Duration of extinction trials as a determinant of instrumental extinction in terrestrial toads (Rhinella arenarum).

Instrumental learning guides behavior toward resources. When such resources are no longer available, approach to previously reinforced locations is reduced, a process called extinction. The present experiments are concerned with factors affecting the extinction of acquired behaviors in toads. In previous experiments, total reward magnitude in acquisition and duration of extinction trials were confounded. The present experiments were designed to test the effects of these factors in factorial designs. Experiment 1 varied reward magnitude (900, 300, or 100 s of water access per trial) and amount of acquisition training (5 or 15 daily trials). With total amount of water access equated in acquisition, extinction with large rewards was faster (longer latencies in 900/5 than 300/15), but with total amount of training equated, extinction with small rewards was faster (longer latencies in 100/15 than 300/15). Experiment 2 varied reward magnitude (1200 or 120 s of water access per trial) while holding constant the number of acquisition trials (5 daily trials) and the duration of extinction trials (300 s). Extinction performance was lower with small, rather than large reward magnitude (longer latencies in 120/300 than in 1200/300). Thus, instrumental extinction depends upon the amount of time toads are exposed to the empty goal compartment during extinction trials.

Runway extinction in terrestrial toads (Rhinella arenarum): Instrumental or Pavlovian?

Instrumental appetitive extinction involves the reduction of a previously reinforced response when its occurrence is no longer rewarded. Two experiments with terrestrial toads (Rhinella arenarum) tested whether the occurrence of a nonreinforced response is necessary for response extinction by varying the time of exposure to nonrewarded goal-box stimuli across groups. In Experiment 1, toads that received the same acquisition training (15 sessions, 1 session/day, 300 s of access to water in the goal box) were randomly assigned to two groups. In Group 600 (n=12), animals spent 600 s in the goal box in 8 daily extinction sessions (water present but inaccessible). In Group 0 (n=11), toads performed the runway response (i.e., walking from the start to the goal box) but were removed as soon as they entered the goal box, thus having minimal exposure to nonrewarded goal-box stimuli. The runway response was weakened in Group 600 across extinction trials, but exhibited little change in Group 0. In Experiment 2, toads were randomly assigned to two groups after the same acquisition training. Group 0 (n=7) was treated the same as Group 0 in the previous experiment. In Group RI (retention interval, n=7), toads remained in their home cage for 13 days. Finally, all animals received 4 extinction sessions with 300 s in the empty goal box. There was little behavioral change in Group 0 during the 13 sessions with minimal exposure to the goal box. In extinction, both groups reduced their runway response at similar rates. Although the procedures were instrumental, extinction of the runway response in toads can be accounted for in terms of a Pavlovian approach response to stimuli paired with reward and nonreward in the goal box.

Comparative study of perceived invalidating environment and stress coping strategies between patients with drug resistant epilepsy and functional dissociative seizures.

BACKGROUND AND OBJECTIVES: We investigated perceived invalidating environment during childhood and stress-coping strategies in patients with; functional dissociative seizures (FDS, n=26), drug-resistant epilepsy patients with no psychiatric comorbidity (DREnc, n=23), and drug-resistant epilepsy patients with psychiatric comorbidity (DREpc, n=34). DESIGN/METHODS: We performed a cross-sectional study. Patients underwent Video Electroencephalography to confirm the diagnosis and completed a psychiatric assessment supported by clinical instruments. Invalidating environment and stress coping were studied through the ICES and CAE questionaries, respectively. A series of multinomial logistic regression analyses were performed with the explored variables. RESULTS: The maternal negative response model predicted a higher probability of FDS condition. A chaotic family type increased the likelihood of DREpc instead of FDS. DREpc and FDS patients displayed many different behaviors to cope with stress other than trying to solve the problem, the most used strategy in the DREnc group. Parental invalidation was higher in DREpc than in FDS. CONCLUSIONS: Our results deepen the data provided by previous studies indicating that multiple variables of biosocial origin have significant effects on these groups of patients. The presence of an invalidating environment may predict FDS but also the presence of psychiatric disorders among DRE. Psychotherapeutic strategies to enhance these variables might be necessary for this population.

