Current Opinion in Neurobiology

Identifying behavioral circuits in Drosophila melanogaster: moving targets in a flying insect.

Publication Date: 2012 Jan 27 PMID: 22285110
Authors: Griffith, L. C.
Journal: Curr Opin Neurobiol

Drosophila melanogaster has historically been the premier model system for understanding the molecular and genetic bases of complex behaviors. In the last decade technical advances, in the form of new genetic tools and electrophysiological and optical methods, have allowed investigators to begin to dissect the neuronal circuits that generate behavior in the adult. The blossoming of circuit analysis in this organism has also reinforced our appreciation of the inadequacy of wiring diagrams for specifying complex behavior. Neuromodulation and neuronal plasticity act to reconfigure circuits on both short and long time scales. These processes act on the connectome, providing context by integrating external and internal cues that are relevant for behavioral choices. New approaches in the fly are providing insight into these basic principles of circuit function.

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Respiratory circuits: development, function and models.

Publication Date: 2012 Jan 24 PMID: 22281058
Authors: Mellen, N. M. - Thoby-Brisson, M.
Journal: Curr Opin Neurobiol

Breathing is a rhythmic motor behavior generated and controlled by hindbrain neuronal networks. Respiratory motor output arises from two distinct, but functionally interacting, rhythmogenic networks: the pre-Botzinger complex (preBotC) and the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG). This review outlines recent advances in delineating the genetic specification of the neuronal constituents of these two rhythmogenic networks, their respective roles in respiratory function and how they interact to constitute a functional respiratory circuit ensemble. The often lethal consequences of disruption to these networks found in naturally occurring developmental disorders, transgenic animals, and highly specific lesion studies are described. In addition, we discuss how recent computational models enhance our understanding of how respiratory networks generate and regulate respiratory behavior.

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Sound source perception in anuran amphibians.

Publication Date: 2012 Jan 19 PMID: 22265243
Authors: Bee, M. A.
Journal: Curr Opin Neurobiol

Sound source perception refers to the auditory system's ability to parse incoming sensory information into coherent representations of distinct sound sources in the environment. Such abilities are no doubt key to successful communication in many taxa, but we know little about their function in animal communication systems. For anuran amphibians (frogs and toads), social and reproductive behaviors depend on a listener's ability to hear and identify sound signals amid high levels of background noise in acoustically cluttered environments. Recent neuroethological studies are revealing how frogs parse these complex acoustic scenes to identify individual calls in noisy breeding choruses. Current evidence highlights some interesting similarities and differences in how the auditory systems of frogs and other vertebrates (most notably birds and mammals) perform auditory scene analysis.

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Global navigation in migratory birds: tracks, strategies, and interactions between mechanisms.

Publication Date: 2012 Jan 12 PMID: 22244742
Authors: Wiltschko, W. - Wiltschko, R.
Journal: Curr Opin Neurobiol

The advancing development of tracking techniques has led to fascinating new insights into avian migration, documenting the immense diversity, complexity, and flexibility of this phenomenon. Tracking studies so far have confirmed many findings from ringing recoveries and cage studies, for example, the change from flying innate compass courses in the first migration to true navigation, as experienced migrants head toward familiar goals. First attempts to analyze the navigational mechanisms by tracking manipulated migrants indicate strong parallels to those of homing pigeons. Findings suggesting that the magnetic compass of migrants is regularly calibrated by the pattern of polarized light could not be replicated with a number of other birds, pointing out differences between species and possibly region and phases of migration. Tracking has become a valuable tool, complimenting traditional methods by documenting migration behavior in the wild; whether it can be used to further unveil the navigational mechanisms of migrants and the factor used remains an open question.

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Neural specializations for small target detection in insects.

Publication Date: 2012 Jan 12 PMID: 22244741
Authors: Nordstrom, K.
Journal: Curr Opin Neurobiol

Despite being equipped with low-resolution eyes and tiny brains, many insects show exquisite abilities to detect and pursue targets even in highly textured surrounds. Target tracking behavior is subserved by neurons that are sharply tuned to the motion of small high-contrast targets. These neurons respond robustly to target motion, even against self-generated optic flow. A recent model, supported by neurophysiology, generates target selectivity by being sharply tuned to the unique spatiotemporal profile associated with target motion. Target neurons are likely connected in a complex network where some provide more direct output to behavior, whereas others serve an inter-regulatory role. These interactions may regulate attention and aid in the robust detection of targets in clutter observed in behavior.

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Functional imaging in freely moving animals.

Publication Date: 2012 Jan 9 PMID: 22237048
Authors: Kerr, J. N. - Nimmerjahn, A.
Journal: Curr Opin Neurobiol

Uncovering the relationships between animal behavior and cellular activity in the brain has been one of the key aims of neuroscience research for decades, and still remains so. Electrophysiological approaches have enabled sparse sampling from electrically excitable cells in freely moving animals that has led to the identification of important phenomena such as place, grid and head-direction cells. Optical imaging in combination with newly developed labeling approaches now allows minimally invasive and comprehensive sampling from dense networks of electrically and chemically excitable cells such as neurons and glia during self-determined behavior. To achieve this two main imaging avenues have been followed: Optical recordings in head-restrained, mobile animals and miniature microscope-bearing freely moving animals. Here we review progress made toward functional cellular imaging in freely moving rodents, focusing on developments over the past few years. We discuss related challenges and biological applications.

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Sequence learning and the role of the hippocampus in rodent navigation.

Publication Date: 2012 Jan 6 PMID: 22226994
Authors: Foster, D. J. - Knierim, J. J.
Journal: Curr Opin Neurobiol

The hippocampus has long been associated with navigation and spatial representations, but it has been difficult to link directly the neurophysiological correlates of hippocampal place cells with navigational planning and action. In recent years, large-scale population recordings of place cells have revealed that spatial sequences are stored and activated in ways that may support navigational strategies. Plasticity mechanisms allow the hippocampus to store learned sequences of locations that may allow predictions of future locations based on past experience. These sequences can also be activated during navigational behavior in ways that may allow the animal to learn trajectories toward goals. Task-dependent alterations in place cell firing patterns may reflect the operation of the hippocampus in associating locations with navigationally relevant decision variables.

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Predator detection and evasion by flying insects.

Publication Date: 2012 Jan 5 PMID: 22226428
Authors: Yager, D. D.
Journal: Curr Opin Neurobiol

Echolocating bats detect prey using ultrasonic pulses, and many nocturnally flying insects effectively detect and evade these predators through sensitive ultrasonic hearing. Many eared insects can use the intensity of the predator-generated ultrasound and the stereotyped progression of bat echolocation pulse rate to assess risk level. Effective responses can vary from gentle turns away from the threat (low risk) to sudden random flight and dives (highest risk). Recent research with eared moths shows that males will balance immediate bat predation risk against reproductive opportunity as judged by the strength and quality of conspecific pheromones present. Ultrasound exposure may, in fact, bias such decisions for up to 24 hours through plasticity in the CNS olfactory system. However, brain processing of ultrasonic stimuli to yield adaptive prey behaviors remains largely unstudied, so possible mechanisms are not known.

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