UPDATE : DIADEM Final Results

15 09 2010

The DIADEM automated neuronal reconstruction contest has finished.  Accurate, fast, and high-resolution automated neuron reconstruction is of vital importance to cracking the mystery of how neural circuits perform. Even with perfect knowledge of the firing patterns of every cell in a circuit, our understanding of how these patterns are produced and how the information is processed would be quite limited.  True understanding requires knowledge of the precise wiring diagram.  This prize is a good first step towards bringing awareness of this tricky problem to the world’s best computer scientists.

$75,000 in prize money was to go to the group that was able to produce high-quality reconstructions of neuronal structures at least 20x faster than by-hand reconstructions.  In the finals, the fastest speed achieved was 10X the by-hand method. Some groups were hindered by slight variances in the source data formatting, which normally isn’t a big deal unless you only have 20 minutes to produce as much reconstruction as possible…

Since no group was able to beat the hard floor, but substantial progress was made, the money was distributed amongst these finalists.

Badrinath Roysam Team, $25,000
“for the better overall generality of their program in producing robust reconstructions by integration of human and machines interactions.”

Armen Stepanyants Team, $25,000
“for the better overall biological results in the spirit of pure automation.”

Eugene Myers Team, $15,000
“for the excellent quality and strength of their algorithm.”

German Gonzalez Team, $10,000
“for their deeper potential, more original approach, and ultimate scalability of their proposed solution.”

Deniz Erdogmus Team
“for elevating themselves above the current state of automated reconstructions…with a deep understanding of the technical and scientific problems.”

Congrats to the placing teams.

Advertisements




Three Cheers for GCaMP : Optogenetic Brain Reading

9 11 2009

Three papers are out online in Nature Methods that show big improvements in calcium imaging with genetically encoded sensors.  They are are based on the fluorescence intensity indicator, GCaMP.   GCaMP, first developed by Junichi Nakai, consists of a GFP that has been circularly permuted so that the N and C termini are fused and new termini are made in the middle of the protein.  Fused to one terminus is calmodulin and the other is a peptide, M13, that calmodulin (CaM) binds to in the presence of calcium. The name is supposed to look like GFP with a CaM inserted into it, G-CaM-P.  Normally the GFP is dim, as there is a hole from the outside of its barrel into the chromophore.  Upon binding calcium, this hole is plugged and fluorescence increases.

Crystal structure of GCaMP2

The first paper, A genetically encoded reporter of synaptic activity in vivo, from Leon Lagnado’s group, targets GCaMP2 to the outer surface of synaptic vesicles. This localization allows the fluorescence signal to be confined to the presynaptic terminal, where calcium fluxes in response to action potentials are high.  This targeting improves the response magnitude of GCaMP2 and permits the optical recording of synaptic inputs into whatever region of the brain one looks at.  They demonstrate the technique in live zebrafish.

In the second paper, Optical interrogation of neural circuits in Caenorhabditis elegans, from Sharad Ramanathan’s group, GCaMP2 has been combined with Channelrhodopsin-2 to perform functional circuit mapping in the worm.   Since the worm’s structural wiring diagram has been essentially solved, functional data could say much about how “thick” the wires between each cell are.  Unfortunately, with GCaMP2, the responses are too slow and weak to distinguish direct from indirect connections.

Finally, we have published a paper, Imaging neural activity in worms, flies and mice with improved GCaMP calcium indicators, describing the improved GCaMP3.  This indicator has between 2-10x better signal to noise than GCaMP2, D3cpv and TN-XXL, depending on the system you are using.  It’s kinetics are faster and it is more photostable than FRET indicators, and the responses are huge.  When expressed in motor cortex of the mouse, neuronal activity is easily seen directly in the raw data.  Furthermore, the sensor can be expressed stably for months, making it a potential tool for observing how learning reshapes the patterns of activity in the cortex.

Screen shot 2009-11-09 at 7.19.27 PM

Imaging of mouse motor cortex (M1) expressing the genetically-encoded calcium indicator GCaMP3 through a cortical window. After 72 days of GCaMP3 expression, large fluorescence transients can be seen in many neurons that are highly correlated with mouse running.

GCaMP3 is not perfect. It cannot reliably detect single action potential in vivo in mammals, though I doubt that any existing GECI can. Work continues on future generations of GCaMP that may achieve 100% fidelity in optical reading of the bits in the brain. However, there is considerable evidence from a number of groups that have been beta-testing the sensor, including the Tank lab of “quake mouse” fame, that it is a significant leap forward and unlocks much of the fantastic and fantasized potential of genetically-encoded calcium indicators.

Screen shot 2009-11-09 at 7.20.12 PM

Comparison of fluorescence changes in response to trains of action potentials in acute cortical slices.

