I spy, I spy with my little eye

For the last couple of years I have been studying the retinal circuits of mice. While it is amazing how similar visual circuitry is among many species, I am always fascinated by surprising unique strategies that have developed in this system. The human visual system (from the retina to visual cortex) is a remarkable network that can see colors, adapt to a wide range of light intensities, perceive depth and distance, and much more. It is perfectly put-together such that each part contributes to a specific function: the lens focuses the image on the retina, different photoreceptors allow for color detection, our two frontal eyes allow for depth perception through parallax. The visual system of some animals has found other strategies to achieve the same functions, sometimes even using the same tools in new ways!

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Shortly after the burst

Prof. Mike Greenberg talks about his research on Immediate Early Genes

Despite similarities in the numbers of genes and structure of neural circuits, primates have evolved vastly more complex brains and behaviors. What do those differences look like in the brain? A recent paper from the labs of Michael Greenberg and Margaret Livingstone at Harvard Medical School examines how a short (85 base pairs!) sequence in the regulatory region of the OSTN gene, which was previously known as a secreted protein in bone and muscle development, has allowed it to be expressed in the brains of primates, but not those of rodents. The expression of OSTN is special for another reason: it is one of the first primate-specific genes regulated by immediate early genes (IEGs) to be found. IEGs are a group of genes whose transcription in neurons is transient and commonly follows a burst of spiking activity. In their short window of expression many IEGs are known to regulate expression of specific downstream genes. The new paper from the Greenberg and Livingstone labs gives us a peak into how small differences in common molecular pathways may be implicated in the diversity of species. The journey of our knowledge and understanding of IEGs and the genetic response to neural activity is also the journey of the scientist who first observed the expression patterns of IEGs, and who has since dedicated a great deal of his scientific career to investigating them: Professor Michael Greenberg. A few weeks ago, I had the pleasure of sitting down with him to talk about his work, past, present and future.

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Golgi stain of human pyramidal neuron

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As simple as random can be

A few weeks ago I was having a discussion about mathematical models for the prediction of the movements of the stock market. The question was whether there was any use to developing complex algorithms trying to predict these fluctuations. My friend (an economist) argued that while he admits the market value isn’t truly random, incorporating random variables may be the best model we have for it. It turns out that many mathematicians (and quants, economists who analyze market fluctuations using algorithms) have been using “random” models for their predictions. These range from sequences randomly drawn from log-normal distributions, to chaotic systems that may allow for the prediction of market crashes and other rare large movements. I was fascinated by the idea of randomness as a model for complex systems. It seemed particularly interesting to explore this in the context of biological processes, especially when the laws of thermodynamics have described that all physical phenomena drift towards the chaotic state of maximum entropy. Could randomness be a model for circuit wiring and function in the brain?

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The Drosophila mushroom body, shown in the MB010B-GAL4 line. Courtesy of Katrin Vogt.

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The secret life of our brains

A peek into the unconscious brain under anesthesia

In our everyday lives we are aware of ourselves, our behavior, and the sensory perception of our environment. This awareness during awake states is known as consciousness. As much as it is central to our brain activity, it has also been one of the greater mysteries of neuroscience. In our lifetimes we all experience changes in our state of consciousness, particularly in the alternation between sleep and wake states. We may also experience changes in consciousness state when fainting, during an epileptic seizure, and through the effects of psychoactive drugs. What is happening in our brains when our conscious selves are not present?

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Morton’s ether inhaler, as used in one of the first successful demonstrations of general anaesthesia in October 1846. (6)

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Degenerative protein aggregates: a whole body view

A few weeks ago, Vivian wrote a post about prion disease, discussing how understanding the mechanisms of Kuru could help us design treatments for other neurodegenerative disorders characterized by protein aggregations. The accumulation of protein as a pathological process has also been investigted outside the brain. Aging and degeneration are complex system-wide phenomena and studies like the one by Demontis and Perrimon (2011) show that by looking outside the brain we can unveil new whole-body regulatory mechanisms for neurodegeneration.FoxO_blog  (more…)

Transitioning puberty

In 2015 The Danish Girl, Ruby Rose, Caitlyn Jenner, and Transparent paved the road for trans-visibility in mainstream media. This has brought a great deal of attention and debate to the medical and political scene, but a large gap still remains between policy making and our understanding of how trans-sexuality develops through childhood and adolescence, and how we can alleviate the pain and discomfort for trans-adolescents of going through the physical changes puberty. This year the NIH launched the largest longitudinal study on long-term psychological and medical effects of puberty suppressors, a drug for sex reassignment therapy for adolescents with gender dysphoria1.

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Lili Elbe (1926), born as Einar Magnus Andreas Wegener, a Danish transsexual painter whose life was portrayed in the movie The Danish Girl

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With a splash of coffee

As many of us go through our daily routines of coffee self-administration, here a few interesting studies on caffeine and the nervous system.

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Zero degrees of separation

How connectomics is revealing the intricacies of neural networks, an interview with Josh Morgan

 

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Complete scan of a volume of mouse cortex, and complete reconstruction of a few neurons within it (Berning et al., 2015).

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Welcome to the brain: ID access only

Just a 3-pound greyish mass, the brain may not look too intimidating. Yet scientists have puzzled for decades over how to dissect the tight network of the brain’s 100 billion connected neurons that at first all seem alike. Over the last century, the field of neuroscience has developed to investigate this intriguing subject, and within it different approaches have grown into distinct disciplines. These all similarly aim to unravel the networks underlying animal behavior, but do so using different techniques and methods.

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Cell types of the retina, morphologically characterized by Ramon y Cajal. Image from superflux.in

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