Sites of Plasticity in the Neural Circuit Mediating Tentacle Withdrawal in the Snail Helix aspersa: Implications for Behavioral Change and Learning Kinetics

The tentacle withdrawal reflex of the snail Helix aspersa exhibits a complex combination of habituation and sensitization consistent with the dual-process theory of plasticity. Habituation, sensitization, or a combination of both were elicited by varying stimulation parameters and lesion condition. Analysis of response plasticity shows that the late phase of the response is selectively enhanced by sensitization, whereas all phases are decreased by habituation. Previous data have shown that tentacle withdrawal is mediated conjointly by parallel monosynaptic and polysynaptic pathways. The former mediates the early phase, whereas the latter mediates the late phase of the response. Plastic loci were identified by stimulating and recording at different points within the neural circuit, in combination with selective lesions. Results indicate that depression occurs at an upstream locus, before circuit divergence, and is therefore expressed in all pathways, whereas facilitation requires downstream facilitatory neurons and is selectively expressed in polysynaptic pathways. Differential expression of plasticity between pathways helps explain the behavioral manifestation of depression and facilitation. A simple mathematical model is used to show how serial positioning of depression and facilitation can explain the kinetics of dual-process learning. These results illustrate how the position of cellular plasticity in the network affects behavioral change and how forms of plasticity can interact to determine the kinetics of the net changes.     

Context effects in visual pattern recognition by pigeons

In the experiments described in this paper we examined the effects of contextual stimuli on pigeons’ recognition of visual patterns. Experiment z showed acontext-superiority effect. Specifically, two target forms that were identical except for location in the visual field were not discriminated when presented alone, but the compounds formed when each of these targets was placed between a nearby pair of flanking stimuli were readily discriminated. The size of the context-superiority effect decreased with increasing target-flanker separation. In Experiments 2 and 3 the two targets differed in form rather than spatial location and were readily discriminated in the absence of Hankers. Under these circumstances, adding an identical pair of flankers to each target resulted in a content-inferiority effect; that is, the two target-plus-Hankers compounds were less readily discriminated than the targets atone. The size of the context-inferiority effect decreased with increasing target-flanker separation. The observed effects of context are predictable from the Heinemann-Chase (1990) model of pattern recognition.     

Parallel processing in item recognition

It is shown that in Sternberg’s item recognition task Ss need not make a judgment of the absolute size or color of the test item before comparing it with memory. However, Ss do use size or color information, when possible, to reduce long reaction times for large memory loads. The results suggest that Ss are able to scan memory for form in parallel with testing for gross stimulus features, like size or color. This finding has important implications for sequential two-stage theories of attention.     

Stimulus learning versus response learning in a discriminated punishment situation

The suppression of bar pressing under two kinds of conditions was compared. Under one condition the response was occasionally punished by shock in the presence of a signal. Suppression to the signal was quickly acquired, indicating rapid learning about the signal-shock relationship (stimulus learning). Under the other condition the response was occasionally punished in the presence of the signal but additional free shocks were given in the absence of the signal. The slow acquisition of suppression found in this case indicated that there was, at best, only gradual learning about the response-shock relationship (response learning).     

Competition and cooperation between groups and between individuals

Groups and individuals were compared in two experiments. In the first, two same-sex individuals or two same-sex dyads played 10 trials of a Prisoner's Dilemma matrix game (PDG) for money. Play between individuals was more cooperative and less competitive than play between groups. In the second experiment subjects played 10 trials of either PDG or mutual-fate-control (MFC) matrices. For the MFC matrix the competitive choice, which reduces the opponent's outcomes, but has no effect on own outcomes, reflects a desire to increase one's relative advantage over the opponent. Although cooperation was greater for MFC, for both PDG and MFC matrices groups were more competitive and less cooperative than individuals. A large component of the groups-individuals effect is attributed to the greater desire of groups to “win” or avoid “losing” to the opponent, regardless of their absolute outcomes.     

Minimized tolerance to the suppressive effects of CCK8 on operant responding

This study was designed to determine if tolerance to cholecystokinin octapeptide (CCK8) could be prevented or minimized by spacing injections, and if an appetitive operant conditioning paradigm provides a sensitive baseline to test the effects of CCK8. Male Sprague-Dawley rats were trained to press a lever for water according to a fixed-interval 60-sec schedule of reinforcement. After response rate stabilized, rats were given a series of CCK8 (0.04 mg/kg, ip) injections spaced several days apart. The first injection of CCK8 produced complete response suppression during the 30-min test session, while later injections produced partial or complete suppression. Thus, tolerance to CCK8, as measured by operant response rate, may be minimized if injections are appropriately spaced.     

"Central arousal" and sexual responsiveness in the snail, Helix aspersa

In molluscs, a "central arousal" system is thought to positively modulate both an animal's level of activity and its behavioral responsiveness. This hypothesis is examined in Helix aspersa by testing the relationships between activity, feeding, and sexual behavior. Activity, feeding, and mating exhibit parallel daily rhythms. Snails are most active, and eat and mate most frequently, during scotophase and the first 3 h of photophase. Handling and injections of serotonin (5 x 10(-7) m/kg body wt) increase general activity. Inducing activity during late photophase increases food consumption, but it does not induce sexual activity. Moreover, serotonin and handling have no effect on sexual arousal; treated snails show no increase in genital eversion stage and require the same length of courtship as controls. If snails are sexually deprived, increasing activity in late photophase does increase copulation frequency, but snails do not copulate more frequently than do unhandled snails tested during early photophase. These results suggest that while manipulations thought to increase central arousal do increase activity and responsiveness to food stimuli, they do not directly affect sexual proclivity or sexual arousal. Moreover, the relationship between feeding and sexual behavior differs between Helix and Aplysia. This difference between the two species may be related to the differences in their reproductive strategies.     

Designing courseware: Prompts from behavioral instruction

Behavior analysis has been at the forefront of instructional design for many years. However, this leadership position is rapidly eroding as teachers, trainers and other educators insist that behavioral instruction is good only for meeting simplistic educational goals. I argue that in order for behavior analysis to continue to influence the field of instructional design, behavior analysts need to help people develop instructional programs that use advanced interactive computer systems and that are based on all the components of behavioral instruction. Therefore, this paper suggests the following strategy. First, it teaches people to select authoring systems that will enable them to design interactive computer programs. Second, in order to improve current authoring systems it provides a set of prompts that integrate the features of behavioral instruction. I claim that the integration of these prompts with an advanced authoring system will facilitate the development of complex, conceptual learning programs and minimize current criticisms of behavioral instruction.     

Comparing Values and Methods in Psychodynamic and Cognitive-Behavioral Therapy: Commonalities and Differences

To determine the underlying values and methods in cognitive-behavioral and psychodynamic therapy and to address the implications of those values and methods for integrating the two therapies, the Process Value and Methods Survey was sent to members of The Association for Advancement of Behavior Therapy (cognitive-behavioral sample) and Division 39 of American Psychological Association (psychodynamic sample). Members were asked to endorse items based on their ideal understanding of their respective orientations. A Principal Components Analysis (PCA) of the combined samples yielded six components for values, of which four were significant according to orientation. A second PCA, for therapeutic methods, yielded six components, five of which were significant according to orientation. In both PCAs, components significant for an orientation were consistent with the corresponding constructs of that orientation. The relationship between method and value components as well as how value components may be related to clinical practice and psychotherapy integration is discussed.