1,721,043 research outputs found
Microcircuits of the Amygdala
No full textThis chapter reviews the unique microcircuits within the subdivisions of the amygdala. Microcircuits of the amygdala remain somewhat of an enigma. The amygdala itself is comprised of laterally located glutamatergic projection neuron structures, which are cortical-like, and medially located GABA projection neuron structures, which resemble neurons of the striatum. Within these are many nuclei and subnuclei that are distinguished on histologic, hodologic, and functional criteria. Significant progress has been made in understanding the organization of microcircuits in the lateral amygdala (LA) and central amygdala (CE), which play important roles in fear learning and fear memory, and the intercalated neurons (ITC), which regulate fear extinction. Emerging data indicate a structured excitatory microcircuit within the LA. Local axon collaterals of excitatory projection neurons are regulated by transverse modules of local GABA inhibition, which control excitation in the dorsal to ventral and ventral to dorsal planes. Bidirectional excitation in this plane may form recurrent networks that contribute to the temporal coordination of sensory signals integrated into the Lad network. Future work on amygdala microcircuits will continue to yield important data on how microcircuits regulate learning, memory, and behavior
Networks in the lamprey optic tectum
No full textCritical to survival is the rapid detection and processing of events, registered by our senses, for the selection of an appropriate motor action. One essential task is to select or prioritize which of the many stimuli is most important for gaze reorientation. In vertebrates, parts of this sensorimotor task are solved by a dorsal mesencephalic region called the optic tectum (OT), also known as the superior colliculus (SC) in mammals. This structure receives direct afferent multisensory inputs, but also indirect cognitive and other nonsensory modulatory inputs from forebrain areas used to bias tectal activity. These inputs interact with the intrinsic tectal circuitry to select orientin or evasive behavior. This chapter explores the phylogenetic conservation of the OT and its connectivity pattern in an accessible and reductionist vertebrate animal model, the lamprey, to develop preparations that allow for isolating components of this sensorimotor process while evaluating their impact on goal-directed behavior.Swedish Research Council | Ref. VR-M-K2013Swedish Research Council | Ref. VR-NT621-2013-4613Karolinska InstitutetParkinsonfonde
A cambrian origin for vertebrate rods
Full text linkVertebrates acquired dim light vision when an ancestral cone evolved into the rod photoreceptor at an unknown stage preceding the last common ancestor of extant jawed vertebrates (~420 million years ago Ma). The jawless lampreys provide a unique opportunity to constrain the timing of this advance, as their line diverged ~505 Ma and later displayed high morphological stability. We recorded with patch electrodes the inner segment photovoltages and with suction electrodes the outer segment photocurrents of Lampetra fluviatilis retinal photoreceptors. Several key functional features of jawed vertebrate rods are present in their phylogenetically homologous photoreceptors in lamprey: crucially, the efficient amplification of the effect of single photons, measured by multiple parameters, and the flow of rod signals into cones. These results make convergent evolution in the jawless and jawed vertebrate lines unlikely and indicate an early origin of rods, implying strong selective pressure toward dim light vision in Cambrian ecosystems
Commentary: Elimination of Left-Right Reciprocal Coupling in the Adult Lamprey Spinal Cord Abolishes the Generation of Locomotor Activity
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Biological Pattern Generation: The Cellular and Computational Logic of Networks in Motion
No full textIn 1900, Ramón y Cajal advanced the neuron doctrine, defining the neuron as the fundamental signaling unit of the nervous system. Over a century later, neurobiologists address the circuit doctrine: the logic of the core units of neuronal circuitry that control animal behavior. These are circuits that can be called into action for perceptual, conceptual, and motor tasks, and we now need to understand whether there are coherent and overriding principles that govern the design and function of these modules. The discovery of central motor programs has provided crucial insight into the logic of one prototypic set of neural circuits: those that generate motor patterns. In this review, I discuss the mode of operation of these pattern generator networks and consider the neural mechanisms through which they are selected and activated. In addition, I will outline the utility of computational models in analysis of the dynamic actions of these motor networks
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