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Dive into the research topics where Brian L. Antonsen is active.

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Featured researches published by Brian L. Antonsen.


Brain Behavior and Evolution | 2002

Metamodulation of the Crayfish Escape Circuit

Donald H. Edwards; Shih-Rung Yeh; Barbara E. Musolf; Brian L. Antonsen; Franklin B. Krasne

Neuromodulation provides a means of changing the excitability of neurons or the effect of synapses, and so extends the performance range of neural circuits. Metamodulation occurs when the neuromodulatory effect is itself modulated, often in response to a change in the behavioral state of the animal. The well-studied neural circuit that mediates escape in the crayfish is modulated by serotonin, and this modulation is subject to two forms of metamodulation. First, the serotonergic modulation of the Lateral Giant (LG) command neuron for escape depends on the pattern of exposure of the cell to serotonin. High and low concentrations, and rapid and slow exposures each produce opposite modulatory effects on sensory-evoked EPSPs in LG. In addition, brief exposures produce transient modulatory effects, whereas longer exposures produce long-term facilitation. These different patterns of exposure may result from serotonin neurotransmission, paracrine transmission, and hormonal release, all of which occur in the vicinity of LG. The second form of metamodulation enables serotonergic modulation to track slow changes in the social status of the crayfish. Slowly applied serotonin facilitates LG’s response in socially isolated crayfish and in new dominant and subordinate animals. Facilitation is retained in the dominant animal during two weeks of continuous pairing of the animals, but facilitation gradually changes to inhibition in the subordinate crayfish. These and related changes in serotonin modulation appear to result from changes in the population of serotonin receptors that mediate the modulatory effects in LG. Whereas the exposure-dependent metamodulation enables rapid changes in serotonergic modulation of LG to occur, the status-dependent metamodulation enables serotonergic modulation of LG to track the slow maturation of social relationships.


The Journal of Comparative Neurology | 2005

Immunocytochemical mapping and quantification of expression of a putative type 1 serotonin receptor in the crayfish nervous system

Nadja Spitzer; Brian L. Antonsen; Donald H. Edwards

Serotonin is an important neurotransmitter that is involved in modulation of sensory, motor, and higher functions in many species. In the crayfish, which has been developed as a model for nervous system function for over a century, serotonin modulates several identified circuits. Although the cellular and circuit effects of serotonin have been extensively studied, little is known about the receptors that mediate these signals. Physiological data indicate that identified crustacean cells and circuits are modulated via several different serotonin receptors. We describe the detailed immunocytochemical localization of the crustacean type 1 serotonin receptor, 5‐HT1crust, throughout the crayfish nerve cord and on abdominal superficial flexor muscles. 5‐HT1crust is widely distributed in somata, including those of several identified neurons, and neuropil, suggesting both synaptic and neurohormonal roles. Individual animals show very different levels of 5‐HT1crust immunoreactivity (5‐HT1crustir) ranging from preparations with hundreds of labeled cells per ganglion to some containing only a handful of 5‐HT1crustir cells in the entire nerve cord. The interanimal variability in 5‐HT1crustir is great, but individual nerve cords show a consistent level of labeling between ganglia. Quantitative RT‐PCR shows that 5‐HT1crust mRNA levels between animals are also variable but do not directly correlate with 5‐HT1crustir levels. Although there is no correlation of 5‐HT1crust expression with gender, social status, molting or feeding, dominant animals show significantly greater variability than subordinates. Functional analysis of 5‐HT1crust in combination with this immunocytochemical map will aid further understanding of this receptors role in the actions of serotonin on identified circuits and cells. J. Comp. Neurol. 484:261–282, 2005.


The Journal of Comparative Neurology | 2001

Serotonergic and octopaminergic systems in the squat lobster Munida quadrispina (Anomura, Galatheidae).

