Crick on consciouness
Astonishing Hypothesis: The Scientific Search for the Soul by Francis Crick
My rating: 5 of 5 stars
After reading Christof Koch’s book, it was natural for me to pick up Crick’s book on the same topic.
Of his mentor, Koch had the following to say:
“They used to say that in his prime, Arnold Schwarzenegger had muscles in places where people didn’t have places. Crick was to scientific creativity what Arnold was to body building.”
The astonishing hypothesis is a strong affirmation of the (now) long held belief that minds follow from brains. As for consciousness itself, the assertion is straightforward - there’s a bunch of facts about the external world that we are consciously aware of. On the other hand experimental data shows a breathtaking amount of brain activity that passes beneath the hood of conscious experience. How are the two different in terms of their neural correlates?
The book is a feverish array of ideas and possible lines of attack. Crick tackles visual awareness as a starting point to explore the various facets of consciousness(parrying philosophical conundrums right off the bat).
Crick presents several possible models for consciousness. Most famous of these is the Global Workspace(GW) model proposed by Bernie Baars which posits the existence of very short term memory. This memory acts like an attentional searchlight, throwing light on a subset of brain processes that are momentarily rendered conscious. The conscious process in its stead can broadcast a particular narrative of the world to other unconscious processes in order to perform a coherent voluntary function. This is much like the workings of a modern democracy where competing groups(lobbies) vie for control of power. Powerful coalitions keep forming and dissolving, each stamping its will on the collective. We are given to believe that these theories are testable, but thumping validation is still elusive(more recent theories like Tononi’s Integrated Information Theory have a slightly different take on things).
Homo Sapiens, being a largely visually driven species, has a very intricate visual apparatus . Broadly speaking, after the initial acquisition from the retina, information gets handled between layers of subsequent processing units. Its like a game of twenty questions, where each layer asks questions about the input until it arrives at a decision as to the state of the visual landscape. These units are highly overlapping, with rich back connections. A map of the various visual hierarchies looks like a veritable zoo of connections and back connections. At the very top is the so called archicortex(Hippocampus).
Not surprisingly, most experimental progress in understanding vision has taken place at the far ends of the visual map(Hubel and Wiesel’s pioneering experiments on the cat V1 and more recent elucidation of rodent spatial navigation system in the entorhinal cortex). The intervening layers are largely unexplored partly due to the messy ways in which evolutionary tinkering works. Anyone who has ever trained a neural net would tell you that ascribing particular feature detection capabilities to specific neurons is erroneous as individual nodes often encode very complex representations. How this messy wiring(laid down by evolution) causes conscious percept is the million dollar question.
Much of our knowledge about the cortex derives from either invasive experiments on non-human primates or non-invasive experiments(except for a few cases where electrodes may be directly implanted for diagnostic purposes) with human subjects. The former approach allows for recording from single units whereas in human subjects researchers have to be content with signals received from potentially billions of neurons(limiting spatial and temporal resolutions in the process). While animals allow greater observational resolution, human subjects can provide linguistic feedback. Another source of information comes from studies on the pathological human brain. Experiments on blindsight(certain lower level visual computations may be preserved in patients with cortical blindness that don’t ordinarily cause awareness) and split brains provide unique insights into the nature of consciousness. The book is a treasure trove of foundational(albeit a tad dated)experiments.
Despite the intimidating nature of the problem, there doesn’t appear to be a poverty of ideas. Crick is characteristically boisterous and pounds the reader with a feverish volley of ideas. Its almost as if he was thinking aloud in the process of writing the book. The bibliography and glossary at the end are well written, making the book a good read for amateurs and professionals alike. The book is sure to take its place as a canon in the field of consciousness research(if it hasn’t already).