Behavioral effects of neurotoxic lesions of the ascending monoamine pathways in the rat brain

Intracranial microinjections of 6-hydroxydopamine or 5,6-dihydroxytryptamine into six ascending monoamine pathways produced the expected patterns of depletion of telencephalic serotonin, dopamine, and norepinephrine. Serotonin level was specifically lowered after dorsal or median raphe lesions but not after mesolimbic or nigrostriatal system lesions which lowered both norepinephrine and dopamine. Lesions in the locus coeruleus or ventral nor-adrenergic bundle lowered only norepinephrine, and locus coeruleus lesions elevated serotonin level. Behavior was examined in an open field, one-way active avoidance, and two passive avoidance tasks, and measures were taken of water consumption and body weight. Dorsal raphe lesions had no effect on any of the measures; the other five lesion groups exhibited deficient acquisition of the one-way active avoidance task. In the appetitive passive avoidance task, only the substantia nigra lesion group exhibited a deficiency. In the step-through passive avoidance task, both the substantia nigra and the median raphe groups exhibited a deficit, with the median raphe group exhibiting hyperactivity in the start box during testing. Water consumption was decreased by lesions in the ventral noradrenergic bundle during the first postoperative week and was increased in the median raphe group by the fourth postoperative week. Lastly, lesions in the locus coeruleus dramatically decreased activity in the open field. The results are discussed in regard to the search for specificity of behavioral functions of the distinct ascending monoamine pathways.     

Inferior temporal lesions do not impair discrimination of rotated patterns in monkeys.

Ablation of inferior temporal cortex in the rhesus monkey produces a visual discrimination learning deficit. The severity of this deficit has often been found to be a function of task difficulty. This report concerns a type of visual discrimination problem that, although difficult, is not sensitive to inferior temporal lesions. Monkeys with anterior, posterior, and complete inferior temporal lesions were repeatedly unimpaired or only slightly impaired in learning to discriminate a pattern from the same pattern rotated 90 degrees or 180 degrees; yet they were very severely impaired in learning equally or more difficult discriminations of two different patterns. This demonstration that discrimination of orientation of patterns is relatively spared after inferior temporal lesions helps specify the pattern-recognition processes that require inferior temporal cortex.     

A functional measurement analysis of the development of dimensional coordination in children

The development of children's dimensional coordination was investigated using kindergarten, second, fourth, and sixth grade subjects (Ages 5, 7, 9, and 11 years, respectively), and an adult sample, by means of a perceptual estimation task requiring the subjects to match in total area a stimulus rectangle to an adjustable square stimulus. The problem was formulated using information integration theory, and the procedures and techniques of functional measurement were used in the analysis. Dimensional coordination was found to develop from a stage of total centration on one dimension to a stage of total decentration with equal weighting applied to both dimensions.Contrary to extant hypotheses, the vertical dimension was not the salient dimension for single dimension centerers. Rather, the spatial axis on which the compared-objects were placed determined the displacement of attention. When this frame of reference effect was controlled, the longer of the two dimensions was the salient dimension for centering subjects.     

Responding maintained under fixed-interval and fixed-time schedules of electric shock presentation

Following initial histories under a schedule of electric shock postponement, lever pressing in squirrel monkeys was maintained under fixed-interval and fixed-time schedules of electric shock presentation. No difference in either rate or pattern of responding was obtained when these schedules were presented as components of a multiple schedule. When they were presented singly for long periods of time, the fixed-interval schedule consistently maintained a higher response rate than the fixed-time schedule. The pattern of responding under both schedules was similar, typically consisting of a pause at the beginning of each interval followed by either a steady or a positively accelerating rate of responding. The results suggest that the response-shock dependency is of critical importance in the maintenance of high rates of responding under schedules of electric shock presentation, and support the general view that such responding may be conceptualized as operant behavior under control of many of the same variables that control responding under comparable schedules of food or water reinforcement.     

Behavioral contrast as differential time allocation

In Experiment I, hooded rats were exposed to multiple variable-interval schedules of reinforcement in which manipulanda and reinforcement magazines at opposite ends of the experimental chamber were associated with the different components. Time allocated to each component was measured by recording the time spent by the subject in the appropriate half of the chamber. Positive behavioral contrast was observed for the comparison between multiple variable-interval 30-second variable-interval 30-second and multiple variable-interval 30-second variable-interval 90-second conditions for both response frequency and time allocation measures, but not for mean local response rate (response frequency per time allocated to a component). In Experiment II, rats were exposed to multiple variable-time schedules in which reinforcement was response independent. Time allocated to each component was measured for two conditions, multiple variable-time 30-second variable-time 30-second and multiple variable-time 30-second variable-time 90-second. Positive behavioral contrast of time allocation was exhibited. The results indicated that time allocation was differentially sensitive to changes in reinforcement probability, and that behavioral contrast may result from the differential allocation of time to the different components of the multiple schedule.     

Field dependence and the effect of REM deprivation on thirst.

Recently a number of studies have concerned the possible function of rapid eye movement (REM) sleep and the mastery of stress. The present study was designed to explore the possibility that REM sleep might play a function in reducing the potency of a stressful physiological stimulus, thirst, as well as the possibility that such a function might be specific to individuals falling at different points along the field-dependence dimension. While there was no difference between REM deprivation and non-REM awakening nights in subsequent morning thirst, there was a significant interaction between field dependence and night on morning thirst measures for 10 college students. These results are discussed in light of previous work on stylistic differences in dreaming and their possible role in adaptation to stress.     

The order of continuous,partial and nonreward trials and resistance to extinction

In the first experiment rats were given either 16 or 48 nonrewarded or continuously rewarded trials prior to 24 continuously or partially rewarded trials, followed by extinction. Increased resistance to extinction was found for increasing numbers of nonrewarded trials when they were followed by partial reward, but not when followed by continuous reward. Similarly, more continuously rewarded trials followed by partial reward tended to increase resistance to extinction. Because of the theoretical importance of the effect of continuous reward followed by partial, a second experiment was performed where the range of the number of continuously rewarded trials was extended to 0, 48, and 96. Contrary to many theoretical predictions, resistance to extinction increased as a function of increasing amounts of continuous reward.