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Biomedical subjects

S A Ferguson

Publications and source records attributed to S A Ferguson.

At least 73 records · Page 4Linked to original sources
PubMed1995

Decreased dominance in a limited access test but normal maternal behavior in micrencephalic rats.

Micrencephalic offspring produced by gestational treatment with the antimitotic compound/methylazoxymethanol acetate (MAM) are remarkable for substantial preservation of function concurrent with severe neural stunting. Altered behaviors in these micrencephalics, including light shyness and response perseveration, are similar to those produced by frontal cortex lesions. Consistent with this, the frontal cortex is one of several regions severely stunted by gestational MAM treatment. Because the frontal cortex has been implicated in rodent social behavior, maternal behavior in females and dominance in both sexes were assessed. Dominance was measured via water competition in 24-h water-deprived dyads (1 control and 1 MAM) matched for sex and body weight. Micrencephalic rats exhibited shorter drinking time than controls (males: 101 vs. 219 s, p < 0.001; females: 114 vs. 176 s, p < 0.03), indicating that micrencephalics were more submissive. For maternal behavior tests, micrencephalic and control females were bred to control males and pup retrieval was measured on postnatal days 3-13. Micrencephalic dams were unimpaired in any aspect of pup retrieval. Of 8 standard behavior measures used here and previously, access time in water competition tests produced the clearest differentiation between control and micrencephalic rats. These studies indicate that at least one aspect of social dominance in both sexes is severely reduced by MAM treatment while maternal behavior remains intact.

Animals↗
PubMed1995

Aging and single versus multiple cues in source monitoring.

Participants heard words said by 2 speakers and later decided who said each word. The authors varied the perceptual distinctiveness of the speakers and the distinctiveness of the cognitive operations participants performed on the words. Relative to younger adults, older adults had significantly lower source monitoring scores when perceptual or cognitive operations conditions were similar but not when either cue was more distinctive. Combining cues did not affect source monitoring of younger adults but hurt older adults' performance relative to the distinctive perceptual condition. Evidently, older adults generate cognitive cues at the expense of encoding perceptual cues; any deficit in binding perceptual and semantic information disadvantages them more in source monitoring than in old/new recognition. There was no correlation between neuropsychological tests assessing frontal function and source monitoring in older adults.

Adolescent↗
PubMed1995

Biomechanical risk factors for occupationally related low back disorders.

A continuing challenge for ergonomists has been to determine quantitatively the types of trunk motion and how much trunk motion contributes to the risk of occupationally-related low back disorder (LBD). It has been difficult to include this motion information in workplace assessments since the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of LBD during occupational lifting in industry. Over 400 industrial lifting jobs were studied in 48 varied industries. The medical records in these industries were examined so that specific jobs historically categorized as either low, medium, or high risk for occupationally-related LBD could be identified. A tri-axial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers worked at these low, medium, or high risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model indicated that a combination of five trunk motion and workplace factors predicted well both medium risk and high risk occupational-related LBD. These factors included lifting frequency, load moment, trunk lateral velocity, trunk twisting velocity, and trunk sagittal angle. Increases in the magnitude of these factors significantly increased the risk of LBD. The analyses have enabled us to determine the LBD risk associated with combined changes in the magnitudes of the five factors. The results indicate that by suitably varying these five factors observed during the lift collectively, the odds of high risk group membership may decrease by over ten times. These results were related to the biomechanical, ergonomic, and epidemiologic literature. The five trunk motion and workplace factors could be used as quantitative, objective measures to redesign the workplace so that the risk of occupationally-related LBD is minimized.

Biomechanical Phenomena↗
PubMed1995

Driver fatalities in 1985-1993 cars with airbags.

