You can lead a horse to water

I’m not sure what to file this thought under, but I figure I may as well share it. I was holding a couple of my wife’s horses today while our farrier, Chris, shoed them, and we got to talking about horses instincts. I think I was asking about horses hooves in the wild, how they responded to injury or heavy use. He joked that the only reason we really needed to clip their hooves was that we kept them in overly-soft paddocks, fed them high energy feed, and thus they didn’t cover the miles and miles that wild horses would have to in order to get enough to eat. In other words, the ecological niche we created for our horses was so unusual that the whole horse physiology was different.

He also pointed out that most domestic horses, unless they are trained to, will not drink from natural water sources. If they’re accustomed to drinking from troughs or buckets, some will die of thirst before drinking out of a creek or lake. They may recognize that it’s water on some level, but they don’t trust the source unless they’re used to encountering water in this way. Obviously, they might be socialized early in order to become acquainted with water in a wider variety of forms.

I don’t have any information on whether or not a horse has ever died from thirst in the presence of lakes or streams, so I can’t confirm this. (I’ll look it up and report back.) If it is true — and I have no reason to doubt Chris as he’s a deeply knowledgeable guy on the subject of horses — it would be a fascinating case of a very useful ‘instinct’ not being inevitable. It also explains the ‘You can lead a horse to water…’ proverb, which I didn’t really understand until today, in retrospect.

Jeff Lichtman’s Brainbows

Take a genetically-engineered mouse and add color. That is what Jeffrey Lichtman, Jean Livet, and Joshua Sanes have done. Start by inserting genes that turn neurons fluorescent hues of yellow, red and cyan. Then add some more DNA that randomly expresses those three genes. Presto, rainbow brains.

As a Harvard Science piece reports, “By activating multiple fluorescent proteins in neurons, neuroscientists at Harvard University are imaging the brain and nervous system as never before, rendering their cells in a riotous spray of colors dubbed a ‘Brainbow.’ This technique… allows researchers to tag neurons with roughly 90 distinct colors, a huge leap over the mere handful of shades possible with current fluorescent labeling.”

So many colors in something as complex and elegant as a neuron produces striking images, and I have included many here. These images also permit the study of fields of neurons, from the life course of one neuron to the patterns of connections between neurons. Hence the emerging field of “Connectomics” which “attempts to physically map the tangle of neural circuits that collect, process, and archive information in the nervous system.”

I stumbled across Lichtman’s images in two publications recently. Harvard Magazine features his work, along with five other Harvard scientists, in this month’s feature article, Shedding Light on Life: Advances in Optical Microscopy Reveal Biological Processes as They Unfold. The magazine also provides an online collection of short video clips called Lights! Microscopes! Action! Across the Charles River, MIT’s Technology Review features Lichtman’s work as one of its Ten Emerging Technologies of 2008, complete with an accompanying video featuring Lichtman.

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Rats’ visual systems made plastic by anti-depressants

Blogging on Peer-Reviewed ResearchMy mind raced for potential titles to a post when I read the recent report from Science, ‘The Antidepressant Fluoxetine Restores Plasticity in the Adult Visual Cortex,’ by a team headed by José Fernando Maya Vetencourt (abstract), but I’ve opted to be demure, rather than go with some of my other options (like ‘Anti-depressants the “Cocoon” pool for brain?’ or something similarly outrageous).

The research team investigated wither fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could restore plasticity in the visual system of adult rats. They chose fluoxetine because long-term regimens of the drug promote neurogenesis and synaptogenesis in the hippocampus and increased activity of neurotrophin brain-derived neurotrophic factor (BDNF) and its primary receptor, TrkB (close paraphrase to the original article). These effects have been shown essential to the drug’s effect; block one of these processes, and the anti-depressant doesn’t work nearly as well. In order to test plasticity, the team studied how rats responded to monocular deprivation — covering one eye — both the initial shift in ocular dominance and then the recovery of visual function after long-term monocular deprivation. In general, the fluoxetine-treated rats responded in exaggerated fashion to both conditions, suggesting that plasticity was greater with long-term administration of the drug. From the abstract:

We found that chronic administration of fluoxetine reinstates ocular dominance plasticity in adulthood and promotes the recovery of visual functions in adult amblyopic animals, as tested electrophysiologically and behaviorally. These effects were accompanied by reduced intracortical inhibition and increased expression of brain-derived neurotrophic factor in the visual cortex. Cortical administration of diazepam prevented the effects induced by fluoxetine, indicating that the reduction of intracortical inhibition promotes visual cortical plasticity in the adult. Our results suggest a potential clinical application for fluoxetine in amblyopia as well as new mechanisms for the therapeutic effects of antidepressants and for the pathophysiology of mood disorders.

