Autoshaped impulsivity: Some explorations with a neural network model.

This study evaluated the effect of delay and magnitude of reinforcement in Pavlovian contingencies, extending the understanding of the phenomenon of autoshaped impulsivity as described in Alcalá's thesis (2017) and Burgos and García-Leal (2015). The effects of adding a trace interval were analyzed on the maintained responses of impulsive choice, seen as the preference of a small and immediate reinforcer over a larger and delayed one, and the role of the contextual unit, as well as the inhibitory units according to the Diffuse Discrepancy Model. In the Simulation, the model with inhibitory units was used, trained in two signals with different delays and reinforcement magnitudes, and subsequently presented concurrently in choice tasks without reinforcement nor learning, using an ABA within-subject design. In general, the DD model successfully simulated the phenomenon of autoshaped impulsivity, consistent with studies from Alcalá's thesis (2017), Burgos and García-Leal (2015), and Picker and Poling (1982). It also predicted the elimination of this effect (autoshaped impulsivity) after introducing a trace interval. The observed results and their implications are discussed, as well as possible future studies with animals and humans.

Assessment of the inbred C57BL/6 and outbred CD1 mouse strains using a progressive ratio schedule during development.

Inbred strains have a genetic similarity of at least 98.6% compared to their outbred counterparts. Several studies have shown that inbred C57BL/6 mice and outbred ICR (CD1) mice differ in locomotion, cognitive flexibility, and aggression. However, their performance in operant paradigms is not well understood. A progressive ratio (PR) schedule of reinforcement is a method of quantitative estimation of the incentive state of an animal for a reward by increasing response requirements for reinforcer delivery, which is relevant to assess the breakpoint (amount of response effort an animal is willing to invest for a single unit of reward). This study tested male and female C57BL/6 and CD1 mice with an open field to analyze locomotion. Then, we used conditioning chambers with a PR3 schedule for ten consecutive days (P30-P40). PR performance was measured with the breakpoint, and the mathematical principles of reinforcement (MPR) were used to estimate motivation, impulsivity, and motor skills to manipulate the operandum. We found that CD1 mice showed higher locomotor activity than C57BL/6 independently of sex. CD1 mice had a higher breakpoint. However, male CD1 mice gradually increased breakpoint until the last session. In the MPR model, CD1 mice showed decreased fixed paused parameter (impulsivity) than C57BL/6, independent of sex. Our data suggest that the higher breakpoint in CD1 strain may partially be related to impulsivity. Therefore, the MPR model can help identify factors that affect performances, such as motivation, impulsivity, and motor skills during a PR in adolescent CD1 and C57BL/6 mice. These findings are essential to characterize the differences in the behavioral performance between C57BL/6 and CD1 strains and their potential as animal models.

Normal pressure hydrocephalus decreases the proliferation of oligodendrocyte progenitor cells and the expression of CNPase and MOG proteins in the corpus callosum before behavioral deficits occur.

Normal pressure hydrocephalus (NPH) compromises the morphology of the corpus callosum (CC). This study aims to determine whether 60- or 120-day NPH disrupts the cytoarchitecture and functioning of white matter (WM) and oligodendrocyte precursor cells (OPCs) and establish whether these changes are reversible after hydrocephalus treatment. NPH was induced in CD1 adult mice by inserting an obstructive lamina in the atrium of the aqueduct of Sylvius. Five groups were assembled: sham-operated controls (60 and 120 days), NPH groups (60 and 120 days), and the hydrocephalus-treated group (obstruction removal after 60-d hydrocephalus). We analyzed the cellular integrity of the CC by immunohistochemistry, TUNEL analysis, Western blot assays, and transmission electron microscopy (TEM). We found a reduction in the width of the CC at 60 and 120 days of NPH. TEM analysis demonstrated myelin abnormalities, degenerative changes in the WM, and an increase in the number of hyperdense (dark) axons that were associated with significant astrogliosis, and microglial reactivity. Hydrocephalus also caused a decrease in the expression of myelin-related proteins (MOG and CNPase) and reduced proliferation and population of OPCs, resulting in fewer mature oligodendrocytes. Hydrocephalus resolution only recovers the OPC proliferation and MOG protein density, but the rest of the WM abnormalities persisted. Interestingly, all these cellular and molecular anomalies occur in the absence of behavioral changes. The results suggest that NPH severely disrupts the myelin integrity and affects the OPC turnover in the CC. Remarkably, most of these deleterious events persist after hydrocephalus treatment, which suggests that a late treatment conveys irreversible changes in the WM of CC.

Chronic exposure to cyclohexane induces stereotypic circling, hyperlocomotion, and anxiety-like behavior associated with atypical c-Fos expression in motor- and anxiety-related brain regions.

