|(Deborah Stalford photos)|
A brainy night in Berkeley
If it's Thursday, this must be the corpus callosum. Has anyone seen my homunculus?
| 07 December 2006
For the inexperienced traveler, Aubrey Gilbert's "whirlwind tour of your nervous system" blows past the hippocampus and cortex of the frontal lobes like a five-day package excursion through the great cities of Europe. Looking back, there's no doubt it's been a remarkable trip, but you're unsure in which region of the brain you encountered Broca's area, or the precise location of the olfactory bulb; your most vivid take-home memory is apt to be Gilbert's admonition never, ever to order brains for lunch.
That, and the indescribable moment following the breakneck slide show when, for the very first time, you cradle a human brain in your hands. Its synapse-bridging days may be over, but Gilbert - as enthusiastic a tour guide as one could possibly hope for - makes it come alive, transforming a lecture hall in the Valley Life Sciences Building into a makeshift planetarium of inner space.
Gilbert, a Ph.D. candidate in the Helen Wills Neuroscience Institute and two-time winner of Berkeley's Outstanding Graduate Student Teaching Award, is partial to the cerebellum, the sack-like structure at the base of the brain that governs posture and balance and regulates the coordination of complex limb movements. But she finds the entire nervous system "beautiful," and sets forth every semester or so - wielding a laser pointer behind a counter laden with buckets and jars of brains, spinal cords, meninges, and cranial nerves - to give a tour-de-force performance on behalf of the Cognitive Science Student Association, which dubs the event "Feel Dead Brains - Show and Tell Neuroanatomy."
"I really am a big ham," admits Gilbert, who speaks fluent French and Spanish in addition to rapid-fire English, made news as the lead author of a widely noted research paper (published earlier this year in the journal Proceedings of the National Academy of Sciences) on how language affects perception, and plans to attend medical school next fall. Elite credentials notwithstanding, she's no elitist, peppering her talk with pop-culture references ranging from Tom Waits - who famously said, "I'd rather have a bottle in front of me than a frontal lobotomy," though Gilbert suspects he cribbed the quote from W.C. Fields - to the Three Stooges, "The Far Side," and Mike the Headless Chicken.
Mike, as everyone knows, was the arguably lucky fowl who survived a beheading by a Colorado farmer in 1945, thriving for 18 months with only a brain stem. Fed on corn dropped directly into his gullet, Mike choked to death during a sideshow tour in 1947, when the farmer - after forging a new and profitable relationship with Mike - was unable to clear his esophagus, having forgotten to bring along the eyedropper he used for that purpose.
Brains, it seems, are far less crucial for chickens than for humans, Berkeley students or not. Humans can do nicely without a corpus callosum - that thick band of nerve fibers that connects the right and left hemispheres of the brain - but only if they're born that way. People whose corpora callosa are severed later in life - a surgical procedure sometimes performed to prevent epilepsy from spreading from one hemisphere to another - will suffer significant effects.
In the course of an hourlong lecture, Gilbert runs through no fewer than 180 slides. ("What was I thinking?" she wonders aloud.) These cover the history of the brain, from Plato and Aristotle through phrenology founder Franz Joseph Gall and beyond, with side trips to trepanation - the drilling of a hole into the skull, whether for medical or mystical reasons - and prefrontal lobotomies.
There is a brisk walk through a gallery of brain-related diseases, including Alzheimer's, multiple sclerosis, myasthenia gravis, spina bifida, and several types of aphasia. There is a brief discussion of "phantom limbs," the phenomenon whereby the brains of people who have lost an arm or leg still register pain in their missing extremities.
There is enough anatomy to make one's head explode.
And there is inspiration. "It's really astounding," she marvels, describing how receptors in our skin transmit sensory information into the spinal cord and up into the brain, and how electrical impulses move via neurons at speeds of up to 250 miles per hour to end up as thoughts, feelings, and movements. "This is going on every millisecond at billions of places throughout your nervous system."
Expanding the theme, she adds, "There are as many neurons in your brain as there are stars in the entire Milky Way," sounding a bit like Carl Sagan. Unfortunately - at least for those in the audience whose student days are behind them - she goes on to say that we lose "about 85,000 neurons a day, or one every second."
The good news comes later, when she mentions the work of Berkeley anatomy professor Marian Diamond, whose research showed that mental stimulation can cause dendrites - the branch-like projections that enable the brain's electrochemical cells to connect to other cells and transmit messages - to grow back.
"Use it or lose it," advises Gilbert, quoting Diamond herself. "The more you exercise your brain, the more you can increase the dendritic growth of your neurons. So keep your brain active, with crossword puzzles and stuff like that."
One fast way to lose it, should that be your goal, is to consume brains, which, if diseased, can cause your own brain to be taken over by prions, infectious agents made up of proteins. Notable prion afflictions include laughing death, Creutzfeldt-Jacob disease, and mad cow disease. "Eating brains," Gilbert says, "is not a good idea."
And, speaking of food: If you stretched out the hemispheres of the cerebral cortex, the thin outer layer of the brain, Gilbert says, they would be "basically the size of an extra-large pizza."
A slide of a homunculus, known as "the little man" inside the brain, provides a sensory map of the body. Based on the amount of cerebral cortex used to process various touch receptors, the homunculus features prominent lips, hands, and genitalia, reflecting the relative sensitivity of those portions of the human anatomy. Gilbert calls it "a representation of the body on your cortex."
When the lecture is over, Gilbert invites everyone up to the front of the hall, where - aided by Elizabeth Mormino and Bradley Voytek, also grad students in the Wills Institute, and undergrad Kevan Wang - she answers questions while the curious handle one of at least a half-dozen brains preserved in jars and buckets. There are also several half-brains - the better to see those hard-to-reach gyri and ganglia - and a number of spinal cords.
The living brain, Gilbert tells us, is "the consistency of unset Jell-O." Dead and soaked in formaldehyde, it feels like a three-pound hunk of ground beef that's begun to defrost.
It is, in fact, astounding.
"Think about it," says Gilbert. "You have all these specific interfaces for interacting with the world around you - everything from taste to vision to olfaction. All of these things involve very special receptors and highly evolved systems that allow you to pick up the information that's in the environment around you.
"So you take this incredibly, overwhelmingly rich, detailed surrounding that you're in, you put all that into your nervous system, and somehow your nervous system manages to create some sort of coherent picture of what reality is."
Unless, of course, you're an inexperienced traveler, trying to take in too much, too fast. In that case, a return trip might be just the ticket.