I will try to post a more complete writeup of GCaMP3 for Brain Windows soon, with an unbiased eye to its strengths and weaknesses.  We worked very hard to carefully characterize this sensor’s effects on cellular and circuit properties.  If you have any questions about GCaMP3, please post them to the comments.

For further info about strategies for GECI use and optimization, check out our previous paper, Reporting neural activity with genetically encoded calcium indicators in Brain Cell Biology.

The official press release from HHMI regarding GCaMP3 is available here.





Annual Reviews worth reading

22 07 2009

Annual Reviews of Neuroscience published their 2009 issue recently.  These articles are usually a great way to catch up with a field, particularly when they are recently published.  Here are a few that might be of interest to the Brain Windows reader.

Daniel E. Feldman

Sensory experience and learning alter sensory representations in cerebral cortex. The synaptic mechanisms underlying sensory cortical plasticity have long been sought. Recent work indicates that long-term cortical plasticity is a complex, multicomponent process involving multiple synaptic and cellular mechanisms. Sensory use, disuse, and training drive long-term potentiation and depression (LTP and LTD), homeostatic synaptic plasticity and plasticity of intrinsic excitability, and structural changes including formation, removal, and morphological remodeling of cortical synapses and dendritic spines. Both excitatory and inhibitory circuits are strongly regulated by experience. This review summarizes these findings and proposes that these mechanisms map onto specific functional components of plasticity, which occur in common across the primary somatosensory, visual, and auditory cortices.

Heidi Johansen-Berg and Matthew F.S. Rushworth

Diffusion imaging can be used to estimate the routes taken by fiber pathways connecting different regions of the living brain. This approach has already supplied novel insights into in vivo human brain anatomy. For example, by detecting where connection patterns change, one can define anatomical borders between cortical regions or subcortical nuclei in the living human brain for the first time. Because diffusion tractography is a relatively new technique, however, it is important to assess its validity critically. We discuss the degree to which diffusion tractography meets the requirements of a technique to assess structural connectivity and how its results compare to those from the gold-standard tract tracing methods in nonhuman animals. We conclude that although tractography offers novel opportunities it also raises significant challenges to be addressed by further validation studies to define precisely the limitations and scope of this exciting new technique.

Nicholas G. Hatsopoulos and John P. Donoghue

The ultimate goal of neural interface research is to create links between the nervous system and the outside world either by stimulating or by recording from neural tissue to treat or assist people with sensory, motor, or other disabilities of neural function. Although electrical stimulation systems have already reached widespread clinical application, neural interfaces that record neural signals to decipher movement intentions are only now beginning to develop into clinically viable systems to help paralyzed people. We begin by reviewing state-of-the-art research and early-stage clinical recording systems and focus on systems that record single-unit action potentials. We then address the potential for neural interface research to enhance basic scientific understanding of brain function by offering unique insights in neural coding and representation, plasticity, brain-behavior relations, and the neurobiology of disease. Finally, we discuss technical and scientific challenges faced by these systems before they are widely adopted by severely motor-disabled patients.

Brian A. Wilt, Laurie D. Burns, Eric Tatt Wei Ho, Kunal K. Ghosh, Eran A. Mukamel, and Mark J. Schnitzer

Since the work of Golgi and Cajal, light microscopy has remained a key tool for neuroscientists to observe cellular properties. Ongoing advances have enabled new experimental capabilities using light to inspect the nervous system across multiple spatial scales, including ultrastructural scales finer than the optical diffraction limit. Other progress permits functional imaging at faster speeds, at greater depths in brain tissue, and over larger tissue volumes than previously possible. Portable, miniaturized fluorescence microscopes now allow brain imaging in freely behaving mice. Complementary progress on animal preparations has enabled imaging in head-restrained behaving animals, as well as time-lapse microscopy studies in the brains of live subjects. Mouse genetic approaches permit mosaic and inducible fluorescence-labeling strategies, whereas intrinsic contrast mechanisms allow in vivo imaging of animals and humans without use of exogenous markers. This review surveys such advances and highlights emerging capabilities of particular interest to neuroscientists.





Symposium : A Revolution in Fluorescence Imaging

11 02 2009

header-jellyfish

This coming Tuesday and Wednesday (Feb 17th & 18th) at UCSD, there will be a symposium honoring Roger Tsien, featuring presentations from 32 former and current members of the Tsien Lab. The topics are quite diverse, concentrated in genetically-encoded indicators, but also featuring fluorescent cell penetrating peptides for cancer therapy, photophore ligases for imaging synaptic development, and even a radical new design for the internal combustion engine.

