Functional Neurogenesis

Some final observations at the 2010 Society for Neuroscience meeting. Read the rest of this entry »

Yesterday morning I checked out the technically-heroic dissection of mossy fiber function from the Tonegawa lab that employed a quadruple transgenic mouse: Mossy fiber input for pattern separation and pattern completion
*T. NAKASHIBA¹, J. CUSHMAN², K. A. PELKEY³, C. J. MCBAIN³, M. S. FANSELOW², S. TONEGAWA¹;
¹The RIKEN-MIT Ctr. For Neural Circuit Genetics, The Picower Inst. For Lear, CAMBRIDGE, MA; ²Dept. of Psychology, UCLA, Los Angeles, CA; ³NICHD, NIH, Bethesda, MD Read the rest of this entry »

Some posters get more attention than others. Either there’s an interesting abstract, an attractive/famous presenter or, my favorite, additional passersby get sucked in by the gravitational force of an existing crowd. Whatever the reason, I’ve started a game called Photos of Popular Posters (PPP). It doesn’t in any way attempt to determine why the poster attracts attention. It’s just a tribute to popularity. So this morning, playing PPP in aisles JJJ and KKK, with an admittedly-small sampling (1 stroll), the largest crowds could be found at:

Corticostriatal and glutamatergic mediation of cognitive flexibility and habit, by Brigman et al. Congratulations – you were popular.

And, Optogenetic manipulation of locus coeruleus norepinephrine neurons: Effects on set-shifting, by Cope et al. Also popular.

Supplemental Methods & Results: Afternoon strolls in the development and in vivo-electrophysiology-during-behavior themes revealed a number of potentially far more popular posters. However, these posters were excluded from the experiment because many of the poster “viewers” were not actively engaged with a poster. Instead, they displayed dazed looks in other directions and appeared to actually be moving, perhaps suffering from SFN exhaustion and traffic jamming.

Today was great because there was a ton of hippocampal-cortical posters I was excited to check out except I was also presenting so I couldn’t actually check them out. Plus, it wasn’t like I could just pop over when my crowd died down because they were all the way in aisle KKK (worst aisle name ever ). Fortunately there were a couple of special presentations I was able to visit, namely the CIA is Demon guy, who had his brain controlled by the CIA. This sounded really interesting but unfortunately I didn’t have time to check out the data – I had a poster to set up.

Brain Control

Read the rest of this entry »

…and now for what is probably my final pre-SFN post. Posters dealing with mossy fiber function! Read the rest of this entry »

Culling through the SFN abstract browser is an imperfect process.  Keyword searches can be helpful, particularly if you’re interested in a fairly specific topic, like, say, “1-bromopropane” (1 hit).  But if you’re interested in “postnatal neurogenesis” (292 hits) or “hippocampus memory” (1118 hits), make sure your scrolling finger is rested and well-fed.  Because there will be scrolling. Or you might try searching by name.  You’ll avoid delayed-onset finger soreness, but you’ll inevitably forget about so-and-so and that other guy, and -worse- you’re certain not to discover anyone new.

So you end up supplementing your name searches with some combinatorial keyword strategy.  You find some cool posters.  And then you discover that your blogging partner already found the same posters and posted about them two days ago.  So you ice your scrolling finger and post about a few cool abstracts he didn’t already mention. Read the rest of this entry »

Continuing on…

1) 31.20/C37 - Dentate network activity modulates integration of newborn granule cells
*F. KLEINE BORGMANN¹, J. GRÄFF², N. TONI³, I. M. MANSUY^4,5, S. JESSBERGER¹;
¹Inst. of Cell Biology, Swiss Federal Inst. of Technol. (ETH), Zürich, Switzerland; ²Brain Res. Inst., Univ. of Zürich, Zürich, Switzerland; ³Univ. of Lausanne, Lausanne, Switzerland; ⁴Brain Res. Inst., Univ. of Zurich, Zürich, Switzerland; ⁵Swiss Federal Inst. of Technol. (ETH), Zürich, Switzerland

This looks interesting because there is so little known about how neuronal activity regulates neurogenesis. In 2007 Toni et al. suggested that dendritic filopodia on new neurons form synapses with presynaptic boutons that have already formed a synapse onto a different (presumably mature) neuron. The question addressed here is whether altering excitability/plasticity at those pre-existing synapses affects the subsequent formation of new neuron synapses. In other words, if you make old neurons more plastic, will they outcompete new neurons for synaptic space? Seems maybe they do.

2) 203.9/KKK52 - Coding of temporal context in the hippocampus: Do rate codes offer insight into a time-of-day signature?
F. T. SPARKS*¹, E. A. MANKIN*², B. SLAYYEH², R. J. SUTHERLAND¹, *J. K. LEUTGEB²;
¹Dept of Neurosci., Univ. of Lethbridge, Lethbridge, AB, Canada; ²Ctr. for Neural Circuits and Behavior, Neurobiol Section, Div. of Biol Sci., UCSD, LA JOLLA, CA

We all know the hippocampus is important for episodic (-like) memory yet activity in hippocampal neurons is usually only measured in relation to spatial information. Memories also often contain temporal information and Rob Sutherland (one of the authors) has shown that rats indeed integrate time-of-day information into their memories. Here, measuring electrophysiological activity in hippocampal neurons, it is reported that 1) hippocampal neurons fire when a rat is in a specific spatial location, as expected; 2) when nearby contextual features are altered (square vs circular exploration chamber) the same population of neurons are active in the same places but they fire at different rates (rate coding); 3) what is unique here: hippocampal neurons also used a rate code to differentiate between a given context explored in the morning vs the afternoon. Thus, time-of-day is a contextual feature that is encoded in the hippocampus. Interestingly, it is reported that the rate codes for spatial and temporal information are carried by different populations of neurons.

3) 330.6/A6 - Experience specific information encoding by newborn neurons of the adult dentate gyrus
*G. D. CLEMENSON, JR, F. H. GAGE;
Salk Inst., La Jolla, CA

This presentation builds on Kee 2007, who showed that 10-week-old neurons are only activated in the water maze if they were functional at the time of the original water maze training, and Tashiro 2006 who claimed that, when a mouse re-experiences something, it is new neurons that were in their critical period during the original experience that are activated. We still have a ways to go before we understand how faithful new neurons are in their responding to different experiences – their enhanced plasticity and unique physiology has caused some speculation that they could be promiscuous, participating in many different experiences. This study seems like it may have the best evidence that young neurons are in fact quite selective in what they encode.