Blogs / The Loom

In my June brain column for Discover, I wrote about the bizarre idea that there are single neurons in your head that can respond to individual people. The so-called “grandmother cell” started out 40 years ago as a thought experiment riffing on Philip Roth’s novel Portnoy’s Complaint. By the 1970s, most neuroscientists considered it more of a joke than a valid concept, but in the years since it hasn’t quite gone away.

In my column, I described the work of the work of Rodrigo Quian Quiroga of the University of Leicester:

For the past eight years, he and his colleagues have been studying epilepsy patients who have had electrodes implanted in a region of their brains called the medial temporal lobe, as part of a study to identify the source of their seizures. Quian Quiroga showed the subjects 100 pictures. The pictures included photos and drawings of celebrities as well as landmarks and various familiar objects. The patients had to press one button if a picture was of a human face and another if it was not.

In their first such study, Quian Quiroga and his team were able to observe the individual activity of 993 neurons. They found that 132 of them responded to at least one picture. And of those responding neurons, 51 fired in response to only a single person or thing. One neuron responded only to Halle Berry, for example.

Amazingly, the “Halle Berry” neuron responded to any picture of her, including one in which she was dressed as the masked Catwoman. Even the name Halle Berry triggered that neuron, which was silent at the sight of other actresses or their names.

Quian Quiroga does not, however, believe these neurons are grandmother cells, at least as they were initially conceived. He suspect that a very sparse network of neurons–perhaps hundreds out of the billions in our heads–can develop this kind of response to an individual. Quian Quiroga just happen to stick his electrodes near single neurons that belonged to these networks.

Which brings us to Quian Quiroga’s latest paper, published in Current Biology. He analyzed the signals from 750 electrodes implanted in seven patients as they looked at pictures of some celebrities like Oprah Winfrey. Quian Quiroga found neurons that responded strongly to the sight of these individuals–and they also responded strongly to their written names and even the sounds of their names.

Quiroga and his colleagues also ran the same test using themselves rather than the celebrities to probe for neurons. They discovered neurons that responded strongly only to individual researchers, too–and once more, the same neurons responded to the sight and sound of their name. Bear in mind–the patients had only met the scientists a day or two earlier. So these neurons had developed their grandmother-ish response in a very short time.

These results offer some clues to how these sparse networks are arranged. Some of the neurons probably get signals from other regions of the brain that recognize faces. Others tap into auditory networks, and others language centers. Yet, remarkably, the information from these far-flung parts of the brain get funneled into tiny sets of neurons that can then encode concepts of people.

They may not be the Grandmother Cells of legend, but in their own way, they’re very cool.

Reference:  Quian Quiroga et al., Explicit Encoding of Multimodal Percepts by Single Neurons in the Human
Brain, Current Biology (2009), doi:10.1016/j.cub.2009.06.060

I wrote about the two sides of our brains in April for Discover. Now some of the scientists whose research I highlighted have an article of their own in Scientific American, focusing on the ancient evolutionary origins of specializations in each hemisphere. So if you still have interhemispheric cravings, check it out!

Not too long ago I was interviewed for episode of the radio show Radiolab. Jad Abumrad and Robert Krulwich led me to a windowless cubicle where they then grilled me for a long, long time. From that interrogation, they produce a medley in which I say:

“Sloppy, sloppy, noisy, chaos, jumble, chance, sloppy, sloppy…”

Fortunately, they also saved a little more of our conversation, which was on a topic near and dear to my heart: the noisiness of life. It’s a subject I discuss at some length in my book Microcosm (ahem–paperback coming out on July 14–ahem). To wit: if you think that down at the level of molecules and atoms our bodies are just regular clock-like devices that go tick-tock-tick-tock, you’d be wrong. It’s a sloppy, noisy process, out of which it’s amazing that the regularities and predictabilities of our lives emerge.

The episode that Jad and Robert produced, called “Stochasticity,” (listen here) looks at the many roles chance plays in our life–from the level of cells, where I tend to lurk, to the myth of the hot hand in basketball.

Of course, like any self-absorbed starlet, I must say now that some of my best work was left behind on the cutting-room floor, or at least inside somebody’s hard drive. It was inevitable, given how cool and multi-faceted the mystery of biological noise can be. For example, I talk about noise filters on Radiolab, but I didn’t talk about one of the most important ones, which keeps signals clear in in our brains. If you want to read more, check out this piece I wrote last year for Wired. And I also didn’t get to explain that noise isn’t just something to get rid of, just an unalloyed bad thing. In fact, life has evolved to use noise to its advantage. Even E. coli knows how to play the odds like a skilled gambler, as I explained last year in the New York Times.

