Stimulus generalization of excitation and inhibition

Five sign-tracking experiments with pigeons investigated the breadth of stimulus generalization of excitatory and inhibitory conditioning. Using a compound stimulus test procedure, these experiments found evidence for a narrower generalization of associative strength in excitation than in inhibition. They also found a narrower associative gradient with a more strongly conditioned excitatory stimulus, although this did not seem to account for the difference between exciters and inhibitors. These results confirm earlier findings comparing generalization after acquisition and extinction and raise various theoretical issues about generalization.     

Stimulus generalization of excitation and inhibition

Five sign-tracking experiments with pigeons investigated the breadth of stimulus generalization of excitatory and inhibitory conditioning. Using a compound stimulus test procedure, these experiments found evidence for a narrower generalization of associative strength in excitation than in inhibition. They also found a narrower associative gradient with a more strongly conditioned excitatory stimulus, although this did not seem to account for the difference between exciters and inhibitors. These results confirm earlier findings comparing generalization after acquisition and extinction and raise various theoretical issues about generalization.     

Sensory and Postural input in the Occurrence of a Gender Difference in Orienting Liquid Surfaces

The Psychological Record - In the water-level task, both spatial skill and physical knowledge contribute to representing the surface of a liquid as horizontal irrespective of the container’s...     

Selection for central excitation in Drosophila melanogaster

In two populations of Drosophila melanogaster, bidirectional selection and single-pair matings for high and low expression of central excitatory state (CES) succeeded in producing from one a high, but not a low, CES line, and from the other a low, but not a high, CES line. Compared with results from the selection studies of the blow fly, Phormia regina, in which one major gene correlate of CES has been found, the results from this study suggest that in D. melanogaster there are several gene correlates of CES, opposite alleles of some of which have become fixed in the divergent lines.     

Septal correlates of conditioned inhibition and excitation in rats

Multiple-unit activity was recorded in the lateral septum of rats during Pavlovian differential conditioning. In Experiment 1, one group of animals received a classical aversive discrimination paradigm, while another group was presented with a control procedure in which the unconditioned stimuli (shocks) were administered randomly with regard to the conditioned stimuli. Septal unit activity increased during presentations of the conditioned inhibitor and was markedly suppressed during presentations of the conditioned excitor in the conditioning-group animals and not in the control animals. Baseline activity remained unchanged in the conditioning group but was suppressed in the random control group. Furthermore, termination of the aversive stimuli was marked by a burst of firing in the conditioning group, but no such rebound was seen in the control group. In Experiment 2, a classical appetitive discrimination paradigm was given, in which septal unit activity was found to increase in the presence of the conditioned excitor and was suppressed in the presence of the conditioned inhibitor. The results are interpreted as indicating a role for the septum in the relief of aversive states.     

A stimulus-compounding assay of conditioned inhibition and excitation

Rats were trained in an operant discrimination involving two panel lights, A and B. Group CI (Conditioned Inhibition) was trained to lever press in the presence of A (S+), and not in the presence of the compound AB (S?). The opposite contingencies held in Group CE (Conditioned Excitation). Response rates were higher in Group CE than in Group CI, especially to the positive stimulus. However, the groups acquired the discrimination at comparable rates. In a separate phase of the experiment, a tone (C) was separately trained in the absence of the lights to control responding. All seven possible combinations of A, B, and C were then presented randomly during extinction. The inhibitory effect of B on C in Group CI was comparable in magnitude to the excitatory effect of B on C in Group CE. B's effect on C was not altered by the presence or absence of A, regardless of whether A was inhibitory or excitatory. The symmetry between CI and CE revealed by the stimulus-compounding test may be partly artifactual.     

Spontaneous recovery of excitation but not inhibition

Five magazine approach experiments with rats and 1 sign-tracking experiment with pigeons explored the possibility of an analogue to spontaneous recovery of excitatory conditioning from extinction: spontaneous recovery of inhibitory conditioning from training. Stimuli were 1st treated as conditioned inhibitors and then as conditioned exciters or as irrelevant to reinforcement. At issue was whether the passage of time after the 2nd treatment would allow partial restoration of the initial conditioned inhibition. The experiments differed in the design used to study recovery, the manner of reinforcing the inhibitor, the means of testing for recovery, the time interval allowed for recovery, and the species used. None of the experiments found evidence for recovery of the inhibitory learning with time, despite the concurrently measured presence of spontaneous recovery of excitatory conditioning after extinction. These experiments suggest that changes with time may be preferential to the learning that occurs during extinction.     

Prefrontal cortex regulates inhibition and excitation in distributed neural networks.

