Cornelia Bargmann, professor of neuroscience at Rockefeller University, has done decades of work on the C. elegans nematode to understand the links between genetics, the molecular functions of neural circuits, and behavior. Bargmann and her work have received quite a nice write-up in Nature with the open-access piece Neuroscience: As the worm turns.
I urge you to read all of it, but here’s the piece later in “As the Worm Turns” that caught my eye:
Bargmann suspects that this broad picture of nervous-system organization sends a counter-intuitive message about the evolution of behaviour: that the sensory apparatus in each species is evolving rapidly and is highly divergent, creating a different set of behavioural cues and responses for different animals, whereas the overarching behavioural coordination exerted by neuropeptides remains largely evolutionarily conserved. “This is not the way we [usually] think of things in neuroscience,” says Bargmann. “We always think the simplest part will be the sensory part, and maybe that will be the most conserved part. But in fact the sensory periphery is crazy unconserved between different animals.”
Bargmann views neuropeptides like oxytocin and vasopressin as doing fundamental organizational and regulatory work in the nervous system, in particular bringing together coordinated behaviors. Just as Hox genes help organize development, so too these genes, and their accompanying peptides, help to organize basic behaviors related to survival and reproduction.
The Nature article relates this view to Bargmann’s work on reproduction in C. elegans.
Other research groups had defined, in exquisite detail, the series of discrete behavioural steps that male worms have to complete to succeed in mating (searching for a mate, contact, reverse turns, prodding for the vulva, insertion of spicule, transfer of sperm) as well as the motor neurons and muscles that rapidly fire and contract to drive these steps. But when Bargmann and her team analysed how the absence of nematocin affected each of these steps, they realized that each one remained intact.
“It’s not that he can’t turn. It’s not that he can’t do the backing movement. It’s not that he can’t transfer sperm. It’s that he doesn’t know when to do them,” she says. The neuropeptide, in essence, had a “global organizing role” and gave reproductive behaviour a forward drive. “There’s something that’s a much slower input that says something more like ‘continue’ or ‘move forwards’, sort of providing momentum that’s superimposed on it. So the nervous system is doing both fast and slow information processing, in parallel, to drive the behaviour.”
In other words, the pieces of the puzzles don’t “naturally” fit together; rather, that depends on mechanisms that help organize the pieces into a more robust and coordinated behavior.
I am struck by the parallels of analysis to Paul Griffiths’ examination of emotion, particularly evolutionary explanations of emotions, in the book What Emotions Really Are: The Problem of Psychological Categories (Science and Its Conceptual Foundations series). Griffiths discusses work by Paul Ekman and others on cross-cultural similarities in the expression of certain basic emotions, making a distinction similar to to Bargmann between “sign stimuli” and “releasing mechanisms” that she draws from classic studies in ethology. Griffiths writes:
The input side of a response is the stimuli that cause it. The output side is the response itself – the organism’s behavior. All the experiments I have discussed deal with the output side of emotion. The experiments of Ekman and others show that people in all cultures respond in a similar way to things that frighten them. They do not show that people in all cultures are frightened of the same things. It is an entirely separate question whether the input side of emotion can be explained in evolutionary terms (55).
In other words, Griffiths is arguing that for basic affects (and not more cognitively mediated emotions), there can be relatively stereotypical emotional expressions, as revealed by work by Ekman and others. For a recent review by Ekman, see this 2011 paper, What Is Meant by Calling Emotions Basic; for a really fascinating study, using more advanced experimental methods (with a reductive East vs. West contrast), see this 2012 paper, Facial expressions of emotion are not culturally universal.
In his analysis of emotion, Griffiths is highlighting that the stimuli/sensory side is where a lot of the action happens, whereas on the mechanistic/reactive side, we have some deeply conserved reactions. These can form some of the basic building blocks of emotions, even if cognitively-mediated emotions get reworked. Here I would return to Bargmann’s idea, that once again there are mechanisms that bring all the different elements together, and make new and novel things happen in a coordinated fashion. For two articles that reflects on that, see A functional architecture of the human brain: emerging insights from the science of emotion (2012) and Human Emotions: Universal or Culture-Specific? (2009).
Final thought for the day – and one that I find quite intriguing: Cultures can be conceived as extended sensory systems, in the way that Bargmann describes and where Greg has done foundational work. Cultures have quite a tremendous diversity, even within particular societies. Our systems of symbols, our human sensory periphery, is “crazy unconserved”, as shown quite well in the book Culture and the Senses. Culture gains traction through how it intersects with embodied nervous systems, which have some of their own organizing effects.
Culture as sensory systems, and how that can radically change the sensory inputs that the encultured brain receives.
Photo credit: Cornelia Bargmann. I found the original here.
Nature News: Neuroscience: As the worm turns
Link to the Bargmann Lab. You can access a lot of her papers there.