The effect of unilateral stellectomy on the regulation of heart rate during behavioral stress

Changes in heart rate were examined during classical aversive conditioning before and after either left (n=10) or right stellectomy (n=8). Heart rate (HR) significantly (p<0.01) increased in response to the conditional stimulus with a further increase noted during the unconditional stimulus. After right stellectomy (RSGx) the aversive stress elicited a significantly (p<0.01) smaller increase in heart rate (peak HR change: control 66.8 +/- 6.0; RSGx 36.1 +/- 6.8 beats/min). In contrast left stellectomy did not significantly alter the heart rate conditional response. Cardioselective beta-adrenergic receptor blockade, metoprolol HCl (BB, 1.0 mg/kg, n=8), significantly (p<0.01) reduced the heart-rate conditional response (peak HR change: control 66.8 +/- 6; BB 25.1 +/- 3.8 beats/min) to the same extent as noted during RSGx. These data suggest that the heart-rate increases elicited by aversive stress are mediated in part by sympathetic nerves that originate or pass through the right stellate ganglion. The residual HR increase noted after RSGx or BB probably results from the withdrawal of cardiac parasympathetic activity.     

Acquisition and discrimination of appetitively and aversively conditioned heart rate responses in rhesus monkeys

This report describes the acquisition of a conditional heart rate response to both classical aversive and appetitive conditioning in eight rhesus monkeys(Macaca mulatta). The behavioral paradigm consisted of two discrete one minute tones followed by the corresponding unconditional stimuli,i.e., electric shock or Purina monkey chow. A third tone followed by neither food nor shock served as a discriminative stimulus (DS). The conditional heart rate responses developed in two phases. The first phase was characterized by similar responses to both conditional stimuli and the DS. Control heart rate rose during this period. During the second phase, control heart rate decreased (five animals), the DS response disappeared, and different conditional heart rate patterns to food and shock emerged. The existence of distinct conditional response patterns indicates probable differences in the autonomic nervous regulation of the heart during aversive and appetitive conditioning.     

Observational Learning From Internal Feedback: A Simulation of an Adaptive Learning Method

Much natural learning occurs by observation without explicit feedback or tutoring, yet few models of learning address this class of tasks. Further, many natural cases of observational learning are complex, and efficient learning seems to demand strategic learning procedures. The present work adopts a design perspective and asks what learning mechanisms would be both useful and feasible for natural induction. Work on closely related learning problems is briefly reviewed and a model for observational rule learning is proposed and simulated. The model extends learning mechanisms developed for explicit learning with feedback to less structured, observational tasks. In particular, the focused sampling mechanism, which is an extension of the attentional learning procedure developed by Zeaman and House (1963), is introduced. The operation of an attentional learning procedure is less clear when extended to learning without feedback, so a simulation was done to evaluate the performance of the model. A series of simulated experiments were run, comparing performance of the learning model with and without the focused sampling component. We evaluated whether and when focused sampling benefits observational learning, investigated the effects of different distributions of systematic and unsystematic features, and compared observational learning to learning with feedback. Results of the simulation suggest that focused sampling does benefit learning, that benefit increases with the complexity of the learning task, and that learning with and learning without feedback exhibit differences in how each is affected by changes in the learning problem. Suggestions about the relation to human data are offered.     

The effect of unilateral stellectomy on the regulation of heart rate during behavioral stress.

Changes in heart rate were examined during classical aversive conditioning before and after either left (n = 10) or right stellectomy (n = 8). Heart rate (HR) significantly (p less than 0.01) increased in response to the conditional stimulus with a further increase noted during the unconditional stimulus. After right stellectomy (RSGx) the aversive stress elicited a significantly (p less than 0.01) smaller increase in heart rate (peak HR change: control 66.8 +/- 6.0; RSGx 36.1 +/- 6.8 beats/min). In contrast left stellectomy did not significantly alter the heart rate conditional response. Cardioselective beta-adrenergic receptor blockade, metoprolol HC1 (BB, 1.0 mg/kg, n = 8), significantly (p less than 0.01) reduced the heart-rate conditional response (peak HR change: control 66.8 +/- 6; BB 25.1 +/- 3.8 beats/min) to the same extent as noted during RSGx. These data suggest that the heart-rate increases elicited by aversive stress are mediated in part by sympathetic nerves that originate or pass through the right stellate ganglion. The residual HR increase noted after RSGx or BB probably results from the withdrawal of cardiac parasympathetic activity.     

Consistent contrast and correlation in free sorting

Two experiments investigated free sorting, a type of unsupervised learning, with multiattribute drawings of alien animals. In previous research on concept formation, with simpler stimulus structure than ours, participants were insensitive to correlational structure in the stimuli, producing primarily "ID sorts," based on the values ofjust 1 dimension or attribute. Our experiments showed that participants used many strategies in categorizing but preferred to generate groupings that reflected the correlations in input when this did not violate consistent contrast. The second experiment used hierarchically structured stimuli to show that participants' sort strategies favor consistency within a set of contrasting categories, distinct from any preference for 1D sorting. Finally, both experiments show that correlational sorts are much more likely when the correlation-based sort contrasts consistently. Our data show complexity at work in free sort tasks: People are sensitive to multiple and sometimes conflicting biases for consistency and correlational structure in the category systems they create.