Biomedical subjects

J L Kobrick

Publications and source records attributed to J L Kobrick.

At least 19 recordsLinked to original sources

PubMed1994

Effects of caffeine or diphenhydramine on visual vigilance.

The effects of two drugs having opposite effects on the central nervous system were investigated using a newly developed visual vigilance task. Twenty-four male volunteers (median age = 20) performed the task on three separate occasions; after consuming placebo, caffeine (200 mg), or diphenhydramine (25 mg), in a double-blind, Latin Square design. At least 2 days intervened between drug administrations. Caffeine use was restricted for 10 h and smoking for 3 h before drug administration. When compared with placebo, caffeine significantly increased the number of correct responses and decreased response times, whereas diphenhydramine decreased the number of correct responses and increased response times. Low habitual consumers of caffeine (< 100 mg/day) and non-smokers had more correct responses than did high habitual caffeine consumers (> 100 mg/day) and smokers, but only in the placebo condition. Non-smokers had faster response times than smokers only in the placebo condition. Both caffeine and diphenhydramine altered certain aspects of mood.

Adult↗

PubMed1993

Effects of caffeine and diphenhydramine on auditory evoked cortical potentials.

Caffeine and diphenhydramine are known to affect cognitive functioning in vigilance tasks. In this study, long-latency auditory evoked potentials (AEPs) obtained during concomitant performance of a visual vigilance task were examined for changes in response to administration of caffeine (200 mg) and diphenhydramine (25 mg). The AEPs were also analyzed for changes over time for up to two hours postdrug administration. Significant increases in N1 and P2 latencies and decreases in amplitude voltage were exhibited over time. The P2-N2 amplitude was significantly lower throughout testing after taking caffeine. A significant increase was seen in the P2-N2 amplitude 40 min. after diphenhydramine ingestion. These changes in amplitude may be the result of the auditory stimulus acting as a diversion to the participants while performing the visual vigilance task. Diphenhydramine was more likely to impair participants' vigilance, resulting in greater attention paid toward the auditory stimulus, whereas caffeine seemed to help participants maintain their focus of attention on the visual vigilance task.

Acoustic Stimulation↗

PubMed1990

Effects of nerve agent antidote and heat exposure on soldier performance in the BDU and MOPP-IV ensembles.

This study assessed the effects of nerve agent antidote (atropine/2-PAM chloride versus saline placebo) and heat-humidity (95 degrees F/60% RH versus 70 degrees F/30% RH) on repeated performance of militarily relevant psychological tasks while wearing the battle dress uniform (BDU) and while wearing chemical protective clothing (MOPP-IV). All BDU heat sessions (6 hours) were completed, but with some task impairments and a few subjective reactions. MOPP-IV heat sessions could not be continued beyond 2 hours; all tasks were impaired and subjective reactions were numerous and severe. Atropine/2-PAM significantly shortened endurance time for heat sessions in MOPP-IV.

Adolescent↗

PubMed1990

Effects of atropine/2-PAM chloride, heat, and chemical protective clothing on visual performance.

Visual acuity, phoria, stereopsis, and contrast sensitivity were assessed over 6 h of continued exposure to combinations of atropine (2 mg) and 2-PAM chloride (600 mg), severe heat/humidity (95 degrees F (35 degrees C); 60% RH), and wearing either the U.S. Army battle dress uniform (BDU) or the BDU and the impermeable chemical protective clothing (MOPP-IV). Subjects were able to complete all 6 h of testing under severe heat when wearing BDU's, but only lasted 2 h under the same severe heat when wearing MOPP-IV. Acuity and phoria were significantly impaired by the drug in the BDU conditions. Acuity, phoria and stereopsis were all significantly impaired by heat, drug and continued exposure under MOPP-IV. Acuity was significantly impaired by drug even during the first 2 h of heat exposure in MOPP-IV. Contrast sensitivity was impaired mainly by continued heat exposure in MOPP-IV.

Adolescent↗

PubMed1988

Operation Everest II: lack of an effect of extreme altitude on visual contrast sensitivity.

Contrast sensitivity thresholds were studied over 40 d during gradual ascent to a simulated terrestrial altitude of 25,000 ft in a decompression chamber. Only ambient pressure, and thus inspired oxygen pressure, was varied, thereby eliminating many of the confounding effects of cold, dehydration, malnutrition and exhaustion, inevitably encountered on very high mountains. Contrast sensitivity thresholds measured by the Ginsburg Vistech test showed no overall impairment as altitude increased. These results are different from those of other previously reported vision studies involving shorter exposures, lower altitudes, and lower test luminances. However, our results can be explained on the basis of the higher stimulus luminances used in our contrast sensitivity testing. Compared to the luminance levels involved in previously reported testing, our higher luminance stimuli would be less likely to be affected by hypoxia.