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The Buzz about Epigenetics: Genes, Behaviour and the Environment

Our contemporaries in Behavioural genomics and Neurobiology are suggesting that epigenetics may be the key to understanding how the environment interacts with genes to produce obesity, longevity, sterility, mental illness, and maybe even cancer. But what is epigenetics? And, why is it important to Neuroanthropology?

Epigenetic processes provide a way for environmental factors to affect gene activity. These processes involve the chemical modification of the genome resulting in an alteration of gene expression. While the underlying DNA sequence remains unchanged, the activity of particular genes can be turned on or off. Nutrition, exposure to toxins and other exogenetic mechanisms can all be potentially involved in epigenetic activity. These environmental influences can act upon RNA transcripts, cellular structures, DNA methylation/chromatin remodeling, and even prions. For example, smoking can effect your epigenome which is believed to result in some forms of cancer.

Human research into epigenetics can be fraught with ethical dilemmas, and can take a number of generations before sufficient data is produced. But, this is where anthropologists come in. Behavioural and environmental data coupled with social statistics from communities across the world can provide scientists with useful data for analyzing long-term mental and physical health in relation to the environment and corresponding socio-cultural behaviours. Such data is particularly useful when collected from communities exposed to biological disasters or specific nutritional limitations.

To study epigenetics inside the very cells of our body, where most anthropologists are not able to venture, there is another option. Now, for the first time in an insect species, epigenetic modification has been identified and functionally implicated. The recent sequencing of the honey bee genome in 2006 has allowed scientists to discover genes that mediate epigenetic effects.

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Snakes and spiders on the brain

A little while ago, I wrote a piece, ‘Innate’ fear of snakes?, in which I took issue with a University of Virginia study that was described by a science writer (and perhaps by the researchers) as showing that humans have an ‘innate’ fear of snakes. At the time, I argued that what their research had shown was a propensity to pay attention to snake shapes, and not that this was an ‘innate’ fear, for reasons that I banged on about for a fair few words (go to the original if you’re a glutton for snake-related musings).

And now, vindication. Well, as much vindication as you can get considering that psychological research is liable to be undermined by another study in the next few months. According to a posting today on Science Daily, ‘Unlocking The Psychology Of Snake And Spider Phobias,’ researchers at the University of Queensland have tested both snake experts and those who are naive about the creatures to see if there is an innate fear.

In the study, researchers compared the responses to stimuli of participants with no particular experience with snakes and spiders, to that of snake and spider experts.
“Previous research has argued that snakes and spiders attract preferential attention (they capture attention very quickly) and that during this early processing a negative (fear) response is generated… as an implicit and indexed subconscious [action],” Dr [Helena] Purkis said.
“We showed that although everyone preferentially attends to snakes or spiders in the environment as they are potentially dangerous, only inexperienced participants display a negative response.”

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The history of mind-altering mechanisms

Katherine MacKinnon of St. Louis University just dropped me a line to point out a recent book review in The New York Times, I Feel Good, by Alexander Star. Star reviews the book, On Deep History and the Brain, by Daniel Lord Smail (University of California Press). Amazon raters are giving it 4.5 stars at the moment, if you want to check it out through the bookseller. Normally, I’d trust Daniel to write our best stuff about ‘mind-altering’ chemicals of all sorts, but this book review just set me to thinking, so I thought I’d put my own two cents in.

Smail wants to tell the story of humanity as a series of ‘self-modifications of our mental states,’ according to the reviewer Star:

We want to alter our own moods and feelings, and the rise of man from hunter-gatherer and farmer to office worker and video-game adept is the story of the ever proliferating devices — from coffee and tobacco to religious rites and romance novels — we’ve acquired to do so. Humans, Smail writes, have invented “a dizzying array of practices that stimulate the production and circulation of our own chemical messengers,” and those devices have become more plentiful with time. We make our own history, albeit with neurotransmitters not of our choosing.

Smail is really a historian, but his venture into a kind of neuro-history shows the robustness of the emerging awareness that the brain is shaped by what humans do. Star points out that most ‘macro-history’ these days — long, sweeping accounts of human evolution and what is sometimes called something prosaic like the ‘rise and fall of civilizations’ — is not being written by historians, but rather by folks like Jared Diamond. In contrast, Smail is a medieval historian.

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