@article {5460, title = {Proprioceptive coupling within motor neurons drives C. elegans forward locomotion.}, journal = {Neuron}, volume = {76}, year = {2012}, month = {2012 Nov 21}, pages = {750-61}, abstract = {

Locomotion requires coordinated motor activity throughout an animal{\textquoteright}s body. In both vertebrates and invertebrates, chains of coupled central pattern generators (CPGs) are commonly evoked to explain local rhythmic behaviors. In C.\ elegans, we report that proprioception within the motor circuit is responsible for propagating and coordinating rhythmic undulatory waves from head to tail during forward movement. Proprioceptive coupling between adjacent body regions transduces rhythmic movement initiated near the head into bending waves driven along the body by a chain of reflexes. Using optogenetics and calcium imaging to manipulate and monitor motor circuit activity of moving C.\ elegans held in microfluidic devices, we found that the B-type cholinergic motor neurons transduce the proprioceptive signal. In C.\ elegans, a sensorimotor feedback loop operating within a specific type of motor neuron both drives and organizes body movement.

}, issn = {1097-4199}, doi = {10.1016/j.neuron.2012.08.039}, author = {Wen, Quan and Po, Michelle D. and Hulme, Elizabeth and Chen, Sway and Liu, Xinyu and Kwok, Sen Wai and Gershow, Marc and Leifer, Andrew M. and Butler, Victoria and Fang-Yen, Christopher and Kawano, Taizo and Schafer, William R and Whitesides, George and Wyart, Matthieu and Chklovskii, Dmitri B and Samuel, Aravinthan D. T.} } @article {2122, title = {Experience-dependent compartmentalized dendritic plasticity in rat hippocampal CA1 pyramidal neurons.}, journal = {Nature Neuroscience}, volume = {12}, year = {2009}, month = {2009 Dec}, pages = {1485-7}, abstract = {

The excitability of individual dendritic branches is a plastic property of neurons. We found that experience in an enriched environment increased propagation of dendritic Na(+) spikes in a subset of individual dendritic branches in rat hippocampal CA1 pyramidal neurons and that this effect was mainly mediated by localized downregulation of A-type K(+) channel function. Thus, dendritic plasticity might be used to store recent experience in individual branches of the dendritic arbor.

}, keywords = {Action Potentials, Animals, CA1 Region, Dendrites, Down-Regulation, Environment, Hippocampal, Memory, Neuronal Plasticity, Potassium Channels, Pyramidal Cells, Rats}, issn = {1546-1726}, doi = {10.1038/nn.2428}, author = {Makara, Judit K and Losonczy, Attila and Wen, Quan and Magee, Jeffrey C} } @article {1236, title = {Maximization of the connectivity repertoire as a statistical principle governing the shapes of dendritic arbors.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, year = {2009}, month = {2009 Jul 28}, pages = {12536-41}, abstract = {

The shapes of dendritic arbors are fascinating and important, yet the principles underlying these complex and diverse structures remain unclear. Here, we analyzed basal dendritic arbors of 2,171 pyramidal neurons sampled from mammalian brains and discovered 3 statistical properties: the dendritic arbor size scales with the total dendritic length, the spatial correlation of dendritic branches within an arbor has a universal functional form, and small parts of an arbor are self-similar. We proposed that these properties result from maximizing the repertoire of possible connectivity patterns between dendrites and surrounding axons while keeping the cost of dendrites low. We solved this optimization problem by drawing an analogy with maximization of the entropy for a given energy in statistical physics. The solution is consistent with the above observations and predicts scaling relations that can be tested experimentally. In addition, our theory explains why dendritic branches of pyramidal cells are distributed more sparsely than those of Purkinje cells. Our results represent a step toward a unifying view of the relationship between neuronal morphology and function.

}, keywords = {Action Potentials, Algorithms, Animals, Axons, Dendrites, Haplorhini, Models, Neural Pathways, Neurological, Purkinje Cells, Pyramidal Cells, Rats, Synapses}, issn = {1091-6490}, doi = {10.1371/journal.pcbi.1001066}, author = {Wen, Quan and Stepanyants, Armen and Elston, Guy N and Grosberg, Alexander Y and Chklovskii, Dmitri B} } @article {1237, title = {A cost-benefit analysis of neuronal morphology.}, journal = {Journal of Neurophysiology}, volume = {99}, year = {2008}, month = {2008 May}, pages = {2320-8}, abstract = {

Over hundreds of millions of years, evolution has optimized brain design to maximize its functionality while minimizing costs associated with building and maintenance. This observation suggests that one can use optimization theory to rationalize various features of brain design. Here, we attempt to explain the dimensions and branching structure of dendritic arbors by minimizing dendritic cost for given potential synaptic connectivity. Assuming only that dendritic cost increases with total dendritic length and path length from synapses to soma, we find that branching, planar, and compact dendritic arbors, such as those belonging to Purkinje cells in the cerebellum, are optimal. The theory predicts that adjacent Purkinje dendritic arbors should spatially segregate. In addition, we propose two explicit cost function expressions, falsifiable by measuring dendritic caliber near bifurcations.

}, keywords = {Algorithms, Axons, Cerebellum, Cost-Benefit Analysis, Dendrites, Models, Neurological, Neurons, Purkinje Cells, Synapses}, issn = {0022-3077}, doi = {10.1371/journal.pcbi.1001066}, author = {Wen, Quan and Chklovskii, Dmitri B} } @article {1240, title = {Segregation of the brain into gray and white matter: a design minimizing conduction delays.}, journal = {PLoS Computational Biology}, volume = {1}, year = {2005}, month = {2005 Dec}, pages = {e78}, abstract = {

A ubiquitous feature of the vertebrate anatomy is the segregation of the brain into white and gray matter. Assuming that evolution maximized brain functionality, what is the reason for such segregation? To answer this question, we posit that brain functionality requires high interconnectivity and short conduction delays. Based on this assumption we searched for the optimal brain architecture by comparing different candidate designs. We found that the optimal design depends on the number of neurons, interneuronal connectivity, and axon diameter. In particular, the requirement to connect neurons with many fast axons drives the segregation of the brain into white and gray matter. These results provide a possible explanation for the structure of various regions of the vertebrate brain, such as the mammalian neocortex and neostriatum, the avian telencephalon, and the spinal cord.

}, keywords = {Animals, Brain, Color, Models, Neural Pathways, Neurological}, issn = {1553-7358}, doi = {10.1371/journal.pcbi.1001066}, author = {Wen, Quan and Chklovskii, Dmitri B} }