Adult↗

PubMed1988

A system for controlled presentation of the Arden contrast sensitivity test.

Contrast sensitivity has been identified as a significant index of visual function, and as an indicator of visual disorders. The Arden test of contrast sensitivity has been recognized as a simple and easily administered technique for measurement of this process. However, the customary method of administration of this test involves manual manipulation and considerable individual subjectivity. The instrument described in this report was designed and developed to minimize variability in the testing procedure due to differences in individual testing techniques, and to standardize testing conditions, ambient illumination, viewing distance and rates of presentation.

Fourier Analysis↗

PubMed1987

Cigarette smoking, field-dependence and contrast sensitivity.

This study examined the separate and combined effects of cigarette smoking and field-dependence on contrast sensitivity. No previous research on these relationships exists; however, all three variables are known to be significantly related to many aspects of human performance. Under carefully controlled conditions, 12 smokers and 16 non-smokers were tested for field-dependence and measured for contrast sensitivity (Nicolet CS 2000 Testing System). No differences in contrast sensitivity of smokers were found when measured immediately after smoking 1 cigarette, as compared with having been deprived of smoking for at least 90 min. Habitual smoking and field-dependence were found to be separately and interactively related to contrast sensitivity. A field-independent non-smoker group performed significantly better than a field-dependent smoker group at all but the lowest spatial frequency. The results have important implications for many types of performance, particularly aircraft and motor vehicle operation, and may be valuable for use in selection and training.

Adult↗

PubMed1987

A computerized system for measuring detection sensitivity over the visual field.

A device is described for comprehensively measuring the capability of human operators to detect and react to visual signals occurring at a variety of locations throughout the functional visual field. The system is completely automated and computerized, and provides both documentation files and descriptive graphics of the operator's performance immediately upon completion of testing. Sensitivity of detection can be measured for red, yellow, and green stimulus colors in a testing configuration which mimics commonplace surveillance of the ordinary viewing field. An abbreviated listing of the main operating program software is provided.

Computer Systems↗

PubMed1987

An automated portable night vision testing system.

This report describes a new testing system designed to assess night vision parameters of the military population in the field, and to quantify the effects of various environmental stress factors, such as extended exposure to high altitude, on the dark adaptation process. The instrument is based on an established procedure for dark adaptation measurement in which the subject continuously adjusts the threshold luminance of a recurrently flashing stimulus. The device described here represents a modernized version of the original technique, which features an automated testing procedure and provides for computerized data translation of the dark adaptation function. It also offers the advantages of rugged construction and field portability not available in clinical style instruments.

Computers↗

PubMed1987

Effect of heat and chemical protective clothing on cognitive performance.

This study examined the effects of heat on the sustained cognitive performance of sedentary soldiers clad in chemical protective clothing. There were 23 men trained for 2 weeks on selected military tasks. Then they performed the tasks for 7-h periods on 4 successive days (Days 1 and 3 = 21.1 degrees C, 35%rh, battle dress uniform; Day 2 = 12.8 degrees C, protective clothing; Day 4 = 32.8 degrees C, 61%rh, protective clothing). After 4-5 h in the heat wearing protective clothing, the cognitive performance of the group began to deteriorate markedly. By the end of 7 h of exposure to heat, increases in percent group error on investigator-paced tasks ranged from 17%-23% over control conditions. Virtually all of the decrements were due to increases in errors of omission. The productivity of the group on a self-paced task (map plotting) diminished by approximately 40% from control conditions after 6 h in the heat in protective clothing; accuracy of plotting was not markedly affected.

Adult↗

PubMed1986

Effect of wearing chemical protective clothing in the heat on signal detection over the visual field.

Sensitivity for detecting visual signals distributed at various locations throughout the visual field was studied in 16 male subjects who were all exposed to two degrees of ambient heat (91 degrees F/61% RH; 55 degrees F/35% RH) while wearing the Army chemical protective clothing system; also to 70 degrees F/35% RH while wearing Army battle-dress uniform (fatigues). Response time for signal detection increased systematically and significantly with peripheralization of stimulus locations. It was most impaired in the superior and inferior visual field areas and least affected along the horizontal axis area. The data support previous results obtained using this task. Both the MOPP and the heat + MOPP exposure conditions produced highly significant systematic increases in response time to all signals; the worst performance occurred under the heat + MOPP combination. Implications for visual performance while wearing chemical protective gear are discussed.

Adolescent↗

PubMed1984

Effects of extended hypoxia on night vision.

The effects of 16 d of sustained hypoxia (4300-m equivalent) on the dark adaptation threshold function were studied in 12 male subjects measured periodically (days 2,4,6,9,11,13,16 of exposure) over a 20-min test period for both red and green stimuli using a new computerized dark adaptometer. Comparison with sea level performance showed negligible elevations of thresholds for red response, but highly significant impairment of green response (p less than 0.00001) over almost the entire dark adaptation function. These losses peaked between the sixth and ninth day followed by little recovery, except at the eleventh day when the subjects descended briefly to 3200 m elevation. Impairments developed rapidly again upon return to the original higher altitude. The results differ from previous findings after shorter exposure periods, which showed only slight impairments of the early segment of dark adaptation. Implications of the results are discussed.

