Brain Never Sleeps

We care about brain stuff blogged by a 2nd year PhD student in neuroscience

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Brain Hat, do you dare to wear it?

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Wooden Brain

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Do you write your posts? or are they entries from other sources? They are really well written..

Thank you for the compliment. It depends on which post you are talking about. I try to write down most of the posts in my own words or at least the essence of other article. Occasionally I move other posts directly to my blog, however in which case I will also post the original source.  

Good luck!

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Informative science video from one of my favoriate youtubers, vividly described how sound was heard by our ears.  

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What happened when there will be a qualification exam next week

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Sensory illusions and lateral inhibition

Lateral inhibition is very widespread within the nervous system.  The general phenomenon is that excitation of a neuron is inhibited by nearby neural activity.  The specifics of the phenomenon take many forms in different parts of the nervous system.

A) A typical receptive field with an inhibitory surround is shown with a “Mexican hat” model, where excitation is shown by a peak and inhibition is shown by a surrounding valley. A single point stimulus generates the same pattern in the spatial distribution of evoked neural activity within the brain.

B) A major function of lateral inhibition is believed to be the sharpening of discrimination, as shown for a two-point stimulus.

This depiction demonstrates “sharpening” of the focus of neuronal activity by lateral inhibition.  At A1, the nervous system is assumed to lack lateral inhibition, so excitation spreads spatially via divergent axonal connections.  The effect of adding inhibitory interneurons is shown at B1.  The right side of the figure shows a graphical representation of the same thing.

The “darkened intersections” illusion can be explained by lateral inhibition.  At the intersections, more of the visual receptive field surrounds is covered by light than elsewhere along the white lines.  Thus there is more lateral inhibition at the intersections and a darker appearance.  The illusion depends on having visual receptive fields with central excitatory regions very roughly the size of the width of the white lines.  When you look  directly at an intersection you place the very tiny receptive fields of the fovea at it, and the illusion disappears.  If the illusion does not work for you, try viewing from a different distance in order to get the right relation of receptive field sizes to line width.

The well-known Muller-Lyer illusion (left) cannot be explained easily by lateral inhibition (though people try).  It may relate to higher-order perceptual processes that interpret the leftmost figure as an intersection of two walls receding toward the intersection and its neighbor as an intersection of two walls extending toward the viewer.  Since the leftmost vertical line is farther away than its neighbor, it must be longer.  Similarly, the Ponzo (railway lines) illusion may be based on interpretation of the near vertical lines as parallel objects receding into the distance.

These illusions may be the result of lateral inhibition between neurons sensitive to different visual slants (orientation detectors).

The twisted cord illusions, or Fraser illusions, also may be the result of inhibition between neurons selective for visual orientation.  The lines of the letters of the word “LIFE” are vertical and horizontal, though they appear slanted.

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This is what happened inside your guitar. This guy puts an iphone into his guitar. Quite amazing string vibration.

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5d old mouse motor neurons from the spinal cord of the standard transgenic mouse model of ALS.

The cone-shaped image is electrode injecting Ca2+ dye into a motor neuron.

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Complete neuron cell diagram

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gyruscinguli:

How I learned our wonderful 12 pairs of cranial nerves.

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Organ of Corti

The organ of Corti (or spiral organ) is the organ in the inner ear of mammals that contains auditory sensory cells, or "hair cells."

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When four is not four, but rather two plus two

Four was long held to be the number of visual objects the brain can keep in mind at once; any more and the system becomes overloaded. New research shows that this limit may, in fact, depend on where in the visual field they appear.

By studying visual working memory in monkeys — whose capacities are surprisingly similar to humans’ — MIT researchers discovered that the limit of four can actually be broken down into two limits of two: one each for the left and right hemispheres of the brain. Because each hemisphere processes input from the right or left half of vision, memory for increasing numbers of objects depends on where in the visual field they appear.

