MBL Lectures

Ritterhof courtyard, Weingut Fitz-Ritter, Bad Dürkheim, Pfalz (founded 1785), watercolor and ink 1984
Ritterhof courtyard, Weingut Fitz-Ritter, Bad Dürkheim, Pfalz (founded 1785), watercolor and ink 1984

We summer in Woods Hole (when our house is not rented, which is most of the summer) and occasionally can go to one of the Friday night public science lectures at the Marine Biological Laboratory, the world-famous research facility in Woods Hole. It is a magnificent privilege to hear and see world-class scientists give beautiful slide lectures on fascinating, cutting-edge science.

On occasion, when the lecture is particularly clear and my brain is fresh, I can go home and write down the gist of the lecture. So since I haven’t posted anything for almost a month, I dug up one of these writeups.

MBL LECTURE 19 JULY 2013

The lecturer, a famous Chinese neuroscientist Mu-Ming Poo, around 70, spoke on neural plasticity.

He started with a much-cited quote by the famous neuroscientist Donald Hebb, to the effect that neurons that fire together wire together, forming more or less permanent circuits – i.e. memories. This is a qualitative statement; Poo and his colleagues sought to explore it quantitatively.

He asked how close together in time the two firings had to be in order to create a memory. He found that the window generally was 40 milliseconds wide, with exceptions in certain animals. He also asked whether the sequence mattered (i.e. what happened if the second neuron fired before the first one), and he found that when the sequence was reversed, exactly the opposite effect occurred: the two neurons became less likely to fire together than previously.

Background: neurons collect inputs from “dendrites”, sum them in complicated ways, and if the incoming stimulus is sufficient, they fire. The electrical signal runs rapidly down the cell’s axon (at about 45 mph), which is the long “wire” that carries the electrical charge from the cell to the other cells to which it is connected, when the cell fires. During development, each neuron seeks out and finds the neurons in the part of the brain to which it “should” be connected. Retinal cells connect via intermediate links to cells in the visual cortex, which in humans is located at the back of the brain (“cortex” is the thin grey-colored coating of neurons on the outer surface of the convoluted brain). Back to the lecture.

To understand why the 40 millisecond window is adaptive, imagine a row of adjacent retinal cells. Each retinal cell connects with a large number of cortical cells in the visual cortex that are adjacent to one another. Call the retinal cells “A” and the cortical cells “B.” This means that each B cell receives inputs from a lot of A cells. So the image created by one A cell is spread out and blurred in the visual cortex.

The goal is to create a sharply focused “map” on the visual cortex that matches the image falling on the retina. To accomplish this, the brain needs to prune away connections between A cells and distant B cells, and strengthen connections between A cells and B cells that are close together.

Imagine a moving spot falling on the retina and hitting one A cell. The A cell will fire and cause all the B cells to which it is connected to fire. Since the B cells fire together within the 40 millisecond window, with the A cell firing first, the connections are strengthened. Now the spot moves to the next A cell (it is moving fast). Again the A cell sets off all the B cells to which it is connected. But some of these will already have fired during the previous 40 millisecond window mentioned above. In those cases, the B cell has fired before the A cell, which weakens the connection. Over many occurrences, this process sharpens the map in the visual cortex.

In the second example of neural plasticity, he explored how mature neurons in a frog’s brain form short term memory by training a string of neurons to fire in sequence. Remarkably, there are instruments that can probe individual neurons in a living animal brain, as well as a brain in a petri dish (in vitro – glass – as opposed to in vivo – life). First the investigators associated neurons in the retina with the corresponding neurons in the visual cortex. Then they passed a moving spot over the retinal cells and noted that the cortical cells lit up one after the other.

After doing this many times, training the cells, they then stimulated just the first retinal cell, which caused the string of cells in the visual cortex to fire one after the other. The neurons had learned that the spot moves on this particular track  (this is short term memory, lasting only about 10 minutes). When they stimulated the last cell in the sequence, nothing happened. They then stimulated the cortical cells directly, and the same thing happened, showing that it was the cortical neurons that learned and not the retinal cells.

