The Pentagon of Neuroscience — An Infographic/Listicle for Understanding the Neuroculture

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brainzNeuroscience has hit the big time. Every day, popular newspapers, websites and blogs offer up a heady stew of brain-related self-help (neuro-snake oil?) and gee wiz science reporting (neuro-wow?). Some scientists and journalists — perhaps caught up in the neuro-fervor — throw caution to the wind, promising imminent brain-based answers to the kinds of questions that probably predate civilization itself: What is the nature of mind? Why do we feel the way we do? Does each person have a fundamental essence? How can we avoid pain and suffering, and discover joy, creativity, and interpersonal harmony?

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Could the brain be a radio for receiving consciousness?

 

bradio.pngHere’s an answer I wrote a while ago to the following question:

 Is there any conclusive proof that the brain produces consciousness? What rules out the case that brain acts as receptor antennae for consciousness?

This is actually a fun question! Taken in the right spirit, it can be a good way to learn about what science is, and also what the limitations of science are.

What would count as proof that the brain produces consciousness? In the future we might try an experiment like this: we build an artificial brain. Let’s say we can all agree that it exhibits consciousness (leaving aside for now the extremely tricky question of what the word “consciousness” even means). Would this prove that the brain “produced” consciousness? Maybe.

But maybe the brain-as-antenna crowd would claim that their favored hypothesis hasn’t been ruled out. After all, if consciousness is somehow floating in the ether, how could we be sure that our artificial brain wasn’t just tuned to the ‘consciousness frequency’, like a gooey pink radio?

We’d need to construct some kind of cosmic-consciousness-blocking material, and then line the walls of our laboratory with it. Then we’d be able to decide on the question one way or the other! If our artificial brain showed no signs of consciousness, the antenna crowd could claim victory, and say “See!, you need cosmic consciousness in order to get biological consciousness! Consciousness is like yogurt: if you have some you can always make more.”

Constructing an artificial brain is hard enough. We have no idea if we will ever have enough understanding of neuroscience to do so. But constructing a consciousness-shield is straight out of science fiction, and just sounds absurd.


In any case, there’s actually a much bigger problem facing any scientific approach to consciousness. No one has any idea what consciousness is. Sure, there’s plenty of philosophical speculation and mystical musing, but in my opinion there’s almost nothing solid from a scientific perspective.

Here’s why I think science cannot ever address the subject of consciousness: science studies objectively observable phenomena, whereas the most crucial aspect of consciousness is only subjectively observable. What are objectively observable phenomena? They’re the ones that more than one person can observe and communicate about. Through communication, they can agree on their properties. So the word “inter-subjective” is a pretty good synonym for “objective”. Objectivity is what can be agreed upon by multiple subjective perspectives.

So the sun is a pretty objective feature of reality. We can point to it, talk about it, and make measurements about it that can be corroborated by independent groups of people.

But consciousness is not objective in the same way that the sun is. I do not observe anyone else’s consciousness. All I observe are physical perceptions: the sights and sounds and smells and textures associated with bodies. From these perceptions I build up a picture of the behavior of an organism, and from the behavior I infer things about the organism’s state of mind or consciousness. The only consciousness I have direct experience of is my own. And even my own consciousness is mysterious. I do not necessarily observe my consciousness. I observe with my consciousness. Consciousness is the medium for observation, but it not necessarily a target of observation.

Clearly all the scientists who claim to study consciousness would disagree with my perspective. Their approach is to take some observable phenomenon — either behavior or some neural signal — and define it as the hallmark of consciousness. There’s nothing wrong with defining consciousness as you see fit, but you can never be completely sure if your explicit definition lines up with all your intuitions about the boundary between conscious and non-conscious.

For example, Information Integration Theory (IIT) proposes that there is a quantity called phi (which at the current historical juncture appears impossible to compute) that captures the degree of consciousness in a system. Armed with this kind of theory, it is possible to argue* that extended, abstract entities — such as the United States as a whole — are conscious. Some people like this generous approach. Why lock up consciousness in skulls? The proponents of IIT have gone so far as to claim that they are okay with panpsychism: the idea that everything from quarks to quasars is at least a little bit conscious.

