It sometimes seems to me that managing my thoughts (and memories) resembles trying to control a pile of sand grains as they sift through my fingers. Now, new neuroscience research suggests that the analogy is not far off the mark. As reported recently in the New Scientist, it appears that the way in which our brain's neurons connect to each other and communicate is very much like the way a pile of sand behaves, and it is this that bestows on our brain some of its "remarkable powers."
Ten years ago, a Danish physicist, Per Bak, published How Nature Works: The Science of Self-Organized Criticality, a book that I devoured and still refer to (the paperback cover has an image of sand ripples; it's now, sadly, out of print and used editions seem to be going for either $130 or £130!). Bak used sand pile avalanches as an illustration of the ubiquity of scaling or power laws in nature: the frequency (or its logarithm) of occurrence of something is proportional to a measure (often size) of that something multiplied by itself a specific number of times (raised to a certain power, mathematically speaking). Newton’s law of gravity is a power law; the pull of gravity on an object decreases with distance to the object squared. Since it decreases, Newton’s law is an inverse power law—and so is that of sand avalanches: the bigger the event, the more rare it is. But what about the “real world”? Scaling laws show up everywhere—in earthquake magnitudes (each successively larger magnitude on the scale is a multiple of the previous), population distributions, city sizes, the brightness of the Sun, and music (the structure of rock music, classical music, and the spoken word all obey scaling laws). Systems displaying this behaviour exist on the boundary between stability and instability, order and chaos, and Bak coined the term self-organized criticality (SOC)to describe this condition. It would now seem that the brain operates in this apparently precarious realm, but generally manages it rather well - and powerfully.
SOC is definitely not characterised by randomness, and, thankfully, neither are our brains (contrary to occasional appearances). If the connections between the neurons in the brain were random and structureless, then the organ would be instantly overwhelmed by the sheer numbers of useless but energy-sapping events. Nor are the neuronal connections simple - the new work makes the comparison with "small-world" networks, more flexible and powerful than simple networks, but perfectly manageable compared to randomness.
Such a network of connections allows powerful "avalanches" of neuron communication across relevant regions of the brain, often with synchronised "phase-locking" of large groups of neurons firing at the same frequency; these groups operate effectively but independently of other groups. These episodes of phase-locking alternate with periods of much greater disorder, "blizzards" of activity in which significant reorganisation seems to take place. The durations of these phases and the avalanches of firing neurons at different frequencies all seem to fit with the characteristics of SOC, apparently providing the brain with its amazing capacity to process information and with its adaptability. And also a great new excuse - "sorry, that part of my brain's phase-locked right now."
It's worth noting that power laws and SOC are compelling phenomena, but often easier to hypothesise than conclusively demonstrate. Phillip Ball has an excellent discussion of the phenomena and the problem in his new book Flow, one of his new trilogy on nature's patterns (plus lots of other good stuff about granular materials).
This fascinating topic has also been discussed on the Neuronarrative blog which includes a link to a piece on which I can't possibly comment, Why a Woman's Brain is Like an Avalanche, a Landslide, an Earthquake, or a Hurricane.
Oh, and there's also real "brain sand" - small quantities of grit often found in the pineal gland, composed of various calcium minerals, referred to as corpora arenacea, and believed by some swamis to carry holographic rhythms of the body's spatial and temporal existence.