In a third demonstration, they found that cells in a zebra-fish could remember the timing between sequential stimuli. This became evident because if they stimulated the cells five times or more, the cells fired one more time after the stimulus was removed at exactly the same interval as the initial sequence. This occurred at intervals up to about 10 seconds. The larger the number of sequential stimuli the more firings occurred after the stimuli stopped, but only up to 3 repetitions. He showed a movie in which the stimuli caused the tail of the fish to twitch to the side (an escape behavior), and sure enough, after the stimuli ceased, the tail twitched twice at exactly the same interval as the stimuli.

Finally, it was believed that only humans and some apes could recognize themselves in a mirror and that monkeys could not. He experimented with Rhesus monkeys. If you paint a spot on the monkey’s face (or even shine a light at the spot so he doesn’t feel anything) he ignores it when looking in the mirror, showing that he is not aware that the image is of himself.

So Poo did a clever thing: he applied the spot in a way that irritated the same location on the monkey’s face, which caused the monkey to reach up and touch the spot. By doing this many times, he trained the monkey to associate the two spots and thereby become aware that the image in the mirror was himself. Once they learned this (2 out of 3 could do so) they took advantage of their new skill by examining parts of themselves that they couldn’t see (their bottoms). It was hilarious to see the contortions they went into in order to inspect their nether regions.

Ritterhof courtyard, contemporary photo
Ritterhof courtyard, contemporary photo

Symbolism – Part One

Lago de Garda, 1968
Lago de Garda, 1968

The subject of symbolism has intrigued me for 60 years. I am not talking about symbols like the Christian cross or a national flag, but about the symbolism of language and mathematics, and how this applies to art.

I was strongly influenced by two books by the aesthetician Suzanne K. Langer, “Feeling and Form” and “Philosophy in a New Key,” both of which were published around the time I was in college. She had an unusually practical mind, and at the same time had a deep understanding of all the (fine) arts, not just easel painting, so often the sole focus of aestheticians.

Langer developed her aesthetic theory out of earlier work on symbolic logic, a field developed by the great logicians of the late 19th and early 20th Centuries and one very fresh and vital at the time she wrote. She was strongly influenced by Alfred North Whitehead, who along with Bertrand Russell prepared much of the foundation for symbolic logic. Both symbolic logic and mathematics are precise formalizations of discursive language (the language of statements), and language is universally acknowledged to be the quintessential example of symbolism (Langer’s lucid writing made her little book ”Symbolic Logic” close to a page-turner).

Symbols point to things: naming is of their essence. When Langer extended to art the language-based concept of symbolic representation, she naturally looked for something concrete that the art symbol could represent. Her solution was to postulate that the art symbol pointed to the form of the life of feeling, something she saw as complex patterns of rising and falling tensions, so complex as to be forever impossible to depict using ordinary language. Only the art symbol could present the life of feeling in a way that made it understandable.

I believe that Langer is correct that a work of art symbolizes patterns of feelings that occur in the lives of people, but I believe she made a mistake when she characterized these patterns as forms. I am an architect, and the word immediately conjures up an image of the forms into which concrete is poured. Forms are rigid, while the patterns of felt experience are fluid and difficult to pin down.

By her insistence that a work of art symbolized some kind of form, Langer created a problem for herself: how do you decipher the work of art to reveal the symbolized form? Langer invoked intuition, a famously vague term, and argued that the work of art must be intuitively seen as a whole, all at once (of course in music, dance, drama and literature the work unfolds over time, but we can still imagine the work as a whole after it is completely presented or read).

The form to which the symbol refers is the meaning of the work of art; in her later work, Langer substituted “import” and especially “significant form” for “meaning,” but the sense was the same: the art symbol referred to some kind of pattern representing the ebb and flow of feelings. (To confuse matters, the expression “significant form” was used by art critic Clive Bell in a famous 1913 article “Art and Significant Form” at http://www.denisdutton.com/bell.htm. Langer strongly disagreed with Bell’s ideas, as do I, but the confusion of terms did not help her argument.)

