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Biomedical subjects

A Baron

Publications and source records attributed to A Baron.

At least 127 records · Page 7Linked to original sources
PubMed1983

Reaction times of younger and older men and temporal contingencies of reinforcement.

Influences of extended training and temporal contingencies on reaction time were studied in relation to developmental differences. Older and younger men were trained on a chained schedule in which completion of a variable interval produced a terminal link in which reaction time was measured. The reaction-time procedure involved a conditional discrimination with matching to sample in one component and oddity matching in the other. During baseline training, no time limit was placed on the response to the discrimination choice stimuli. Subsequently, increasingly severe time limits were imposed over a series of sessions. Older and younger men showed increased speeds (decreased reaction times) when temporal contingencies were imposed, and these changes were maintained during post-training baseline sessions when there was unlimited time in which to respond. The younger men generally responded faster than the older ones, and age differences were not appreciably reduced during the course of the experiment. The results indicated the feasibility of studying reaction time in human subjects using operant procedures analogous to those developed for the study of nonverbal organisms.

Achievement↗
PubMed1982

Age-related effects of pacing on acquisition and performance of response sequences: an operant analysis.

Single-subject methods were used to study response speed in three younger men (M = 22 years) and three older men (M = 71 years). Monetary reinforcement depended on predetermined sequences of 10 responses. Training sessions consisted of alternating components; in one the sequence changed each session, but in the other the sequence never changed. During self-paced sessions stable patterns of acquisition (increasing rates of sequence completion, decreasing error rates) and of performance (uniform rates) emerged in the two components. During paced sessions responses had to occur within an interval ranging from .5 to 3 sec across conditions. Pacing had little effect on the younger men but disrupted the behavior of the older men, with increases in both omission and commission errors. Acquisition of new sequences was disrupted far more than performance of the established sequence. In both cases, however, the older men adjusted to pacing over the course of most sessions.

Adolescent↗
PubMed1982

Stimulus generalization of lifted weights in older and younger women.

Older (62 to 86 years) and younger (17 to 30 years) women were essentially similar in acquisition of weight discriminations and in generalized responding to a range of weights during postdiscrimination tests. In both age groups, acquisition was facilitated by increases in the difference between the positive and negative stimuli, and postdiscrimination gradients were displaced away from the value of the negative stimulus, particularly when it was the heavier of the training pair. The finding from personality test scores that the older women were more introverted than the younger ones, together with the absence of age differences in acquisition and generalization, does not support the Eysenck-Gray hypothesis that introversion influences conditioning processes. The results do suggest that basic conditioning processes are maintained with increasing age in healthy older adults.

Adolescent↗
PubMed1982

Clinical results of coronary bypass in 500 patients at least 10 years after operation.

We determined the outcome of coronary artery bypass surgery in 500 consecutive patients followed for at least 10 years after operation. There were 446 males (89.2%). Angina pectoris was the major indication for operation. Four hundred six patients (81%) had multivessel coronary artery disease and 348 (69.9%) had good left ventricular function. At 10 years of follow-up, 48% of patients were asymptomatic and 41% were improved. Propranolol was being used by 36% of patients and nitrates by 49%. Of the 355 patients younger than 65 years of age at the time of follow-up, 57% were employed full time and 24% were working part-time. Reoperation was performed in 9% of patients. Analysis of survival by Kaplan-Meier curves indicated that overall 10-year survival rates were 78% for one-vessel disease, 69% for two-vessel disease, 48% for three-vessel disease and 67% for left main coronary artery disease. For patients with good left ventricular function, the 10-year survival rates were 83% for one-vessel disease, 73% for two-vessel disease, 53% for three-vessel disease and 73% for left main disease. For patients with poor left ventricular function, the rates were 56%, 59%, 40% and 54%, respectively. Cox multivariate analysis indicated that preoperative diuretic use, history of heart failure, the number of diseased vessels, and infarct on the preoperative ECG were all good predictors of survival. This study shows that the outcome of coronary artery bypass surgery 10 years operation is highly favorable.

Angina Pectoris↗
PubMed1981

Improved digit symbol substitution by older women as a result of extended practice.

Older women (mean = 69 yr) and younger women (mean = 23 yr) received 100 administrations of the Digit Symbol Substitution subtest of the Wechsler Adult Intelligence Scale, modified so that the digit-symbol keys differed on each of the five training days. The older women improved substantially both within and between training sessions, but equally large gains wee made by the younger women so that age differences were not reduced by training. As a consequence of practice, scores of the older women on the standard WAIS subtest increased from the 25th to the 90th percentile relative to norms for young adults, and these scores maintained during a follow-up test 10 days later. Although practice effects transferred to digit-symbol keys different from the training keys, improvements did not generalize to WAIS Digit Span performance or to a matching task containing some of the elements of the training task.

Adolescent↗
PubMed1980

Physiological responses to exercise in chronic cigarette and marijuana users.