If everything is conscious, then the question of whether the brain “produces” consciousness — or the universe “transmits” it — becomes moot. There is no ‘problem of consciousness’, since it’s already everywhere.

Neuroscientists like me will probably still have jobs even if society decides to bite the panpsychist bullet. We have other things to worry about beyond consciousness. In fact many of us are actively uninterested in talking about consciousness — we call it “the c-word”. We’re happy to just study behavior in all its objectively observable glory, and hope to understand how the brain produces that. Whether and where exactly consciousness arises during this process seems like a question we can leave unanswered for a generation or two (while enjoying the various after-work conversations about it, of course!). For now we can focus on how our gooey pink radios give rise to language, or memory, or emotion, or even the basic control of muscles.


Notes

* Philosopher Eric Schwitzgebel wrote a very interesting essay entitled ‘If Materialism Is True, the United States Is Probably Conscious’.

More on the dreaded c-word!

Here are some consciousness-related answers that may be of interest:

How does the brain create consciousness?

What percent chance is there that whole brain emulation or mind uploading to a neural prosthetic will be feasible by 2048? [I’ve posted this one on this blog too.]

What are some of the current neuroscientific theories of consciousness?

What do neuroscientists think of the philosopher David Chalmers?

Is anything real beyond our own perspective?

What is the currently best scientific answer to the psycho-physical (body-mind) question?

Why an organism is not a “machine”

I just came across a nice article explaining why the metaphor of organism as machine is misleading and unhelpful.

The machine conception of the organism in development and evolution: A critical analysis

This excerpt makes a key point:

“Although both organisms and machines operate towards the attainment of particular ends that is, both are purposive systems the former are intrinsically purposive whereas the latter are extrinsically purposive. A machine is extrinsically purposive in the sense that it works towards an end that is external to itself; that is, it does not serve its own interests but those of its maker or user. An organism, on the other hand, is intrinsically purposive in the sense that its activities are directed towards the maintenance of its own organization; that is, it acts on its own behalf.”

In this section the author explains how the software/hardware idea found its way into developmental biology.

“The situation changed considerably in the mid-twentieth century with the advent of modern computing and the introduction of the conceptual distinction between software and hardware. This theoretical innovation enabled the construction of a new kind of machine, the computer, which contains algorithmic sequences of coded instructions or programs that are executed by a central processing unit. In a computer, the software is totally independent from the hardware that runs it. A program can be transferred from one computer and run in another. Moreover, the execution of a program is always carried out in exactly the same fashion, regardless of the number of times it is run and of the hardware that runs it. The computer is thus a machine with Cartesian and Laplacian overtones. It is Cartesian because the software/hardware distinction echoes the soul/body dualism: the computer has an immaterial ‘soul’ (the software) that governs the operations of a material ‘body’ (the hardware). And it is Laplacian because the execution of a program is completely deterministic and fully predictable, at least in principle. These and other features made the computer a very attractive theoretical model for those concerned with elucidating the role of genes in development in the early days of molecular biology.”

The machine conception of the organism in development and evolution: A critical analysis

I’ve actually criticized the genetic program metaphor myself, in the following 3QD essay:

3quarksdaily: How informative is the concept of biological information?

____

Image source: Digesting Duck – Wikipedia

“Conscious realism”: a new way to think about reality (or the lack thereof?)

Venn

Interesting interview in the Atlantic with cognitive scientist Donald D. Hoffman:

The Case Against Reality

“I call it conscious realism: Objective reality is just conscious agents, just points of view. Interestingly, I can take two conscious agents and have them interact, and the mathematical structure of that interaction also satisfies the definition of a conscious agent. This mathematics is telling me something. I can take two minds, and they can generate a new, unified single mind. Here’s a concrete example. We have two hemispheres in our brain. But when you do a split-brain operation, a complete transection of the corpus callosum, you get clear evidence of two separate consciousnesses. Before that slicing happened, it seemed there was a single unified consciousness. So it’s not implausible that there is a single conscious agent. And yet it’s also the case that there are two conscious agents there, and you can see that when they’re split. I didn’t expect that, the mathematics forced me to recognize this. It suggests that I can take separate observers, put them together and create new observers, and keep doing this ad infinitum. It’s conscious agents all the way down.”

