Transfer of visual motion information via graded synapses operates linearly in the natural activity range

Kurtz R, Warzecha A-K, Egelhaaf M. Transfer of visual motion information via graded synapses operates linearly in the natural activity range. The journal of neuroscience. 2001;21(17):6957-6966.Synaptic transmission between a graded potential neuron and a spiking neuron was investigated in vivo using sensory stimulation instead of artificial excitation of the presynaptic neuron. During visual motion stimulation, individual presynaptic and postsynaptic neurons in the brain of the fly were electrophysiologically recorded together with concentration changes of presynaptic calcium (Delta[Ca(2+)](pre)). Preferred-direction motion leads to depolarization of the presynaptic neuron. It also produces pronounced increases in [Ca(2+)](pre) and the postsynaptic spike rate. Motion in the opposite direction was associated with hyperpolarization of the presynaptic cell but only a weak reduction in [Ca(2+)](pre) and the postsynaptic spike rate. Apart from this rectification, the relationships between presynaptic depolarizations, Delta[Ca(2+)](pre), and postsynaptic spike rates are, on average, linear over the entire range of activity levels that can be elicited by sensory stimulation. Thus, the inevitably limited range in which the gain of overall synaptic signal transfer is constant appears to be adjusted to sensory input strengths

A global response of the total electron content of the ionosphere to the magnetic storm of 17 and 18 June 1972

A global study is made of the response of the total electron content of the ionosphere to the sudden commencement (S.C.) geomagnetic storm of 17 June 1972. Using data from 18 sites, a comparison is made of the seasonal differences between this storm and the 17 December 1971 ionospheric storm studied on a similar global basis by Schödel et al. (1974). When storm induced total electron content enhancements occur, they generally occur within 24 h of the S.C. and they tend to be larger in the winter hemisphere; subsequent depletions are generally more severe in the summer hemisphere. The best-defined storm effect is the positive phase evening enhancements seen in the American longitude sector. The local times of the peak enhancements show a coupled seasonal/longitudinal/latitudinal pattern with latitude being the clearest ordering parameter. The magnitudes of the subsequent negative phase depletions show a longitudinal gradient from east to west. © 1981

A global response of the total electron content of the ionosphere to the magnetic storm of 17 and 18 June 1972

A global study is made of the response of the total electron content of the ionosphere to the sudden commencement (S.C.) geomagnetic storm of 17 June 1972. Using data from 18 sites, a comparison is made of the seasonal differences between this storm and the 17 December 1971 ionospheric storm studied on a similar global basis by Schödel et al. (1974). When storm induced total electron content enhancements occur, they generally occur within 24 h of the S.C. and they tend to be larger in the winter hemisphere; subsequent depletions are generally more severe in the summer hemisphere. The best-defined storm effect is the positive phase evening enhancements seen in the American longitude sector. The local times of the peak enhancements show a coupled seasonal/longitudinal/latitudinal pattern with latitude being the clearest ordering parameter. The magnitudes of the subsequent negative phase depletions show a longitudinal gradient from east to west. © 1981