ABSTRACT
The Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS), a proposed Astrophysics MIDEX-class mission concept, has an innovative 14-meter diameter inflatable primary mirror that will provide the sensitivity to study far-infrared continuum and line emission from galaxies at all redshifts with high spectral resolution heterodyne receivers. OASIS will have the sensitivity to follow the water trail from galaxies to the comets that create oceans. It will bring an understanding of the role of water in galaxy evolution and its part of the oxygen budget, by measuring water emission from local to intermediate redshift galaxies, observations that have not been possible from the ground. Observation of the ground-state HD line will accurately measure gas mass in a wide variety of astrophysical objects. Thanks to its exquisite spatial resolution and sensitivity, OASIS will, during its one-year baseline mission, detect water in galaxies with unprecedented statistical significance. This paper reviews the extragalactic science achievable and planned with OASIS.
ABSTRACT
BACKGROUND: Deep brain stimulation (DBS) administered in the basal ganglia is an effective therapy for movement disorders; however, the mechanism(s) of action remain poorly understood. OBJECTIVE: Because high-frequency electrical stimulation (HFS) preferentially activates fibers, one hypothesis of DBS action is that local release of transmitters from axon terminals underlies the inhibitory effects on spontaneous spiking observed in human intraoperative recordings. We hypothesize that blocking presynaptic release of transmitters will reduce any stimulation-induced effect and blocking of postsynaptic GABA receptors will reduce the inhibitory effect of HFS. METHODS: We recorded neuronal responses after short HFS trains (2-37 microA, 0.5 seconds, 300 Hz) delivered through the recording electrode or via an adjacent electrode in 42 single globus pallidus (GP) units of anesthetized rats before and after injection of the synaptic blockers cobalt chloride (100 mM) and bicuculline methiodide (2 microg/microL). RESULTS: Responses to HFS trains were mainly transient ( approximately 350 milliseconds) inhibition of firing, but a late response ( approximately 1-2 seconds) and rebound burst were also found. Excitation was observed in 4 of 43 neurons studied. Neurons with transient inhibition had the response attenuated by 47% after injection of either synaptic blocker, in part supporting the local gamma-aminobutyric acid release hypothesis. Bicuculline methiodide and cobalt attenuated the late response as well as the rebound burst response, but the late inhibitory response was increased by bicuculline methiodide in one case. HFS-induced excitatory responses were not altered by synaptic blockers suggesting direct stimulation of postsynaptic elements of GP neurons. CONCLUSIONS: The results indicate HFS induces the local inhibition of ongoing activity of the somal region of GP neurons as well as the stimulation of axons and active dendrites. These observations serve to shed light on the mechanism(s) of DBS.
