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Biomedical subjects

D B Hamilton

Publications and source records attributed to D B Hamilton.

6 recordsLinked to original sources
PubMed1996

The seventh star: Dorothy Ford Buschmann and the founding of Sigma Theta Tau.

Several women from the Indiana University Training School for Nurses founded Sigma Theta Tau in 1922. While the legend identifies six student founders, this historical study examined the contributions of Dorothy Charlotte Ford Buschmann (1895-1953), a key advisor whom some might consider the seventh founding star. Sources include primary data from Sigma Theta Tau archives. The findings suggest that Dorothy Buschmann believed that the foundations of professional nursing were love, honor, and courage and that the enduring value of nursing was its contribution to the social good. While Buschmann did not claim credit as a founder, she played a vital role in designing Sigma Theta Tau's philosophy and constitution, extended membership throughout the Midwest, and served as the first national president from 1927-1934.

Education, Nursing↗
PubMed1993

The idea of history and the history of ideas.

Professional nurses understand that the historian's task is to inquire into the issues and ideas of nursing's past, but may not comprehend the nature and methods of historical research. Although historical research is similar to other qualitative methods, the results are usually presented in the form of "story." The story, called the historical narrative, is intended to enlighten the reader but it may disguise the historian's method and mislead the reader into thinking that historical method is either non-existent, simple or non-important. The purpose of this article is to begin a dialogue which will negate the myths that historical method is neither rigorous nor significant and to encourage other nurse historians into articulating, sharing and teaching others "how historians think."

Historiography↗
PubMed1989

Visual cortical receptive fields in monkey and cat: spatial and temporal phase transfer function.

The response amplitude of simple cortical cells to spatiotemporal sine-wave patterns has been thoroughly documented in both cat and monkey. However, comparable measurements of response phase are not available even though phase measurements are essential for estimating the complete transfer function of a cell, and thus its spatiotemporal receptive field. This report describes a simple procedure for measuring both the amplitude and the phase transfer functions of striate cells. This technique was applied to 15 monkey and 27 cat simple cells. The spatiotemporal phase response functions were found to be adequately described by linear equations in four parameters. Both the amplitude and phase responses were found to satisfy several strong constraints implied by the class of linear quadrature models proposed recently in theories of biological motion sensitivity. Because the data satisfied these constraints, it was possible to determine four important receptive field properties from the phase data: the spatial symmetry, the temporal symmetry, the response latency, and the spatial position. The receptive fields were found to have a wide range of spatial symmetries, but a more narrow range of temporal symmetries. Spatiotemporal receptive fields reconstructed from complete transfer functions are used to illustrate some of the differences between direction selective and nondirection selective cells. Finally, the effects of linear and nonlinear mechanisms on amplitude, phase, and direction selective responses are considered.

Animals↗
PubMed1986

Sampling-theory analysis of spatial vision.

Spatial-vision research has been largely concerned with measuring and understanding the consequences of receptive-field properties measured by single-unit recording. However, in order to understand spatial-information processing in the visual system, it is equally essential to know the densities and the distribution patterns of the receptive fields. If the receptive fields are not arrayed properly across the visual field, spatial information will be lost. It has been argued, on the basis of the Whittaker-Shannon sampling theorem, that the receptors of the fovea sample the retinal image at a high enough rate to preserve essentially all the available spatial information. In this paper we show how two-dimensional sampling theory can be used to determine which combinations of receptive-field shapes and sampling patterns would preserve all spatial information from the receptors. This analysis will prove useful for determining, in conjunction with electrophysiological and anatomical evidence, what spatial information is or is not being transmitted by a given stage of the visual pathway. It may also prove useful for developing and testing theories of spatial vision.

Humans↗
PubMed1984

Spatial contrast adaptation characteristics of neurones recorded in the cat's visual cortex.

Spatial contrast adaptation, produced by prolonged exposure to high contrast grating patterns, has become an important psychophysical method for isolating spatial and orientation selective channels in the human visual system. It has been reasonably argued that this adaptation may be fundamentally dependent upon the activity of neurones in the striate cortex. To test the validity of this hypothesis, and several others, we measured the general adaptation characteristics of 144 striate neurones using a stimulus protocol comparable to the typical psychophysical methods. In general, during prolonged high contrast stimulation, the responses of most cells exponentially decayed from a transient peak response to a sustained plateau response; following adaptation, the responses to lower contrasts were depressed relative to the unadapted state but then gradually recovered from the transient depression to a sustained plateau. Such adaptation was a property common to both simple and complex cells (the distributions of the quantitative of adaptation were overlapping); there were however small but reliable differences. We compared the neurophysiological contrast adaptation with two psychophysical estimates of human contrast adaptation (threshold contrast elevation and apparent contrast reduction) and found that the time courses and the magnitudes were quite similar. The effect of contrast adaptation on the spatial frequency tuning was assessed by measuring the contrast response function at several different test spatial frequencies before and after adaptation at the optimum centre frequency. We found that the effect of adaptation decreased as the difference between test and adaptation frequency increased. Grating contrast adaptation has been alternatively described as 'constructive gain control' on the one hand and as 'deleterious fatigue' on the other. We tested the effect of contrast adaptation on the contrast response function and found (a) that adaptation shifts the curves vertically downward parallel to the response axis (thus reflecting a decrease in the maximum rate of firing and a deleterious compression of the response range) and (b) that adaptation shifts the curves horizontally to the right parallel to the contrast axis (thus reflecting a true sensitivity shift of the remaining response range for constructive maintenance of high differential sensitivity around the prevailing background level).(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Ocular↗