Plant neuroscience

Plants Found to Show Preferences for Their Relatives – NYTimes.com

Two amazing things here:

  1. Plants missing photosynthetic enzymes of their own that migrate directionally toward “victim” plants. This behavior has an uncanny resemblance to axon guidance. Make sure to view the time-lapse video in the NYT article. Here’s an image from the PSU website:

  2. Plants capable of identifying kin and “being nice” to kin while going into a competitive mode of root growth with non-kin. Amazing.

It refreshing to see this kind of interesting behavior without any neurons involved. It makes me think (realize) that the idea of a neuron or a neural system has many components and there might not be any good reason to assume that a single cell must have all of those properties or none of them. Something like a neuron-like cell that’s not a neuron in the classical sense. Anyone know of other examples?

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Your Brain Is A Cartographer

The concept that the brain holds maps of the surface of the body in the primary sensory and motor cortex is a fascinating but well known fact to the field of neuroscience since the early work of Wilder Penfield. What is less broadly appreciated is the concept of “peripersonal space”. A new book by Sandra and Matthew Blakeslee describes peripersonal space in the following way:

The maps that encode your physical body are connected directly, immediately, personally to a map of every point in that space and also map out your potential to perform actions in that space. Your self does not end where your flesh ends, but suffuses and blends with the world, including other beings. […] Your brain also faithfully maps the space beyond your body when you enter it using tools. Take hold of a long stick and tap it on the ground. As far as your brain is concerned, your hand now extends to the tip of that stick. […] Moreover, this annexed peripersonal space is not static, like an aura. It is elastic. […] It morphs every time you put on or take off clothes, wear skis or scuba gear, or wield any tool. […] When you eat with a knife and fork, your peripersonal space grows to envelop them. Brain cells that normally represent space no farther out than your fingertips expand their fields of awareness outward, along the length of each utensil, making them part of you.

What I appreciate about this, besides the stretchy comic book characters that it makes me think about, is that it provides a powerful perspective to begin piecing together a mass of disparate neuroscience data, which the Blakeslee’s capitalize on.

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Postdoctoral positions at Janelia Farm

Postdoctoral/research scientist positions are available in the inter-disciplinary group of Dmitri Chklovskii at the new Janelia Farm Research Campus of the Howard Hughes Medical Institute located in the suburbs of Washington, D.C. Candidates are expected to have a PhD in neuroscience, physics, computer science or electrical engineering. Most of the work is theoretical or computational and is done in collaboration with several experimental laboratories. Successful applicants will work on projects centered on neuronal circuits such as high-throughput reconstruction of wiring diagrams as well as combining structural and physiological data to infer circuit function. Salary will be commensurate with qualifications. For more information about research directions in the group please see: http://www.hhmi.org/research/groupleaders/chklovskii.html
Interested applicants should send their CV and a statement of research interests to mitya (at) janelia.hhmi.org, and arrange for three recommendation letters to be emailed to me.

A ubiquitous human parasite that shapes human culture?

In the provocative-hypothesis-of-the-week department:

Kevin Lafferty, a parasitologist, has put forth the idea that a fairly ubiquitous parasite (infecting O(10%) of Americans, and up to 2/3 of people in places like Brazil) is responsible for some of the diversity of human culures (1). The parasite uses common housecats to increase its transmission to the next host in the life cycle, and has a subtle effect on human personality, with some studies claiming that it even causes neuroticism, and even schizophrenia. (One clinical report (2) claims that “subjects with latent toxoplasmosis had higher intelligence [and] lower guilt proneness.” Hmm!)

Anyway, Lafferty noted that toxoplasmosis varies in prevalence from world region to world region, and then tries to draw correlates between these prevalences and local cultures:

“Drivers of the geographical variation in the prevalence of this parasite include the effects of climate on the persistence of infectious stages in soil, the cultural practices of food preparation and cats as pets. Some variation in culture, therefore, may ultimately be related to how climate affects the distribution of T. gondii, though the results only explain a fraction of the variation in two of the four cultural dimensions, suggesting that if T. gondii does influence human culture, it is only one among many factors.”