[…]

Here’s the striking thing about that. I can pull the W out of the model and stick a conscious agent in its place and get a circuit of conscious agents. In fact, you can have whole networks of arbitrary complexity. And that’s the world.

[…]

“As a conscious realist, I am postulating conscious experiences as ontological primitives, the most basic ingredients of the world. I’m claiming that experiences are the real coin of the realm. The experiences of everyday life—my real feeling of a headache, my real taste of chocolate—that really is the ultimate nature of reality.”

I don’t agree with everything in the article (especially the quantum stuff) but I think many people interested in consciousness and metaphysics will find plenty of food for thought here:

The Case Against Reality

Also, the “conscious agents all the way down” is the exact position I was criticizing in a recent 3QD essay:

3quarksdaily: Persons all the way down: On viewing the scientific conception of the self from the inside out

The diagram above is from a science fiction story I was working on, back when I was a callow youth. It closely related to the idea of a network of conscious agents. Here’s another ‘version’ of it.

TriHead

Not sure why I made it look so morbid. 🙂

What’s the deal with “brainwaves”?

I was asked this question on Quora recently:

The brain has neurons which approximately perform function evaluations on their inputs. How would this cause brainwaves of different frequencies? Why are they related to the level of arousal in the brain (sleep/meditation etc)?
Is there some sort of “controller” that synchronizes the firing?

Here’s my answer:

This is an excellent set of questions!

Short(ish) answers:

1. Why does the brain have waves?

There is no consensus on their functional role, but some researchers think oscillations facilitate flexible coordination and communication among neurons.

2. The brain has neurons which can approximately be understood as performing function evaluations on their inputs, though the actual mechanisms are more complex. But how would this cause brainwaves of different frequencies to exist?

There are several possible mechanisms that can cause the input-output transformation of neurons to lead to oscillations when the neurons are connected in networks. Furthermore, neurons themselves often have intrinsic oscillatory properties (other than basic spiking), such as rebound excitation following inhibition.

3. Is there some sort of “controller” that synchronizes the firing?

There is no single controller causing synchronization or oscillation — there are actually several local and meso-scale mechanisms, often involving inhibitory interneurons*. (Note that synchronization and oscillation are distinct phenomena. You can have synchronized non-oscillatory processes, and oscillations that are not synch-ed.)


Long answers:

What are brain waves?

Even though we use the generic term ‘brain waves’, there are actually a variety of distinct mechanisms at work that lead to rhythmic behavior in different frequency bands. And in many cases we still don’t know what the mechanism is that causes a particular brain rhythm, or can’t decide among multiple plausible mechanisms.

Even though I’m a computational neuroscientist, I find it hard to conceptually integrate all the different perspectives on neural activity. But I’ve been thinking about this a lot lately, so here goes!

The most fine-grained perspective involves measuring the voltage of an individual neuron. This voltage can change in various ways. The most well known is the spike, or action potential. Spikes travel efficiently down the axon, and typically cause vesicle release in the synapse, which allows neurotransmitters to affect the post-synaptic neuron. But spiking is not the only kind of voltage fluctuation in a neuron. There are also ‘sub-threshold’ fluctuations, which are often oscillatory. These oscillations may represent oscillatory and/or synchronized inputs to the neuron that are insufficient to cause spiking. Single-electrode and multi-electrode recordings of cell activities can pick up both the sub-threshold fluctuations and the supra-threshold spiking.

Brain waves were first discovered through electroencephalography (EEG), which has been around for a century or so. Unlike electrode-based recording, EEG is non-invasive (meaning we don’t have to poke any sharp objects into anyone). But the main drawback of EEG is that it is a coarse-grained measure of neural activity. It measures the cumulative electrical activity of very large numbers of neurons.

It’s also important to realize that EEG essentially measures the synchronized inputs to a brain area, rather than the firing outputs. This has to do with the biophysics of the technique, which you can read about in more detail in my answer to the question “Are EEG voltages related to the average action potential firing rate of the cortical neurons near the electrode or are the voltages the average of low frequency voltage oscillations of the neurons?” EEG effectively measures the degree of synchronization of neurons that send inputs to the brain region directly underneath the EEG electrode.

