Biomedical subjects
Publications and source records attributed to J Beatty.
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Three studies are described in which the task-evoked pupillary response is recorded during simple and disjunctive reactions in order to examine its contribution as a measure of the motoric and cognitive aspects of performance in these tasks. In simple reactions a pupillary dilation began about 1.5 sec before the imperative stimulus and peaked about 1 sec after the stimulus. The rate of dilation was inversely related to the interstimulus interval. In disjunctive reactions, both "Go" and "No-Go" responses elicited significant dilations but the No-Go dilation was smaller than the Go dilation. When the response was delayed 2.5 sec after the discrimination stimulus, the dilation to both Go and No-Go responses was much reduced. The pupillary response related to response selection was estimated at 55% of that associated with motor preparation and execution. The probability of responding was found to affect the amplitude of the dilation to No-Go responses but not that to Go responses. The data point to a significant contribution of preparatory motor processing in No-Go reactions and to an overlap between decisional and motoric processing in disjunctive reactions.
A 19-yr-old woman developed adult respiratory distress syndrome (ARDS) in the postnatal period after treatment with dexamethasone and ritodrine for premature labor. An assay of complement activation was positive, suggesting a possible mechanism for this patient's ARDS.
Local paroxysmal discharges of epileptic tissue within the human brain, which may be electrically recorded as voltage spikes in the electroencephalogram, also generate extracranial magnetic fields. These fields were assessed by means of recently developed neuromagnetometric techniques. Surface measurements of magnetic spike field strength in the region of the focus appear sufficient to establish the location, depth, orientation, and polarity of currents underlying the paroxysmal discharge.
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Explore the source record for details and available documents.
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Through the use of a quantitative extension of signal detection theory, the brain events associated with the detection and recognition of weak acoustic signals were examined by recording brain event-related potentials. The early N100 componenet of the event-related potential varied only with detection, whereas the late P300 component varied with both detection and recognition. P300 amplitude accurately predicted recognition performance on a trial-by-trial basis. The results suggest that detection and recognition are partially concurrent processes in perception and demonstrate that the electrocortical events occurring during the perception of sensory stimuli are closely associated with both detection and recognition of these stimuli by the nervous system.
Lateralized functional specialization of cortical processing of linguistic and spatial information and anatomical lateralization of processing of hemiretinal stimuli were investigated with a randomized factorial design in 14 right-handed male undergraduates using EEG alpha-contingent visual stimulation. Words or geometric designs of equal luminosity and size were presented by computer to randomly selected visual half-fields contingent on the occurrence of alpha at one of 4 placements (left and right occipital and left and right temporal). The replicative reliability of alpha block and, by implication, the control of each stimulus type over different cortical sites, was assessed with the alpha control ratio (mean alpha duration/standard deviation of alpha durations). The alpha control ratio was significantly greater for alpha-contingent vs. random (non-contingent) stimulation. Within alpha-contingent data alone, cerebral lateralization was significantly demonstrated in the 2-way interactions of EEG hemisphere X visual field of stimulation, and of EEG hemisphere X type of stimulus (verbal or spatial). The alpha control ratio was higher for contralateral visual half-field stimulation compared to ipsilateral stimulation. Control was also significantly higher for cognitively appropriate stimulus-hemisphere combinations (verbal stimuli and left cerebral hemisphere, or spatial stimuli and right hemisphere) vs. inappropriate combinations (verbal, right hemisphere, or spatial, left hemisphere). These electrophysiological data corroborate in normal subjects the previous conceptions of hemispheric specialization ascertained with brain-damaged patients.
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.
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.
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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.
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.
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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.
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