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Biomedical subjects

R C Howard

Publications and source records attributed to R C Howard.

24 records · Page 2Linked to original sources
PubMed1978

Thoracoscapular fusion for facioscapulohumeral dystrophy.

Eleven thoracoscapular fusion operations have been done on six patients. The indication is symptomatic winging of the scapula caused by thoracoscapular muscle paresis with intact function in the deltoid. This situation almost exclusively occurs in facioscapulohumeral dystrophy. The operation is successful in achieving stability of the scapula and in greatly improving function and cosmesis. Although the course of this type of muscular dystrophy is variable, the benefits of operation have not deteriorated with progression of the disease over a maximum follow-up period of twenty-three years.

Adolescent↗
PubMed1978

Time-dependent changes in conditioned suppression.

Time-dependent changes in a response following aversive conditioning were investigated using a conditioned suppression procedure in a within-subjects design. Four groups of pigeons received Pavlovian conditioning "off the baseline", immediately followed by an operant task. During the Pavlovian phase, two groups received a forward pairing of a tone with shock, one group received a backward pairing, and one group received a truly random pairing. One of the forward pairing groups also received a delay between the Pavlovian and operant phases. For all groups, key pecking was reinforced on a variable-interval schedule during the operant phase. Testing sessions were identical to training sessions, except that the tone used during Pavlovian conditioning was presented either 0, 15, 30, 45, of 60 minutes after the operant phase began. Testing sessions in which the Pavlovian phase was omitted were also included. The results showed suppression to change as a function of the retention interval, with maximum suppression occurring at intermediate intervals. This U-shaped function was obtained for 11 of the 12 pigeons in the forward-pairing groups and for three of the five in the truly random group. Pigeons in the background pairing group did not show changes in suppression as a function of the retention interval.

Journal Article↗
PubMed1975

Inhibitory stimulus control following errorless discrimination learning.

Three generalization procedures were used to investigate inhibitory stimulus control following discrimination learning with few errors. Three groups of pigeons acquired a discrimination between a green stimulus (the positive stimulus) and a vertical or horizontal line (the negative stimulus) through differential autoshaping followed by multiple schedule presentation of the two stimuli with gradually increasing stimulus durations. Genereralization testing was along a line-tilt continuum. For one group, the test involved a resistance-to-reinforcement procedure in which responses to all line tilts were reinforced on a variable-interval schedule. For a second group, also tested with the resistance-to-reinforcement procedure, the lines were superimposed on the green field that formerly served as the positive stimulus. A third group was tested in extinction with the combined stimuli. Control groups had no discrimination training but responding to green was nondifferentially reinforced. The control subjects responded more to all line tilts during testing than did the comparable experimental subjects, indicating that the negative stimulus had become an inhibitory stimulus. Both resistance-to-reinforcement groups revealed inhibitory gradients around the negative stimulus, but the gradient for the extinction group was relatively flat. These data are consistent with others that modify Terrace's early conclusion concerning the failure of inhibition to develop during errorless training.

Journal Article↗