@article {1693, title = {Asymmetric ephaptic inhibition between compartmentalized olfactory receptor neurons.}, journal = {Nat Commun}, volume = {10}, year = {2019}, month = {2019 04 05}, pages = {1560}, abstract = {

In the Drosophila antenna, different subtypes of olfactory receptor neurons (ORNs) housed in the same sensory hair (sensillum) can inhibit each other non-synaptically. However, the mechanisms underlying this underexplored form of lateral inhibition remain unclear. Here we use recordings from pairs of sensilla impaled by the same tungsten electrode to demonstrate that direct electrical ("ephaptic") interactions mediate lateral inhibition between ORNs. Intriguingly, within individual sensilla, we find that ephaptic lateral inhibition is asymmetric such that one ORN exerts greater influence onto its neighbor. Serial block-face scanning electron microscopy of genetically identified ORNs and circuit modeling indicate that asymmetric lateral inhibition reflects a surprisingly simple mechanism: the physically larger ORN in a pair corresponds to the dominant neuron in ephaptic interactions. Thus, morphometric differences between compartmentalized ORNs account for highly specialized inhibitory interactions that govern information processing at the earliest stages of olfactory coding.

}, keywords = {Animals, Drosophila, Imaging, Three-Dimensional, Models, Biological, Olfactory Pathways, Olfactory Receptor Neurons, Sensilla, Smell}, issn = {2041-1723}, doi = {10.1038/s41467-019-09346-z}, author = {Zhang, Ye and Tsang, Tin Ki and Bushong, Eric A and Chu, Li-An and Chiang, Ann-Shyn and Ellisman, Mark H and Reingruber, J{\"u}rgen and Su, Chih-Ying} } @article {1697, title = {A neural data structure for novelty detection.}, journal = {Proc Natl Acad Sci U S A}, volume = {115}, year = {2018}, month = {2018 12 18}, pages = {13093-13098}, abstract = {

Novelty detection is a fundamental biological problem that organisms must solve to determine whether a given stimulus departs from those previously experienced. In computer science, this problem is solved efficiently using a data structure called a Bloom filter. We found that the fruit fly olfactory circuit evolved a variant of a Bloom filter to assess the novelty of odors. Compared with a traditional Bloom filter, the fly adjusts novelty responses based on two additional features: the similarity of an odor to previously experienced odors and the time elapsed since the odor was last experienced. We elaborate and validate a framework to predict novelty responses of fruit flies to given pairs of odors. We also translate insights from the fly circuit to develop a class of distance- and time-sensitive Bloom filters that outperform prior filters when evaluated on several biological and computational datasets. Overall, our work illuminates the algorithmic basis of an important neurobiological problem and offers strategies for novelty detection in computational systems.

}, keywords = {Algorithms, Animals, Drosophila, Models, Biological, Nerve Net, Neural Networks (Computer), Odorants, Olfactory Pathways}, issn = {1091-6490}, doi = {10.1073/pnas.1814448115}, author = {Dasgupta, Sanjoy and Sheehan, Timothy C and Stevens, Charles F and Navlakha, Saket} } @article {166, title = {A comprehensive wiring diagram of the protocerebral bridge for visual information processing in the Drosophila brain.}, journal = {Cell Rep}, volume = {3}, year = {2013}, month = {2013 May 30}, pages = {1739-53}, abstract = {

How the brain perceives sensory information and generates meaningful behavior depends critically on its underlying circuitry. The protocerebral bridge (PB) is a major part of the insect central complex (CX), a premotor center that may be analogous to the human basal ganglia. Here, by deconstructing hundreds of PB single neurons and reconstructing them into a common three-dimensional framework, we have constructed a comprehensive map of PB circuits with labeled polarity and predicted directions of information flow. Our analysis reveals a highly ordered information processing system that involves directed information flow among CX subunits through 194 distinct PB neuron types. Circuitry properties such as mirroring, convergence, divergence, tiling, reverberation, and parallel signal propagation were observed; their functional and evolutional significance is discussed. This layout of PB neuronal circuitry may provide guidelines for further investigations on transformation of sensory (e.g., visual) input into locomotor commands in fly brains.

}, keywords = {Animals, Brain, Drosophila, Models, Biological, Neurons}, issn = {2211-1247}, doi = {10.1016/j.celrep.2013.04.022}, author = {Lin, Chih-Yung and Chuang, Chao-Chun and Hua, Tzu-En and Chen, Chun-Chao and Dickson, Barry J and Greenspan, Ralph J and Chiang, Ann-Shyn} } @article {162, title = {Biological indeterminacy.}, journal = {Sci Eng Ethics}, volume = {18}, year = {2012}, month = {2012 Sep}, pages = {447-52}, abstract = {

Reductionist explanations in biology generally assume that biological mechanisms are highly deterministic and basically similar between individuals. A contrasting view has emerged recently that takes into account the degeneracy of biological processes--the ability to arrive at a given endpoint by a variety of available paths, even within the same individual. This perspective casts significant doubt on the prospects for the ability to predict behavior accurately based on brain imaging or genotyping, and on the ability of neuroscience to stipulate ethics.

}, keywords = {Brain, Genotype, Humans, Models, Biological, Morals, Neuroimaging, Neurosciences, Psychophysiology, Social Behavior}, issn = {1471-5546}, doi = {10.1007/s11948-012-9379-2}, author = {Greenspan, Ralph J} } @article {174, title = {Adult neurogenesis: integrating theories and separating functions.}, journal = {Trends Cogn Sci}, volume = {14}, year = {2010}, month = {2010 Jul}, pages = {325-37}, abstract = {

The continuous incorporation of new neurons in the dentate gyrus of the adult hippocampus raises exciting questions about memory and learning, and has inspired new computational models to understand the function of adult neurogenesis. These theoretical approaches suggest distinct roles for new neurons as they slowly integrate into the existing dentate gyrus network: immature adult-born neurons seem to function as pattern integrators of temporally adjacent events, thereby enhancing pattern separation for events separated in time; whereas maturing adult-born neurons possibly contribute to pattern separation by being more amenable to learning new information, leading to dedicated groups of granule cells that respond to experienced environments. We review these hypothesized functions and supporting empirical research and point to new directions for future theoretical efforts.

}, keywords = {Adult, Adult Stem Cells, Animals, Cell Proliferation, Hippocampus, Humans, Models, Biological, Neurogenesis, Neurons}, issn = {1879-307X}, doi = {10.1016/j.tics.2010.04.003}, author = {Aimone, James B and Deng, Wei and Gage, Fred H} }