I wonder how one could test this hypothesis? Look for recent immigrants from one culture to another, who have lower Toxoplasmosis incidence? (Preferably finding populations that go in opposite directions, as a control.) Track culture change vs. migration vs. climate change?

Unlikely, perhaps. But nice that people are still thinking big 🙂

Ed

(1) Lafferty, K
Can the common brain parasite, Toxoplasma gondii, influence human culture?
Proceedings of the Royal Society B: Biological Sciences
doi:10.1098/rspb.2006.3641

Picked up by the popular press here

(2) Flegr J, Havlicek J.
Changes in the personality profile of young women with latent toxoplasmosis.
Folia Parasitol (Praha). 1999;46(1):22-8.

Personality in animals

The Animal Self – New York Times

Interesting read on the return of personality psych (and the use of the term “personality”) to ethology.

Some tidbits:

It was back in 1991 that Anderson and Jennifer Mather, a psychologist from the University of Lethbridge in Alberta, Canada, first decided to undertake a joint personality study of 44 smaller red octopuses at the aquarium as a way to begin to codify and systematize what they thought they had been observing. Using three categorizations from a standard human-personality-assessment test – shy, aggressive and passive – their data would ultimately show that the animals did consistently clump together under these different categories in response to various stimuli, like touching them with a bristly test-tube brush or dropping a crab into the tank.

“The aggressive ones would pounce on the crab,” Anderson told me. “The passive ones would wait for the crab to come past and then grab it. The shy animal would wait till overnight when no one was looking, and we’d find this little pile of crab shell in the morning.”

Anderson and Mather’s resulting 1993 paper in the Journal of Comparative Psychology, entitled “Personalities of Octopuses,” was not only the first-ever documentation of personality in invertebrates. It was the first time in anyone’s memory that the term “personality” had been applied to a nonhuman in a major psychology journal.

And,

Alison Bell has done related experiments with sticklebacks. It has long been clear to researchers that fish that have lived for many generations in the proximity of dangerous predators are less bold and less aggressive than animals that have lived relatively risk-free. What Bell discovered is that those cautious tendencies outlast the presence of risk, even by a generation. When she moved sticklebacks who had always lived in a high-risk environment into a low-risk environment, she found that not only did they retain their cautious tendencies, but so did their offspring. Even fish raised from birth in a low-risk environment behave more fearfully if raised by a particularly vigilant father from a high-risk background.

“There’s definitely the effect of genetic difference,” Bell explained, “but there’s also the effect of what is experienced as they grow up. Genotype and environment interactions make it difficult to detect the effects of genes, because you have to take the environment into account. This is annoying to geneticists.” To scientists like Bell who are studying the interplay of genes and environment, however, it is of profound interest.

On the function of sleep

The nice NYT article on the function of sleep follows on a recent NIH-funded Nature insight series.

Some interesting facts from the NYT article:

  • Sleep patterns vary greatly. Some bats sleep 20 hours, giraffes get 2 hours. (hmmm… grad students might be evolving toward giraffes…)
  • Sleep has recently been found to occur in invertebrates too. Alternatively stated: Sleep is evolutionarily very old.
  • Slow wave sleep is also found in fruit flies. (Divergence from fruit flies for us was 600 million years ago.)
  • Some people don’t have any REM sleep. Behaviorally, these people are entirely normal, implying that it’s purpose might not be as obvious as one had thought (ie. required for the preservation of new memories, etc.)
  • If you put a bunch of ducks in a row, the ones on the inside will sleep more often with both eyes closed. The ones on the outside will sleep with one eye open and it is (always?) the eye facing outward from the huddle. They are able to “sleep” one half of the brain at a time and, apparently, this sleeping with one eye open was lost in higher mammalian evolution. Fascinating.