of the brain are active when you recall different types of information, and we now know that different types and durations of memory are stored in different places.  But the other two pieces -- how memory is stored and how it is retrieved -- we honestly have no idea about.

We got another piece of the puzzle last week with some new research by Gabriel Radvansky of Notre Dame University and Aya Ben-Yakov and Rik Henson of the University of Cambridge.  What they were interested in is episodic memory, our brain's ability to slice what it recalls up into discrete chunks, rather like the chapters in a story.  They looked at what happens at the boundaries -- what we perceive as the end of one episode and the beginning of another.

"So much research is done with these little bits and pieces — words, pictures, things like that,” Radvansky says.  "But those dry tidbits aren’t what the human brain usually handles.  The mind is built to deal with complex events... Research like this helps us identify ‘What is an event, from the point of view of the brain?’"

[Image is in the Public Domain]

They had participants watching one of two movies, Forrest Gump and Bang! You're Dead!, and using fMRI watched what happened when obvious boundaries were reached -- a scene fade-to-black, a jump to a new location or new characters, and so on.  But what is interesting is that the brain perceives other moments as boundaries as well.  At any of those moments, activity in the hippocampus increases dramatically, suggesting that this is the structure that helps us divide what we remember into distinct episodes.

Laura Sanders, writing about the research in Science News, explains further.  "These transitions didn’t always involve jumps to new places or times in the story. One such boundary came near the beginning of Forrest Gump as Forrest sits quietly on a bench.  Suddenly, he blurts out his famous greeting: 'Hello. My name’s Forrest. Forrest Gump.'  The hippocampus may have helped slice that continuous bench scene into two events: before talking and after talking.  Such divisions may help package information into discrete pieces that can then be stored as memories."

In real life, of course, there are seldom such definitive boundaries.  A few artificial ones exist -- when it's quitting time at work, when the bell rings in a school, when your alarm clock goes off.  Most of the rest of life proceeds along fairly smoothly, but what this research suggests is that you don't store or recall memories that way.

Which is another nail in the coffin of the idea of our memories being accurate.  Research has been chipping away for years at the notion that we have any kind of a decent record of the past, but the results have shown the reality is very much the opposite.  Here, we find that our brains are slicing up what we've experienced into chunks with more-or-less arbitrary boundaries, leaving us with the sense of life being a series of disjointed episodes rather than any kind of continuous record of events.  

I'm also interested in what we remember of the boundaries themselves.  In movies, when a scene shifts, it usually doesn't occur to us to ask what's happening during the gap, and we don't form any kind of strong memory of the jump itself (at least, I don't).  What the Radvansky et al. research suggests is that when discrete edges don't exist, we superimpose them on what we remember.  So do we have the same kind of foggy sense of recall during these brain-created boundaries as we do when we're watching movies?

In any case, this is an interesting new piece of the puzzle of our memory, and how we create a picture of past events.  Now, I wish they'd get to work on two of the most intriguing memory-related events -- déjà vu and the "tip of the tongue" phenomenon.  Since we finally seem to be closing in on how we store memories, I have no doubt that scientists will one day be able to account for these, as well.

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This week's Skeptophilia book recommendation is from the brilliant essayist and polymath John McPhee, frequent contributor to the New Yorker.  I swear, he can make anything interesting; he did a book on citrus growers in Florida that's absolutely fascinating.  But even by his standards, his book The Control of Nature is fantastic.  He looks at times that humans have attempted to hold back the forces of nature -- the attempts to keep the Mississippi River from changing its path to what is now the Atchafalaya River, efforts in California to stop wildfires and mudslides, and a crazy -- and ultimately successful -- plan to save a harbor in Iceland from a volcanic eruption using ice-cold seawater to freeze the lava.

Anyone who has interest in the natural world should read this book -- but it's not just about the events themselves, it's about the people who participated in them.  McPhee is phenomenal at presenting the human side of his investigations, and their stories will stick with you a long time after you close the last page.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

Stop me if I've already told you about this

One of the most ubiquitous, but mysterious, phenomena in neuroscience is déjà vu.

