Note: Christof Koch's 2012 Consciousness: Confessions of a Romantic Reductionist will be an easier place to start. The Quest requires a knife & fork to properly consume it, but it is more that worth the effort.
Christof Koch's research goal is "to link the molecular and biophysical properties of coalitions of neurons to stimulus of awareness". (p. 100) That is to pinpoint the NCC, the neuronal correlates of consciousness. What is actually happening when we have a conscious percept. This very specific goal allows him to side step many sorts of philosophical problems of defining consciousness.
This is a fairly acedemic book with 70 pages of bibliography (mostly research papers), 18 pages in indices and 18 pages of glossary. Koch's course. I'm glad I read Zeman's Book first. Zeman is in the bibiography. Koch's book is more hard core.
Koch published several papers with Francis Crick (DNA) and dedicates the book to him. Crick should have been a co-author, but declined. Nobel Bio and WikiPedia
An election metaphor is often used to represent coalitions of neurons that sustain a conscious thought process. Our sensory processors - the visual cortex being the most well known - can be churning away full tilt, but, it will not effect our conscious thought - as long as nothing unexpected and urgent appears. It is some set of inputs that coalesces to take over the conscious uni-processor.
A fascinating supposition is that the frontal cortex is not part of our consciousness. The basic idea is that we have sensory processors which feed information (a net wave) up a recognition hierarchy until they become objects or properties that we can articulate. In addition, they pass thru to the frontal cortex where decisions get made, but we are only conscious of the inputs and the outputs of the decision process.
1A) Forward Projections are strong to the front of the cortex. Feedback modulates feed forward.
2) Zombie Agents handle much of our actions. Anything we do unconsciously, things we train for. Things handled by the Dorsal pathways & "gist perception"
3) Conscious precepts are the results of a single winning coalition of neurons with at some prefrontal parts of the network
4) Explicit representation of some stimulus is a set of neurons. Lose those and you no longer perceive that stimulus.
5) Net wave from V1 up hierarchy (See Van Essen) to the prefrontal cortex. Then it travels back down the hierarchy as feedback. Visual Consciousness probably starts at teh upper stages of the ventral pathway in teh Inferior Temporal cortex. (Ventral congizes, Dorsal does)
6) Driving and modulatory loops: To understand coalitions we must understand the neural connections. Excitatory cells send driving or modulatory charges. From the back of the cortex to the front are mostly driving charges. Loops of driving charges are bad.
7) Perceptual awareness may be a series of snapshots with motion "painted on". Each snap lasts 20-200 milliseconds (ms) (it takes 250 ms to "see" something)
8A) Attention: There are two types of attention: a) bottom up saliency driven and b) top down and volitionally controlled. Bottom up would be a sensory net wave that breaks thru. For example, a ball flying at you.
9) synchrony of action potentials discharge in the 30-60Hz range may help in forming nascent coalitions. Firing in the 4-12 Hz band may be part of snapshot processing.
10) Winning coalitions recruit from the cortex, thalmus, basal ganglia and other networks. In addition to the neurons that are explicitly part of the NCC is the penumbra which includes past associations, background and future plans. The penumbra provides meaning or the potential for meaning which might only happen if the NCC expands to those nodes.
The bandwidth from the LGN to V1 is 1/10 the bandwidth from V1 to the LGN in cats p.59
Almost enough detail to totally comprehend the circuit diagram for the visual system.
Many forms of memory: associative conditioning (bell & food), procedural (hot to), episodic (recollections), semantic (knowledge). Then there is "working" memory - short term buffers and a special form of short term memory: iconic.
Massive amount of information on teh visual system and its quirks. Systematic ascension of the visual hierarchy (See circuit link below) with most of the little boxes accounted for. Much more discussion of the Ventral and Dorsal pathways.
Talk about visual search and why differences in color, size, form and motion makes things stand out. This agrees to a high degree with the Info Viz Book, which has color, form, motion and spatial positioning.
Check these out:
Circuit Diagram of the Macaque, from from Felleman, D. J. and Van Essen, D. C. (1991) Cerebral Cortex 1:1-47.
10 working assumptions
At the end of the book. It is hard to say which of the many assertions are actually the numbered assumptions, but who am I to quibble?