And if you want to head straight for the scientific literature behind this story, a great place to start is with the wonderfully-named 2008 review, “Nature, Nurture, or Chance: Stochastic Gene Expression and Its Consequences” (pdf at author’s site)

[Image: jaxpix on Flickr, via Creative Commons Licence]

Mind wandering is the subject of my new column for Discover. Far from just useless mental static, mind-wandering actually creates a distinctive pattern of activity in our brains–a pattern that suggests that it may actually be playing a crucial role in our mental life. Check it out.

This year marks the fortieth anniversary of the publication of Philip Roth’s novel Portnoy’s Complaint. In 1969, the book also became fodder for one of the oddest ideas in neuroscience: the grandmother cell. What if a neuron in your head only responded to the sight of your grandmother? For a long time, many neuroscientists have dismissed it out of hand. And yet the idea will not quite die.

Earlier this year a psychologist published an intriguing review of the grandmother cell, arguing that we should not be so hasty to run its obituary. Other scientists I’ve spoken to don’t think grandmother cells actually exist, but their own ideas about how we recognize individuals are equally fascinating. I’ve put together what I’ve learned about Philip Roth’s unexpected contribution to neuroscience in my latest Brain column for Discover. You can read it here.

Marcel Salathe, a biologist I know at Stanford, is running a very cool study on swine flu psychology that you can be a part of. Here’s the dope from Marcel:

 As you have heard in the news, there has been an outbreak of swine flu in Mexico and the United States. There is a possibility that this situation might develop into a pandemic if the virus continues to spread around the globe. The news media report excessively about this threat, and while health officials urge people to stay calm, there is an increased level of anxiety in the population.

Models have predicted that when a disease breaks out, changes in behavior in response to an outbreak, and in particular in response to information about an outbreak, can alter the progression of an epidemic. While this makes intuitive sense, there is no good data to test such a hypothesis. One of the major problems is that emotional reactions and behavioral response to an epidemic is generally assessed quite some time after the epidemic has fizzled out.

We would like to address this problem by starting a survey about risk assessment and personal responses to a potential epidemic as it unfolds – that is, right now.

Please help us achieve this goal by filling out a simple questionnaire (link below) – it shouldn’t take more than five minutes.

This is the link:
https://opinio.stanford.edu:443/opinio/s?s=1403

I’ve just taken the survey, and I can vouch it’s quick and painless. When Marcel has results to share, I’ll make sure we get his analysis. So please help him out–take the test and spread the word.

My new Discover column about the brain has just been posted. I take a look at that most obvious–and most puzzling–thing about a brain: its two sides. Check your left-brain/right-brain cliches at the door and check it out.

I’ve only been put under general anesthesia once in my life, and ever since I’ve wondered what exactly happened to me during those lost hours. It turns out nobody really knows. But if they ever find out, they may get a little closer to solving the riddle of consciousness. That’s the subject of my newest brain column for Discover. Check it out.

I’m about to fly to California for my talk tomorrow at the Sage Center for the Study of the Mind in Santa Barbara, “Soul Made Flesh: Neuroscience in 1659 and 2009.” Here are the details.

Hope to meet some Santa Barbarans. (Or is that Santa Barbarians? Suddenly I have visions old Saint Nick with a pole-axe.)

[Image: Frontispiece to a Dutch edition of Anatomy of the Brain and Nerves (1665) by Thomas Willis. For more on Willis, see my book of the same name as my lecture]

Several commenters checked out the 3-D video of the world’s oldest fossil brain I posted yesterday and were struck by just how tiny the 300-million-year-old fish’s brain was in comparison to its braincase. Their verdict: shrinkage. In the paleontological sense of the word, not the Seinfeldian one. After death, brains that do not simply disappear sometimes get smaller. In this particular fish, Sibyrhynchus denisoni the brain must have gotten a lot smaller. Check out this image, in which the braincase is in red, and the brain is in yellow. (The scale bar is 5 millimeters.)