The quality of speakers and subjects looks to be outstanding.  Here is a complete schedule.  You may notice that at 11:15 AM on Tuesday in Price Center East Ballroom, I will be presenting recent progress we have made in the development of genetically-encoded calcium indicators and their application to in vivo imaging.  Don’t miss that one!  🙂  Roger’s talk, which will assuredly be equal parts absorbing, humorous, and illuminating, is at 4pm Wednesday in the Price Center Theater.

If you live in Southern California and are interesting in imaging technology, there isn’t a better place to be than this symposium.  If you can’t make it, Brain Windows will have a full write-up following the event.

Here is the un-official schedule.

Tuesday February 17th – Price Center East Ballroom

9:00 -9:05 Varda  Levram -Ellisman Opening

9:05-9:15 Palmer Taylor

Designing the next generation of genetically encoded sensors

9:15-9:30 Roger Heim

FRET for compound screening at Aurora/Vertex

9:30-9:45 Amy Palmer

Designing and using genetically encoded sensors: Lessons I learned from Roger

9:45-10:00 Robert Campbell

Beyond brightness: colony screens for fluorescent protein photo stability and biosensor FRET changes

10:00-10:15 Colette Dooley

GFP sensors for reactive oxygen species: Tying up loose ends and looking forward.

10:15-10:30 Peter Wang

Fluorescent Proteins and FRET biosensors for visualizing cell motility and mechanotransduction

Fluorescent proteins in neuroscience

11:00-11:15 Brian Bacskai

Aberrant calcium homeostasis in the Alzheimer mouse brain

11:15-11:30 Andrew Hires

Watching a mouse think: Novel fluorescent genetically-encoded calcium indicators applied to in vivo brain imaging

11:30-11:45 Alice Ting

Imaging synapse development with engineered photophore ligases

11:45-12:00 Rex Kerr

3D calcium imaging in C. elegans

Clinical applications

12:00-12:15 Todd Aguilera

Activatable Cell Penetrating Peptides for use in clinical contrast agent and therapeutic development

12:15-12:30 Quyen Nguyen

Surgery with Molecular Fluorescence Imaging Guidance

Fluorescent probes (Chemistry)

1:30-1:45 Tito Gonzalez

Voltage-Sensitive FRET Probes & Applications

1:45-2:00 Paul Negulescu

From watching ions to moving them

2:00-2:15 Timothy Dore

Roger-Inspired Photochemistry: Releasing Biological Effectors with 2PE

2:00-2:15 Joe Kao

Electron Paramagnetic Resonance Imaging in Living Animals

2:15-2:30 Brent Martin

Chemical probes for studying protein acylation

2:30-2:45 Jianghong Rao

Non-GFP based probes for imaging of the hydrolytic enzyme activity

Cellular research with and without Fluorescent probes

3:15-3:30 Carsten Schultz

Cell membrane repair visualized by GFP fusion proteins

3:30-3:45 David Green

Transcriptomes and Systems Biology: application to early mammalian embryogenesis

3:45-4:00 Clotilde Randriamampita

Paradoxical aspects of T cell activation revealed with fluorescent proteins

4:15-4:30 Wen-Hong Li

Studying dynamic cell-cell communication in vivo by Trojan-LAMP

4:30-4:45 Martin Poenie

Aim and Shoot: Two roles for dynein in T cell effector function

4:45-5:00 Gregor Zlokarnik

From bla to blah, blah in 20 years

5:00-5:15                        James Sharp

President, Zeiss MicroImaging Gmbh

February 18 2009 – Leichtag 107

Cellular research with and without fluorescent proteins

9:00-9:15 David Zacharias

Fluorescent Proteins, Palmitoylation and Cancer: two out of three ain’t bad

9:15-9:30 Jin Zhang

Visualization of Cell Signaling Dynamics: A Tale of MAPK

9:30-9:45 Paul Sammak

Nuclear organization and movement in pluripotent stem cells measured by Histone GFP H2B

Branching out

9:45-10:00 Yong Yao

NIH Toolbox Program

10:00-10:15 Oded Tour

The Tour Engine – A novel Internal Combustion Engine with the potential to boost efficiency and cut emissions

Into the future

10:45-11:00 Xiaokun Shu

Visibly and infrared fluorescent proteins: photophysics and engineering

11:00-11:15 Michael Lin

Engineering fluorescent proteins for visualizing newly synthesized proteins and improving FRET-based biosensors

11:15-11:30 Jeremy Babendure

Training our next generation of Fluorescent Protein Enthusiasts

Main Event – Price Center Theater

4:00-5:00 Roger Tsien

Chancellor invitational lecture 2008 Nobel Prize in Chemistry






Some interesting posters @ SfN

20 11 2008

Here’s a few posters that caught my eye at SfN.  Click the meeting planner for the full abstract

Optimizing two-photon activation of channelrhodopsin-2 for stimulation at cellular resolution

J. P. RICKGAUER1,2, D. W. TANK1,2

Spiral pattern of 2-photon excitation can drive neurons to spike.  A low NA objective helps. Need to do piezo-based Z-scanning if you use high NA, don’t with low NA.

