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Two experiments attempted to train pigeons to produce variable response sequences. In the first, naive pigeons were exposed to a procedure requiring four pecks on each of two keys in any order, with a reinforcer delivered only if a given sequence was different from the preceding one. In the second experiment, the same pigeons were exposed to this procedure(More)
Three models of postnatal eye enlargement in leghorn chicks (surgical fusion of the eyelids, MES; exposure to continuous light, 24L; prolonged darkness, OL) were characterized on a morphologic and temporal basis, and a relationship between photoperiod and eye growth was described. While pronounced enlargement of the eye was evident in the OL and MES groups(More)
A pigeon's peck on one key moved a light down one position in a 5x5 matrix of lights, while a peck on another key moved the light across one position. Reinforcement depended upon the occurrence of four pecks on each key (moving the matrix light from the top left to the bottom right), and a fifth peck on either key ended a trial without food. Though there(More)
We measured the rate of change of visual field threshold values over time (mean follow-up, 44.9 +/- 17.4 months) by trend analysis in 40 eyes of 40 patients with chronic open-angle glaucoma. Twenty-eight eyes had stable visual fields, and two eyes had significant visual field improvement. Ten eyes had significant visual field deterioration and showed a(More)
In order to determine the optimum stimulus conditions for the detection of optic nerve damage due to glaucoma and ocular hypertension, checkerboard pattern reversal visual evoked potentials (VEPs) were recorded from 20 glaucoma patients, 20 ocular hypertensive patients, and 20 age-matched normals. Two check sizes (12' and 48'), two field sizes (14 degrees(More)
Magnetic measurements of average power of human alpha and beta activity over the occipital and parietal areas of the scalp reveal spatially selective suppression of the activity of the occipital cortex when abstract figures are briefly presented visually and subjects simply indicate that they saw the figure. However, the duration of the suppression(More)
The visual fields of 30 patients (subjects) with glaucoma were sent to six experienced clinicians (observers). Each subject had at least four visual field examinations on the OCTOPUS 201 automated perimeter spanning at least one year. Each observer was asked to review the visual field data of each subject and determine whether the visual fields were stable,(More)
Four pigeons were exposed to a series of multiple schedules of variable-interval reinforcement in which pecks were required on one key (operant key) and components were signalled on a second key (signal key). Four additional pigeons experienced identical conditions, except that a yoking procedure delivered food on variable-time schedules, with no key pecks(More)
Pinealectomized and intact chicks raised under cyclic (14L:10D) and noncyclic (OL;24L) conditions of environmental lighting were sampled 60 hr and 6 weeks after pinealectomy to evaluate the effects of pineal ablation on plasma and ocular melatonin concentrations. Little or no immunoreactive melatonin was present in plasma 60 hr after pinealectomy, while(More)
Pigeons were required to produce exactly four pecks on each of two keys in any order for reinforcement. Correct response sequences were reinforced on either fixed-interval two-minute or fixed-ratio four schedules, with each correct sequence treated as a single response. Each pigeon developed a particular dominant sequence that accounted for more than 80% of(More)