The self, Joseph LeDoux tells us, is “the totality of the living organism”. Most disciplines in the natural sciences focus on only one or two levels of organization. Indeed, Dmitri Mendeleev figured out the periodic table of the elements without knowing any of the underlying quantum mechanics or stereochemistry. There are, however, at least a dozen levels of organization within the neurosciences — and, if we use a metaphor, we temporarily create yet another. This leads to considerable confusion and arguments (...) at cross purposes over whether learning is an alteration at the level of gene expression, ion channels, synapses, neurons or circuits. Each neuron has thousands of synapses, which produce currents that summate to form an impulse train. But only rarely is the activity of a single neuron sufficient to cause a perception or trigger an action. Neurons usually act as members of ‘committees’ — what Donald Hebb in 1949 called cellassemblies. Just as in academia, one individual may function in different committees on different occasions. A concept, including any explicit memory that we can talk about, is probably formed by such a committee. Implicit memories (the ones you can’t talk about) are less differentiated — they are part of the ‘feltwork’, together with motivations and emotions, that biases the choice of one’s next act. In this well-written 400-page appreciation of behavioural neuroscience, LeDoux argues that synapses are the seat of self. He says, in effect, that you are your memories; that it is the uniqueness of an array of synaptic strengths that distinguishes one twin from another. Fair enough, but why not instead focus on one’s unique array of ion channels? Or neurons, because a neuron is the closest thing we have to a computational unit (synapses have to reach a threshold before they have any influence at all)? Or one’s unique arrangement of those overlapping, redundant hebbian committees? None of these make for a catchy book title, but relating other things to the synapses proves to be a good way of covering a lot of fascinating material at the overlying levels, including a few updates to LeDoux’s earlier book The Emotional Brain (Simon & Schuster, 1996).. (shrink)
Plan-ahead becomes necessary for those movements which are over-and-done in less time than it takes for the feedback loop to operate. Natural selection for one of the ballistic movements (hammering, clubbing, and throwing) could evolve a plan-ahead serial buffer for hand-arm commands that would benefit the other ballistic movements as well. This same circuitry may also sequence other muscles (children learning handwriting often screw up their faces and tongues) and so novel oral-facial sequences may also benefit (as might kicking and (...) dancing). An elaborated version of the sequencer may constitute a Darwin Machine that spins scenarios, evolves sentences, and facilitates insight by offline simulation. An example is given of an evolutionary scenario from an apelike ancestor, demonstrating the transition behaviors and growth curve considerations that any such theory needs to have; this particular scenario (involving throwing improvements) also suggests an explanation for the puzzling design of the Acheulean "handaxe.". (shrink)
The title is not a metaphor, though past tense might be better as this chapter is about how each of the many hundred abrupt coolings of the last several million years could have served as a pump stroke, each elevating intelligence a small increment - even though what natural selection was operating on was not intelligence per se.
An expanded version has now appeared: HOW BRAINS THINK: Evolving Intelligence, Then and Now in the Science Masters series (BasicBooks 1996 in the USA and Weidenfeld & Nicolson in the UK, various translation editions elsewhere, including China). My Darwin Machines model for cerebral cortical circuitry has now appeared as THE CEREBRAL CODE: Thinking a Thought in the Mosaics of the Mind (MIT Press 1996).