Brian L. Antonsen; Dorothy H. Paul

Immunocytochemical mapping of serotonergic and octopaminergic neurons in the central nervous system of the squat lobster Munida quadrispina reveal approximately 120 serotonin‐immunoreactive cell bodies (distributed throughout the neuromeres except in abdominal ganglion 5) and 48 octopamine‐immunoreactive cell bodies (in brain and thoracic neuromeres but none in the circumesophageal or abdominal ganglia). Immunopositive neuropils for both amines are distributed in multiple areas in each neuromere and overlap extensively. Serotonergic and octopaminergic neurons have extensive bilateral projections in abdominal ganglia, whereas the majority of projections in thoracic and subesophageal ganglia are unilateral (contralateral to soma). This difference correlates with typical differences between abdominal and thoracic motor system coordination. Processes of immunoreactive cells for both amines form extensive, peripheral, neurosecretory‐like structures. Serotonin seems to be released peripherally in more segments, and from more nerves per segment, than octopamine. M. quadrispina has fewer serotonergic and octopaminergic immunoreactive cells, in particular, fewer segmentally repeated cells, than other species studied to date. Nevertheless, the general organization of the aminergic systems is similar, and several aminergic cells have locations and morphologies that strongly suggest homology with identified aminergic cells in other crustaceans. Among these are segmentally repeated neurons that, in M. quadrispina, form serotonin‐immunopositive tubular structures in the thoracic hemiganglia innervating pereiopods 1–3 that are unlike anything reported previously for any species. Comparisons of immunocytochemical maps within one species and between species exhibiting different behaviors provide insights into possible sites of action, functional differences between, and evolution of biogenic aminergic systems. J. Comp. Neurol. 439:450–468, 2001.


The Journal of Comparative Neurology | 2003

Differential dye coupling reveals lateral giant escape circuit in crayfish

Brian L. Antonsen; Donald H. Edwards

The lateral giant (LG) escape circuit of crayfish mediates a coordinated escape triggered by strong attack to the abdomen. The LG circuit is one of the best understood of small systems, but models of the circuit have mostly been limited to simple ball‐and‐stick representations, which ignore anatomical details of contacts between circuit elements. Many of the these contacts are electrical; here we use differential dye coupling, a technique which could help reveal connection patterns in many neural circuits, to reveal in detail the circuit within the terminal abdominal ganglion. Sensory input from the tailfan forms a somatotopic map on the projecting LG dendrites, which together with interafferent coupling mediates a lateral excitatory network that selectively amplifies strong, phasic, converging input to LG. Mechanosensory interneurons contact LG at sites distinct from the primary afferents and so maximize their summated effect on LG. Motor neurons and premotor interneurons are excited near the initial segments of the LGs and innervate muscles for generating uropod flaring and telson flexion. Previous research has shown that spatial patterns of input are important for signal integration in LG; this map of electrical contact points will help us to understand synaptic processing in this system. J. Comp. Neurol. 466:1–13, 2003.


Brain Behavior and Evolution | 2000

The Leg Depressor and Levator Muscles in the Squat Lobster Munida quadrispina (Galatheidae) and the Crayfish Procambarus clarkii (Astacidae) Have Multiple Heads with Potentially Different Functions

