Evidence for positive, but not negative, behavioral contrast with wheel-running reinforcement on multiple variable-ratio schedules

Resurgence and Behavioral Contrast, Compared and Contrasted

This is a review of the relation between operant response resurgence and behavioral contrast. Both are defined by rate changes in a target response as a function of environmental changes spatially or temporally distal to the location of the target response. The typical procedures for investigating these two phenomena differ in that (1) resurgence is studied using concurrent schedules and behavioral contrast predominantly with multiple schedules and (2) resurgence is assessed against an extinction baseline of the target response and behavioral contrast has been assessed under a variety of reinforcement schedules. The distinctions between concurrent and multiple schedules, however, may be ones of degree rather than kind. Research into both phenomena reveals considerable overlap in the controlling variables of the two. With certain caveats, resurgence appears to be an instance of behavioral contrast measured against an extinction baseline. Because of Point 2 above, most instances of behavioral contrast do not meet the definition of resurgence. Investigating resurgence while maintaining target responding by a schedule of reinforcement might be useful, but such a procedure would not qualify as resurgence because it violates the definition of resurgence as the return of a previously reinforced but currently extinguished response. Several implications of the similarities and differences between the two are discussed.

Comparing extinction and contrast effects for operant wheel running and lever pressing on a multiple schedule

Extinction and positive contrast effects were assessed on a multiple schedule with lever pressing as the operant in one component and wheel running as the operant in the other component. FR 15 schedules produced 15% sucrose reinforcement in each component. Contrast for both operants was generated by placing responding in the alternate component on extinction. Results showed that extinction decreased and contrast increased both lever-pressing and wheel-running rates. However, the magnitude of the changes was greater for lever pressing. Extinction increased and contrast decreased postreinforcement pause (PRP) duration for lever pressing, but for wheel running, extinction decreased PRP duration while contrast did not change PRP duration. Finally, outcomes for lever pressing decreased with extinction and increased with contrast, but for wheel running, outcomes did not change with extinction and increased with contrast. These differences in contrast and extinction effects were explained by an automatic reinforcement effect generated by wheel-running, but not lever pressing. These findings provide further support for an automatic reinforcement effect generated by wheel running.

Shared Behavioral and Neurocircuitry Disruptions in Drug Addiction, Obesity, and Binge Eating Disorder: Focus on Group I mGluRs in the Mesolimbic Dopamine Pathway

Accumulated data from clinical and preclinical studies suggest that, in drug addiction and states of overeating, such as obesity and binge eating disorder (BED), there is an imbalance in circuits that are critical for motivation, reward saliency, executive function, and self-control. Central to these pathologies and the extensive topic of this Review are the aberrations in dopamine (DA) and glutamate (Glu) within the mesolimbic pathway. Group I metabotropic glutamate receptors (mGlus) are highly expressed in the mesolimbic pathway and are poised in key positions to modulate disruptions in synaptic plasticity and neurotransmitter release observed in drug addiction, obesity, and BED. The use of allosteric modulators of group I mGlus has been studied in drug addiction, as they offer several advantages over traditional orthosteric agents. However, they have yet to be studied in obesity or BED. With the substantial overlap between the neurocircuitry involved in drug addiction and eating disorders, group I mGlus may also provide novel targets for obesity and BED.

Positive and negative emotions in dairy cows: Can ear postures be used as a measure?

Applying objective measures to assess the emotional states of animals is an important area of research and essential for improving animal welfare. In this study, we have built upon previous research to test whether ear postures can be used as an indicator of emotional states in dairy cows. By using a positive and negative contrast paradigm, we elicited the emotional states of excitement and frustration in 22 dairy cows. Each cow was first conditioned to expect the delivery of standard feed when a bell was rung. Once they were familiar with the experimental set-up and the delivery of the feed, they were then given concentrates feed instead. As concentrates are highly desired, this was considered to elicit the emotional state of excitement. This was then repeated five times. On the following trial, the cows were given inedible woodchip, and the cows' unfulfilled expectations were considered to elicit a state of frustration. We observed the cows' ear postures and mean heart rate (beats per minute) during 15-minute focal observations, each comprised of 5 min of pre-feeding (baseline), 5 min of feeding, and 5 min of post-feeding. Both the woodchip treatment and the concentrates elicited significantly higher mean heart rates compared with the standard feed, indicating that both treatments elicited a high arousal emotional state. The woodchip and concentrates treatments were also significantly associated with the increased performance of different ear postures, indicating that cows do perform certain ear postures in relation to both positive and negative high arousal emotional states. Our results complement previous research performed with both cows and sheep, and indicate that with training and contextual knowledge, ear postures may be suitable as a reliable measure of emotional state in dairy cows.