We all get it from time to time -- the uncanny sense that what we're experiencing has happened before.  For some people, it's usually visual in nature; that they've seen that room, seen those people, know that particular part of the city, despite a certainty that such foreknowledge is impossible.  For me, it's most often auditory.  Just a few weeks ago, I was talking with a colleague about the discovery of some new fossils from the early Cambrian era (the age of the "Cambrian Explosion," the sudden diversification of animal life into multitudes of forms), and I had the unsettling feeling that I'd had that conversation with her already.

"Didn't we already talk about this?" I asked her.

She assured me that we hadn't.

There are a multitude of unsupported woo-woo explanations for the phenomenon -- a premonition, a memory from a previous life, even a momentary side-slip into an alternate timeline (à la the "Many Worlds" interpretation of quantum mechanics).  Predictably, I don't think much of these, mostly because they have little testability and even less evidence in their favor.  So they really don't count as scientific explanations.

The problem is, science has come up pretty much empty-handed itself.  Déjà vu is so unpredictable, so quick to strike and so quickly over, that it's not like you can stick someone in an fMRI machine and just sit around and wait until it happens.  It's known that there are some medications that can increase the frequency of déjà vu -- a combination of phenylpropanolamine and amantidine, used to relieve flu symptoms, has been documented to trigger intense and recurrent déjà vu in some people.

No one is really certain why.

[image courtesy of the National Institute for Aging and the Wikimedia Commons]

Other explanations include a subconsciously-recalled memory being stimulated by a different, but similar, stimulus, creating a sensation of the event having already been experienced; and a dreamed scene producing what amounts to an "invented memory" that could be similarly triggered.

Neither of these, to me, explains the commonness, nor the power, of these experiences.  I know that memory is unreliable and plastic, but even so, déjà vu is so striking that it deserves a better explanation.

Recently, however, a study by Christine Wells et al. has shed some interesting light on this phenomenon.  Wells and her team found that a patient with severe anxiety disorder was experiencing profound and repeated déjà vu, and the researchers speculate that this is no coincidence:

Whereas previous cases with déjà vu due to MCI [mild cognitive impairment] and dementia have largely been anosognosic [not acknowledged as clinically relevant by the patient], our case is aware of the abnormal familiarity in his memory, and is in fact greatly distressed by it.  This suggests two dimensions along which déjà vu experiences can vary: awareness and distress.  In this psychogenic case, our patient is similarly aware of the unreality of his experiences and they are constantly accompanied or caused by pathological levels of anxiety...  In relation to our case, distress caused by the déjà vu experience may itself lead to increased levels of déjà vu: similar feedback loops in positive symptoms are reported in other anxiety states (e.g. panic attacks). 

It is plausible on neurobiological grounds that anxiety might lead to the generation of déjà vu.  The hippocampal formation, a structure of central importance in declarative memory and the ability to engage in recollection, is also implicated in anxiety as part of the septo-hippocampal system.  Although this report does not prove a link between anxiety and déjà vu, it does further support the suggestion that this area is worthy of further investigation.

It certainly is.  You have to wonder if even people who do not suffer from a clinical anxiety disorder might experience déjà vu more commonly when they're distressed or anxious about something.  Stress does affect health -- there's no real doubt about that -- could it also be responsible for fleeting pseudo-memories?

All of which is fascinating and suggestive.  It's further evidence of what a friend of mine once said -- she's a retired professor of human genetics at Cornell, and she said if she were going into research now, she'd go into neurology instead of genetics.  "Right now, in terms of our understanding of the brain, we're where our understanding of genes was in the early 20th century.  We know a little about what's going on, mostly descriptively, but little real comprehension of how it's all happening.  The 20th century was the century of the gene; the 21st will be the century of the brain."

But I've told you that quote before, haven't I?  I'm sure I've used that quote before.