Brian L. Antonsen; Dorothy H. Pau

The proximal leg muscles of decapod crustaceans, controlling movements at the first two joints, are anatomically more complex than the better-studied distal leg muscles. Despite extensive research on their involvement in diverse behaviors, no complete descriptions of the anatomy and innervation of these muscles for any species have been published. We describe the anatomy and innervation of the depressor muscle in the second leg of the squat lobster Munida quadrispina and compare its anatomy with that of its homologue in the crayfish Procambarus clarkii and its antagonist, the levator, in both species. Of the six anatomically distinct heads comprising M. quadrispina’s depressor muscle, one arises in the coxa (coxal head) and five are bi-articular (cross two joints), arising from widely dispersed sites on the thoracic endophragmal skeleton (dorsal, sternal, caudal, ventral-rostral, ventral-caudal heads). The heads’ widely divergent force vectors are accommodated by the depressor apodeme’s bifurcation at a thin flexible point. In total, eighteen neurons with central somata were backfilled from nerve branches to the heads. The common inhibitor and at least one neuron of unknown function with rostro-lateral soma and extremely sparse neurites innervate all heads. The sixteen excitatory motoneurons’ somata are clustered in two locations, five rostral and eleven caudal to the neuropil. Rostral motoneurons innervate the two ventral heads (rostral and caudal). Their integrating segments lie rostral to those of the caudal group motoneurons and are straight or ‘Y’-shaped, the latter longer and larger in diameter. Both morphological types have one prominent medial neurite that crosses the midline and could allow direct interaction between bilateral pairs of rostral motoneurons. The caudal motoneurons provide partially shared innervation to the remaining four heads. Six provide exclusive innervation, one to the caudal head, two to the sternal head, and three to the bi-articular dorsal head and uni-articular coxal head which share innervation. Of the remaining five caudal motoneurons, two are shared by the caudal head and the dorsal-coxal pair of heads and three are shared by the caudal and sternal heads. P. clarkii has two depressor muscles; the rostral depressor has a single head morphologically similar to the ventral rostral head in M. quadrispina; the caudal depressor muscle has four heads (dorsal, coxal, caudal, sternal) that insert on the large caudal depressor apodeme. The overall organization of depressor muscle heads in P. clarkii and M. quadrispina is similar, taking into consideration the different internal and external thoracic anatomies and the different resting stances, horizontal and tilted, respectively. As in other species, M. quadrispina and P. clarkii have two levator muscles, each with an apodeme of complex structure attributable to the levators’ role in leg autotomy. The caudal levator arises in the coxa; it has two heads in M. quadrispina, but only one in P. clarkii. In both species the rostral levator has three heads all arising within the thorax. Divergent force vectors and partially independent innervation of different heads composing complex musculature at single joints constitute an anatomical level of organization that neural mechanisms must accommodate to produce adaptive movements.


The Journal of Neuroscience | 2005

The Retrograde Spread of Synaptic Potentials and Recruitment of Presynaptic Inputs

Brian L. Antonsen; Jens Herberholz; Donald H. Edwards

Lateral excitation is a mechanism for amplifying coordinated input to postsynaptic neurons that has been described recently in several species. Here, we describe how a postsynaptic neuron, the lateral giant (LG) escape command neuron, enhances lateral excitation among its presynaptic mechanosensory afferents in the crayfish tailfan. A lateral excitatory network exists among electrically coupled tailfan primary afferents, mediated through central electrical synapses. EPSPs elicited in LG dendrites as a result of mechanosensory stimulation spread antidromically back through electrical junctions to unstimulated afferents, summate with EPSPs elicited through direct afferent-to-afferent connections, and contribute to recruitment of these afferents. Antidromic potentials are larger if the afferent is closer to the initial input on LG dendrites, which could create a spatial filtering mechanism within the network. This pathway also broadens the temporal window over which lateral excitation can occur, because of the delay required for EPSPs to spread through the large LG dendrites. The delay allows subthreshold inputs to the LG to have a priming effect on the lateral excitatory network and lowers the threshold of the network in response to a second, short-latency stimulus. Retrograde communication within neuronal pathways has been described in a number of vertebrate and invertebrate species. A mechanism of antidromic passage of depolarizing current from a neuron to its presynaptic afferents, similar to that described here in an invertebrate, is also present in a vertebrate (fish). This raises the possibility that short-term retrograde modulation of presynaptic elements through electrical junctions may be common.


Archive | 2002

Synergies Between Disparate Motor Systems: Loci For Behavioral Evolution

Dorothy H. Paul; Zen Faulkes; Brian L. Antonsen

Evolutionary experimentation (Bullock 1984) has given rise to a large repertoire of locomotor, and other, behaviors in malacostracan crustaceans. Just within the Decapoda (Fig.1), behavioral diversity exceeds the considerable morphological diversity. More than half a century of research on the neurobiology of decapods has led to the insight that neurobehavioural circuits are often fractionated into subsets of neurons (e.g.,central pattern generators: Ikeda and Wiersma 1964; Mendelson 1971; Skorupski et al. 1984; Sillar et al. 1987; Murchison et al. 1993; groups of motor units operating muscles at single joints or even single muscles: Ayers and Clarac 1978) which are responsible for discrete aspects of behavior and that separate mechanisms exist to link the activities of these units. These latter coordinating mechanisms, which include coordinating interneurons (Wiersma and Ikeda 1964; Stein 1971; Namba and Mulloney 1999; Mulloney, this Vol.) and neuromodulatory neurons (Bartos et al. 1999; Blitz et al. 1999; Marder this vol), provide much of the adaptive flexibility of motor behavior as a whole. This organization suggests that evolutionary flexibility of motor systems might also be greatest in the coordinating mechanisms linking subsets of neurons or motor modules which themselves are more evolutionarily conserved. We summarize evidence from decapod locomotion for this hypothesis, then briefly address evolution of motor modules themselves.