Instrumental successive negative contrast in rats: Trial distribution, reward magnitude, and prefrontal cortex activation.

Successive negative contrast (SNC) has been used to study reward relativity, reward loss, and frustration for decades. In instrumental SNC (iSNC), the anticipatory performance of animals downshifted from a large reward to a small reward is compared to that of animals always reinforced with the small reward. iSNC involves a transient deterioration of anticipatory behavior in downshifted animals compared to unshifted controls. There is scattered information on the optimal parameters to produce this effect and even less information about its neural basis. Five experiments with rats trained in a runway to collect food pellets explored the effects of trial distribution (massed or spaced), amount of preshift training, reward disparity, and reward magnitude on the development of an iSNC effect. Start, run, and goal latencies were measured. Using spaced trials (one trial per day), evidence of the iSNC effect was observed with 24 preshift trials and a 32-to-4 pellet disparity. With massed trials (4 trials per session separated by 30-s intertrial intervals), evidence of iSNC was found with 12 preshift sessions (a total of 48 trials) and a 16-to-2 pellet disparity. The massed-training procedure was then used to assess neural activity in three prefrontal cortex areas using c-Fos expression in animals perfused after the first downshift session. There was evidence of increased activation in the anterior cingulate cortex and a trend toward increased activation in the infralimbic and prelimbic cortices. These procedures open a venue for studying the neural basis of the instrumental behavior of animals that experience reward loss.

Telencephalic neural activation following passive avoidance learning in a terrestrial toad.

The present study explores passive avoidance learning and its neural basis in toads (Rhinella arenarum). In Experiment 1, two groups of toads learned to move from a lighted compartment into a dark compartment. After responding, animals in the experimental condition were exposed to an 800-mM strongly hypertonic NaCl solution that leads to weight loss. Control animals received exposure to a 300-mM slightly hypertonic NaCl solution that leads to neither weight gain nor loss. After 10 daily acquisition trials, animals in the experimental group showed significantly longer latency to enter the dark compartment. Additionally, 10 daily trials in which both groups received the 300-mM NaCl solution after responding eliminated this group effect. Thus, experimental animals showed gradual acquisition and extinction of a passive avoidance respond. Experiment 2 replicated the gradual acquisition effect, but, after the last trial, animals were sacrificed and neural activation was assessed in five brain regions using AgNOR staining for nucleoli-an index of brain activity. Higher activation in the experimental animals, relative to controls, was observed in the amygdala and striatum. Group differences in two other regions, lateral pallium and septum, were borderline, but nonsignificant, whereas group differences in the medial pallium were nonsignificant. These preliminary results suggest that a striatal-amygdala activation could be a key component of the brain circuit controlling passive avoidance learning in amphibians. The results are discussed in relation to the results of analogous experiments with other vertebrates.

Vulnerability of long-term memory to temporal delays in amphibians.

Two experiments with toads were designed to test the memory-decay hypothesis that extinction (i.e., nonreinforced) performance is a function of time since the last reinforcement. In Experiment 1, toads (Rhinella arenarum, formerly Bufo arenarum) received 15 daily acquisition trials each reinforced with access to water during 300 s in a runway and were then randomly assigned to one of 6 retention intervals (RIs): 1, 4, 8, 16, 32, and 64 days. Extinction started after the RI and lasted 8 additional daily trials. Overall extinction performance was a logarithmic function of the RI. Although 4 extinction trials produced similar performance than 4 days of RI (consistent with memory decay), 8 extinction trials produced lower performance than 8 days of RI (consistent with a decremental effect of nonreinforcement). In Experiment 2, two groups of toads received 15 daily acquisition trials each reinforced with access to water for either 30 or 600 s, thus producing two reward magnitudes. After an 8-day RI, extinction performance was weaker after training with the small, than with the large reward magnitude. These results suggest that, at least in early extinction, the instrumental performance of toads is strongly influenced by the time since the last reinforcement.