Prefrontal cortex provides both inhibitory and excitatory input to distributed neural circuits required to support performance in diverse tasks. Neurological patients with prefrontal damage are impaired in their ability to inhibit task-irrelevant information during behavioral tasks requiring performance over a delay. The observed enhancements of primary auditory and somatosensory cortical responses to task-irrelevant distractors suggest that prefrontal damage disrupts inhibitory modulation of inputs to primary sensory cortex, perhaps through abnormalities in a prefrontal-thalamic sensory gating system. Failure to suppress irrelevant sensory information results in increased neural noise, contributing to the deficits in decision making routinely observed in these patients. In addition to a critical role in inhibitory control of sensory flow to primary cortical regions, and tertiary prefrontal cortex also exerts excitatory input to activity in multiple sub-regions of secondary association cortex. Unilateral prefrontal damage results in multi-modal decreases in neural activity in posterior association cortex in the hemisphere ipsilateral to damage. This excitatory modulation is necessary to sustain neural activity during working memory. Thus, prefrontal cortex is able to sculpt behavior through parallel inhibitory and excitatory regulation of neural activity in distributed neural networks.     

Protective inhibition: A central factor in auditory fatigue

Summary A signal detection experiment was performed to investigate the sensitivity shift after stimulation with discontinuous octave-band noise of 95 dB (A). The influence of psychological factors on the sensitivity shift in the stimulated and the unstimulated ear was investigated in a two-factorial experimental design. In four independent groups of 12 Ss each, the psychological meaning of the noise and the side of sensitivity measurement were varied. Half of the Ss listened passively to the noise stimuli (control groups), the other half was made to believe that the noise signaled errors in a tracking task (experimental groups). After exposure of noise stimuli to the right ear the sensitivity of either the right or the left ear was determined. After exposure to noise the sensitivity of the stimulated ear was shown to be significantly more reduced in the experimental than in the control group. Thus, depending on the meaning of the noise physically identical stimuli produce sensitivity shifts of different amounts. After stimulation of the right ear with noise the sensitivity of the left ear remained completely unaffected. The sensitivity shift of the right ear did not persist as long as a threshold shift would have done. The hypothesis is that intensive auditory stimuli will produce negative feedback which protects — within certain limits — the stimulated ear from the fatiguing after-effects of overstimulation. The effectiveness of this protective inhibition depends on psychological factors.We are grateful to S. Jörg-Wagner for his competent handling of the experiment.     

Generalization of excitation and inhibition after different amounts of training of an avoidance baseline

After acquisition of a treadle-pressing response maintained by an avoidance contingency, four groups of pigeons received interdimensional discrimination training. For two groups, the positive stimulus was a 1000-Hertz tone correlated with the avoidance schedule and the negative stimulus was noise correlated with extinction. The discriminative stimuli were reversed for the other two groups. For two groups, the test stimuli were presented during extinction without any shocks during the test stimuli, for the other two groups, an unavoidable shock was presented during each test stimulus. Generalization was measured daily during discrimination training by randomly substituting each of six test frequencies for the 1000-Hertz tone. When the 1000-Hertz tone was correlated with the avoidance schedule, the number of responses to it increased and the excitatory gradient became steeper as a function of the amount of training. When the 1000-Hertz tone was associated with extinction, the number of responses to it decreased as a function of days of training and the inhibitory gradient became slightly steeper, provided that responding to the test stimulus was elevated by unavoidable shock. The training effects parallel those obtained with positive reinforcement.     

The role of input and output modality pairings in dual-task performance: evidence for content-dependent central interference

Recent debate regarding dual-task performance has focused on whether costs result from limitations in central capacity, and whether central operations can be performed in parallel. While these questions are controversial, the dominant models of dual-task performance share the assumption that central operations are generic--that is, their interactions are independent of stimulus and response modalities. To examine these issues, we conducted a series of dual-task experiments with different input and output modality pairings. One condition combined a visual-manual task with an auditory-vocal task, and the other condition reversed the input-output pairings, combining a visual-vocal task with an auditory-manual task. Input/output modality pairings proved to be a key factor; throughout practice, dual-task costs were generally more than twice as large with visual-vocal/auditory-manual tasks than with the opposite arrangement of modalities (Experiments 1 and 2). These differences could be explained neither by competition for peripheral resources nor by differences in single-task response times (Experiment 3). Moreover, the persistent dual-task costs did not appear to stem from a central bottleneck. Contrary to the dominant models of dual-task performance, we propose that central interference between tasks depends not just on the duration of central operations, nor just strategic adaptation, but also on the content of those operations. Implications for structural and strategic accounts of dual-task interference are discussed.     

Conditioned inhibition is not the symmetrical opposite of conditioned excitation: A test of the Rescorla-Wagner model

Rescorla and Wagner's (1972) linear associative model of learning predicts that a neutral stimulus will become weakly excitatory if it is paired with a conditioned inhibitor and the compound is not reinforced. If the inhibitor is not allowed to extinguish during these pairings, the model predicts that the neutral stimulus will become strongly excitatory. Rescorla (1971) has presented some evidence to support the former prediction of a weak effect. Experiment I tested the latter prediction of a strong effect using rats in a conditioned emotional response paradigm, and found no evidence that the pairings made the neutral stimulus excitatory. Experiment II replicated Rescorla's results, but showed that even on a relearning test the experimental group learned no faster than a novel stimulus control group.