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Biomedical subjects

R K Moore

Publications and source records attributed to R K Moore.

13 recordsLinked to original sources
PubMed1990

Relationships between reproduction traits, age and body weight at calving, and days dry in first lactation Ayrshires and Holsteins.

Individual cow test day records collected between December 1979 and June 1986 were used to calculate measures of reproductive performance, age and weight at calving, and days dry for 7824 Ayrshire and 79,755 Holstein cows in first lactation. Separate analyses by breed were carried out according to a multiple-trait mixed model. Sixty-two Ayrshire and 369 Holstein sires were treated as random in the analyses. Ayrshires were, on average, older and lighter at calving than Holsteins, but the breeds differed little in reproduction measures and days dry. Heritabilities of fertility traits, days to first breeding, days open, and services per conception were all less than .015 in the multi-trait analyses. With the exception of body weight, heritability estimates for the other traits were less than .05. Phenotypic correlations between traits were almost identical for the two breeds, and genetic correlations tended to be similar. Exceptions involved the trait days to first breeding and services per conception, but heritabilities of these traits were close to zero (p less than .008) in Ayrshires. Fertility traits were positively correlated genetically. Genetic correlations between days open and both age and body weight at calving were small. The genetic correlation between age and weight at calving was -.90 and -.68 in Ayrshires and Holsteins, respectively. Genetic correlations between days dry and all traits except body weight were moderate and positive.

Aging↗
PubMed1987

A retinal smear technique for varying grating contrast.

We present here a technique for modulating contrast in gratings seen in Maxwellian-view or on a projection screen. The method can be used with achromatic or chromatic grating stimuli. It is based on a high frequency oscillatory displacement of the grating image, which in turn produces a smearing of the image on the observer's retina. The waveform of the displacement and its amplitude determine the appearance and contrast of the image produced on the retina.

Form Perception↗
PubMed1985

A method for determining threshold from single-unit neural activity.

A computationally straightforward method is described for determining the latency, duration and magnitude of stimulus-evoked single-unit neural activity. A unique feature of the method is its ability to define the neural response without reference to stimulus parameters. First, the temporal component of the spike train that represents the response is located and then that component is analyzed to determine the magnitude of the response. Intensity-response functions can then be constructed, using the number of extra spikes above baseline activity as a measure of response magnitude. Threshold can be defined as any point on the intensity-response function.

Action Potentials↗
PubMed1982

Changes in the human visually evoked cortical potential in response to chromatic modulation of a sinusoidal grating.

Human visually evoked cortical potentials (VECPs) were recorded from 4 subjects in response to the counterphase alternation of an equal brightness chromatic grating pattern. The pattern was constructed from 2 monochromatic sinusoidal gratings registered 180 deg out of phase. Eleven wavelengths from 450 to 650 nm (at 20 nm intervals) were used. Each wavelength was paired in the grating stimulus with every other to produce a total of 55 different chromatic gratings. The chromatic modulation depth (contrast) of each grating was varied and resulting VECPs were recorded. VECP amplitude was found to vary linearly with log chromatic modulation depth. VECP threshold values were inferred by extrapolation of linear regression lines to zero VECP amplitude. Chromatic modulation sensitivity functions were derived and a multidimensional scaling analysis of the data for each subject was performed. The data were adequately described by a two-dimensional geometric configuration of the 11 wavelengths used. The configurations were similar in shape to those obtained psychophysically by Butler and Riggs (1978) Vision Res. 18, 1407-1416, who used a similar stimulus pattern. Their shapes are consistent with an opponent-color model of color vision.

Adult↗
PubMed1982

Measurements of visual suppression during opening, closing and blinking of the eyes.

We have previously shown that the sensitivity of human vision, as measured with a stimulus that bypasses the eyelids, is briefly impaired at the time of an eyeblink. We now find that the visual loss is almost equally extensive during eye closure if the eyes then remained closed. But little impairment occurs during eye opening when the eyes then remain open. We have previously concluded that, in blinking, visual suppression is associated with an inhibitory signal sent out by the brain. We now conclude that this signal arises primarily as a corollary to the efferent discharge that closes the eyelids.

Adult↗
PubMed1982

Perception of suprathreshold stimuli during saccadic eye movements.

We have investigated the extent to which a graded series of suprathreshold stimuli are perceptually weakened by saccadic suppression. Stimuli were brief decrements of variable amplitude in the illumination of a Ganzfeld. For each of several decrements presented during fixation, we determined a matching amplitude of decrement presented during saccades. The measure of saccadic suppression was the ratio of these two amplitudes. The matches made by three observers exhibit ratios as high as 6:1 (0.8 log unit of suppression) near the threshold. Suppression decreases systematically as the strength of the stimulus increases, reaching 0.1 log unit or less for stimuli 2 log units above threshold.

Eye Movements↗
PubMed1982

Rapid ventilatory responses to changes in insufflated CO2 in awake roosters.

The ventilatory responses to pulses or steps in the fraction of CO2 in the insufflated gas stream (FICO2) in awake, unidirectionally ventilated White Leghorn roosters (Gallus domesticus) were studied. Within 0.2-0.5 s of the change in FICO2 at the syrinx, a change in inspiratory or expiratory flow occurred. Increases in FICO2 increased flow and tidal volume (VT), whereas decreases in FICO2 decreased flow and VT. Expiratory duration (TE) was markedly prolonged by decreases in FICO2 and shortened by increases. Inspiratory duration was affected little by FICO2 changes. The TE response to pulses of FICO2 (0.2-0.4 s duration) revealed a time dependency such that a maximum effect occurred when the pulses arrived at the syrinx at approximately midexpiration. The magnitudes of the responses were approximately proportional to the amplitude and duration of the FICO2 changes, but decreases in FICO2 had greater effects than increases. A likely receptor site for these responses is the intrapulmonary chemoreceptors, which appear to function in a reflex controlling airflow and timing of the ongoing breath.

Animals↗