Other techniques that can pick up oscillatory activity include magnetoencephalography (MEG) and Electrocorticography (ECoG).

Brain rhythms tend to be grouped into frequency bands. The most well-studied bands have been assigned Greek letters that reflect the order of their discovery. Here’s a list of the bands, along with their frequency ranges in hertz (Hz). I’ve linked to their Wikipedia pages, when available.

  • Slow 3: 0.025-0.067
  • Slow 2: 0.200-0.500
  • Slow 1: 0.500-1.429
  • Delta: 1 – 4
  • Theta: 4 – 8
  • Mu and SMR: 7.5 – 12.5
  • Alpha: 9 – 13
  • Beta: 14 – 30
  • Gamma: 30 – 80
  • Fast: 80 – 200
  • Ultrafast: 200 – 600.000

What are the mechanisms that cause brain waves?

Through a combination of experimental techniques and theoretical approaches, neuroscientists have come up with several mechanisms that can explain oscillations in various frequency bands. In many cases it is not clear which mechanism is in fact at work.

I can’t really go though all the theoretical mechanisms that have been proposed, but I can talk about one that is very intuitive to understand: the PING model of Gamma activity. This model, developed by Nancy Kopell, has been widely corroborated by experimental work. (There may be different types of Gamma, however, and not all of them are covered by this model.)

PING stands for pyramidal-interneuronal network gamma, and involves interaction between excitatory cells and inhibitory cells, resulting in the creation of a nonlinear oscillator. The following diagram [1] illustrates the mechanism quite nicely:

The E(xcitatory) cells excite the I(nhibitory) cells, which in turn inhibit the same excitatory cells. This results in an oscillation whose frequency is determined by the rate of integration of the I-cells. Fast I-cells can produce fast rhythms.

There are plenty of other mechanisms for oscillations, but the PING model will give you a flavor of how they can be constructed. Arousal levels can by incorporated into models by incorporating factors such as neurotransmitter level fluctuations, and the effects of such fluctuation on the sub-threshold and/or firing properties of neurons. Changes in behavioral state can also change the inputs to various brain areas from the body and from the outside world, which in turn will affect the network activity mode. This is a vast topic for theory and computational modeling.

What is the purpose of brain waves?

This is actually still a very contentious issue. The field of neuroscience can be broadly divided into researchers who care about oscillations, and researchers who don’t. People who don’t care about oscillations are more interested in the firing activities and the input-output transformations of neurons and networks. Some of these researcher even go so far as to claim that oscillations are ‘epiphenomena’ — mere side-effects of the ‘main’ neural processes, such as integration, contrast enhancement, switching, resetting, and so on. I was broadly in the ‘skeptics’ category for many years, but I’ve started to realized that oscillations can’t be ignored. The power in various frequency bands often correlates strongly with behavioral measures, so oscillations are at the very least telling us something important about how the brain works.

One theory of brain waves that is becoming popular is the idea of coordination, or “communication through coherence”. The idea is that neurons which are in the same sub-threshold oscillatory state are more likely to be able to communicate spikes with each other. This is shown diagrammatically below [2]. The black neuron is out of phase with the blue neuron, so it communicates with the blue neuron less effectively that the red neuron.

As I mentioned earlier, synchrony and rhythmicity are completely distinct. Presumably you can get coherence without any rhythms, just by synchronizing groups of neurons. But maybe rhythmic behavior is more easy to control.

I’ve only scratched the surface of this topic. There is definitely a lot more to the story of brain waves, and in the coming decades hopefully researchers will work towards an integrated theory.


Images from:

[1] Cortical enlightenment: are attentional gamma oscillations driven by ING or PING? | pdf

[2] A mechanism for cognitive dynamics: neuronal communication through neuronal coherence. | pdf


Further reading

* What do inhibitory neurons do in the brain? by Yohan John on Neurologism

Are EEG voltages related to the average action potential firing rate of the cortical neurons near the electrode or are the voltages the average of low frequency voltage oscillations of the neurons?

What changes occur in the brain when we close our eyes?

Is working memory associated with synchronization between oscillations in the prefrontal cortex and oscillations elsewhere in the brain? (e.g. parietal cortex)?

Medical Imaging: How strong is the correlation between a fMRI and an EEG?