The Biological Bulletin | 2009

Serotonergic Modulation of Crayfish Hindgut

Barbara E. Musolf; Nadja Spitzer; Brian L. Antonsen; Donald H. Edwards

The crayfish hindgut is a morphologically differentiated tube that varies along its length in the distribution of muscles and glands, contractile properties, serotonergic innervation, patterns of 5-HT receptor expression, and sensitivity to serotonin (5-HT). Anatomical differences divide the hindgut into five distinct segments along its length. Spontaneous pulsatile contractions produced by the isolated hindgut decrease in force and increase in frequency along the anterior-posterior axis. Central input to the hindgut comes from a large cluster of 5-HT-immunoreactive neurons in the terminal abdominal ganglion that form a large nerve plexus on the hindgut. 5-HT1α and 5-HT2β receptors vary in their distribution along the hindgut, and are associated with longitudinal and circular muscles and with axon collaterals of the 5-HT-immunoreactive neurons. Application of 30 nmol l−1 to 1 μmol l−1 5-HT to rostral, middle, or caudal sections of hindgut produced tension changes that varied with the concentration and section. 5-HT also initiated antiperistaltic waves in the posterior hindgut. These results indicate that 5-HT is an important neuromodulator for initiating contractions and coordinating activity in the different functional compartments along the rostral-to-caudal axis of the hindgut.


ieee international conference on fuzzy systems | 2006

Fuzzy Contour Matching for 3D Reconstruction and Retrieval

Yong Li; Saeid Belkasim; Xiujuan Chen; Donald H. Edwards; Brian L. Antonsen

An approach for 3D reconstruction and partial retrieval from 2D image stacks using contour tree structure and fuzzy contour matching model is proposed. We use a contour-based image segmentation method to extract object contours from 2D image slices and convert the original image stack into a standard XML database. A fuzzy contour matching model is designed to group the related contour objects on different image slices to form 3D components. The proposed methods have been implemented for various parts of Crayfish neuron represented in 2D confocal images. The experimental results suggest the suitability of the system for individual neuron branch search in 3D image stacks.


Archive | 2002

Aminergic Systems in the Squat Lobster Mundia Quadrispina (Anomura, Galatheidae): a Case Made for Comparative Neurobiology

Brian L. Antonsen; Dorothy H. Paul

The use of model animals or model systems for studying biological problems is increasingly pervasive. Proponents of consolidation of research effort on a few species argue that using many different animals to study the same system or problem results in unfruitful duplication and unjustifiable wastefulness. Of course, thoughtlessly repeating experiments over and in a wide array of animals is pointless and wasteful. However, we note a fundamental problem with limiting research to a few model organisms: it ignores the fact that biological evolution has tinkered with the genes and ontogenies of each species (that is why we distinguish them!). Model species, often initially chosen for no reason other than being easily accessible or maintainable, may be representative of a larger taxonomic group with respect to some features but prove to be very unusual with respect to the particular features under study, so that findings have only limited application to other animals. In addition to providing insight into evolutionary relationships, comparative approaches can give us clues about the structure and function of systems in extant organisms that might not be apparent from study of single species. This approach has lead to important discoveries in both vertebrate and invertebrate neuroscience (Paul 1991; Bullock 1993; Paul and Wilson 1994; Striedter 1998). What we as researchers must do is to choose carefully when comparative studies are merited, and to use them to try to investigate specific problems in the species most amenable to the particular research.

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Nadja Spitzer

Georgia State University

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Shih-Rung Yeh

Georgia State University

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