205 research outputs found

    Connections of the corticomedial amygdala in the golden hamster. I. Efferents of the “vomeronasal amygdala”

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    The medial (M) and posteromedial cortical (C3) amygdaloid nuclei and the nucleus of the accessory olfactory tract (NAOT) are disignated the “vomeronasal amygdala” because they are the only components of the amygdala to receive a direct projection from the accessory olfactory bulb (AOB). The efferents of M and C3 were traced after injections of 3 H-proline into the amygdala in male golden hamsters. Frozen sections of the brains were processed for autoradiography. The efferents of the “vomeronasal amygdala” are largely to areas which are primary and secondary terminal areas along the vomeronasal pathway, although the efferents from C3 and M terminate in different layers in these areas than do the projections from the vomeronasal nerve or the AOB. Specifically, C3 projects ipsilaterally to the internal granule cell layer of the AOB, the cellular layer of NAOT, and layer lb of M. Additional fibers from C3 terminate in a retrocommissural component of the bed nucleus of the stria terminalis (BNST) bilaterally, and in the cellular layers of the contralateral C3. The medial nucleus projects to the cellular layer of the ipsilateral NAOT, layer lb of C3, and bilaterally to the medial component of BNST. Projections from M to non-vomeronasal areas terminate in the medial preoptic area-anterior hypothalamic junction, ventromedial nucleus of the hypothalamus, ventral premammillary nucleus and possibly in the ventral subiculum. These results demonstrate reciprocal connections between primary and secondary vomeronasal areas and between the secondary areas themselves. They suggest that M, but not C3, projects to areas outside this vomeronasal network. The medial amygdaloid nucleus is therefore an important link between the vomeronasal organ and areas of the brain not receiving direct vomeronasal input.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50012/1/901970107_ftp.pd

    Differential projections of the anterior and posterior regions of the medial amygdaloid nucleus in the syrian hamster

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    The medial nucleus of the amygdala is important for the neural control of reproductive behavior in the adult male Syrian hamster. Two types of signals are essential for this behavior, chemosensory stimuli and gonadal steroids; these signals appear to be received in different parts of the medial nucleus. The anterior region receives input from olfactory and vomeronasal systems, both of which are required for this behavior, whereas the posterior region receives gonadal hormone inputs. Behavioral studies have also suggested a functional differentiation of these two areas; electrolytic lesions of the anterior, but not the posterior, part eliminates normal sexual behavior. In this study, the efferent projections of the anterior and posterior divisions of the medial nucleus of the amygdala in the Syrian hamster were analyzed throughout the forebrain after injections of the anterograde neuronal tracer, Phaseolus vulgaris -leucoagglutinin. Neurons of the anterior, but not the posterior, medial nucleus, were found to project to numerous olfactory bulb projection areas and to the ventral striatopallidal complex. Within areas of the chemosensory circuitry that control reproductive behavior, the anterior region of the medial nucleus projects to the intermediate part of the posterior bed nucleus of the stria terminalis and the lateral part of the medial preoptic area, whereas the posterior region of the medial nucleus projects to the medial parts of these areas. Differences in targets were also observed in the ventromedial nucleus of the hypothalamus where the anterior region projects to the core while the posterior part projects to the shell of this nucleus. Furthermore, reciprocal projections between the anterior and posterior regions of the medial nucleus were observed. Taken together, these studies support the hypothesis that the anterior and posterior regions of the medial amygdaloid nucleus provide substantially different contributions to the control of reproductive behaviors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50051/1/903170208_ftp.pd

    Lawson criterion for ignition exceeded in an inertial fusion experiment

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    For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

    Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

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    Demonstration of Ignition Radiation Temperatures in Indirect-Drive Inertial Confinement Fusion Hohlraums

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