Questions to Ask a Reductionist Neurobiologist
Can the totality of the brain be described in terms of its neurons? Is consciousness an artifact of the movement of signals in the brain? Can the complexity of the brain be described in terms of its evolutionary history? Does the hardware define the software that runs on it? Gy�rgy Buzs�ki attempted to address these questions from an evolutionary standpoint in a “Connections” essay in Nature last week.1
Perhaps nowhere is the truism ‘structure defines function’ more appropriate than for the brain. The architecture of different brain regions determines the kinds of computations that can be carried out, and may dictate whether a particular region can support subjective awareness. Also, the degree of architectural complexity may determine susceptibility to neurological and psychiatric diseases – complex architectural schemes being more prone to disruption than simpler ones. Understanding how such structure-function relationships govern brain operations requires a systems-level approach that explores how local computation relates to global patterns of neural activity.
He went on to describe the different kinds of networks that parts of the brain can construct: local modules, as in the cerebellum; random connections, as in the hippocampus; and combination “scale-free” networks, as in the cerebral cortex.
Though Buzsaki attempted to engage a systems approach, his answers were reductionist in the sense of describing all brain functions in terms of their physical architecture. The “structure” of consciousness, therefore, in his view, is structurally based. He did not speak as if this might challenge the validity of his own opinions on the subject.
1Gy�rgy Buzs�ki, “Connections: The structure of consciousness,” Nature 446, 267 (15 March 2007) | doi:10.1038/446267a.
It is one thing to measure, describe and understand the physical action of neurons, but quite another to reason about them. If reason can be subsumed under the structure of neurons, how can I know it is reason? If consciousness is merely an artifact of firing patterns in a network, how do I know I am not just dreaming?
Whenever evolutionary neurobiologists, who are obligate physicalists, attribute consciousness and reason to networks of physical parts with a presumed evolutionary history, we need to ask them some pointed questions. Let’s take some of his statements and play with them.
- “I propose that the distinct network architectures translate into unique functional consequences.”
Is a proposition an artifact of a hardware network, or does it have an external validity?
- “In cortical networks, a dynamic balance between excitation and inhibition gives rise to an array of network oscillations involving neuronal populations of varying sizes.”
Was that thought an excitation or an inhibition? Suppose the pattern is different next time. Will the first thought evaporate?
- “This self-organized, or so called ‘spontaneous’ activity is the most striking and yet perhaps least appreciated feature of the cerebral cortex.”
Where is the “appreciation module” in this structure? How can it be appreciated if it is self-organized? What is a self? Whose self can demand that I appreciate something?
- “Without inhibition, excitatory activity caused by any one stimulus would ripple across the entire neuronal network and a confused jumble of overlapping signals would result.”
How would an observer of similar signals in a computer chip be able to reverse-engineer the software that produced it? Would the engineer attempting the feat be an artifact of his own circuits?
- “Inhibitory interneurons and the rhythms they generate can temporally and spatially structure the activity of excitatory cell assemblies to ensure that information flows to just the right place at just the right time.”
Please define “right” in this view. This seems to imply goal-directed software that is directing the patterns. What is information? What directs the inhibitory neurons to inhibit, and when? How can we know that the right inhibitions occured to generate your thoughts on this subject? Would different inhibitory rhythms generate a completely different opinion? If so, on what basis would other humans subject to their own rhythms decide that your opinion has more – or less – validity than that of a schizophrenic?
- “The interaction and interference of multiple brain rhythms often gives rise to the appearance of ‘noise’ in an electroencephalogram. This noise is the most complex type known to physics and reflects a metastable state between the predictable behaviour of oscillators and the unpredictability of chaos.”
In a physicalist view, who determines what is noise and what is signal?
- “A special case is the hippocampus whose highly recursive connection matrix is thought to function as a large ‘autoassociator’, allowing the reconstruction of entire episodes from remembered fragments.”
What does “is thought to” mean? Who thinks? Is thinking valid? What is determining the end result of these associations to produce the “right” reconstruction?
- “I suggest that the local-global wiring of the cerebral cortex and the perpetual, self-organized complex dynamics it supports are necessary ingredients for subjective experiences.”
If experiences are artifacts of network activity, who decides what is subjective? Could this statement itself be considered subjective? Does objectivity exist?
- “If they manage to perturb ongoing activity for a sufficiently long time in a big enough population of neurons, their effect will be noticed; that is, we will become conscious of them.”
Whoa. Define consciousness. If my neurons focused on that sentence, and thought about it, how am I to know your proposition or my thoughts about it are verifiable?
- “Complex neuronal networks are a useful product of brain evolution but come at a price. Greater resources and volume are required to sustain long-distance wiring in complex networks, and the risks of malfunction increase with complexity.”
Please define useful. Please define malfunction. Can you defend the proposition that a mindless, aimless process of evolution will inevitably converge on truth and integrity?
- “Timing errors present particularly difficult problems in complex networks, because of limits to how much information can be conveyed through restricted numbers of long-range conduits. Not surprisingly, diseases of the cerebral cortex are manifold – including epilepsies, Alzheimer’s and schizophrenia.”
What is information? What is disease? Is disease a continuum or an on-off state? If the former, who decides at what point something is normal and something else is a timing error? If the latter, and schizophrenics were in the majority, could they lock up the minority in the insane asylum?
- “One of the greatest challenges left for systems neuroscience is to understand the normal and dysfunctional operations of the cerebral cortex by relating local and global patterns of activity at timescales relevant for behaviour.”
Is a pattern of activity equivalent to consciousness? Could the patterns of impulses in a mechanical machine wired like the brain and connected to a power source be considered conscious? Would those patterns be able to judge the validity of your propositions, and if so, who would judge the debate? Suppose a group of robots reasoned that their circuits had been designed, therefore the humans’ circuits must also have been designed; would you accept their verdict?
Here is another case of a scientist with the Yoda Complex (09/25/2006 commentary). He stands at a pulpit outside of his own brain and speaks wisdom to the rest of us stuck inside our brains. This is a technical foul. He cannot play the game of trying to answer the age-old mind-body problem* unless he first acknowledges the independent validity of reason and the laws of logic. If his subjective thoughts can be completely described by the firing of neurons and the timing of rhythms of excitory/inhibitory signals, then his opinions are self-refuting and necessarily false. His own system, i.e., just crashed. We’ve seen the Darwin malware do this many times. The only solution in these cases is to reformat the hard drive, load the ID disk and reboot.