Relación entre conducta y activación de áreas cerebrales: Empleo de la técnica de AgNOR en Psicología Comparada / Relationship between behavior and activation of brain areas: Using the AgNOR technique in comparative psychology

Se presenta una revisión de distintos estudios que emplearon la técnica de AgNOR en el campo de las neurociencias del comportamiento. AgNOR es una técnica histológica que permite estudiar la activación cerebral de una región específica. Esta técnica ha sido utilizada en distintos grupos zoológicos que comprenden desde peces y anfibios hasta mamíferos, incluyendo actividad neural tanto en procesos normales como patológicos. En conjunto, la técnica de AgNOR tiene tres notables ventajas con respecto a otras técnicas histológicas como las inmunohistoquímicas. En primer lugar, su bajo costo. En segundo lugar, su robustez. Finalmente, la posibilidad de ser aplicada con facilidad a cualquier especie animal, siendo esto último particularmente relevante en el campo de la Psicología Comparada. Paradójicamente a pesar de estas ventajas, es una técnica poco conocida y empleada. El propósito de este artículo es contribuir a su difusión dentro de la comunidad de científicos del comportamiento.

In this paper we review the use of AgNOR technique in the field of behavioral neuroscience. AgNOR is a histological technique used to study the activation of a specific brain region. NORs (nucleolar organizer regions) are the cell nucleus compartments where part of the ribosomal synthesis occurs. When a neuron enhances its protein synthesis demand, for example during a learning process, NORs increase their size. Staining with silver nitrate, colors the cell nucleus in brown and the cell nucleolus in dark brown, nearly black. Thus, the size of the nucleus and the nucleolus can be easily measured in histological preparations treated with silver nitrate through any appropriated image processing software. In this manner, AgNOR technique consist in staining the tissue of subjects that have received different treatments and comparing the average size of the nucleolus of a particular brain region, which is an indirect marker of cellular activity. The use of AgNOR technique in the study of neural basis of learning, typically involves: (1) training animals in a particular task, (2) after acquisition, animals in the trained group along with animals from a control condition are sacrificed in order to obtain a brain sample, (3) brains of animals from both conditions are processed and compared. This procedure was successfully used to study telencephalic activation during spatial learning in fish (Carassius auratus). The task consisted in using visual cues to identify the correct exit from a trap. In the case of fish, the histological analysis showed an increase of the nucleolus size in the lateral pallium, proposed as homologous to the mammalian hippocampus, observing that this area is involved in spatial memory. In our laboratory this technique was also used to analyze the neural activity after spatial learning in the terrestrial toad Rhinella arenarum. We conducted several studies where dehydrated animals had to use visual cues to locate the correct position of a water source. In accordance with fish’s data, our results indicated a higher activity of the hippocampal homologous region (the amphibian medial pallium), showing a high degree of functional equivalence. On the other hand, we also studied in toads the telencephalic activity during an aversive learning task. Here, it was observed an increase in the average of NORs size in the ventrolateral telencephalic region, the striatum (proposed as homologous to the mammalian amygdala), also showing a highly preserved functional equivalence. In mammals, AgNOR technique was used with different purposes, such as the study of changes in hippocampal activity during development in rats, the comparison of the basal activity of two regions of the rats hippocampus, the CA1 and the CA3, both strongly related with learning, or the the hippocampal activity in two different situations in which the liver activity was altered (by an artificial cholestasis, or by alcohol consumption). Finally, AgNOR technique was also used in the study of human brain activity of subjects that had committed suicide. On the whole, the AgNOR technique has three distinct advantages over other histological techniques such as the immunohistochemical. First, their low cost. Second, their robustness. Finally, the fact that it can be easily applied to any animal species, which makes it particularly attractive to the field of the Comparative Psychology. But paradoxically, despite these advantages it is a poorly known and used technique. The aim of this paper is to contribute to the diffusion of the AgNOR technique in the community of behavioral scientists, showing that its use has provided a valuable contribution to research in different fields and animal species.