OBJECTIVE: Analyses were conducted to estimate the effectiveness of airbags in reducing driver fatalities in motor vehicle crashes. DESIGN: Airbag effectiveness was estimated by (1) comparing driver fatalities in frontal crashes with driver fatalities in nonfrontal crashes for cars with airbags and manual belts and cars with manual belts only, and (2) by comparing driver fatal crash rates per 10,000 registered vehicles for cars with airbags and manual belts and cars with manual belts only. MATERIALS AND METHODS: Fatal Accident Reporting System data for 1985-1993 model year cars were compared. MEASUREMENTS AND MAIN RESULTS: The two methods yielded similar results. In the analysis based on location of damage, driver fatalities in airbag equipped cars were reduced by 24 percent in frontal crashes relative to comparable cars with manual belts only and by 16 percent in all crashes. In the analyses based on vehicle registration data, fatality rates for frontal crashes were reduced by 23 percent for cars with airbags and manual belts compared with the same cars equipped with manual belts only and by 16 percent for all crashes. CONCLUSIONS: Various estimates of airbag effectiveness are beginning to yield consistent results. These analyses confirm that driver airbags are reducing fatalities in the frontal crashes for which they are designed.

Accidents, Traffic↗
PubMed1995

Daylight saving time and motor vehicle crashes: the reduction in pedestrian and vehicle occupant fatalities.

Fatal crashes were tabulated for 6-hour periods around sunrise and sunset, from 13 weeks before the fall change to standard time until 9 weeks after the spring change to daylight saving time. Fatal-crash occurrence was related to changes in daylight, whether these changes occurred abruptly with the fall and spring time changes or gradually with the changing seasons of the year. During daylight saving time, which shifts an hour of daylight to the busier evening traffic hours, there were fewer fatal crashes. An estimated 901 fewer fatal crashes (727 involving pedestrians, 174 involving vehicle occupants) might have occurred if daylight saving time had been retained year-round from 1987 through 1991.

Accidents, Traffic↗
PubMed1994

Effects of methylazoxymethanol-induced micrencephaly on temporal response differentiation and progressive ratio responding in rats.

Micrencephalic Sprague-Dawley rats were produced by an injection of 20 mg/kg methylazoxymethanol acetate on gestational Day 14. Brain weights of the offspring were 70% of controls while weights of frontal cortex and hippocampus were approximately 58% (Ferguson, Racey, Paule, & Holson, 1993). Operant performance was measured with particular emphasis on assessment of time estimation. The temporal response differentiation (TRD) and the progressive ratio (PR) tasks, previously used in the NCTR operant test battery for monkeys, were chosen for evaluation. The TRD schedule is notably different from other temporal tasks in that it requires subjects to initiate and maintain a lever press for 10-14 s. The PR task was included as a measure of motivation to work for food reinforces. Micrencephalics acquired and performed both tasks comparably to controls. During extinction, however, micrencephalics exhibited an increased TRD lever hold duration. This suggests an atypical response perservation, that is, perseverating the previously correct response. Previously, frontal cortical alterations were suggested to contribute heavily to micrencephalic-induced behavioral alterations (Ferguson et al., 1993). This study provides further evidence that response perseveration, a hallmark of frontal cortical lesions, is expressed in micrencephalic rats.

Animals↗
PubMed1994

Aging and the effects of affective and factual focus on source monitoring and recall.

Pairs of young and elderly Ss participated in a short play and were then instructed to talk about factual or affective aspects of the play or to talk about the play without any particular focus suggested. In both the affective and control condition, older adults' ability to discriminate what they had said from what the other person had said was poorer than that of young adults. In contrast, when induced to focus on the factual content of the events, older Ss' source monitoring improved, and the age difference was reduced. The pattern was similar when Ss' ability to discriminate what they had said from what they had thought was examined. Furthermore, affective focus lowered the overall level of recall for both young and older Ss and led older Ss, in particular, to introduce more elaborations into their recall. The possibility that age difference in remembering content and source are related to type of focus is discussed.

Adolescent↗
PubMed1993

Acute effects of pentobarbital in a monkey operant behavioral test battery.

