neurosciencestuff:

Definitive proof for receptor’s role in synapse development

Jackson Laboratory researchers led by Associate Professor Zhong-wei Zhang, Ph.D., have provided direct evidence that a specific neurotransmitter receptor is vital to the process of pruning synapses in the brains of newborn mammals.

Faulty pruning at this early developmental stage is implicated in autism-spectrum disorders and schizophrenia. The definitive evidence for N-methyl-D-aspartate receptor (NMDAR) in pruning has eluded researchers until now, but in research published in the Proceedings of the National Academy of Sciences, Zhang’s lab had serendipitous help in the form of a mouse model containing brain cells lacking NMDAR side-by-side with cells containing the receptor.

Soon after birth, mammals’ brains undergo significant development and change. Initially, large numbers of synapses form between neurons. Then, in response to stimuli, the synaptic connections are refined—some synapses are strengthened and others eliminated, or pruned.

In most synapses, glutamate serves as the neurotransmitter, and NMDAR, a major type of post-synaptic glutamate receptor, was previously known to play an important role in neural circuit development. Previous research has implicated the importance of NMDARs in pruning, but it remained unclear whether they played a direct or indirect role.

Zhang and colleagues focused on the thalamus, a brain region where synapse pruning and strengthening can be monitored and quantified with relative ease. They got unexpected help when they realized the mouse model they were using had thalamus cells lacking NMDARs right next to cells with normal NMDAR levels.

The researchers showed that the refinement process was disrupted in the absence of NMDARs. At the same time, neighboring neurons with the receptors proceeded through normal synaptic strengthening and pruning, clearly establishing the necessity of NMDARs in postsynaptic neurons for synaptic refinement.

“Whenever I give a talk or meet colleagues,” Zhang says, “the first question that comes up is whether the NMDA receptor is important. It’s good that this is now settled definitively.”

There has been extensive research into synaptic strengthening, and most of these studies indicate that the presence of NMDARs may support the recruitment of larger numbers of another kind of glutamate receptor to strengthen the synaptic connections. How NMDARs regulate the pruning process remains largely unknown, however.

neurosciencestuff:

Unless you have been deaf and blind to the world over the past decade, you know that functional magnetic resonance brain imaging (fMRI) can look inside the skull of volunteers lying still inside the claustrophobic, coffinlike confines of a loud, banging magnetic scanner. The technique relies on a fortuitous property of the blood supply to reveal regional activity. Active synapses and neurons consume power and therefore need more oxygen, which is delivered by the hemoglobin molecules inside the circulating red blood cells. When these molecules give off their oxygen to the surrounding tissue, they not only change color—from arterial red to venous blue—but also turn slightly magnetic.

(Image: Todd Davidson/Stock Illustration Source)

Activity in neural tissue causes an increase in the volume and flow of fresh blood. This change in the blood supply, called the hemodynamic signal, is tracked by sending radio waves into the skull and carefully listening to their return echoes. FMRI does not directly measure synaptic and neuronal activity, which occurs over the course of milliseconds; instead it uses a relatively sluggish proxy—changes in the blood supply—that rises and falls in seconds. The spatial resolution of fMRI is currently limited to a volume element (voxel) the size of a pea, encompassing about one million nerve cells.

Neuroscientists routinely exploit fMRI to infer what volunteers are seeing, imagining or intending to do. It is really a primitive form of mind reading. Now a team has taken that reading to a new, startling level.

A number of groups have deduced the identity of pictures viewed by volunteers while lying in the magnet scanner from the slew of map­like representations found in primary, secondary and higher-order visual cortical regions underneath the bump on the back of the head.

Jack L. Gallant of the University of California, Berkeley, is the acknowledged master of these techniques, which proceed in two stages. First, a volunteer looks at a couple of thousand images while lying in a magnet. The response of a few hundred voxels in the visual cortex to each image is carefully registered. These data are then used to train an algorithm to predict the magnitude of the fMRI response for each voxel. Second, this procedure is inverted. That is, for a given magnitude of hemodynamic response, a probabilistic technique called Bayesian decoding infers the most likely image that gave rise to the observed response in that particular volunteer (human brains differ substantially, so it is difficult to use one brain to predict the responses of another).

The best of these techniques exploit preexisting, or prior, knowledge about pictures that could have been seen before. The number of mathematically possible images is vast, but the types of actual scenes that are encountered in a world populated by people, animals, trees, buildings and other objects encompass a tiny fraction of all possible images. Appropriately enough, the images that we usually encounter are called natural images. Using a database of six million natural images, Gallant’s group showed in 2009 how brain responses of volunteers to photographs they had not previously encountered could be reconstructed.

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neurosciencestuff:

July 30, 2012

UC Irvine scientists have discovered intriguing differences in the brains and mental processes of an extraordinary group of people who can effortlessly recall every moment of their lives since about age 10.

The phenomenon of highly superior autobiographical memory – first…

neurosciencestuff:

Tuesday, July 31, 2012

TAU researchers develop bioactive coating to “camouflage” neutral electrodes

Brain-computer interfaces are at the cutting edge for treatment of neurological and psychological disorder, including Parkinson’s, epilepsy, and depression. Among the most promising advance is…

Eyes and Attention of Men and Women Meander in Distinctly Different Ways

Dr. Itti’s lab studied 34 participants as they watched videos of people being interviewed. Behind the interview subjects, within the video frame, pedestrians, bicycles and cars passed by — distractions included to pull attention away from the filmed conversation.

While participants watched and listened to the interview, another camera was pointed at participants’ eyes, recording the movement of their pupils as they glanced across the screen.

Researchers discovered the following:
• Men, when focused on the person being interviewed, parked their eyes on the speaker’s mouth. They tended to be most distracted by distinctive movement behind the interview subjects. 
• By contrast, women shift their focus between the interview subject’s eyes and body. When they were distracted, it was typically by other people entering the video frame.

asktheimprobableinvestigators:

I’M GLAD YOU ASKED. A BOSUN IS THAT MEMBER OF A SHIP’S CREW WHO IS IN CHARGE OF THE NONLICENSED, OR NOT-ALL-THAT-SENIOR, CREW (OFTEN CALLED RATINGS). TRADITIONALLY THE BOSUN WOULD BE REQUIRED TO BE SKILLED IN THE CRAFT OF MARLINSPIKE SEAMANSHIP, BUT THESE…

neurolove:

Who doesn’t love brainbow?

For people who don’t know, brainbow is a type of stain created by a researcher at Harvard.  Essentially, differing amounts of flourescent proteins in every single cell mean that each neuron is a different color.  This means it is much easier to follow a single neuron along the axon and dendrites and see where it connects to, etc. since all the surrounding cells are different colors. I just love the way it looks!

[Image Source]

neurosciencestuff:

ScienceDaily (May 24, 2012) — Researchers have identified a protein necessary to maintain behavioral flexibility, which allows us to modify our behaviors to adjust to circumstances that are similar, but not identical, to previous experiences. Their findings, which appear in the journal Cell…

I’m curious as to whether or not these findings hold true in people with Autism Spectrum Disorders. 

neurosciencestuff:

ScienceDaily (May 24, 2012) — Experiencing strong emotions synchronizes brain activity across individuals, a research team at Aalto University and Turku PET Centre in Finland has revealed.

Experiencing strong emotions synchronizes brain activity across individuals. (Credit: Image courtesy…

neurosciencestuff:

ScienceDaily (May 10, 2012) — Research into hearing loss after exposure to loud noises could lead to the first drug treatments to prevent the development of tinnitus.

Researchers in the University of Leicester’s Department of Cell Physiology and Pharmacology have identified a cellular…