Friday, December 18, 2009

Move over, monkeys, there's a new smart animal in town

We used to think that the use of tools was a hallmark of our human species. Then we learned that in fact, some primates also use tools. For example, orangutans will use a stick to poke at ant hills to collect the fleeing ants for a tasty snack. The real piece of humble pie came when we discovered that birds also use tools. That’s right. Tiny-brained crows are able to use a curved stick to get at a treat in a tight spot. So I can’t say that it came as a shock to learn that the octopus, an invertebrate, also recently joined the smarty-pants tool-using club.

Most people who spend all day procrastinating working at their desk and have internet access probably already saw this neat video featuring an octopus carrying around a coconut shell and hiding in it:

In a recent article published in the journal Current Biology (which includes the video above), researchers describe how octopuses (also called octopodes, I had to look this up) carry coconut shells for later defensive use. The octopuses are seen scurrying around (on distances up to 20 meters!) with the shells cumbersomely positioned between their tentacles, and later assemble the two halves of coconut shells and hide inside. The authors stress that the interesting feature of this behavior is that when the octopuses are carrying the shells, they are at an increased predator risk, because they move slower than normal and their heads are exposed. Therefore, the only benefit of carrying the shells is the future use of these shells as a shelter. Apparently, that’s an amazing display of foresight for an organism that uses most of it brain cells to control its too many limbs.

While the video is definitely captivating, I think that whether this study is groundbreaking or not depends a lot on what the definition for “tool use” is. In the article, the researchers state that “a tool provides no benefit until it is used for a specific purpose”, so shelters like those of the hermit crabs don’t qualify. But even though the shells are used at a later time point, I’m not sure about calling them “tools”. I guess I mostly see them as a shelter. Is a shelter a defensive tool? Ah, semantics…

Reference: Defensive tool use in a coconut-carrying octopus. (2009) Finn JK, Tregenza T, Norman MD. Current Biology 19(23) :1069-70.

Friday, December 11, 2009

Personal space invaders

My last post was about H.M., a man who was missing a part of his brain called the hippocampus. Studying H.M. helped us to greatly improve our understanding of several functions of this brain region. Needless to say, after all the attention generated by the study of this patient, every neuroscientist out there was on the hunt for a patient missing different parts of their brain. By this time, gone was the era when we could butcher people just for kicks, so scientists waited around.

Luck struck a group of scientists from California recently. They came across patient S.M., a 42 year-old woman missing her entire amygdala, a part of your brain not very far from the hippocampus. Studying this woman confirmed a lot of things we already knew about the amygdala, for example that it’s important for fear. However, S.M. thought us something new: the amygdala is the part of your brain that controls your perception of an elusive concept: personal space.

The study of S.M. consisted of having her indicate to the experimenter at which point she felt uncomfortable while a person would approach her from across the room. The chin-to-chin preferred distance was then compared with that of healthy, age-matched controls. S.M.’s preferred distance was significantly smaller than the preferred distance of the control subjects. To make sure this wasn’t due to some random fluke, quite a few factors that may influence personal space were controlled for, including presence or absence of eye-contact, familiarity with the person approaching, etc. All in all, there was really no situation that could make S.M. uncomfortable, even when the person would move towards her all the way to the point of touching. The weird thing is that S.M. knew she should feel uncomfortable, and she understood the concept of personal space, but she just wasn’t experiencing it.

It always amazes me to find out that something so vague, so variable (people who live in densely populated places typically have smaller personal spaces), and so elusive is actually regulated by a huge chunk of your brain. It leads me to wonder: is there a part of us, of our mind, of our personality, that isn’t already hardwired in our brain?

While S.M. gave us great insight into the biological basis of personal space, the greatest contribution of this study is possibly the ugliest journal cover image of all times:

Is the point of this story really conveyed by
a woman's face in some guy's armpit?

Reference: Personal space regulation by the human amygdala. (2009) Kennedy D.P., Glascher J., Tyszka J.M., Adolphs R. Nature Neuroscience, 12(10):1226-7.

Friday, December 4, 2009

A memorable amnesiac

When little Henry Molaison was 7 years old, he fell off his bicycle. Little did he know that this event was possibly the first link in a chain of events that eventually made him the most famous patient in the history of neuroscience.

Sometime after his bicycle accident, Henry started having seizures. At first they were just little seizures. Then, when he was 16, he had his first major seizure, and it all went downhill from there. Unable to hold a job and not responding to the anticonvulsant drugs that were available, Henry and his family considered a brain operation. His surgeon, Dr. Scoville, wanted to try a new experimental type of surgery, and Henry went for it. So in 1953, when Henry was just 27 years old, he got both his medial temporal lobes removed (kind of like a lobotomy, but instead of removing the front of the brain, they removed part of the sides, just about at the level of your ears).

The operation was extremely successful: the seizures stopped! Unfortunately, this happy outcome was overshadowed by a very strange “side effect”: Henry now suffered from severe anterograde amnesia, meaning he could no longer form new memories. He also suffered from retrograde amnesia: he could not remember events from three to four days prior to the operation, and other events from a more distant past. But the anterograde amnesia was the most astonishing. You could have a conversation with Henry, then leave the room for a few minutes, and when you came back, it was as if he had never met you. Can you imagine?

Dr. Scoville called on one of his friends, Dr Penfield (that’s right, Wilder Penfield, from MontrĂ©al!) who then sent his graduate student, Brenda Milner, to study Henry. Even after all that had happened to him, Henry remained a friendly guy and was okay with being studied extensively. The knowledge we gained from Henry (known as H.M. until his death to preserve his anonymity) laid the foundations for much of what we know today about memory (which, I agree, isn’t all that much, but still). For example, prior to Henry, it was thought that memories formed all over the brain. Studying him taught us that instead it is the hippocampus, a part of the brain that was removed during his operation, that is crucial in forming memories. Studying Henry also taught us that there are multiple memory systems, a most unexpected discovery. While Henry couldn’t remember what he had for breakfast 10 minutes ago, he could learn a new task, like drawing a star while only looking at his hand in a mirror (do try this at home to understand the challenge it represents). He would get progressively better and faster at it but never remembered doing the task before. This went on until one day he drew the star and exclaimed: “This was much easier than I thought it would be!”. This lead to the notion that there are different types of memory such as declarative (conscious knowledge of facts and events) and procedural (skill-based knowledge).

The reason I’m bringing up Henry today is because this week, one year after his death, neuroscientists at UCSD started slicing up Henry’s brain in extremely thin slices. These slices will be available for scientists all over the world to look at, analyze and study. Even though he’s gone, there is no doubt we still have much to learn from the most famous neuroscience patient.

Reference: The legacy of patient H.M. for neuroscience (2009) Squire, L. R. Neuron 61(1):6-9

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