Patient outcomes and nurses' classification data.

The patient classifications done by nurses for all adult patients (n = 15,500) discharged from an urban teaching hospital in one year were retrieved and analyzed by discharge status. Classification results were summarized by physical-functional, psychological-social, and dependence categories and were associated with discharge disposition; patients discharged home were less dependent than others discharged to nursing homes or those who died in the hospital. Diagnosis related group (DRG) payment weights were somewhat independent of the patient classification scores and were not associated with adverse outcomes.

Effect of hematin in porphyric neuropathy.

Early, intravenous administration of hematin in a patient with acute intermittent porphyria and severe quadriparesis may have produced partial but remarkable improvement of neuropathy, and resulted in simultaneous decline of porphyrin precursors in the blood. Intermittent, biweekly hematin infusions given 1 month after the onset of the porphyric relapse had no effect on recovery of the residual neuropathy. We believe hematin may be effective in the treatment of porphyric neuropathy, if administered before irreversible neuronal damage has occured.

Distributed relaxation processes in sensory adaptation.

Dynamic description of most receptors, even in their near-linear ranges, has not led to understanding of the underlying physical events-in many instances because their curious transfer functions are not found in the usual repertoire of integral-order control-system analysis. We have described some methods, borrowed from other fields, which allow one to map any linear frequency response onto a putative weighting over an ensemble of simpler relaxation processes. One can then ask whether the resultant weighting of such processes suggests a corresponding plausible distribution of values for an appropriate physical variable within the sensory transducer. To illustrate this approach, we have chosen the fractional-order low-frequency response of Limulus lateral-eye photoreceptors. We show first that the current "adapting-bump" hypothesis for the generator potential can be formulated in terms of local first-order relaxation processes in which local light flux, the cross section of rhodopsin for photon capture, and restoration rate of local conductance-changing capability play specific roles. A representative spatial distribution for one of these parameters, which just accounts for the low-frequency response of the receptor, is then derived and its relation to cellular properties and recent experiments is examined. Finally, we show that for such a system, nonintegral-order dynamics are equivalent to nonhyperbolic statics, and that the efficacy distribution derived to account for the small-signal dynamics in fact predicts several decades of near-logarithmic response in the steady state. Encouraged by the result that one plausible proposal can account approximately for both the low-frequency dynamics (the transfer function s(k)) and the range-compressing statics (the Weber-Fechner relationship) measured in this photoreceptor, we have described some formally similar applications of these distributed effects to the vertebrate retina and to analogous properties of mechanoreceptors and chemoreceptors.

Dynamics of excitation and inhibition in the light-adapted Limulus eye in situ.

The dynamics of spike discharge in eccentric cell axons from the in situ lateral eye of Limulus, under small sinusoidal modulation of light to which the eye is adapted, are described over two decades of light intensity and nearly three decades of frequency. Steady-state lateral inhibition coefficients, derived from the very low-frequency response, average 0.04 at three interommatidial spacings. The gain vs. frequency of a singly illuminated ommatidium is described closely from 0.004 to 0.4 cps by the linear transfer function s(0.25); this function also accounts approximately for the measured phase leads, the small signal adaptation following small step inputs, and for Pinter's (1966) earlier low-frequency generator potential data. We suggest that such dynamics could arise from a summation in the generator potential of distributed intensity-dependent relaxation processes along the dendrite and rhabdome. Analysis of the dynamic responses of an eccentric cell with and without simultaneously modulated illumination of particular neighbors indicates an effect equivalent to self-inhibition acting via a first-order low-pass filter with time constant 0.42 sec, and steady-state gain near 4.0. The corresponding filters for lateral inhibition required time constants from 0.35 to 1 sec and effective finite delay of 50-90 msec.

Objective measure of the dynamics of a visual movement illusion.

Apparent movement in peripheral vision can be induced by sequential flashing of two dots that are spatially unresolved. Subjects used this illusion to make forced-choice estimates of the directional sequence of the two dots. Performance at this task defines spatiotemporal conditions that induce the illusion without reliance upon subjective distinctions of "movement" from "successivity" and "simultaneity." The dynamics of the illusion, defined in this way, are measured and compared with those for after-flash inhibition and the perception of real movement.

Auditory responses of neurones in the lateral mesencephalic nucleus (inferior colliculus) of the Barbary dove.

1. Auditory responses have been recorded from forty-five single neurones in the lateral mesencephalic nucleus of the dove, confirming the suspected auditory function of this nucleus.2. Most of the neurones with sustained responses to tones fell into three response-categories: inhibitory only, excitatory in a central range of frequencies with inhibition in adjacent frequency regions, and predominantly inhibitory with one or more relatively small excitatory regions. Seven of the neurones studied showed only transient responses: these had high thresholds or were restricted to a narrow range of frequencies.3. Responses to clicks were sometimes obtained, but were variable in different units and in a single unit were often dependent on repetition rate.4. Many properties of these neurones are similar to those in the cat inferior colliculus. The most notable difference is the existence in the dove of neurones with exclusively or predominantly inhibitory responses.

Source mechanisms for unit activity in isolated crayfish central nervous system.

As a tool for the identification of source mechanisms underlying the activity of single interneurons in the isolated crayfish abdominal cord, pulse trains from a sample of such neurons are statistically described (shape, mean, standard deviation, and serial correlation coefficient of interval distributions). These statistics were measured under four independent means of obtaining different average frequencies: (a) naturally occurring frequencies under standard conditions, (b) temperature control, (c) dc polarization, and (d) electrical stimulation of presynaptic fibers. 40 of 44 units studied had unimodal histograms, symmetrical when the mean interval was small and positively skewed with large means. Under standard conditions these units had SD = k (mean)(n), with n approximately 2. Fifteen single units were caused to fire at varied frequencies by cooling or dc stimulation. The resulting SD-vs.-mean plots for single units showed: (a)all points for a given unit fell approximately on a single line, regardless of whether temperature, dc, or neither was used to vary frequency, and (b) the average value of n (slope of log SD vs. log mean) for the fifteen units was 1.9 +/- 0.2. A paradox arises from interpretation of these data via gamma distributions. It is concluded that most of the spontaneous activity in the isolated abdominal cord may result from pacemaker activity within each cell and does not require a network of active units. Finally, the fact that the SD-mean relation was found not to depend measurably on temperature is interpreted as a useful restriction on models for neuronal noise processes.