Neuroelectric potentials derived from an extended version of Hodgkin-Huxley model.
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Animals↗
Biomedical subjects
E R Lewis
Publications and source records attributed to E R Lewis.
The role of the college and university in providing continuing education--from the viewpoint of the nurse educator.
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Education, Continuing↗
Neonatal septal implants: development of afferent lamination in the rat dentate gyrus.
The technique of tissue implantation into neonatal rats was used to assess mechanisms underlying the development of afferent lamination in the rat hippocampal formation. Septal nuclei, dissected from the brains of rat embryos (E17-E20), were implanted into the occipital or entorhinal cortex of 2--3 day old neonates that simultaneously received fimbrial transections to remove hippocampal innervation by native septal efferents. As visualized with acetylcholinesterase (AChE) histochemistry, the distribution of enzyme activity in implant-innervated hippocampi is qualitatively identical to the pattern in unoperated animals. Fibers from septal implants placed into the entorhinal cortex, appear to interact with commissural/associational afferents and produce altered laminar zones in the dentate gyrus.
Acetylcholinesterase↗
Essential roles of noise in neural coding and in studies of neural coding.
We present examples of results from our studies of auditory primary afferent nerve fibers and populations of such fibers in the frog and gerbil. We take advantage of the natural dithering effect of internal noise, where it is sufficient, to construct highly predictive descriptive models (based on the Wiener series with kernels derived from white-noise analysis). Where the internal noise is insufficient, we enhance dithering by applying external acoustic noise together with our stimuli. Using acoustic noise as a background sound, orthogonal to the stimulus waveform, we show that under some circumstances such background sound can enhance the ability of individual fibers and populations of fibers to encode the stimulus waveform.
Action Potentials↗
A pyrolysis product, anhydroecgonine methyl ester (methylecgonidine), is in the urine of cocaine smokers.
A method using combined gas chromatography/mass spectrometry (GC/MS) for determination of the cocaine pyrolysis product anhydroecgonine methyl ester (AEME) in urine is described. Using this method, we found that human subjects who smoked cocaine under laboratory conditions excreted substantial amounts of AEME in their urine. Little, if any, AEME was excreted in the urine when the same subjects were administered cocaine by intravenous and intranasal routes. AEME may be a useful marker for cocaine (crack) smoking. The pharmacology of AEME is unknown. The possibility that AEME may play a role in the effects associated with cocaine smoking needs to be examined.
Administration, Intranasal↗
Structure and development of vestibular hair cells in the larval bullfrog.
Structure and development of hair cells in vestibular sensory organs of the larval bullfrog were examined with scanning electron microscopy. The larval vestibular sensory epithelia resembled those of the adult frog. Based on morphology of the ciliary tufts, seven hair cell types were identified. One of them, the type A hair cell, appears to be the morphogenetic precursor of other hair cell types. The size of the stereocilia of type A hair cells is comparable to the surrounding microvilli. The distribution of immature type A hair cells suggests that the periphery of the sensory epithelia is the principal growth zone and the site of formation of new hair cells. However, a far greater number of type A hair cells were found in high frequency sensitive sensory organs (sacculus, amphibian and basilar papillae) than low frequency sensitive vestibular sensory structures (canal cristae, utriculus and lagena). This phenomenon may suggest that the time period required for the maturation of type A hair cells to their ultimate hair cell types in the low frequency sensitive vestibular organs is shorter than in the high frequency sensory structures. It is also possible that the low frequency sensitive vestibular organs may have completed their morphogenetic development in the early larval stages, while morphogenesis of hair cells in the high frequency sensory structures continues throughout the lifetime of a bullfrog.
Animals↗
History and progress of the journal.
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Forecasting↗
Theoretical bases of short-latency spike volleys in the peripheral vestibular system.
If a spike trigger zone exhibits the same sort of accommodation that has been found universally in peripheral axons and is an emergent property of the Hodgkin-Huxley model and other synthetic models of axonal membrane (1,2), then spike production will be favored by steep positive slopes of the waveform of the current into the trigger zone. Thus, large positive steps of axial current flowing nearly simultaneously into the trigger zones of many vestibular axons should produce a short-latency spike volley over those axons. Reasoning in terms of the small-signal (linear) transfer relationship for the cascade of components preceding the trigger zone, one can show that the ability to translate a stepwise change in head acceleration into a rapid increase in axial current into the trigger zone is more strongly dependent on the number of zeros at infinity from poles with long time constants (longer than those of the spike initiator) than it is on the values of the time constants themselves. Larger numbers of zeros at infinity make such translation increasingly difficult. Evidence from the work of Fernandez and Goldberg and others suggests (3-7) that the number is low. It may be lowest in jerk-sensitive units (8-9), in which case one would expect such units to make the greatest contributions to short-latency spike volleys.
Animals↗
High-frequency tuning properties of bullfrog lagenar vestibular afferent fibers.
A common property of vertebrate acoustic sensors, including otoconial acoustic sensors in lower vertebrates, is steep slopes on the high- and low-frequency band edges of the amplitude tuning curves. Bullfrog otoconial acoustic fibers are responsive to sound and exquisitely responsive to substrate vibrations in the frequency range from 20 Hz to 300 Hz. The sum of the absolute values of the two band-edge slopes of the amplitude tuning curve of such a fiber typically ranges from 100 dB/decade to 160 dB/decade (sometimes as high as 220 dB/decade), implying typical dynamic order of at least five to eight. We wondered if such steep slopes and the high dynamic order implied by them reflect special adaptations in acoustic sensors or if they are inherent in all lower-vertebrate otoconial sensors excited in this frequency range. To address this question, we examined the amplitude tuning characteristics of afferent nerve fibers from a bullfrog otoconial vestibular sensor in the same frequency range. In this paper, we report observations of tuning for bullfrog lagenar vestibular fibers in the frequency range from 10 Hz to approximately 500 Hz. To make these observations, we stimulated the frog with random dorsoventral motion that exhibited Gaussian amplitude distribution and that was flat in velocity from 10 Hz to 1.0 kHz. For each afferent fiber studied, we used discrete cross-correlation (between stimulus waveform and axon spike train) and discrete Fourier transformation to compute an amplitude tuning curve. In contrast with the amplitude tuning curve. In contrast with the amplitude tuning curves from saccular and lagenar acoustic fibers, those from the lagenar vestibular fibers typically had band-edge slopes whose absolute values summed to approximately 20 dB/decade, implying typical dynamic order of one. We conclude that steep band-edge slopes and high dynamic order are indeed special features of acoustic sensors, not shared by vestibular sensors.
Afferent Pathways↗