Sunday, September 26, 2010

Earliest Instance of the Cortical Volume Hypothesis?

More good stuff from Gomulicki's article on the history and status of the theory of the memory trace. In this passage, Gomulicki discusses the hypothesis that intelligence depends on the size of your cortex: 

"Aristotle's view that the heart was the seat of mental processes, including memory, was short-lived. It was, in fact, overthrown by his own grandson, Erasistratus (c. 310-250 B.C.) and Herophilus (335-280 B.C.), who, working together carried out what were probably the first dissections of the human brain and studies of the sensory and motor systems. They accepted the view that the heart was the seat of the 'vital spirits' (pneuma zolicon), but held that the 'animal spirits' (pneuma psychicon)--the physical mediators of mental processes--were located in the nervous system, and in particular in the brain. They even had the astuteness to attribute the superior intelligence of man as compared with other animals to the greater development of the convolutions in man, though this view was only a deduction from a quantitative correlation for which they did not attempt a functional explanation." (Gomulicki p. 2) ...Basically, it didn't occur to them that the convolutions made it possible to pack a large cortical sheet into the human skull...If I remember right, Galen thought that the size of a donkey's brain and the stupidity of the donkey served as an adequate counter-example to the notion that brain size effects intelligence. Given the later authority conferred on Galen's thought, it's no surprise that Erasistratus and Herophilus' conjecture would fail to take hold.

Saturday, September 25, 2010

The Reverberating Theory of the Memory Trace

Not a lot of histories of the theory of the memory trace floating around. Today, I loaded up the microfilm for Gomulicki' s "The Development and Present Status of the Trace Theory of Memory", which seemed like a well-received history on the subject, as far as things on this kind of topic are 'received' at all. It'll be nice when someone finally renders this in pdf. At any rate...

One topic that was well-represented was the reverberating theory of the memory trace, according to which you hold on to a memory so long as its effect keeps cycling in you somewhere, somehow, physiologically. From Aristotle to Nicolas Rashevksy:

Aristotle offered the first physiological theory of the memory trace, where "sensory impressions were transmitted from the sense-organs to the heart by movements in the pneuma--movements that persisted, though on a decreased scale, after the external stimuli had ceased. The persistence of the movements of the pneuma was held to constitute the physical basis of memory, forgetting being due to the gradual subsidence of the movements..." (p. 2) Then, some time later...

Rafael Lorento de Nó's "most important discovery as far as memory theory is concerned is the existence, in addition to the long-known open neural circuits (nerve 'pathways' and 'arcs'), of closed chains of several neurons, within which an impulse once set up can continue to circulate almost indefinitely without assistance from new afferent impulses." (p. 33)

From Nó's findings, Nicolas Rashevsky developed the theory of reverberating circuits, wherein the memory trace would persist so long as the activity trapped in one of Nó's closed loops persisted. The consensus among the historians I've seen discuss the reverberating theory is that no one was ever able to gather any evidence for it. Of course, at present, synaptic theories dominate. But it was an interesting idea and it seems to fit with reverberating models of active maintenance.

Saturday, September 18, 2010

Vesalius, Galen, and Pissed Off Mentors

Galen was never able to perform human dissections. The law of his time didn't permit it. So instead, he would study other species (e.g. monkeys) and guess at what must be going on inside humans. If he was lucky, he would encounter a human corpse out and about and get to stare at it a bit, but that was it. Consequently, there were some errors in his neuroanatomy, etc.

Andreas Vesalius (1514 –1564) was not outlawed from performing human dissections. When he came across some of the errors in Galen's anatomy, he noted them and eventually published his report in his book, De humani corporis fabrica. At the time that the Fabrica was published, Galen's word was gospel. So when Vesalius' mentor and devoted Galenist, Jacobus Sylvius, found out that Vesalius sought to correct Galen's observations, it didn't sit well.