To fit the magnificence of this setting in Beijing’s Great Hall of the People, and the honor of giving the 2007 Sir John Crawford Memorial Lecture, it is well to have a subject of suitable proportions. I have chosen one of global size and urgent time frame: our climate crisis. We only have one future and one global climate–and now it looks as if we only have one chance to rescue our civilization from collapse and prevent a mass extinction of (...) species during the 21st century. Unless you have been keeping up with climate science for the past twenty-five years, you likely do not know how serious the matter has become. The notion that we might slowly get into serious trouble by mid-century has been conveyed by the media and understood by at least some political leaders. But that scenario depends on somehow avoiding sudden shifts in climate in the meantime, instant setbacks at a time when we lack maneuvering room. An abrupt shift in drought area occurred in 1983 and we had a near-miss of a mass extinction of Amazon species in 1999. It is easy to appreciate that one more degree of global warming will seriously reduce crop yields in the tropics, but in the words of climate scientist Claudia Tebaldi 1, “It’s the extremes, not the averages, that cause the most damage to.. (shrink)
Since Richard Dawkins' The Extended Phenotype got me to thinking about copying units in the mid-1980s, I have been trying to define a cerebral code (the spatiotemporal firing pattern that represents a word, image, metaphor, or even a sentence) by searching for what can be successfully replicated in the brain's neural circuitry, a minimum replicable unit. I indeed found such circuitry (it implies that the firing pattern within several hundred minicolumns of neocortex, contained in a 0.5 mm hexagon, is (...) such a copying unit). But to explore creativity in higher intellectual function, I wanted to see if the resulting copies could compete in a Darwinian manner, the process shaping up quality as it goes. And that forced me to try and boil down a lot of evolutionary biology, attempting to abstract the features that were essential (for what I came to call "the full-fledged Darwinian process") from those that merely contributed to speed or stability. This isn't the place to describe the neural outcome -- it's in The Cerebral Code and, more briefly, in the seventh chapter of my other 1996 book, How Brains Think -- but this does seem an appropriate place to review what I started calling "The Six Essentials." They seem applicable to a wide range of problems within memetics9 as the field attempts to cope with evolutionary models of information transmission. For a more.. (shrink)
The most interesting of our 1997 travels was Bellagio, Italy. It's hard to explain this without lapsing into superlatives over and over, so let me try bare facts first. The Rockefeller Foundation was, in the 1950s, given a 50-acre estate known as the Villa Serbelloni. It was also given enough endowment to maintain the place and run it as a retreat ("The Bellagio Study and Conference Center") for..
I have two tales to tell. Well, maybe three. Presently I will get to the good news concerning what knowledge of the brain will do to education and training by 2025, making adults far more mentally capable than most of us are now, with all its implications for warfare and other less lethal forms of competition.
That’s Bill Calvin, whose brain is worthy of study in its own right. Technically, he’s a theoretical neurophysiologist and affiliate professor of psychiatry and behavioral sciences at the University of Washington. But he’s also known as a scientist with a wide-ranging intellect and a prolific (and accessible) writer who constantly offers remarkable insights about the world around him. As I sat down to interview Calvin in his book-lined Seattle home last Fall, I recalled the comments of someone who had come (...) to GBN to hear Calvin speak. He said that he didn’t know—or care—what Calvin was going to talk about because everything that Bill Calvin said was not only interesting, but worth learning about. After more than three hours of conversation with Calvin, I couldn’t agree more. (shrink)
Computer simulations may allow us to understand the earth’s fickle climate and how it is affected by detours of the great ocean currents. These detours cause abrupt coolings -- the average global temperature can drop dramatically in just a few years, with droughts that set up El-Niño-like forest fires even in the tropics. While volcanic eruptions and Antarctic ice shelf collapses can also abruptly cool things, what we’re talking about here is a flip-flop: a few centuries later, there’s an equally (...) abrupt rewarming. This cycle has repeated every few thousand years (though it has been 12,000 years since the most recent one). (shrink)
When surveying the spectrum from pop psych to neurology in works addressed to general readers, one is struck by how few major figures there have been - certainly when cognitive neuro is compared to a far smaller field (1), evolutionary biology, where real literary talents like Loren Eiseley once flourished, where "media dons" like Richard Dawkins regularly clarify our thinking, where there are magnificent series like those of Stephen Jay Gould (fifteen major essays a year, plus scholarly books and research (...) papers, spanning three decades) which have influenced millions to read more. Many writers in the cognitive spectrum have occasionally written an influential book or two, but few could fill the largest available campus auditorium on name recognition alone, even without announcing a topic for the lecture. (shrink)