“Surprisingly, we found that monkeys, and by extension humans, do not have a general capacity [for working memory] in the brain,” says Earl Miller, the Picower Professor of Neuroscience in MIT’s Picower Institute for Learning and Memory. “Rather, they have two independent, smaller capacities in the right and left halves of the visual space.” So, not all groups of four objects are created equal: The brain can indeed remember up to four things, but it does best when those things are spaced out into two on the right side and two on the left. Any more than two on one side, and working memory starts to break down.

Source: http://web.mit.edu/newsoffice/2011/miller-memory-0623.html

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Burning tumor in a magnetic field

Tumor cells can be heated to death by using magnetic hyperthermia, an experimental cancer treatment based on the idea that magnetic nanoparticles, when subjected to the magnetic field, and produce heat and cause cell death. Targeted tumor cells are injected with magnetic nanoparticles and then will be placed in a magnetic coil to escalate temperature. Normal cells without the injection of nanoparticles will not be heated up by magnetic field, but tumor cells will quickly be burned due to the heat produced by magnetic nanoparticles.

However, this treatment is not extensively adopted in clinic now due to the modest results from human. The amount of nanoparticles required to produce killing heat can be unacceptable by our immune system, which will start to attack other cells as a result. A group of nanoscientists in South Korea successfully create special nanoparticles that can generate as much as 10 times heat of traditional nanoparticles. These newly created nanoparticles can possibly be used for cancer treatment without negative impact on immune system.

Reference:

Science Now

http://news.sciencemag.org/sciencenow/2011/07/magnetic-nanoparticles-fry-tumor.html?ref=hp

Magnetic Hyperthemia in Wikipedia 

http://en.wikipedia.org/wiki/Magnetic_hyperthermia

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jtotheizzoe:

Beautiful Ramon y Cajal illustration of brain cross-section. Complete, amazing slideshow here.

(via Discover Mag)

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Gene predisposing to homosexuality may benefit success of heterosexual mating

No matter you are gay, bi or straight, you probably wonder why, evolutionarily,  gay gene can not only survive from the nature selection but also spread among a large population given that reproduction is impossible for homosexual couples. There got to be a reason for that. Well, here is a possible explanation. A group of scientists recently find that a heterosexual man with a non-heterosexual twin tends to have more opposite-sex partners than do heterosexual twin pairs. these suggest that genes predisposing to homosexuality may confer a mating advantage in heterosexuals, which may answer the question about the evolution and maintenance of homosexuality in the population.

How to explain that? This study hypothesizes that there should be a corresponding trait that is associated with homosexuality but confers some selective advantage in heterosexuals. This sounds counterintuitive. Right, no girls like her boyfriend to be sissy. However, it is true that some feminine traits in male are appreciated by ladies. Females are more attracted to males who are caring, considerable, kind and tender. They even prefer men with a feminized face (Buss & Barnes, 1986; Howard, Blumstein & Schwartz, 1987). These traits definitely make heterosexual men cuter and sexier.

Phenotypic relationship (A) between gender identity and non-heterosexuality (Kinsey 1-6), and (B) between gender identity and lifetime number of opposite sex sexual partners (with non-heterosexuals removed from the sample)

 They actually recruit a large number sample, consisted of 4904 twins. They measure their sexual orientation, gender identity, and number of opposite-sex partners. What they found out is shown in the above figure, that, a non-heterosexual twin tend to have a higher number of opposite-sex partners than heterosexuals who have a heterosexual twin. Although the approches used in this study is not convincing (e.g. they use number of partners as the index of mating success), it is still enlightening to see the difference considering it's impossible to completely measure all the index objectively.

This is one of many pieces of evidence to show the evolutionary reason for the existence of gay genes. Nevertheless, you are beautiful in you way 'cause God made no mistakes. 

Congratulations, New York!!

Find the original paper here:

http://www.sciencedirect.com/science/article/pii/S1090513808000688

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Cranial Nerves

There are 12 pairs of cranial nerves that arise from the brain.

They are numbered from I – XII in a rostral to caudal direction.

In addition, each nerve is named.

They leave the cranial cavity by passing into foramina, fissures and canals to reach the structures they innervate.

(Felten & Jozefowicz, 2003, p. 157)