To move along the discussion of shrinkage, I thought it might be helpful to post the following passage from the paper itself, which will not be published until later this week in the Proceedings of the National Academies of Science. (For some reason, the journal lifts its embargo on us journalists days before they put papers online. So the link to the paper won’t work just yet.)

Assuming that this object is a mineral replica of the brain and some cranial ner ves, it shows an  import ant size discrepancy relative to the endocranial cavity. The question of the size and proportions of the brain, relative to the endocranial cav it y been much debated by early vertebrate paleontologists, but anatomical studies of ext ant vertebrates show that the brain generally fills the endocranial cavity and that size discrepancy between the brain and endocranial cavity invoked for some t axa is in fact a consequence of inadequate preservation techniques (10, 20, 21). The size discrepancy observed in Sibyrhynchus could be explained by shrinking of the brain tissues that might have occurred just before phosphatization, hence the position of the cerebellum far anterior to the otic capsule (18). Yet the optic tract reaches its foramen in a normal position, as do the other putative cranial nerves, thereby suggesting that the shrinking of the brain was minor.

Two possibilities come to mind. One is that the scientists are wrong, and the brain of Sibyrhynchus managed to shrink without disturbing the connections from the cranial nerves to their corresponding openings in the skull. Or they’re right, and this fish had a very tiny brain lodged deep inside a big space. Why there would be such a mismatch between brain size and braincase size the scientists can’t yet say. (Update: I forgot to mention that in many sharks and other fishes, the brain stops growing after birth, while the skull keeps growing.)  Which is all the more reason, as Pierre Kerner points out in the comments, for paleontologists to start opening museum drawers and do some more scanning. Let’s see what pattern emerges.

Update, minutes later: Alan Pradel, the lead author of the paper just left a comment on all this in the previous post. Here’s part of it:

…some extant fishes possess a small brain compared to the endocranial cavity (e.g. coelacanths). In iniopts, the nerves perfectly reach their respective foramen without any deformation and the overall morphology of the endocranial cavity is different from the morphology of the brain. Consequently we supposed that the brain did not fill the endocranial cavity. Concerning the optic foramen which is very large, a lot of other thing passed through it (e.g. the efferent pseudobranchial artery) as in extant ratfishes.

Paleontologists don’t go looking for brains, and I’m not surprised. I once got to hold a fresh brain in my hands (it was at a medical school–nothing fishy, I promise), and I can vouch that they are marvelously delicate: a custard for thinking. When any vertebrate with a brain dies, be it human, turtle, or guppy, that fragile greasy clump of neurons is one of the first organs to vanish. Scientists must infer what ancient brains were like very often by examining the case that held it–that is, if they can find a relatively intact braincase.

In recent years, scientists have been able to get important clues about brains by scanning the brain cases. They can create virtual fossils in their computers that reveal a wealth of details. Alan Pradel of the Museum National d’Histoire Naturelle in Paris and his colleagues recently scanned a 300-million-year old fossil of an ancient relative of sharks called Sibyrhynchus denisoni. They recognized many details of the skull. But when they looked closer, they saw something they could not quite believe. They saw something that looked like a fossilized brain.

Even without a brain, Sibyrhynchus is very interesting. It belonged to a group known as iniopterygians, whose closest living relatives are ratfish. While there are few species of ratfishes today, 300 million years ago they enjoyed a much bigger diversity. Iniopterygians were small (6 inches long) and had big eyes and pectoral fins, along with a club on their tail.

Pradel and his colleagues were pleased enough to see the braincase of Sibyrhynchus, but they were stunned to see a chunk of rock deep inside that looked like a very small fish brain (and I do mean small–its length was 7 mm, or a quarter of an inch). Fossils sometimes form strange structures, but Pradel and his colleagues are pretty sure that they’re actually seeing a brain. It has the shape of a ratfish brain, including the various sections of a ratfish brain. And it even has nerves that extend to the right places to connect to the eyes and ears.

You may be struck by how small the brain (yellow) is compared to the braincase (red). If the scientists are right, it’s a cautionary tale for those who would estimate the size and shape of ancient fish brains from their braincases. But perhaps, in the future, researchers will find more actual brains, and will be able to chart the evolution of these delicate organs in greater detail.

Source: Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography.

Movie: Courtesy of Alan Pradel

Here are excerpts from the panel discussion on the brain I moderated at the Franklin Institute. The scurrilous rumor about me and toy soldiers pops up about 4 minutes into Sam Wang’s discussion of false memories.