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Many neurons use graded membrane-potential changes, instead of action potentials, to transmit information. Traditional synaptic models feature discontinuous transmitter release by presynaptic action potentials, but this is not true for synapses between graded-potential neurons. In addition to graded and continuous transmitter release, they have multiple(More)
Pseudorandom white-noise stimulation followed by direct spectral estimation was used to obtain linear frequency response and coherence functions from paired, but dynamically different, spider mechanosensory neurons. The dynamic properties of the two neuron types were similar with either mechanical or electrical stimulation, showing that action potential(More)
We studied the properties of voltage-activated outward currents in two types of spider cuticular mechanoreceptor neurons to learn if these currents contribute to the differences in their adaptation properties. Both types of neurons adapt rapidly to sustained stimuli, but type A neurons usually only fire one or two action potentials, whereas type B neurons(More)
1. Photoreceptor cells in Calliphora stygia were stimulated with randomly fluctuating green light while the resulting fluctuations in membrane potential were recorded with intracellular micro-electrodes. 2. Fourier analysis was used to obtain the frequency response functions between the light intensity fluctuations and the membrane potential fluctuations at(More)
Photoreceptor cells in both vertebrates and invertebrates respond to a flash of light with a slow graded change in membrane potential, which is generally depolarising in invertebrates and hyperpolarising in vertebrates. Although some of the early photochemical and biochemical stages of the transduction process have been elucidated in both cases, these(More)
1. We have developed an isolated mechanoreceptor-organ preparation in which the intact sensory structures are available for mechanical stimulation and electrical recording. The anterior lyriform slit sense organ on the patella of the spider, Cupiennius salei Keys., consists of seven or eight cuticular slits, each innervated by a pair of large bipolar(More)
The lyriform slit-sense organ on the patella of the spider, Cupiennius salei, consists of seven or eight slits, with each slit innervated by a pair of mechanically sensitive neurons. Mechanotransduction is believed to occur at the tips of the dendrites, which are surrounded by a Na+-rich receptor lymph. We studied the ionic basis of sensory transduction in(More)
Low-voltage-activated Ca(2+) currents (LVA-I(Ca)) are believed to perform several roles in neurons such as lowering the threshold for action potentials, promoting burst firing and oscillatory behavior, and enhancing synaptic excitation. They also may allow rapid increases in intracellular Ca(2+) concentration. We discovered LVA-I(Ca) in both members of(More)
1. Photoreceptor cells in the compound eye of the fly Phormia regina were stimulated with a green light emitting diode whose output was modulated by a pseudo-random noise generator while the resulting fluctuations in membrane potential were measured with intracellular microelectrodes. 2. The responses to repeated sequences of identical pseudorandom patterns(More)
1. Randomly modulated light stimuli were used to characterize the nonlinear dynamic properties of the synapse between photoreceptors and large monopolar neurons (LMC) in the fly retina. Membrane potential fluctuations produced by constant variance contrast stimuli were recorded at eight different levels of background light intensity. 2. Representation of(More)