@article {3421, title = {Precise olfactory responses tile the sniff cycle.}, journal = {Nature Neuroscience}, volume = {14}, year = {2011}, month = {2011 Jul 17}, pages = {1039-44}, abstract = {

In terrestrial vertebrates, sniffing controls odorant access to receptors, and therefore sets the timescale of olfactory stimuli. We found that odorants evoked precisely sniff-locked activity in mitral/tufted cells in the olfactory bulb of awake mouse. The trial-to-trial response jitter averaged 12 ms, a precision comparable to other sensory systems. Individual cells expressed odor-specific temporal patterns of activity and, across the population, onset times tiled the duration of the sniff cycle. Responses were more tightly time-locked to the sniff phase than to the time after inhalation onset. The spikes of single neurons carried sufficient information to discriminate odors. In addition, precise locking to sniff phase may facilitate ensemble coding by making synchrony relationships across neurons robust to variation in sniff rate. The temporal specificity of mitral/tufted cell output provides a potentially rich source of information for downstream olfactory areas.

}, issn = {1546-1726}, doi = {10.1038/nn.2877}, author = {Shusterman, Roman and Smear, Matthew C and Koulakov, Alexei A and Rinberg, Dmitry} } @article {4147, title = {Sparse incomplete representations: a potential role of olfactory granule cells.}, journal = {Neuron}, volume = {72}, year = {2011}, month = {2011 Oct 6}, pages = {124-36}, abstract = {

Mitral/tufted cells of the olfactory bulb receive odorant information from receptor neurons and transmit this information to the cortex. Studies in awake behaving animals have found that sustained responses of mitral cells to odorants are rare, suggesting sparse combinatorial representation of the odorants. Careful alignment of mitral cell firing with the phase of the respiration cycle revealed brief transient activity in the larger population of mitral cells, which respond to odorants during a small fraction of the respiration cycle. Responses of these cells are therefore temporally sparse. Here, we propose a mathematical model for the olfactory bulb network that can reproduce both combinatorially and temporally sparse mitral cell codes. We argue that sparse codes emerge as a result of the balance between mitral cells{\textquoteright} excitatory inputs and inhibition provided by the granule cells. Our model suggests functional significance for the dendrodendritic synapses mediating interactions between mitral and granule cells.

}, issn = {1097-4199}, doi = {10.1016/j.neuron.2011.07.031}, author = {Koulakov, Alexei A and Rinberg, Dmitry} } @article {2369, title = {How to find decision makers in neural networks.}, journal = {Biological Cybernetics}, volume = {93}, year = {2005}, month = {2005 Dec}, pages = {447-62}, abstract = {

Nervous systems often face the problem of classifying stimuli and making decisions based on these classifications. The neurons involved in these tasks can be characterized as sensory or motor, according to their correlation with sensory stimulus or motor response. In this study we define a third class of neurons responsible for making perceptual decisions. Our mathematical formalism enables the weighting of neuronal units according to their contribution to decision making, thus narrowing the field for more detailed studies of underlying mechanisms. We develop two definitions of a contribution to decision making. The first definition states that decision making activity can be found at the points of emergence for behavioral correlations in the system. The second definition involves the study of propagation of noise in the network. The latter definition is shown to be equivalent to the first one in the cases when they can be compared. Our results suggest a new approach to analyzing decision making networks.

}, keywords = {Animals, Computer Simulation, Decision Making, Electric Stimulation, Humans, Models, Nerve Net, Neural Networks (Computer), Neurological, Neurons, Nonlinear Dynamics, Stochastic Processes}, issn = {0340-1200}, doi = {10.1523/JNEUROSCI.3613-08.2008}, author = {Koulakov, Alexei A and Rinberg, Dmitry A and Tsigankov, Dmitry N} } @article {1256, title = {Maps in the brain: what can we learn from them?}, journal = {Annual Review of Neuroscience}, volume = {27}, year = {2004}, month = {2004}, pages = {369-92}, abstract = {

In mammalian visual cortex, neurons are organized according to their functional properties into multiple maps such as retinotopic, ocular dominance, orientation preference, direction of motion, and others. What determines the organization of cortical maps? We argue that cortical maps reflect neuronal connectivity in intracortical circuits. Because connecting distant neurons requires costly wiring (i.e., axons and dendrites), there is an evolutionary pressure to place connected neurons as close to each other as possible. Then, cortical maps may be viewed as solutions that minimize wiring cost for given intracortical connectivity. These solutions can help us in inferring intracortical connectivity and, ultimately, in understanding the function of the visual system.

}, keywords = {Animals, Axons, Brain Mapping, Dendrites, Humans, Nerve Net, Neural Pathways, Visual Cortex, Visual Fields, Visual Pathways}, issn = {0147-006X}, doi = {10.1016/j.tins.2005.05.006}, author = {Chklovskii, Dmitri B and Koulakov, Alexei A} } @article {1267, title = {Orientation preference maps in mammalian visual cortex: A wire length minimization approach.}, journal = {Neuron}, volume = {29}, year = {2001}, month = {2001 Feb}, pages = {519-27}, abstract = {

In the visual cortex of many mammals, orientation preference changes smoothly along the cortical surface, with the exception of singularities such as pinwheels and fractures. The reason for the existence of these singularities has remained elusive, suggesting that they are developmental artifacts. We show that singularities reduce the length of intracortical neuronal connections for some connection rules. Therefore, pinwheels and fractures could be evolutionary adaptations keeping cortical volume to a minimum. Wire length minimization approach suggests that interspecies differences in orientation preference maps reflect differences in intracortical neuronal circuits, thus leading to experimentally testable predictions. We discuss application of our model to direction preference maps.

}, issn = {0896-6273}, author = {Koulakov, Alexei A and Chklovskii, Dmitri B} } @article {1270, title = {A wire length minimization approach to ocular dominance patterns in mammalian visual cortex.}, journal = {Physica A}, volume = {284}, year = {2000}, month = {2000}, pages = {318-34}, author = {Chklovskii, Dmitri B and Koulakov, Alexei A} }