The effects of acute pentobarbital treatment were assessed using a complex operant test battery containing five tasks in which correct performance is thought to depend upon processes associated with short-term memory and attention [delayed-matching-to-sample (DMTS)], color and position discrimination [conditioned position responding (CPR)], motivation [progressive ratio (PR)], time perception [temporal response differentiation (TRD)], and learning [incremental repeated acquisition (IRA)]. Adult, male rhesus monkeys were tested 15 min after IV injection of saline or pentobarbital (1, 3, 5.6, 10, or 15 mg/kg). Behavioral endpoints measured included percent task completed, response rate or latency, and response accuracy. The order of task sensitivity to disruption by PBT was TRD > IRA = DMTS = PR > CPR, in which sensitivity was defined as a significant disruption in any aspect of task performance. PBT slowed response rates at 10.0 and/or 15.0 mg/kg in all tasks. Accuracy was decreased in the TRD task at > or = 5.6 mg/kg but doses of > or = 10.0 mg/kg were required to decrease accuracy in the IRA, DMTS, and CPR tasks. Thus, behavior thought to model time perception (TRD) was more sensitive than behavior modeling learning (IRA), short-term memory and attention (DMTS), and motivation (PR). CPR was the least sensitive behavior. Because pentobarbital exerts its effects at least in part via GABA systems, the effects in the current study were compared with those of a previous study of the acute effects of diazepam. The two compounds exerted fundamentally different effects on operant test battery performance.

Animals↗
PubMed1993

Behavioral effects of methylazoxymethanol-induced micrencephaly.

This study was prompted by reports of functionally normal humans with micrencephaly or cortical hypoplasia. Methylazoxymethanol acetate (MAM) treatment, which induces micrencephaly in rats, was administered by injection (20 mg/kg) on gestational day 14. Prior to weaning and into adulthood, offspring were assessed on many behavioral tests. There were 3 findings. First, MAM rats (forebrain weight less than 2/3 of controls) were not profoundly hyperactive. Increased activity was seen only on prolonged tests or after amphetamine administration. Second, MAM rats were hypoactive in some conditions. These rats were light shy and less likely to explore lighted areas. MAM rats appeared hyperreactive to environmental stimuli, but not hyperactive. Finally, no MAM effect on behavior was as large as that on brain weight. Thus, as with clinical findings, rat micrencephalics are more remarkable for functional sparing than for behavioral abnormalities.

Alkylating Agents↗
PubMed1993

The role of dynamic three-dimensional trunk motion in occupationally-related low back disorders. The effects of workplace factors, trunk position, and trunk motion characteristics on risk of injury.

Current ergonomic techniques for controlling the risk of occupationally-related low back disorder consist of static assessments of spinal loading during lifting activities. This may be problematic because several biomechanical models and epidemiologic studies suggest that the dynamic characteristics of a lift increase spine loading and the risk of occupational low back disorder. It has been difficult to include this motion information in workplace assessments because the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of low back disorder during occupational lifting in industry. More than 400 repetitive industrial lifting jobs were studied in 48 varied industries. Existing medical and injury records in these industries were examined so that specific jobs historically categorized as either high-risk or low-risk for reported occupationally-related low back disorder could be identified. A triaxial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers lifted in these high-risk or low-risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model was developed, based on biomechanical plausibility, and indicated that a combination of five trunk motion and workplace factors distinguished between high and low risk of occupationally-related low back disorder risk well (odds ratio: 10.7). These factors included 1) lifting frequency, 2) load moment, 3) trunk lateral velocity, 4) trunk twisting velocity, and 5) the trunk sagittal angle. This analysis implies that by suitably varying these five factors observed during the lift collectively, the odds of high-risk group membership may decrease by almost 11 times. The predictive power of this model was found to be more than three times greater than that of current lifting guidelines. This study, though not proving causality, indicates an association between the biomechanical factors and low back disorder risk. This model could be used as a quantitative, objective measure to design the workplace so that the risk of occupationally-related low back disorder is minimized.

Biomechanical Phenomena↗
PubMed1992

Acute effects of chlorpromazine in a monkey operant behavioral test battery.