The problem of how to decipher the underlying form to which the symbol refers was clarified for me through an article I found on the web by chance. It was written by Berel Lang, who I find is a philosopher at Wesleyan University, and is entitled “Langer’s Arabesque and the Collapse of the Symbol” (see http://www.anthonyflood.com/langlanger.htm). In this essay, Lang argues that it is not possible to distinguish the art symbol from what Langer argued that it represents, the form of the life of feeling. She notes that this problem was raised in a review of Langer’s seminal book “Philosophy in a New Key” by philosopher Ernest Nagel, and that Langer took his criticism seriously and tried to resolve the problem in her later writings, in Lang’s view without success.

Summarizing Lang’s critique, a work of art is not a symbol because instead of referring to an objective content, a meaning, the work is itself the content. There is no symbolism because it is impossible to abstract the symbolic form from the details of the work. Here Langer herself makes this point:

But a work of art does not point us to a meaning beyond its own presence.  What is expressed cannot be grasped apart from the sensuous or poetic form that expresses it. In a work of art we have the direct presentation of a feeling, not a sign that points to it.” (Principles of Art, pp.133-34)

Put another way, the patterns that one detects in a work of art are far too complex to be perceived as a single form, no matter how elaborate. Think about how you take in a work of art: at each viewing or hearing, it always takes time, and all art lovers comment that you can come back to a familiar painting or piece of music hundreds of times and never cease to discover something new. How, if we perceive the whole work as a single form (a gestalt, as Langer would put it), can we continue to reconstruct it as we experience it over time? Would we not each time find a new overall form?

If all the intricate details of a work are cast into the form, it must be a very flexible form indeed to accommodate the reinterpretations by each perceiver, not to mention the dramatic reinterpretations that take place as cultural norms change over the decades – so flexible as to lose its character as a form. And Nagel’s and Lang’s telling criticism also applies, that the form is so intricately trapped in the actuality of the work of art that you cannot separate the work from its import. The work, as the quote from Langer above suggests, is the import.

The solution to this dilemma, I maintain, is that the pattern and flow of human feeling cannot be symbolized as a form, a conceptual object, something that is remembered in the same way that we remember objective things. Instead, the art symbol needs to be thought of as a process rather than an objective thing, as a verb instead of a noun. What this means is not obvious, but I will try to make my idea clear in subsequent essays in this series.

Essay I on Function: Does Reality Have a Purpose?

orrery

Leaving aside ceremonial dinners and mathematical expressions, “function” is a synonym for purpose, or is the role something plays, whether by itself or as part of a larger assembly. So if we substitute “role or purpose” for “function” we will not be far off. My ultimate goal is to explore the concept of function in the context of architecture, but in this first essay, I want to explore function in the context of nature.

Does the sun or a rock or the atmosphere play a role or have a purpose? Well, if you believe that this land was made for you and me, then the sun functions to light and heat us, rock provides us with building material, and the atmosphere delivers oxygen to breathe and protects us from ultraviolet radiation. If you adopt the Enlightenment notion of a clockwork universe, then each has a function as part of God’s grand clock that he wound up and let run according to the Newton’s laws. Einstein had such a view of God; he was certain God made orderly, logical laws, and didn’t at all like the uncertainty that is fundamental to the theory of quantum mechanics he helped formulate.

A modern scientific point of view rejects such ideas. Stars and rocks and gases are things that emerge naturally, given the laws of physics. You can trace cause and effect step by step back to the big bang, beyond which for the moment we are blind. If you want to interject a deity, you can be a Deist and have God set off the Big Bang or design the laws of physics, but I don’t think this kind of deity would satisfy many people’s spiritual needs, although it seemed to satisfy Einstein. For today’s science, there is no one behind the scenes deciding what comes next. Arguments on the subject continue unabated; I stake my claim on the side of materialism.

A role or purpose needs context. To define the role or purpose of a rock, you need to have some kind of goal, for example, making a rock wall. When you set a goal, everything in the universe suddenly has a role or purpose relative to the goal. Rocks, yourself, tools, a plan, and a location all have essential functions, while the Andromeda galaxy takes no part, and the sun functions to keep you warm while you work and to provide light. Invent a goal, and function follows; if there is no goal, nothing has a function.

But does this line of thinking apply to life? It seems natural to think of one’s heart as having an essential function, doing its part to keep you alive so you can reproduce. Richard Dawkins argued in “The Selfish Gene” that it is your genes that have the goal, and you are just the vehicle they use to make more of themselves (as a chicken is an egg’s way to make another egg, or a scholar is a library’s way to make another library).

