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Biomedical subjects

J Beatty

Publications and source records attributed to J Beatty.

At least 19 recordsLinked to original sources
PubMed1992

Prolongation of magnetic resonance T2 time in hippocampus of human patients marks the presence and severity of Alzheimer's disease.

Spin-spin relaxation time (T2) was measured in the hippocampal formation, thalamus, and cortical white matter in 13 patients with probable Alzheimer's disease (AD), 11 elderly normal individuals, 23 healthy young persons, and 9 subjects diagnosed with multi-infarct dementia. A 0.04 tesla magnetic resonance scanner was used. Hippocampal T2 values for all AD patients exceeded those of any non-AD individual, regardless of age or dementia due to infarction. Further, these T2 values were highly correlated (+ 0.96) with the severity of functional and cognitive impairment of the AD patients. This T2 prolongation was not observed at the other sites examined. These results suggest that hippocampal T2 prolongation may provide a specific marker by which AD pathology can be detected, characterized, and followed in vivo.

Adult↗
PubMed1991

Remotely controlled positioning lasers.

Positioning lasers used in radiotherapy generally require little adjustment. When required, this is easy to do for sidelights, but can be difficult and time consuming for ceiling mounted lasers. For this purpose, we have modified a commercial positioning laser by incorporating a device for rotating the alignment adjustment screws. This device is driven by a pair of motors remotely controlled through a cable. Two units have been built and installed. In practice, experience with these drive units has shown that it is now easier to adjust the ceiling lasers than the sidelights. Adjustment sensitivity in both units is considerably better than 1 mm, so there is little problem aligning the laser quickly and accurately.

Equipment Design↗
PubMed1990

Group A variants defined with a monoclonal anti-A reagent.

Unusual serologic findings mimicking the B(A) phenomenon were noted in two group B blood donors using blended murine monoclonal anti-A reagent. With additional studies, including a binding experiment using affinity chromatography, the presence of aberrant group A activities was confirmed. This observation suggests that persons with atypical B(A) phenotype may warrant further investigation to delineate the ABO blood group.

ABO Blood-Group System↗
PubMed1988

Ureteric ganglia in the guinea pig.

We studied the ureter of guinea pigs to ascertain whether there are ganglia and ganglion neurons directly associated with this structure. We consistently observed ureteric ganglia and individual neurons in the adventitia of the ureter or very close to it. There were on average 87 neurons per ureter, and they were scattered over the entire length of the tube.

Animals↗
PubMed1986

Intracellular currents of interictal penicillin spikes: evidence from neuromagnetic mapping.

To analyze the net intracellular current produced by interictal spikes, we mapped the extracranial magnetic fields of the rat brain following application of penicillin to the right or left medial cingulate cortex. Averaged interictal spikes in both the magnetoencephalogram (MEG) and in the electrocorticogram (ECoG) were composed of 4 temporal components, a biphasic spike and slow wave. Magnetic field maps for each of these components indicated a source at the location of penicillin application, with intracellular currents oriented perpendicular to the surface of the cingulate cortex, along the axis of the major pyramidal cells. The polarity of the magnetic fields for each of the components was reversed between the two cingulate groups, reflecting the respective orientation of pyramidal cells between the juxtaposed faces of the medial cingulate cortex. This neuromagnetic study of net intracellular current complements and extends the analysis of extracellular currents within the penicillin focus obtained using laminar electrodes. These data also demonstrate how animal neuromagnetometry may provide an empirical foundation for the neurogenesis of the MEG and a new unique method for the non-invasive study of population cell physiology.

Animals↗
PubMed1986

Magnetic localization of a dipolar current source implanted in a sphere and a human cranium.

Magnetic fields produced by a dipolar source implanted in a spherical conductor and a human cranial specimen were measured in the magnetoencephalogram (MEG). The location of the source was accurately computed in the spherical conductor from the identified magnetic field extrema using equations for a current dipole in a sphere. This same method was insufficient for localizing the source in a human cranium, where magnetic field maps appeared as distortions from the classical dipolar pattern. A more complete computer modeling procedure was used, adjusting for the non-spherical dimensions of the recording matrix on the cranium. By fitting the gradient of computer simulated fields to those measured outside the cranium, the accuracy of source localization was substantially improved. The greatest distortion of the extracranial magnetic field was an inequality in the measured amplitude of the two extrema, produced by an increased distance and angle of the MEG probe when recording over the lower face and ear. However, gross heterogeneities in the resistance of the skull due to a craniectomy and an implanted insulating balloon had a negligible effect on the extracranial magnetic field pattern.

Bone Diseases↗
PubMed1979

Pupillary responses during information processing vary with Scholastic Aptitude Test scores.

The magnitude of task-evoked pupillary dilations during mental activity has previously been shown to index the cognitive capacity utilized in the performance of the mental task. To determine the relation between "intelligence" and capacity demands during mental activity, task-evoked pupillary dilations were measured while two groups of university students differing in their scores on the Scholastic Aptitude Test solved mental arithmetic problems. Over three levels of problems difficulty, more intelligent subjects showed smaller task-evoked pupillary dilations than did their less intelligent counterparts. Thus, the more intelligent appear to possess more efficient cognitive structures of information processing. These data provide evidence that physiological differences between individuals of differing psychometric intelligence emerge during mental activity.

Adult↗
PubMed1978

Pupillometric signs of brain activation vary with level of cognitive processing.

The idea that hierarchically higher brain processes require greater amounts of central nervous system vigilance or activation for their execution was tested in two experiments measuring pupillary dilation during the decision interval of a hierarchically structured letter-matching task. Larger dilations indicative of increased activation were observed for letter pairs requiring higher levels of processing.

Adult↗
PubMed1976

Visual evoked potentials during the development of a spiking cobalt focus in rat neocortex.

Averaged visual evoked potentials recorded from three electrode placements in visual cortex in response to single and paired light flashes were acquired from rats with epileptogenic cobalt implants or with stainless-steel control implants. Evoked potentials acquired after computer-detected epileptic spikes were also recorded from rats in the cobalt group. Epileptic spiking began between the 6th and 9th postoperative days and flashes then began to evoke epileptic spikes. Excitability cycles were assessed. On the day showing the maximum rate of spiking, excitability at the site of the cobalt was markedly reduced following flash-triggered or spontaneous epileptic spikes in almost all cases. By contrast, the electrode placement in contralateral homotopic cortex showed nearly normal excitability despite the presence of large amplitude epileptiform spikes and sharp waves projected from the site of the cobalt. The results are discussed with reference to other experimental findings.

Animals↗
PubMed1976

Catecholamine correlates of radar monitoring performance.

Two experiments were concluded in which target detection performance was measured for male and female subjects engaged in a simulated radar monitoring task. In the first, 20 subjects performed for 2 h; in the second, 28 subjects for 1 h. Adrenaline excretion rate was significantly correlated with performance efficiency in both cases. Task duration and subject sex had no effect upon that correlation. The results of the two experiments were combined to show a general adrenaline/performance relationship.

Arousal↗
PubMed1974

Operant control of occipital theta rhythm affects performance in a radar monitoring task.

Detection efficiency of human observers deteriorates rapidly in monotonous monitoring tasks; this effect (the vigilance decrement) has been associated with increased theta band activity in the electroencephalogram. Suppression of theta activity by operant methods enhances monitoring efficiency, whereas theta augmentation further degrades task performance. These results demonstrate a lawful relationship between operantly regulated cortical activity and behavior in man.

Conditioning, Operant↗