Recreational abuse of solvents continues, despite cyclohexane (CHX) is used as a safe replacement in gasoline or adhesive formulations. Increasing evidence indicates that CHX inhalation affects brain functioning; however, scanty information is available about its effects on behavior and brain activity upon drug removal. In this study, we used CD1 adult mice to mimic an intoxication period of recreational drugs for 30 days. During the CHX exposure (~30,000 ppm), we analyzed exploratory and biphasic behaviors, stereotypic circling, and locomotion. After CHX removal (24 h or a month later), we assessed anxiety-like behaviors and quantified c-Fos cells in motor- and anxiety-related brain regions. Our findings indicate that the repeated inhalation of CHX produced steady hyperactivity and reduced ataxia, sedation, and seizures as the exposure to CHX progressed. Also, CHX decreased grooming and rearing behaviors. In the first week of CHX inhalation, a stereotypic circling behavior emerged, and locomotion increased gradually. One month after CHX withdrawal, mice showed low activity in the center zone of the open field and more buried marbles. Twenty-four hours after CHX removal, c-Fos expression was low in the dorsal striatum, ventral striatum, motor cortex, dorsomedial prefrontal cortex, basolateral amygdala, lateral hypothalamus, and ventral hippocampus. One month later, c-Fos expression remained low in the ventral striatum and lateral hypothalamus but increased in the dorsomedial prefrontal cortex and primary motor cortex. This study provides a comprehensive behavioral characterization and novel histological evidence of the CHX effects on the brain when is administered in a recreational-like mode.

Similar attention and performance in female and male CD1 mice in the peak procedure.

Inaccurate and distorted timing are associated with neurodegenerative disorders such as Alzheimer's disease and schizophrenia in humans, which generates interest in the discovery and understanding of the factors behind such timing difficulties. Timing research in mice has taken an important role, because the availability of genetically-altered strains allows establishing the causal role of specific genes on such neurodegenerative disorders. Nevertheless, few studies have considered mice's sex and some have found sex differences in timing, although results are not yet conclusive. We tested female and male CD1 mice, an outbred strain not yet studied in a peak procedure. By varying the percentage of peak trials and the presence of a gap and/or a distractor in the tests, we found no sex differences in accuracy, precision, or attention. Both females and males followed a stop-clock strategy after distractor and gap + distractor trials. This suggests that both male and female CD1 mice may be exposed to a peak procedure to study factors associated to neurotoxicology or neurogenesis.

Increased generalization in a peak procedure after delayed reinforcement.

Temporal control of behavior might be impaired by reinforcement devaluation and other motivational operations such as delaying reinforcement of the instrumental response. Here, we report an experiment that assessed the effect of delayed reinforcement on a timing peak procedure. Using a within-subject design with a multiple two-component schedule of reinforcement, we found evidence of flat temporal generalization gradients, along with degraded response-reinforcer contingency, lower response rates and changes in the responding patterns due to delayed reinforcement. This result is consistent with the Learning to Time (LeT) and some versions of Scalar Expectancy Theory (SET).

Cyclohexane Inhalation Produces Long-Lasting Alterations in the Hippocampal Integrity and Reward-Seeking Behavior in the Adult Mouse.

Cyclohexane (CHX) is an organic solvent commonly used as a drug-of-abuse. This drug increases the oxidative stress and glial reactivity in the hippocampus, which suggests that this brain region is vulnerable to CHX effects. This study aimed to establish the behavioral changes and the pathological alterations that occur in the Cornu Ammonis 3 (CA3) and Dentate Gyrus (DG) after a long-lasting exposure to CHX. We exposed CD1 mice to a recreational-like dose of CHX (~ 30,000 ppm) for 30 days and explored its consequences in motor skills, reward-seeking behavior, and the CA3 and DG hippocampal subfields. Twenty-four hours after the last administration of CHX, we found a significant decrease in the number of c-Fos+ cells in the hippocampal CA3 and DG regions. This event coincided with an increased in NMDAR1 expression and apoptotic cells in the CA3 region. At day 13th without CHX, we found a persistent reduction in the number of c-Fos+ and TUNEL+ cells in DG. At both time points, the CHX-exposed mice showed a strong overexpression of neuropeptide Y (NPY) in the CA3 stratum lucidum and the hippocampal hilus. In parallel, we used an operant-based task to assess motor performance and operant conditioning learning. The behavioral analysis indicated that CHX did not modify the acquisition of operant conditioning tasks, but affected some motor skills and increased the reward-seeking behavior. Altogether, this evidence reveals that CHX exposure provokes long-lasting changes in the hippocampal subfields, induces motor impairments and increases the motivation-guided behavior. These findings can help understand the deleterious effect of CHX into the adult hippocampus and unveil its potential to trigger addiction-like behaviors.

Reinforcement value and fixed-interval performance.

The concept of reinforcement value summarizes the effect of different variables, such as reinforcement delay, reinforcement magnitude, and deprivation level, on behavior. In the present set of experiments, we evaluated the effect of reinforcement devaluation on performance under FI schedules. The literature on timing and reinforcement value suggests that devaluation generates longer expected times to reinforcement than the same intervals trained under control conditions. We devalued reinforcement with delay in Experiments 1A, 1B, and 2, and diminished deprivation in Experiments 3A and 3B. Devaluation reduced response rates, increased the number of one-response intervals, and lengthened postreinforcement pauses, but had inconsistent effects on other timing measures such as quarter life and breakpoint. The results of delayed reinforcement and diminished deprivation manipulations are well summarized as reinforcement devaluation effects. These results suggest that devaluation may reduce stimulus control. In addition, we argue that the process by which delayed reinforcement affects behavior might also explain some effects observed in other devaluation procedures through the concept of reinforcement value.