I maintain that we have invented the goal. Genes don’t have goals, they are just doing their thing, even if it seems to us that they “want” to persist into the next generation. It is a compelling metaphor, but it is just that: a gene is the pathway through time taken by the atoms that make up the gene, a part of the unfolding evolution of our universe.

The injection of purpose, intention, role, agency, goals and the like into our thinking about things is probably essential for understanding. We seem compelled to personify things, to think of them as if they were people, applying our hyper-developed social skills as a tool for understanding. In this way, we endow objects and events with an essence, a thingness that helps us makes sense of the world.

This is a highly useful tendency (which is no doubt why it evolved), since on our planet, nature clumps into identifiable objects and events. But our planet is highly unusual: very little of nature clumps into identifiable objects and events, important as these are to us. Most of nature consists of undifferentiated aggregations of dust, gas, plasmas, particles and fields. Only a few percent of the mass of the universe is in the form of what we call matter. But we didn’t know that when our mental equipment evolved. It was tuned to a pre-scientific world.

Nature doesn’t have a purpose, and being a part of nature, neither do you. This idea creates cognitive dissonance, so we seek meaning and purpose in our lives: it’s the only way we can avoid existential despair. But when we try to find out how nature actually works, we need temporarily to abandon our search for meaning and purpose and accept reality as it presents itself.

Life in a Bubble

Norwalk boatyard

I see four fundamental characteristics of all living things: they process resources from the environment and return waste products (i.e. they metabolize); they reproduce; they evolve; and (the focus of this essay) they are separated from their environment by some kind of membrane.

The origin of the chemical processes that make life possible, and the place or places of their origin, are the subject of active research. But all agree that these processes need to be concentrated so they don’t dissipate into the outer environment. Even if life processes can arise in an open environment that is rich with the necessary energy and chemical resources, evolution is not possible until there is some kind of “it” to evolve.

The key component required to contain life is a “lipid bilayer” that forms a membrane. This remarkable structure surrounds each living cell. It is formed of a double layer of molecules packed side by side, with other molecules embedded in the membrane that act as gates for passing chemicals through the membrane. You can learn about them in the Wikipedia article on lipid bilayers at https://en.wikipedia.org/wiki/Lipid_bilayer.

Because of this need to be separated from its outer environment, a cell is its own mini-universe. Whatever behavior it exhibits results from processes occurring within that universe, informed by information and chemicals from outside. This in turn requires the cell to form a model of what is both inside and outside its boundary.

Information and chemicals pass through the membrane in both directions, informing the cell of what is going on outside its membrane; internal machinery tracks what is going on within the cell. Each cell is specialized to process only certain kinds of chemicals and information.

Assemblies of specialized cells can process a great deal more information and chemicals than a single cell. A single-cell bacterium can configure itself as a lens to focus light on the inside of its membrane, allowing it to move toward the light. But a human’s eye and brain can form incredibly more elaborate models of what is visible.

Yet the principle is that same: only certain kinds of information and chemicals can get through the barriers surrounding individual cells and the vast collections of cells forming a complex organism, and only certain processes within the cell are monitored. It is impossible for a living organism to form a perfect model of itself or its outer environment.

Each organism’s model of its self in its environment is created out of a rich and constantly changing stew of inheritance and experience – “nature versus nurture” is entirely void of meaning. The model is volatile; what astonishes is not its malleability, but its apparent stability. If a human brain decides every tenth of a second what its brain-body is to do next, which seems to be approximately the case, the model created by a person my age (80) must have been updated 25 billion times through exceedingly complex neural transformations. This is either a miracle, or we are kidding ourselves regarding the stability of the model.

I leave you with two take-aways. One is that indeed our sense of self and our memories are transient and inaccurate, something science is probing with unsettling consequences. The other is that the organism must have some sort of criteria to decide on the appropriate next behavior. Without such criteria, no consistent model could be formed, and therefore no consistent behavior.

I feel that not enough attention is being paid to the subtleties of these criteria, and that art is a way of laying bare at least some of them. This leads me to believe that art can be a window into the workings of human brains, a subject I will pursue in other essays.