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Saturday, January 23, 2010

Something Fishy

  
He's Dead Jim
The 18-inch-long Atlantic salmon lay perfectly still for its brain scan. Emotional pictures —a triumphant young girl just out of a somersault, a distressed waiter who had just dropped a plate — flashed in front of the fish as a scientist read the standard instruction script aloud. The hulking machine clunked and whirred, capturing minute changes in the salmon’s brain as it assessed the images. Millions of data points capturing the fluctuations in brain activity streamed into a powerful computer, which performed herculean number crunching, sorting out which data to pay attention to and which to ignore.
By the end of the experiment, neuroscientist Craig Bennett and his colleagues at Dartmouth College could clearly discern in the scan of the salmon’s brain a beautiful, red-hot area of activity that lit up during emotional scenes.
An Atlantic salmon that responded to human emotions would have been an astounding discovery, guaranteeing publication in a top-tier journal and a life of scientific glory for the researchers. Except for one thing. The fish was dead.  
Trawling the Brain
Ah, well, they managed to eliminate that error, but it did bring out one important notion.  Not the emotional lives of fish, but our peculiar tendency to equate things with their material entanglements. 
Less dramatic studies have also called attention to flawed statistical methods in fMRI studies. Some such methods, in fact, practically guarantee that researchers will seem to find exactly what they’re looking for in the tangle of fMRI data.
 In the great layer cake of science

it is always useful to distinguish between what is actually being measured and what that measurement is attributed to.  A famous example is the 1936 Literary Digest sample that measured the stated voting preferences of telephone owners and thought they were measuring the percentage of voters who would actually vote.  In fact, voters who did not own telephones also voted, and voted very differently from the phone owning voters. 


The fMRI does not measure "thoughts" or "decisions" or "acts of will", as some experimenters have carelessly stated.  It measures blood flow.

Surrogate measures are all well and good, but before you measure Y and declare you have seen X, you better make sure that only X can account for the Y you saw.  It's not enough to say that in your model IF x, THEN y when the real world also throws up IF q, THEN y and IF g, THEN y, and so on. 
Das and Sirotin used electrodes to measure neuronal activity at the same time and place as blood flow in monkeys who were looking at an appearing and disappearing dot. As expected, when vision neurons detected the dot and fired, blood rushed into the scrutinized brain region. But surprisingly, at times when the dot never appeared and the neurons remained silent, the researchers also saw a dramatic change in blood flow. This unprompted change in blood flow occurred when the monkeys were anticipating the dot, the researchers found. The imperfect correlations between blood flow and neural firing can confound BOLD signals and muddle the resulting conclusions about brain activity.  [Emph. added]

This has obvious implications on the experiment that "discovered" that subjects were "making decisions" up to ten seconds before they self-reported making them, and therefore (somehow) disproved "free will."  At the time, I commented that was was being measured was blood activity in the brain, not decision-making, and that it was circular reasoning to decide a priori that this activity was equated to decision-making [and that decision-making was the same thing as free will.]  Of couse, if the same blood activity is triggered by anticipation of the dot as by actually seeing the dot, it is clear that that anticipation of flipping the switch would be just as actuating as flipping the switch.  As the article points out, hungry babies cry, but not all crying babies are hungry.  






        
In Aristotelian-Thomism (A-T), the intellect is immaterial, but sensation and perception (imagination) - Sen and Per in the diagram - are not. This is as inseparable as the hylomorphic union between the figure of a triangle and its three-sidedness.  (We can conceive three-sidedness independently of any particular triangle, but no actual triangle can be perceived independently of its three-sidedness.) 

Thus, no surprise to A-T that neuroscience discovers neural correlates to mental imagery and perceptual experience.  A-T also holds that the operation of the intellect requires the presence of the images ["phantasms"] of the imagination.  Hence A-T would expect that neural damage affects the intellect's functioning.

Most importantly, the anima [of which intellect, sensation, and imagination are powers - cf. diagram, above],  is the form of the body, not an independent substance.  It is not a ghost in the machine, but what informs the machine. The relationship of intellectual activity to a particular human action is not like "X-causes-Y" causation, but is the formal/final side of an event of which the physiological processes are the material/efficient side. "That alterations to the body have mental consequences is thus no more surprising than the fact that altering the chalk marks that make up a triangle drawn on a chalkboard affects how well those marks instantiate the form of triangularity."

A-T has always said that about the relationship between soul and body. Nothing in modern neuroscience need trouble A-T philosopher.  Except for the technicalia and the occasional infelicity of the modern mode, this article could have been written by Aquinas: The Vulcanization of the Human Brain

Nicely put, but forgotten where:
Consider the following analogy: A typed, written, or spoken token of the word “bark,” considered merely as a material object, has all sorts of complex physical properties, and those physical properties are highly relevant to its status as a word, as a bearer of linguistic meaning. Alter the physical properties of the token too radically, and it can no longer convey the meaning it once did. For example, if the ink should smear, the sound be muffled, or the power source to a word processor be cut off, the word will disappear, or might at least become so distorted that it becomes unintelligible. It would be absurd, though, for someone to suggest that these facts lend any support whatsoever to the claim that a word token qua word token is exhausted by its physical properties. It clearly is not. It is, for example, indeterminate from the physical properties alone whether the “bark” in question is the bark of a dog or the bark of a tree. Indeed, since the fact that the relevant sounds and shapes are associated with a certain meaning is entirely contingent, an accident of the history of the English language, it is indeterminate from the physical properties alone whether the word has any meaning at all. In short, the physical properties are a necessary condition for any particular physical object’s counting as a word token, but they are not a sufficient condition.
Which brings us back to the dead fish.  Brain activity is a necessary condition for intellectual activity, but it is not a sufficient condition.  C.S. Lewis once wrote:
If minds are wholly dependent on brains, and brains on biochemistry, and biochemistry (in the long run) on the meaningless flux of the atoms, I cannot understand how the thought of those minds should have any more significance than the sound of the wind in the trees.

1 comment:

  1. Ah, another excellent post, Mike! I'm working on my next Alt View, which will be a reply of sorts to Brass Tacks letters and Stan's latest editorial concerning AGW. I, too, will also have to make the point about the difference between what is measured and how it is interpreted. I wish scientists in general had a bit more appreciation of philosophy. Come to think of it, of psychology as well.

    Cheers,

    Jeff

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