Adolescent↗

PubMed1983

Individual differences in distance estimation: comparison of judgments in the field with those from projected slides of the same scenes.

This study was designed to determine the comparative accuracy with which trained and untrained observers could judge distances to a target and to assess the correspondence of those judgments with other judgments, by the same observers, from photographic slides of the same target and scene at identical viewing distances. 9 experienced and 15 untrained observers estimated distances ranging from 600 to 1550 m in 50-m increments. Photographic slides were made of the target at each distance and, 1 mo. later, observers made the same judgments from the slides. It was found that averages of the group's judgments in the field very closely approximated true target distances. However, judgments of the individual observers were so erratic and inaccurate as to render questionable the interpretation of those averages. In addition, while the averages of the group indicated that judgments from two-dimensional slides could be substituted fro three-dimensional real-world judgments, detailed analysis of the individual observers' performances dramatically contradicted this conclusion.

Discrimination Learning↗

PubMed1980

Field dependence, practice, and low illumination as related to the Farnsworth-Munsell 100-Hue Test.

36 soldiers were given the Farnsworth-Munsell 100-Hue Test to: (1) validate published research in which a field-independent group had been found to be superior to a field-dependent group in discriminating colors; (2) investigate unpublished findings in which substantial improvement had been shown in color discrimination performance over five trials of the 100-Hue test; and (3) determine the effect of low illumination (25 w, 40 w, and 60 w) on performance of the color discrimination task. A field-independent and a field-central group each performed significantly more accurately than a field-dependent group under all illumination conditions, and seven repeated administrations at 100 w resulted in significant improvements in performance. Color discrimination in the 25-w condition was significantly poorer than in the other illumination conditions. The implications are discussed.

Color Perception Tests↗

PubMed1980

The environmental symptoms questionnaire: revisions and new filed data.

The Environmental Symptoms Questionnaire (ESQ) was developed to obtain information about the incidence and severity of symptoms produced by exposure to several different climatic conditions. A subsequent revision is reported here, along with a description of its use in two studies involving physical stresses frequently encountered by military personnel. The first study examined the effects of prolonged flight on the health and physical work performance of men assigned to an overseas station. The second study tested the effects of acute altitude exposure on the load-carrying capacity of men over a period of several days. Five independent symptom factors were identified in the data of the first study, and then were applied to the analyses of treatments of both studies. The factor scores exhibited predictable and meaningful data in both cases. The factors are described, results are compared to previous studies, and general recommendations for use of the questionnaire are made.

Aerospace Medicine↗

PubMed1979

New inventory for the assessment of symptom occurrence and severity at high altitude.

A new inventory, called the Environmental Symptoms Questionnaire (ESQ), was devised to provide improved assessment of symptoms occurring during exposure to high altitude. The ESQ was field tested with 12 subjects exposed to 4300 m altitude for 4 d, and was compared with responses to the General High Altitude Questionnaire (GHAQ). Both instruments reflected significant symptom occurrence, but the ESQ was more sensitive on certain items focal to altitude conditions, and showed significant responses to items not contained in the GHAQ. Based on this test, the ESQ was judged easier to use, more sensitive, and more comprehensive for assessing medical symptoms at altitude.

Acute Disease↗

PubMed1976

Effects of prior hypoxia exposure on visual target detection during later more severe hypoxia.

Three groups of 15 subjects each were exposed to 3 different combinations of intermediate (staging) altitudes and exposure times, and were then tested for visual target detection capability at a final altitude of 4300 m. All groups with staging exposure performed better at altitude and had fewer symptoms of acute mountain sickness than a fourth group which went directly to 4300 m altitude from sea level. The data showed that task factors of both viewing distance and degree of peripheral placement of the target significantly influenced detection time within all groups regardless of variations in exposure to altitude.

Adaptation, Physiological↗

PubMed1976

Note on the relationship between introversion-extraversion, field-dependence-independence and accuracy of visual target detection.

49 soldier-observers viewed 40 slides in which a stimulus soldier was identically posed in a constant background [corrected] but a different viewing distance (175, 200, 225, 2508 and 275 ft.) and viewing angles (14 degrees and 21 degrees, left and right) from the observer. Accuracy of target detection was compared with viewers' scores on the Hidden Shapes Test and the Maudsley Personality Inventory. Field-dependence-independence and extraversion-introversion were determined to be separately and jointly related to accuracy of target detection. The major effects were attributable to the notably poorer perfromance of Ss characterized of field-dependent extraverts.

Altitude↗