1)Nonconscious Homonunculus: We are not conscious of the highest levels of cognition.
Consciousness handles the exceptions (See Hawkins) and it presents an executive summary to the planning stages.
The cortex is a large set of nodes. A "column" is the smallest useful node.
There is also "gist perception" which allows us to go thru the world on auto pilot. As long as nothing salient happens, we are not really conscious of a lot of our daily activities. Like when we drive home and remember no details of the drive.
8B) Binding: Various attributes of a single object are identified by essential nodes. How these are tied together is the "binding problem". There are three types of binding: 1) lower level, V1 binds location and orientation; 2) trained binding, face, voice and hair mean Grandma; 3) novelty binding - requires top down attention
Other notes:
Qualia are a symbolic form of representation within oceans of explicit and implicit information. Why qualia "feel" the way they do remains an enigma.
Great Book!!!
I have many, many more notes in my margins, but, they will have to wait!
A similar circuit diagram exists for the auditory channel: Lloyd Watts (PDF)
September 24, 2005
2015-07-12 update
Gist Perception
When does the Prefrontal Cortex (PfC) get involved with vision? We process most of what we see on auto-pilot, see quote from Consciousness and the Brain below. Are those conscious percepts, or as Bernard Baars would say, a "gestalt". Is the PfC involved if things are preconscious or pre-attentive? See Collin Ware.
Koch, from page 135
One of the many pleasures of living in North America is driving in solitude for hours on end across the high plateaus, deserts, and mountains of the West, with its sweeping vistas. I can ponder life's mysteries or listen to the complete Ring des Nibelungen without interruption. I drive as if on automatic pilot (an example of an on-line or automatic system introduced in Chapter 12), while I concentrate on the music but not on the scenery streaming past. Yet under these spaced-out conditions, I am still conscious of the gently curving road ahead, a slow moving truck in front of me, a billboard off to the right, the over-pass coming up, and so on. Although little studied in the laboratory, humans often wander through the world lost in thought.What I see is the gist, a high-level, semantic representation of familiar scenes that can literally be apprehended in a flash. It's a vignette, a succinct summary of what is in front of me, devoid of details—a crowd at a football game, a lone cyclist, a mountain. Gist might even include the fact that some animal is present, without knowing its identity or location (as in the experiment that I just discussed). I suspect that gist perception does not require focal attention. [26]
Neurons in the upper stages of the visual system may directly encode gist explicitly. These semantic neurons might respond, for example, to any animal, or to office scenes, or to a crowd of kids. [27] Gist perception probably occurs before you are aware of the details of the scene.28 Because gist neurons are found in the upper stages of the hierarchy (while the details are represented in earlier areas), they may very quickly establish a dominant coalition, sufficient for conscious perception of the gist. I argue in Chapter 15 that the NCC require some sort of feedback from the prefrontal cortex, affecting higher areas before it influences lower ones. This explains why, if the image is only flashed for a very brief time, you still have the distinct feeling of seeing everything in front of you, but not being about to report any of the particulars. Gist is seeing the forest but not the trees!
[26]Gist is immune from inattentional blindness (Mack and Rock, 1998).
[27]For the psychophysics of visual gist, see Potter and Levi (1969); Biederman (1972); Wolfe and Bennett (1997); and Wolfe (1998b). Individual neurons in the medial temporal lobe of humans respond to fairly high level semantic categories, such as images of animals or famous people (Kreiman, Koch, and Fried, 2000a). They may be part of the neuronal correlate of gist percep-tion. Gist is, by its very nature, invariant to large changes in the content of the scene. Thus, the gist stays the same during the image manipulation that occurs in change blindness (Figure 9.1). 28A similar argument is made in Hochstein and Ahissar (2002).
From page 47, Dehaene, Consciousness and the Brain:
Recent experiments in psychology and brain imaging have tracked the fate of unconscious pictures in the brain. We recognize and categorize masked images unconsciously and we even decipher and interpret unseen words. Subliminal pictures trigger motivations and rewards in us all without our awareness. Even complex operations linking perception to action can unfold covertly, demonstrating how frequently we rely on an unconscious "automatic pilot." Oblivious to this boiling hodgepodge of unconscious processes, we constantly overestimate the power of our consciousness in making decisions-but in truth, our capacity for conscious control is limited.