Order, computation and creativity in biology

Current research into the neuroscience of our visual system tells us that what we see is constructed through the coordinated effect of cells sensitive to particular aspects of a visual scene. Attributes such as motion, form and color are processed in individually specialized areas, along paths that lead to the primary visual cortex, creating what we see. The latest issue of Scientific American reports on research that tells us that one of the ways the brain communicates with itself about sensory data is based on the timing of neuron firings. Terry Sejnowski of the Howard Hughes Medical Institute and Tobi Delbruck at the University of Zurich describe how the synchronization of spikes in the firing of neurons, is a very useful conduit of information.

This is because a group of spikes that fire almost at the same moment can carry much more information than can a comparably sized group that activates in an unsynchronized fashion.

The development of computer models of the nervous system, and new results from experimental data have encouraged new efforts to explore how timing permits communication among neurons.  Each cell in the visual cortex may be activated by a specific physical feature of an object (like color or orientation) but, the authors explain,

When several of these cells switch on at the same time, their combined activation constitutes a suspicious coincidence because it may only occur at a specific time for a unique object.  Apparently the brain takes such synchrony to mean that the signals are worth noting because the odds of such coordination occurring by chance are slim.  (emphasis my own)

The suspicious coincidence idea rests on a judgment of likelihood which I always find to be an intriguing biological process.

This research has helped inspire the development of a new kind of camera that mimics the way parts of he retina encode images for our brain.  Instead of recording the average light intensities of every pixel that covers the visual scene in 40 milliseconds, the new camera senses only the parts of a scene that change when any pixel detects a change in brightness from the recorded value.  This encoding of change gives the camera what the author’s call, “sparse yet information-packed output.”

The key to this idea does seem to be about packing in information and encoding change. But the complexity of the brain’s computation of images seems enormous.  It also happens, for example, that stimulating the region surrounding a particular neuron’s receptive field will affect the precision of the spike timing.  When input from surrounding areas is removed, in order to target the neurons triggered by inputs from a receptive field, it has been observed that precision in the timing of spikes is lost.

Attention itself may be rooted in sequences of synchronized spikes, as these may serve to mark the importance of a particular perception or memory passing through our awareness.

The title of the article is The Language of the Brain, since the subject of the authors’ research is how information gets passed around in the brain, how cells in the brain are communicating.  The transfer of information is becoming a more and more interesting player in modern science.  Some consider it the fundamental stuff of the universe.  And in biology, it participates in building life.  In the context of this article, information, ordered and transmitted, produces our visual experience.

What I find interesting about these more recent findings is that we are beginning to see that the kind of ordering that will create meaning in our experience is as abstract as any mathematical map.  The actions that describe living processes seem to be very complex sets of ordering principles.

In a talk given in 2005, Gregory Chaitin said some interesting things about mathematics, information, complexity and biology.  For example, he said:

….when dealing with complex systems such as those that occur in biology, thinking about information processing is also crucial. As I believe Seth Lloyd said, the most important thing in understanding a complex system is to determine how it represents information and how it processes that information, i.e., what kinds of computations are performed.

The inexhaustible creativity of biological systems does seem to resemble the inexhaustible creativity of mathematics.  And Chaitin finds them linked.  In fact in his concluding statements he offers this:

I believe that this is actually the central question in biology as well as in mathematics, it’s the mystery of creation, of creativity:

“Where do new mathematical and biological ideas come from?”
“How do they emerge?”

Normally one equates a new biological idea with a new species, but in fact every time a child is born, that’s actually a new idea incarnating; it’s reinventing the notion of “human being,” which changes constantly.

He doesn’t try to answer the question, but encourages its consideration.  I hope to write soon about his most recent publication, Proving Darwin: Making Biology Mathematical, where he explores a new way to think about biology and mathematics that highlights the mathematical structures on which the biological world rests.