Of Vesalius, Sylvius wrote, "Honest reader, I urge you to pay no attention to a certain ridiculous madman, one utterly lacking in talent who curses and inveighs against his teachers." He then went on to write a book entitled A Refutation of the Slanders of a Madman Against the Anatomy of Hippocrates and Galen, wherein he continued, "Let no one give heed to that very ignorant and arrogant man who through his ignorance, ingratitude, impudence, and impiety denies everything his deranged or feeble vision cannot locate." He then basically tried to call the cops on Vesalius to "punish severely, as he deserves, this monster born and bred in his own house, this worst example of ignorance, ingratitude, arrogance, and impiety, to suppress him so that he may not poison the rest of Europe with his pestilent breath." Nice.

*All quotations are from Stanley Finger's The Minds Behind the Brain (2000).

Thursday, September 16, 2010

George Oliver, Adrenaline Junky Physician

If you don't have test animals, you always have family...

"One of the most significant discoveries began with some personal observations by George Oliver, an English physician. Oliver had a penchant for inventing simple instruments and testing them on himself and his family members. He tried to invent an instrument for measuring the diameter of an artery under the skin. To test the sensitivity of his new device, he administered extracts from various animal glands to his young son and recorded changes in his arteries. To his surprise, injecting adrenal gland extract caused a large artery from which he was recording to narrow dramatically, raising his blood pressure." from Stanley Finger's Minds Behind the Brain

Monday, September 13, 2010

When Did Textbook Neuroscience Get Its Start?

How do you count revolutions in a science?

One of the signs that your work has become part of the prevailing paradigm is that your findings appear in a textbook. It would stand to reason that uncovering a field's first textbook would reveal its first paradigm and that the progressive displacement of content across textbooks would reveal paradigm shifts.

We normally think of textbooks as being a fairly recent form of (very lucrative) publication. But textbooks have been around for a very long time. The Edwin Smith Surgical Papyrus of ancient Egypt records some of the earliest neurological observations. Galen's writings are some of the earliest we have on Greek and Roman medicine (Galen was a Roman).

Which of Galen's treatises would an ancient student of the brain go to as their authority? Not being a Galen scholar, I don't know the answer to this question, but it would be nice to know. The answer to this question might not only point to the dawn of neuroscience, but to its first revolution as well.

Saturday, September 11, 2010

Jevons and Menger, Discoverers of Diminishing Marginal Utility

I've been interested in exchanges of ideas between the neuroscience of motivation and economic theory for some time. The field of neuroeconomics of course is the current forum for such exchanges. I came across some of the first mentions of diminishing marginal utility in economics today and thought they were worth an entry.

"Every appetite or sense is more or less rapidly satiated. A certain quantity of an object received, a further quantity is indifferent to us, or may even excite disgust. Every successive application will commonly excite the feelings less intensely than the previous application. The utility of the last supply of an object, then, usually decreases in some proportion, or as some function of the whole quantity received. This variation theoretically existing even in the smallest quantities, we must recede to infinitesimals, and what we shall call the coefficient of utility, is the ratio between the last increment or infinitely small supply of the object, and the increment of pleasure which it occasions, both, of course, estimated in their appropriate units." William Jevons, A General Mathematical Theory of Political Economy (1862)

"The satisfaction of every man's need for food up to the point where his life is thereby assured has the full importance of the maintenance of his life. Consumption exceeding this amount, again up to a certain point, has the importance of preserving his health (that is, his continuing well-being). Consumption extending beyond even this point has merely the importance--as observation shows--of a progressively weaker pleasure, until it finally reaches a certain limit at which the satisfaction of the need for food is so complete that every further intake of food contributes neither to the maintenance of life nor the preservation of health--nor does it give pleasure to the consumer, becoming first a matter of indifference to him, eventually a cause of pain, a danger to his health, a danger to life itself." Carl Menger, Principles of Economics (1871)

Friday, September 10, 2010

Experimental Design--Where in the Hell Did it Come From?

Lately, I've been interested in learning something about the history of statistical experimental design. This has led me to Stigler's The History of Statistics: The Measurement of Uncertainty Before 1900. Interesting book. Apparently Legendre introduced Least Squares in 1805, quite some time after the rise of Francis Bacon's experimental philosophy. I'm under the impression that the first book in experimental design was Ronald Fisher's The Design of Experiments (1935). The lag between developments in the logic of experiment and experimentalism is pretty astounding.