In vivo two-photon imaging 1 mm deep into cortical brain tissue with novel microprism probe 

*T. H. CHIA, M. J. LEVENE; 

A cute method to image 1mm into cortex with 2-photon imaging. They used 2-6 month old mice. The just took a triangular prism whose hypotenuse was silvered and stuck it in the cortex. Then they internally reflected the beam off the prism and fired it sideways into cortex. Got good SNR to 300um lateral distance.  Some clippling of beam at edges of the prism gave somewhat inconsistent spatial resolution.

Self-complementary adeno-associated viral vectors for fast, efficient labeling of neurons and astrocytes in visual cortex in vivo

R. L. LOWERY1, Y. ZHANG2, C. LAMANTIA1, B. K. HARVEY3, A. K. MAJEWSKA1

AAV is the way to go for expression of GECIs and ChR2 in vivo, but it takes a long time to express at high levels (2 weeks). They show that using a double stranded DNA version of AAV rather than single stranded gets protein expression up high much faster. Very high expression after one week. This is because the virus doesn’t need to take the time to make the second strand before expressing the protein.  See Xiao, X J. Virol 1998

Detection of single action potentials in vitro and in vivo with genetically-encoded Ca2+ sensors

S. MEYER ZUM ALTEN BORGLOH1, D. J. WALLACE2, S. ASTORI3, Y. YANG3, M. BAUSEN3, S. KUGLER4, M. MANK5, O. GRIESBECK5, J. NAKAI6, A. MIYAWAKI6, A. E. PALMER7, R. Y. TSIEN7, R. SPRENGEL3, J. N. D. KERR2, W. DENK3, M. T. HASAN3

Everything in the poster was in the Nature Methods paper.  Conversation reveled that YC3.60 works as well or better than D3cpv. Only have done up to whisker evoked stimulation, no imaging of spontaneous YC3.60 signals yet.

Characterization of improved probes for the hybrid voltage sensor method of voltage imaging

D. WANG1, Z. ZHANG2, B. CHANDA1, M. B. JACKSON1

A nice little sensor optimization poster.  They took the hVOS hybrid voltage sensor of dipicrylamine with membrane tethered GFP and improved it by changing the chromophore to Cerulean, and by using the “membrane-staple” strategy. Having membrane anchors on both the N and C-termini gave better quenching. Fast response, ~0.5ms, and 20% dF/F.

Crystal structure of the genetically encoded calcium indicator gcamp2

*J. AKERBOOM1, L. TIAN1, S. VISWANATHAN1, S. A. HIRES1, J. S. MARVIN1, E. R. SCHREITER2, L. L. LOOGER1

Jasper made crystal structures of G-CaMP2 in the apo and bound states.  Bound states crystalized as a heterodimer, but he was able to also crystalize the monomer. The structures show a pore to the chromophore in the apo state that is plugged in the Ca-bound state. Thus, the quenched apo state is due to solvent access to the chromophore.  This structural data should help rational design of better G-CaMP sensors.






SFN Neuroscience Picower MIT Party 2008

10 11 2008

Lots of people searching for “SFN MIT party” for this information in google… Here’s the answer you are looking for.  Right next to the convention center. Much more convenient than three years ago at Cobalt.  No excuse to be late…

Someone send me an invite to the Neuron, Nature and Emory parties, pretty please! 

 

Is that a man in a tuxedo wearing stilts?

Is that a man in a tuxedo wearing stilts?

 

 

The Picower Institute, The McGovern Institute, and the Department of Brain and Cognitive Sciences at MIT

Invite you to the sixth annual party at the 2008 meeting of the Society for Neuroscience

Monday, November 17th, 2008  

9pm – 2am  

Avenue Nightclub
649 New York Ave NW

Washington, DC





UPDATED : UCSD Neuroscience Movies Back Online

27 03 2008

Almost every year, the UCSD Neurosciences Graduate program makes a movie or performs some skits lampooning the faculty (and sometimes other students). These videos used to be hosted on my server in the Tsien Lab, but that machine came with me to DC. I’ve finally taken the time to re-encode them and upload them to Google Video. I also uncovered the DVD of the excellent 2003 movie “Les Lettres Perdues”. The video quality is not as good from this host as from a private server, but at least they will be universally accessible. Email me if you want a higher quality version.

UCSD Neuroscience Skits 2006

The Investigator – UCSD Neuroscience Movie 2005

Les Lettres Perdues – UCSD Neuroscience Movie 2003

Tsien Lab Baby