Does the membrane time constant of neurons put a constraint on the frequencies seen in neuronal brain waves?

The Emotional Gatekeeper — a computational model of emotional attention

My paper is finally out in PLoS Computational Biology. It’s an open access journal, so everyone can read it:

The Emotional Gatekeeper: A Computational Model of Attentional Selection and Suppression through the Pathway from the Amygdala to the Inhibitory Thalamic Reticular Nucleus

Here’s the Author Summary, which is a simplified version of the abstract:

“Emotional experiences grab our attention. Information about the emotional significance of events helps individuals weigh opportunities and dangers to guide goal-directed behavior, but may also lead to irrational decisions when the stakes are perceived to be high. Which neural circuits underlie these contrasting outcomes? A recently discovered pathway links the amygdala—a key center of the emotional system—with the inhibitory thalamic reticular nucleus (TRN) that filters information between the thalamus and cortex. We developed a neural network model—the Emotional Gatekeeper—that demonstrates how the newly discovered pathway from the amygdala to TRN highlights relevant information to help assess threats and opportunities. The model also shows how the amygdala-TRN pathway can lead normal individuals to discount neutral but useful information in highly charged emotional situations, and predicts that disruption of specific nodes in this circuit underlies distinct psychiatric disorders.”

journal.pcbi.1004722.g001.PNG

Here’s the full citation:

John YJ, Zikopoulos B, Bullock D, Barbas H (2016) The Emotional Gatekeeper: A Computational Model of Attentional Selection and Suppression through the Pathway from the Amygdala to the Inhibitory Thalamic Reticular Nucleus. PLoS Comput Biol 12(2): e1004722. doi:10.1371/journal.pcbi.1004722

Is it possible for the Internet to one day gain consciousness?

A recent Quora answer I wrote:

Sometimes I wonder if Quora bots are conscious! 🙂
I often think about whether the internet could become sentient… and also whether it is already! But the most important question is this: how would we tell one way or the other? Perhaps each of us is like a neuron in the internet’s hive brain.
Neurons and brains are separated by a gulf of scale, structure, and complexity. How could a neuron ‘know’ that the brain it is part of is conscious? How could a brain know if a neuron (or group of neurons) is conscious? It may be an unbridgeable gap. And the same sort of gap may exist between humans and the internet. To paraphrase Wittgenstein, if the internet could talk we would not understand it.
In any case, the internet doesn’t even have a ‘mouth’ or a central communication device. How do we decide what the internet is ‘saying’? I could imagine a future in which ‘analysts’ read into the internet’s dynamic trajectories in the way astrologers read into the stars’ trajectories.
Sometimes I think of consciousness as an irreducibly social phenomenon. Consciousness may be the ‘fire’ produced by the ‘friction’ between different intelligent agents that each have partial knowledge of the world. Perhaps the test of whether the internet is conscious involves encountering an alien internet. Perhaps when civilizations from two different planets interact, their ‘planetary consciousnesses’ (or internets) interact in a way that their inhabitants only have a dim awareness of.

 

Is it possible for the Internet to one day gain consciousness?

Can science account for taste?

I was asked the question “From a scientific point of view, how are our tastes created?” Here’s my answer.

“There’s no accounting for taste!”

Typically we explain taste — in food, music, movies, art —  in terms of culture, upbringing, and sheer chance. In recent years there have been several attempts to explain taste from biological perspectives: either neuroscience or evolutionary psychology. In my opinion these types of explanations are vague enough to always sound true, but they rarely contain enough detail to account for the specific tastes of individuals or groups. Still, there’s much food for thought in these scientific proto-theories of taste and aesthetics.

[An early aesthete?]

Let’s look at the evolutionary approach first. An evolutionary explanation of taste assumes that human preferences arise from natural selection. We like salt and sugar and fat, according to this logic, because it was beneficial for our ancestors to seek out foods with these tastes. We like landscape scenes involving greenery and water bodies because such landscapes were promising environments for our wandering ancestors. This line of thinking is true as far as it goes, but it doesn’t go that far. After all, there are plenty of people who don’t much care for deep-fried salty-sweet foods. And many people who take art seriously quickly tire of clichéd landscape paintings.

