NEWS List

TUGraz has recenlty published new papers:

L. Büsing, J. Bill, B. Nessler, and W. Maass. Neural dynamics as sampling (2011) A model for stochastic computation in recurrent networks of spiking neurons. PLoS Computational Biology. doi:10.1371/journal.pcbi.1002211.

R. Legenstein and W. Maass (2011) Branch-specific plasticity enables self-organization of nonlinear computation in single neurons. The Journal of Neuroscience, 31(30):10787-10802

This paper has also elicited a dedicated commentary by R. P. Costa and P. J. Sjöström in Frontiers in Synaptic Neuroscience.

Another publication is in press, and will be published soon: D. Pecevski, L. Büsing, and W. Maass. Probabilistic inference in general graphical models through sampling in stochastic networks of spiking  neurons. PLoS Computational Biology, 2011. in press.

Randal A. Koene, Betty Tijms, Peter van Hees, Frank Postma, Sander de Ridder, Ger Ramakers, Jaap van Pelt, Arjen van Ooyen. NETMORPH: A framework for the stochastic generation of large scale neuronal networks with realistic neuron morphologies. Neuroinformatics 7(2009)195-210.

Douglas RJ, Martin KA, Inhibition in Cortical circuits, Curr Biol. 2009 May 26;19(10):R398-402. 

Anderson J., Da Costa N, Martin KAC, The W cell pathway to cat primary visual cortex., J CompNeurol. 2009 Sep 1;516(1):20-35.

The thalamic input to area 17 in the cat can be divided into at least three parallel pathways, the W, X, and Y. Although the latter two are some of the best studied synaptic connections in the brain, the former remains poorly understood both in structure and in function. By combining light and electron microscopy, we have reconstructed in 3-D single W axons and described quantitatively the synapses that they form. We have also made a structural comparison of reconstructed synapses from the three visual pathways. Thalamic axons were labeled in vivo by injections of biotinylated dextran amine into the dLGN. W axons originating from C laminae injections arborized in layers 1, 2/3, and 5. Axons that traversed layer 1 supplied a few descending collaterals to layer 2/3, but the most extensive innervation in layer 2/3 was provided by axons ascending from the white matter. Most W boutons formed a single synapse, dendritic spines being the most common target, with dendritic shafts forming the remaining targets. In layer 1, the area of the postsynaptic density of spine synapses (0.16 microm(2)) was significantly larger than that of layers 2/3 (0.11 microm(2)) and 5 (0.09 microm(2)). Synapses from X and Y axons in layer 4 were similar in size to synapses formed by W boutons in layer 1. In layer 1, the main targets of the W axons are likely the apical dendrites of pyramidal cells, so that both proximal and distal regions of pyramidal cell dendritic trees can be excited by the W pathway.

Anderson JC, Da Costa NM, Martin KA, The proportion of synapses formed by the axons of the lateral geniculate nucleus in layer 4 of area 17 of the cat, J Comp Neurol. 2009 Oct 1;516(4):264-76.

The connection between the dorsal lateral geniculate nucleus (dLGN) and area 17 of the cat is a classical model for studying thalamocortical relations. We investigated the proportion of asymmetric synapses in layer 4 of area 17 of cats formed by axons of the dLGN, because this is an important morphological parameter in understanding the impact of dLGN axons on their target neurons. Although the present consensus is that this proportion is small, the exact percentage remains in doubt. Most previous work estimated that the thalamus contributes less than 10% of excitatory synapses in layer 4, but one estimate was as high as 28%. Two issues contribute to these widely different estimates, one being the tracers used, the other being the use of biased stereological approaches. We have addressed both of these issues. Thalamic axons were labeled in vivo by injections of biotinylated dextran amine into the A lamina of the dLGN of anesthetized cats. After processing, the brain was cut serially and prepared for light and electron microscopy. The density of asymmetric synapses in the neuropil and the density of synapses formed by labeled dLGN boutons were measured by using an unbiased sampling method called the physical disector. Our counts indicate that, in the fixed cat brain, there are 5.9 x 10(8) +/- 0.9 x 10(8) asymmetric synapses per cubic millimeter of layer 4 in area 17, and the dLGN input provides only 6% of all asymmetric synapses in layer 4. The vast majority of synapses of layer 4 probably originate from other neurons in area 17.