Several physiologic responses to graded exercise were determined in four groups of young adult blue-collar workers identified as users of (1) marijuana, (2) cigarettes, (3) both marijuana and cigarettes, or (4) neither substance. Using covariate analysis of variance to control for race, age, height and weight, the groups did not differ in estimated percent fat, lean body mass, hematocrit levels, or blood hemoglobin values. Heart rate and oxygen consumption responses also were similar at all levels of exercise. The mean minute ventilation and perceived exertion were found to be higher in cigarette smokers than non-smokers of cigarettes but aerobic power and the physical work capacity did not differ. The differences in pulmonary function observed suggest the need for further study on older populations of chronic cigarette and marijuana users.

Adult↗
PubMed1980

Reinforcement of human observing behavior by a stimulue correlated with extinction or increased effort.

Young men pulled a plunger on mixed and multiple schedules in which periods of variable-interval monetary reinforcement alternated irregularly with periods of extinction (Experiment 1), or in which reinforcement was contingent on different degrees of effort in the two alternating components (Experiment 2). In the baseline conditions, the pair of stimuli correlated with the schedule components could be obtained intermittently by pressing either of two observing keys. In the main conditions, pressing one of the keys continued to produce both discriminative stimuli as appropriate. Pressing the other key produced only the stimulus correlated with variable-interval reinforcement or reduced effort; presses on this key were ineffective during periods of extinction or increased effort. In both experiments, key presses producing both stimuli occurred at higher rates than key presses producing only one, demonstrating enhancement of observing behavior by a stimulus correlated with the less favorable of two contingencies. A control experiment showed that stimulus change alone was not an important factor in the maintenance of the behavior. These findings suggest that negative as well as positive stimuli may play a role in the conditioned reinforcement of human behavior.

Journal Article↗
PubMed1979

Chained schedules of avoidance: Reinforcement within and by avoidance situations.

Four rats were exposed to chained schedules with variable-cycle avoidance in both links. Responding in the initial link cancelled shocks scheduled once per minute and, according to a conjoint fixed-ratio schedule, produced a terminal link where scheduled shock rates varied from 0 to 8 shocks per minute in different conditions of the experiment. Response rates in the terminal link increased as a function of the scheduled shock rate. Response rates in the initial link, on the other hand, decreased as a function of the shock rate actually received (rather than scheduled) in the terminal link. While consistent with other studies of aversive control, these results differ from those obtained in chained schedules of positive reinforcement in that increases in reinforcement within the terminal link of the chain did not systematically increase the reinforcing value of that link.

Journal Article↗
PubMed1978

[Non resectable colonic cancer. Results from a test of chemotherapy with simultaneous prescription of VM26, methyl-CCNU and 5 fluoro-uracile (author's transl)].

Thirty nine patients with non resectable colonic carcinoma entered into a phase II combination chemotherapy trial. The patients were treated with a sequential cyclic combination of 3 drugs: VM 26 (60 mg/m2), methyl-C.C.N.U. (120 mg/m2) and 5 fluoro-uracile. Seventeen patients out of 39 (43.6%) are considered as good responders. The median survival time of the overall of this group is 12.6 months; it is of 15,6 months for good responders and of 7 months for non responders. The simultaneous application of B.C.G. do not change neither the level of responses nor the median of survival time. The good tolerance of this protocol let us to propose this combination as an adjuvant treatment for patients surgically treated for a Dukes'C colonic cancer.

Adult↗
PubMed1978

[Non resectable squamous cell carcinoma of the bronchus. Study of the immunological status as prognosis factor and attempt at immunorestoration with B.C.G. (author's transl)].

Sixty-six patients with bronchus non resectable squamous cell carcinoma (stage III and 14) entered into a protocol of chemotherapy depending upon their initial immunological status. These patients with (+) skin tests to recall antigens were allocated to a chemotherapy programme; patients with initially (-) skin tests were submitted to a protocol of immunorestauration with B.C.G. After three weeks of B.C.G. applications on scarifications 17 patients out of 31 presented with (+) skin tests and were considered as immunocompetent patients. All the patients then were submitted to chemotherapy protocol. The comparison of different median of survival have demonstrated that immune status appears as the more fundamental prognosis factor; the B.C.G. is able to transitory restore the immunity of the patients without any modification of the tumour progress. The median of survival of patients with initially (+) skin tests was ten months, and only two months for patients with (-) skin tests. The median of survival of patients whom immunity was restored with B.C.G. was nine months. The results of this trial let us to propose new strategy for treatment of these patients.

Adult↗
PubMed1978

Semantic representations of drug terms by industrial workers.

Studied semantic representations of drug terms as a function of reported use of illicit drugs, with young-adult industrial workers as the Ss (college students served in a preliminary study). Procedures for describing semantic organizations included the semantic differential, similarity ratings, sorting, and verbal production of drug names. In general, structured representations of drug terms were produced, in line with the categories: illicit drugs, medicinal drugs, alcohol products, and substances containing nicotine or caffeine. Increased drug use was accompanied by more positive evaluations of illicit drugs on the semantic differential and more extensive clustering on the verbal production task. It was concluded that use of illicit drugs is accompanied by distinctive semantic representations, that these patterns mainly involve drugs used illicitly, and that they are most apparent on tasks in which responses are least constrained, such as verbal production.

Adult↗