In particular, one of Gould's important contributions as a paleontologist was to convince us that there are long periods in evolution where species don't change very much, that Darwinian gradualism doesn't guarantee a steady course of improvements. And that there are periods -- not at all inconsistent with Darwinian gradualism -- when things progress considerably faster. I tuned right into what Steve was saying since both of my main interests in evolution, the evolution of the big brain in only several (...) million years, and the use of the Darwinian process in the brain to improve the quality of the next sentence you speak in a matter of seconds, involve the search for speedy ways of evolving things. (shrink)
Placez la photographie du cerveau d’Einstein au milieu d’une centaine d’autres clichés du même type : il ne fait aucun doute que n’importe quel étudiant en neurosciences le repérerait immédiatement. “ C’est aussi étrange que d’avoir deux pieds gauches , dirait-il. Comment cet individu pouvait-il danser avec deux cerveaux droits ? S’agissait-il d’un attardé mental ou d’un génie ? ” Les règles de l’origami prénatal nous sont encore largement inconnues, mais chaque étudiant apprend vite à distinguer les replis les plus (...) profonds du cerveau, tels le sillon central (tout ce qui est situé en avant de ce sillon est appelé le “ lobe frontal ”) et la scissure de Sylvius (tout ce qui est situé en dessous de cette scissure est appelé le “ lobe temporal ”). Habituellement, les deux hémisphères n’ont pas la même apparence : dans un cerveau droit typique, la scissure de Sylvius prend un tournant abrupt, un peu en arrière du sillon central, tandis que, dans le cerveau gauche, sa courbure est beaucoup moins prononcée (voir l’article d’Olivier Robain). Il sauterait donc aux yeux de notre étudiant que ces pliures dans les cerveaux droit et gauche d’Einstein sont curieusement similaires. Autre bizarrerie, les coudes des scissures de Sylvius sont situés plus en avant qu’à l’ordinaire : chez Einstein, toutes les deux aboutissent dans le sillon central. (shrink)
A: That's easy: abrupt climate change, the sort of thing where most of the earth returns to ice-age temperatures in just a decade or two, accompanied by a major worldwide drought. Then, centuries later, it flips back just as quickly. This has happened hundreds of times in the past.
Neurons run on electricity 1, producing many impulses each second when they are working hard. These brief (1/1000 second, as rapid as a fast camera shutter), 0.1 volt impulses (though a hundred times smaller if recorded from outside the cell) can be amplified and heard via a loudspeaker. Neurophysiologists routinely listen to neurons via loudspeakers in their laboratories, much as anesthesiologists listen to a patient's heartbeat in the operating room.
I will actually talk mostly about evolutionary processes in the brain as we think about what to say next; I'll be happy to answer questions later, however, about how this system we call consciousness itself evolved on the usual evolutionary time scale of the ice ages.
Antonio R. Damasio , The Feeling of What Happens: Body and Emotion in the Making of Consciousness . This is clearly a must-read book for anyone wanting a neurologist's perspective on one of the greatest of the unsolved mysteries, human consciousness and the ways in which it exceeds that of the other apes. By the author of Descartes' Error.
Psychology's fascination with memory and its imperfections dates back further than we can remember. The first careful experimental studies of memory were published in 1885 by German psychologist Hermann Ebbinghaus, and tens of thousands of memory studies have been conducted since. What has been learned, and what might the future of memory be?
Homo erectus made symmetrical tools. The handaxe is a flattened tear-drop shape, but often with edges sharpened all around. Before we assign their obsession with symmetry to an esthetic judgment, we must consider whether it is possible that the symmetry is simply very pragmatic for one particular use of the many suggested.
Long before signs of staged toolmaking appeared, Homo erectus made symmetrical tools. The handaxe is a flattened tear-drop shape, but often with edges sharpened all around. Before we assign their obsession with symmetry to an aesthetic judgment, we must consider whether it is possible that the symmetry is simply very pragmatic for one particular use in the many suggested.
Treating consciousness as awareness or attention greatly underestimates it, ignoring the temporary levels of organization associated with higher intellectual function (syntax, planning, logic, music). The tasks that require consciousness tend to be the ones that demand a lot of resources. Routine tasks can be handled on the back burner but dealing with ambiguity, groping around offline, generating creative choices, and performing precision movements may temporarily require substantial allocations of neocortex. Here I will attempt to clarify the appropriate levels of explanation (...) (ranging from quantum aspects to association cortex dynamics) and then propose a specific mechanism (consciousness as the current winner of Darwinian copying competitions in cerebral cortex) that seems capable of encompassing the higher intellectual function aspects of consciousness as well as some of the attentional aspects. It includes features such as a coding space appropriate for analogies and a supervisory Darwinian process that can bias the operation of other Darwinian processes. (shrink)