Encephalon 22: A neuroscience blog carnival08 May 2007
Welcome, everyone, to the twenty-second edition of the neuroscience carnival, Encephalon. Never in my life have I received so many e-mails with the subject line, "Submission". Whoa! I checked the spam filter to make sure they weren't going into the wrong bin.
Meanwhile life intervened, and we're starting a day late here, but you'll see we're not a dollar short -- with 11 contributions.
Ome sweet ome
Bohemian Scientist, who has to have the coolest banner ever, writes an ode to the -ome:
it's not news that scientists aren't all linguists. but that ain't no excuse for the nominal slop that pervades biological appelation. perhaps the most notorious of cases, and the subject of today's exposé, begins in the 1920s: flappers were a dime a dozen, histologists were still arguing over the neuron doctrine, and a forty-something german botanist was coining the term genome. with it, he unwittingly hacked open a pandora's box of lingual lament, unleashing the phoneme-turned-meme -ome to a world poised to beat it to death. the inevitable ome-philia is now as annoyingly crazy as its shakespearean counterpart; one can only wish it were as self-destructive.
The suffix has invaded neuroscience, with the "connectome" and Bohemian Scientist may not be ready for the change! Of course, this is a topic I hit last year -- my complaint being that people were doing genomics without bothering to learn genetics. I suspect that will be true in neuroscience as well -- why learn about the brain when you're really studying the connectome?
Sounds like a drinking game
The Neurocritic writes in with two posts on the neural correlates of attention. The first, "Bottoms Up" reviews a paper on top-down versus bottom-up attention. The second, "Tops Down" describes some experiments intended to localize aspects of the conscious control of perception:
Unique opportunities to record intracranially in awake behaving humans occur clinically in the neurosurgical arena, to monitor for seizures in patients with intractable epilepsy (Dubeau & McLachlan, 2000). In a series of such experiments in the mid-90's, Halgren and colleagues recorded local field potentials from over two thousand cortical and subcortical sites...
Read on to see what they found.
Pure Pedantry's Jake Young also enters two articles. In "Do autistic people have a deficit in reading faces?", he reviews research that shows that an original conclusion was not as simple as it appeared:
In the Thatcher illusion, two picture of Margaret Thatcher's face are inverted. One has (in the inverted form) the mouth and eyes turned right-side-up. The faces are then rotated such that now one of the faces is correct and the other is right-side-up with the mouth and eyes now inverted....
This discrepancy -- the feeling of wrongness associated with the altered right-side-up face -- is due to a preference in the human visual system for correctly oriented faces. Originally, it was believed that people with autism lacked this discrepancy -- the difference in the wrong feeling between the inverted Thatcher face and the correctly oriented with upside down mouth and eyes Thatcher face -- suggesting a general deficit in face processing.
This one is worth looking at for the links to the weird Margaret Thatcher faces alone! The second post, "Monkey Economics" has a connection to the Freakonomics guys, capuchin monkeys, and money. What more could you ask for?
A dramatic turn
In The Idiot, Myshkin's epilepsy is first mentioned in chapter one. In the online edition of the book, which I quoted in the post about Dostoyevsky's epilepsy, his condition is described as "some strange nervous malady - a type of epilepsy, with convulsive spasms." But in McDuff's translation, the same passage reads slightly differently; Myshkin is said to suffer from "some strange nervous illness akin to epilepsy or St. Vitus's Dance, with tremors and convulsions." This aroused my curiosity - I'd never before heard of Saint Vitus's Dance, so I decided to investigate further.
The intersection of history and neuroscience also infuses the post, "Old Brains, New Ideas". This is a really good presentation of the recent reevaluation of the brains of Paul Broca's patients -- the ones that led him to identify what we now call Broca's area:
Dronkers and her group re-examined the brains using high resolution magnetic resonance imaging (MRI). Although two neuroimaging studies have recently been performed on Leborgne's brain, Lelong's brain has remained unexamined, since the nineteenth century, in the Paris museum.
This re-examination revealed that, in both Leborgne and Lelong, the most extensive damage is not in the part of the frontal lobe most often designated as Broca's, but rather in the region just anterior to it - thus, the area considered by Broca to be crucial for speech atriculation is not the same as the region that is today called Broca's area. Further, in both Leborgne's and Lelong's brains, the damage extended far deeper than the lateral surface of the frontal lobe than Broca's reports suggested, and it is probable that these deeper lesions contributed to the speech deficits that the patients presented with.
Some mainstream micro
On the subject of historical rediscoveries, journalist Michael Balter writes in with his recent article in Science titled, "Brain evolution studies go micro." </p>
During the 1990s, [Patrick] Hof and his team were studying human brains when they spotted a type of nerve cell they had never seen before, in a small area associated with higher cognition. At first they thought the long, narrow cell was an artifact. But then they realized that they had rediscovered a cell type first described during the 1920s. So Hof turned to his collection and got an even bigger surprise: These cells were found only in apes and humans, not other primates.
His discovery was the first demonstration that the ape lineage had evolved an entirely new type of brain cell. Since then, he and other neuroscientists have been putting primate brains under the microscope, looking for clues to how the extraordinary information-processing capabilities of the human brain evolved.
If you didn't get a chance to read this article when it came out, take advantage of Michael's free link to it, on his list of articles.
There's no welt like umwelt
Chris Chatham's Developing Intelligence takes a stroll in the sensory system of a bat:
In his famous essay, Thomas Nagel suggested that science's reductionist methods can never provide a complete understanding of the "subjective qualities" of consciousness. To illustrate this problem, he wrote that there was "no reason to suppose that" we would ever be able to comprehend what it's like to be a bat - because we can't truly understand the subjective experience of, for example, echolocation.
Ironically, scientific advances in "sensory substitution" technology have demonstrated that it's possible to simulate (or stimulate) one modality (sight, hearing, touch) with sensory data from another.
Will "sensory substitution" lead to new technologies to supplement the senses? Augment human consciousness? Fight the Penguin?
The timekeeper inside
From Bora's Blog Around the Clock, we have a review of "clock" genes. These genes underlie circadian rhythms, and as a recent paper shows, their action is modulated by network effects in the suprachiasmic area (SCN) of the brain:
And what they found, over and over, is that particular genetic knock-outs eliminate rhythms in individual cells (both SCN and peripheral), and in peripheral tissues, yet intact SCN tissue remains rhythmic and whole animal even more so. A peripheral clock is a collection of cells, a pacemaker is a network of cells.
Bora's background post on the basics of biological clocks is good background to his summary of the cutting-edge research.
Cephalized is centralized
Our next host, Madam Fathom, investigates the early evolution of the central nervous system in vertebrates compared to their hypothetical ancestor, Urbilateria:
The striking similarities between these two animals, separated by hundreds of millions of years of evolution, implies a common evolutionary origin from an equally complex ancestral pattern. In other words, Urbilateria must have had these same sets of genes, in the same spatial orientation, patterning its nervous system, which must have likewise been centralized. Of course, this is still a matter of probability, but it seems highly unlikely that such a complex arrangement of genes could have been recruited independently to specify evolutionarily unrelated cell populations.
Read on to discover the identity of this animal, and what it tells us about the genetic patterns underlying the development of the central nervous system.
The next edition, Encephalon 23, will be hosted by Madam Fathom on May 21. You may send submissions directly there, or to encephalon.host [at] gmail.com.