[Are you a homo sapien? They you must love this. 😉 ]

Evolutionary psychology can provide broad explanations for why humans as a species tend to like certain things more than others, but it really provides us with no map for navigating differences in taste between individuals and groups. (These obvious, glaring limitations of evolutionary psychology have not prevented the emergence of a cottage industry of pop science books that explain everything humans do as consequences of the incidents and accidents that befell our progenitor apes on the savannahs of Africa.)

Explanations involving the neural and cognitive sciences get closer to what we are really after — an explanation of differences in taste — but not by much. Neuroscientific explanations are essentially half way between cultural theories and evolutionary theories. We like things because the ‘pleasure centers’ in our brains ‘light up’ when we encounter them. And the pleasure centers are shaped by experience (on the time scale of a person’s life), and by natural selection (on the time scale of the species). Whatever we inherit because of natural selection is presumably common to all humans, so differences in taste must be traced to differences in experience, which become manifest in the brain as differences in neural connectivity and activity. If your parents played the Beatles for you as a child, and conveyed their pleasure to you, then associative learning might cause the synapses in your brain that link sound patterns with emotional reactions to be gradually modified, so that playing ‘Hey Jude’ now triggers a cascade of neural events that generate the subjective feeling of enjoyment.

[What’s not to love about the Beatles?]

But there is so much more to the story of enjoyment. Not everyone likes their parents’ music. In English-speaking countries there is a decades-old stereotype of the teenager who seeks out music to piss off his or her parents. And many of us have a friend who insists on listening to music that no one else seems to have heard of. What is the neural basis of this fascinating phenomenon?

We must now enter extremely speculative territory. One of the most thought-provoking ‘theories’ of aesthetics that I have come across was proposed by a machine learning researcher named Jürgen Schmidhuber. He has a provocative way of summing up his theory: Interestingness is the first derivative of beauty.

What he means is that we are not simply drawn to things that are beautiful or pleasurable. We are also drawn to things that are interesting: things that somehow intrigue us and capture our attention. These things, according to Schmidhuber, entice us with the possibility of enhancing our categories of experience. In his framework, humans and animals are constantly seeking to understand the environment, and in order to do this, they must be drawn to the edge of what they already know. Experiences that are already fully understood offer no opportunity for new learning.  Experiences that are completely beyond comprehension are similarly useless. But experiences that are in the sweet spot of interestingness are not boringly familiar — but they are not bafflingly alien either. By seeking out experiences in this ‘border territory’, we expand our horizons, gaining a new understanding of the world.

For example, I’m a Beatles fan, but I don’t listen to the Beatles that often. I am, however, intrigued by music that is ‘Beatlesque’: such music can lead me in new directions, and also reflect back on the Beatles, giving me a deeper appreciation of their music.

The basic intuition of this theory is well-supported by research in animals and humans. Animals all have some baseline level of curiosity. Lab rats will thoroughly investigate a new object introduced into their cages. Novelty seems to have a gravitational pull for organisms.

But again, there are differences even in this tendency. Some people are perfectly content to eat the same foods over and over again, or listen to the same songs or artists. At the other extreme we find the freaks, the hipsters, the critics, the obsessives, and all the assorted avant garde seekers of “the Shock of the New”.

Linking back to evolutionary speculation, all we can really say is that even the desire for novelty is a variable trait in human populations. (Actually it’s multiple traits: I am far more adventurous when it comes to music than food.) Perhaps a healthy society needs its ‘conservatives’ and its ‘progressives’ in the domain of taste and aesthetic experience. Group selection  — natural selection operating on tribes, societies and cultures — is still somewhat controversial in mainstream evolutionary biology, so to go any further in our theories of taste we have to be willing to wander on the wild fringes of scientific thought…

… those fringes are, after all, where everything interesting happens! 🙂

For more speculation on interestingness, beauty, and the pull of the not-completely-familiar, see this essay I wrote. I go into more detail about Schmidhuber’s theory about interestingness:
From Cell Membranes to Computational Aesthetics: On the Importance of Boundaries in Life and Art

This has nothing to do with science, but I find this David Mitchell video on taste very funny:

After writing this answer I realized that the questioner was most probably asking about gustation — meaning, the sense of taste. Oh well.