The effects of acute chlorpromazine treatment were assessed using a complex operant test battery (OTB) containing five tasks thought to depend upon processes associated with short-term memory and attention [delayed-matching-to-sample (DMTS)], color and position discrimination [conditioned position responding (CPR)], motivation [progressive ratio (PR)], time perception [temporal response differentiation (TRD)], and learning [incremental repeated acquisition (IRA)]. Adult male rhesus monkeys were tested 15 min after IV injection of saline or chlorpromazine (0.010, 0.030, 0.100, or 0.175 mg/kg). Behavioral endpoints measured included percent task completed, response rate or latency, and response accuracy. The order of task sensitivity to disruption by chlorpromazine was TRD = PR = IRA = DMTS = CPR in which sensitivity was defined as a significant alteration in any aspect of task performance. Chlorpromazine slowed response rates in all tasks except TRD but did decrease accuracy in that task. These effects were similar to those noted in previous studies of acute chlorpromazine treatment. Specific motoric effects suggested decreased task initiation at doses that left general motor ability intact. This finding is similar to that noted in parkinsonism caused by chronic chlorpromazine treatment.

Animals↗
PubMed1992

Age differences in using source-relevant cues.

Subjects heard words originating from 2 speakers and later decided which of the 2 speakers said the words. Older adults had difficulty with source monitoring when perceptual cues from 2 sources were similar (2 female speakers), but this difficulty was overcome when perceptual cues were distinctive (a male and a female speaker) and were the only salient cues to source. Older adults also benefited from distinctive spatial cues when these were the only salient cues to source. Older adults, however, experienced difficulties in using multiple cues (both perceptual and spatial) to source effectively, whereas younger adults were able to use multiple cues to enhance their source-monitoring performance. It is suggested that age differences in source monitoring result from differential cue utilization.

Adult↗
PubMed1991

Clinical utility of high-resolution portal films.

We have evaluated the film quality and overall clinical utility of a unique high-resolution portal film system which utilizes high contrast graphics art film. A total of 127 unselected patients had their conventional portal films and high-resolution films of the same site, compared and graded subjectively for a variety of parameters by an independent panel of radiotherapists and radiographers. Although consistent improvements in most aspects of image quality were noted, improved overall clinical usefulness of the high-resolution portal film system in comparison to the conventional films, when subjected to multiple regression analysis, was confined to lateral neck views only. High-resolution portal film utility was also found to depend significantly on field size with areas less than 110 cm2 having a markedly worse clinical utility score.

Humans↗
PubMed1988

Behavioral effects of developmental lead exposure in rhesus monkeys.

Postnatal lead exposure has been found to cause long-term learning and memory deficits in monkeys. Pulse-chronic exposure, consisting of acute high-level exposure followed by chronic lower-level exposure, has been particularly effective in causing these impairments. We investigated possible antecedents of lead-induced cognitive dysfunction by evaluating the behavioral effects of pulse-chronic lead exposure in rhesus monkeys during the first 6 months of postnatal life. Blood lead concentrations in the monkeys reached a peak of 55.8 +/- 7.8 ug/dl during week 5 after birth and then averaged between 33.1 and 42.9 ug/dl during the rest of the first 6 months after birth. Zinc protoporphyrin levels were increased by lead exposure, but hematocrits were unaffected. Significant lead-related effects were detected on a visual exploration test and a neonatal behavioral assessment battery. Lead-treated monkeys exhibited decreased looking behavior on the visual exploration test and decreased muscle tonus and increased arousal or agitation on the behavioral assessment battery. No effects were seen on a Piagetian object permanence task and no toxic effects on health or growth were detected. In addition to providing indices of behavioral dysfunction during postnatal lead exposure, performance on these early behavioral tests may predict later lead-induced cognitive dysfunction.

Animals↗
PubMed1988

Data-driven and conceptually driven processes in partial-word identification and recognition.

Three experiments examined priming in partial-word identification (Warrington & Weiskrantz, 1968) and its relation to recognition memory. The results showed that changes in modality of presentation between study and test reduced performance on both identification and recognition. In contrast, changes in elaborative processing enhanced recognition but had no effect on identification. Furthermore, when explicit memory instructions were given, identification was changed to a cued recall test and was consequently affected by elaborative processing. We also found that the time course of forgetting in priming was different from that in recognition; priming in identification did not change over a 24-hr interval, whereas recognition declined rapidly during this interval. Overall, these results suggest that identification relies primarily on data-driven processing, whereas recognition can rely on both data-driven and conceptually driven processing.

Adult↗