Valor de la Recompensa: ¿Cómo y Para Qué se Usa el Concepto? / Value of the Reward: How Is the Concept Used and for What? / Valor de Recompensa: como e para que se usa o Conceito?

El escrito ofrece un panorama general sobre el valor de la recompensa, respondiendo los interrogantes: ¿qué es?, ¿cómo se ha conceptualizado? y ¿qué investigaciones han utilizado el concepto? En sentido general, este se utiliza para calificar una recompensa como más o menos efectiva: mientras mayor sea el valor, mayor es su eficacia. Primero se describe la medición histórica del valor y cómo lo define la literatura sobre economía conductual. A continuación aparecen dos usos diferentes del concepto: (a) como constructo hipotético y (b) como variable interviniente. También se incluyen definiciones operacionales, en las que no se definen exhaustivamente las variables asociadas, entonces no se le considera variable interviniente, pero tampoco se agrega significado, más allá del nivel de observación, por lo que no son ejemplo de constructo hipotético. Posteriormente se explora la relación entre demora del reforzador y descuento temporal. Las consideraciones finales retoman la discusión sobre su valor heurístico en la investigación contemporánea.

The article offers a general panorama on the value of the reward, answering the questions: What is it? How has it been conceptualized? What investigations have used the concept? In general, a reward is rated as more or less effective: the greater the value, the greater its efficiency. First, the article discusses the historical measurement of value and how the literature on behavioral economics defines it. Next, two different uses of the concept are presented: (a) as a hypothetical construct and (b) as intervening variable. The text includes operational definitions where the associated variables are not defined exhaustively and therefore not considered as intervening variable, but which also add no meaning beyond the level of observation and therefore are not an example of a hypothetical construct. The article then explores the relationship between delay of the reinforcing agent and temporal discount. Finally, the article considers the discussion about the concept's heuristic value in contemporary research.

Este texto oferece um panorama geral sobre o valor da recompensa ao responder aos questionamentos: o que é, como vem sendo conceituado e quais pesquisas têm utilizado o conceito? Em sentido geral, este se utiliza para qualificar uma recompensa como mais ou menos efetiva: quanto maior for o valor, maior será sua eficácia. Primeiramente, descreve-se a medição histórica do valor e como a literatura sobre economia comportamental o define. A seguir, aparecem dois usos diferentes do conceito: (a) como construto hipotético e (b) como variável interventora. Também são incluídas definições operacionais, nas quais não se definem exaustivamente as variáveis associadas, portanto não é considerada variável interventora nem se agrega significado mais além do nível de observação, razão pela qual não são exemplos de construto hipotético. Posteriormente, explora-se a relação entre demora do reforçador e desconto temporal. As considerações finais retomam a discussão sobre seu valor heurístico na pesquisa contemporânea.

Temporal discrimination and delayed reinforcement.

We attempted to determine the effect of reinforcement delay on time discrimination in an interval bisection task. Three groups of rats were exposed to immediate, delayed reinforcement and longer signals with immediate reinforcement in acquisition and test. Results show differences in the amount of training necessary to reach the acquisition criteria, the Weber fraction and the range or overall stimulus control. The results suggest an increased difficulty to discriminate the difference among durations rather than an increase in estimated time as main effect of delayed reinforcement.

Extinction of food-reinforced instrumental behavior in Japanese quail (Coturnix japonica).

Japanese quail (Coturnix japonica) were reinforced with food for traversing a runway for either 18 or 36 trials, administered at a rate of 1 trial per day. Then, all animals received 18 extinction trials. The latency to run from the start box to the goal box was the dependent variable. Extinction was significantly slower in animals that had received 50% partial reinforcement during acquisition, whether relative to a group matched in terms of acquisition trials (36 trials, twice the number of reinforced trials) or relative to a group matched in terms of reinforcements (18 trials). The latter group was also matched in terms of the temporal distribution of acquisition trials with the partial reinforcement group, being trained only on days when the partial group was scheduled to receive a reinforced trial. Thus, there was evidence of a spaced-trial partial reinforcement extinction effect. A comparison of groups receiving large versus small reward magnitudes yielded no evidence of the spaced-trial magnitude of reinforcement extinction effect, even though the large-reward group consumed approximately 3 times more food than the small-reward group. Moreover, a comparison of groups that received 36 versus 18 acquisition trials produced no evidence of the spaced-trial overtraining extinction effect, even though acquisition latencies were significantly lower for the group that received 36 acquisition trials. These results are discussed in relation to comparative research on learning phenomena involving incentive downshift manipulations.