neurodudes

This new technique from Cori Bargmann’s lab is one of the neatest that I’ve seen in a while. The authors split GFP into two pieces, expressing one piece presynaptically and the other postsynaptically. This creates functional (ie. fluorescing) GFP only at sites of synaptic contact where the protein can reconstitute. They call the technique GFP Reconstitution Across Synaptic Partners (GRASP). Check out an example labeling here:

The neurons are expressing mCherry in the cytoplasm but GFP is expressed only at the site of synaptic contacts where the split GFP peptides can be reconstituted into a complete GFP fluorophore.

We’ve certainly come a long way. (And I never knew about Music Portal behind that thing.)

Download MP3It’s hard to judge the merits of this particular interface but I’m sure this is just the first of many such devices that we’re about to see (demo starts 2:00):

This is an Emotiv headset. More than the gaming application, I like the idea of using it for IM emoticons.

Anyone know if the consumer version will require gel for the scalp electrodes? Hmmm… if gamers are the target audience, I think I have a good idea for a cross-promotional opportunity here.

Video-Rate Far-Field Optical Nanoscopy Dissects Synaptic Vesicle Movement

Just the optical engineering alone here deserves mention: 28 frames per second at 62nm resolution (well below the diffraction limit of 260nm for light of the wavelength used)! STED (or stimulated emission depletion, developed in Stefan Hell’s group) is ideal for visualizing synaptic vesicles, whose small size (~50nm) has typically confined them to the domain of electron microscopists. The ability to get high-speed STED allowed the researchers to track individual vesicles and their path dynamics. They conclude that vesicle movement has both motor-driven and diffusive components (ie. a biased random walk). I’m sure with more time and more analysis there will be a lot of interesting applications for this kind of real-time vesicle tracking. Perhaps in the near future we will have single vesicle “minis” monitored at multiple sites through microscopy instead of just one or two sites electrophysiologically…

Here’s the resolution difference between STED and confocal for a single vesicle:

And, for those of you with ~$1.25M lying around, you can now purchase a STED setup directly from Leica!

The relatively recently discovered cannabinoid receptors has me wondering how many other neuroreceptors may be left to discover. One way to estimate the number of these is to screen the genome and look for sequences that look like receptors. This paper says that people have done that for the special case of G protein-coupled receptors (GPCRs), and that the result is that, excluding receptors involved in “chemosensory responses such as taste and olfaction”, there are “367 receptors (1), of which some 200 have been shown to bind known transmitters (3). This leaves about 160 orphan GPCRs that are not activated by any known transmitters and thus are genes with unknown function.”

Pascual-Marqui has posted a preprint and would like comments. Read on for details.

(more…)

Emotiv is a company trying to do a neuro (EEG) interface to game platforms.

Emotiv Home

Seems ambitious. Do EEG interfaces have a fast enough information transfer rate (bits/sec) for gaming? Maybe it’s not necessary if the game is just detecting your “mood” in conjunction with a standard keypad controller but seems to me you’d want to try and boost bit rates (as several EEG groups, like this one at Fraunhofer, are doing) as much as possible.

Anyone used this device?

Finally, they’ve figured out something that neural systems have capitalized on for a while: Using all 3 dimensions. Check it out:

NYT article on Stuart Parkin and racetrack memory
IBM Almaden page on racetrack memory

And a nice semi-technical discussion from EE Times on current 2D RAM and how racetrack memory takes advantage of 3 dimensions. A key concept here (and an old one, see bubble memory below) is “massless motion”: Applying a current to a tape moves the magnetic domains along in a similar manner to mechanically moving the tape.

On the macro scale, a similar type of memory called bubble memory was available up to the early 1980s when it was replaced with hard disks. Seems like high speed (pushing the correct magnetic portion of the nanowire to the read head) and doing so without excessive current are what really make this a viable technology now.

“It sounds like a science-fiction version of stupid pet tricks: by toggling a light switch, neuroscientists can set fruit flies a-leaping and mice a-twirling and stop worms in their squiggling tracks. But such feats, unveiled in the past two years, are proof that a new generation of genetic and optical technology can give researchers unprecedented power to turn on and off targeted sets of cells in the brain, and to do so by remote control…”

Reviews the use of photosensitive proteins in neuroscience and even gives a shout-out to Ed Boyden, of Stanford and MIT fame…

– Davie (who had the same advisor as Ed for about a day and is therefore 0.01% more famous by association)

There’s a nice NRN review on the many recent papers on therapeutic use of transcranial magnetic stimulation.

Is there a future for therapeutic use of transcranial magnetic stimulation?

The past year has seen the publication of a remarkable number of papers about the potential therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) in conditions ranging from cocaine addiction to stroke and depression. Are we witnessing the discovery of a miraculous cure-all or will this bubble burst like the magnetotherapies of the Victorian era1? We argue below that there is good evidence that rTMS can produce after-effects on the brain, and that these translate into effects on simple behaviours. However, the rationale for applying the same methods to treat disease is in many cases unclear.

Braintool.org is a project, recently launched by Dejan Vucinic at the Salk Institute, which acts as a Wiki for the basic-science neural tools field. I highly encourage people to contribute, and to make use of, the information. Topics of note include:

• Tissue preparation and surgery
• Labeling cells
• Extracellular electrode recording
• Stimulation and remote control of neurons
• Electroencephalography (EEG)
• Optical microscopy
• Optical functional imaging
• Electron microscopy
• Functional magnetic imaging (fMRI)

In its own words, Braintool “contains hands-on advice, contributed by experts, for the practicing experimental neuroscientist. Here you will find information that often gets buried into obscure methods journals or into the invisible Supplementary Materials section of published articles.” Let’s face it — there is almost an infinite amount of work to do on the brain, and if we don’t leverage our technological innovations towards great progress, we are never going to understand the whole thing. Start accelerating neuroscience now!

–Ed