Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
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Most previous attempts to condition schedule-induced drinking (SID) to arbitrary stimuli have involved classical-conditioning procedures, with mixed results. Considering the hypothesis that SID reduces to the operant reinforcement of the water-producing response, in a previous experiment the control of a stimulus on SID was established using a multiple water reinforcement schedule. To show that the operant discrimination of SID is sensitive to the duration of the extinction component of a multiple schedule as any other operant, food deprived rats were exposed to a 60-s random time food schedule and concurrently to mixed and multiple water-reinforcement schedules. On both schedules, reinforcement components lasted 32 s and rats lever-pressed for water on a 6-s random interval schedule. Extinction components lasted either 16 or 256 s, for each three rats. During the multiple schedule an operant discrimination was formed when the extinction component lasted 256 s, but not when it lasted 16 s. This result show that SID can be subjected to an operant discrimination and that such discrimination follows the principle of relative time.

Objective: To develop a computerized task Stroop type to evaluate attentional biases towards food and shape words with bulimia nervosa patients. We developed four larger, homogeneous valenced- negative and positive word lists, describing food and body shape. Method: Thirty two women with bulimia nervosa matched to 32-control women, answered original and modified attention Stroop Tests in a computerized version. Results: Bulimia nervosa patients were slower than controls to name body shape color words, as positive as negative valence, and committed more errors on positive- valenced- body shape word list. Discussion: This study confirms the existence of attentional biases, specific for shape word-related in bulimia nervosa patients, and the highest utility in the adapted version of the Stroop Test related to the typical version for the diagnosis of these populations.

Some evidence suggests that conditioning history may affect the temporal control acquisition on Fixed Interval Schedules. To further evaluate this possibility, reinforcement frequency during conditioning history was varied. Four groups of rats were initially submitted to different Variable Interval schedules, with mean values of 20, 60, 60 and 180-s. Afterwards, rats were submitted to Fixed Interval Schedules of 30 and 90-s, resulting in groups of rats experiencing increments or decrements in frequency of reinforcement, as compared with the obtained frequency during the conditioning history. No effects were observed between groups of comparable FI values in three measures of temporal control: post reinforcement pause, quarter life or response pattern. Findings are discussed in the context of temporal control acquisition and the quantitative representation of acquisition.

The purpose was to analyze the kind of writing mistakes that are modified by the “Classwide Peer Tutoring” (CWPT) program. Two second grade elementary school groups participated and were evaluated weekly with a dictation of 20 words in which the number of correct answers and the mistakes according to the Academic Execution Inventory (IDEA) were measured. The results were that all rule mistakes were reduced while only some specific mistakes were decreased. In addition a difference in the size of the mistakes reduction between both groups was found. The results are discussed in terms of the program’s goals and their relationship to the previous literature.

A Stroop discriminative test was built to assess interference produced by words associated to tobacco use among teenagers. In the first phase of the study 473 junior high school students, men and women, wrote positive and negative words related to smoking or to tobacco, and neutral words not associated to the subject. Fifteen of the most frequent positive, negative and associated words were selected to create pairs with neutral words equal in length and frequency of use. Three versions of the computerized smoking risk Stroop test were built based upon selected dyads, by varying the order of the blocks. In the second phase of the study, 164 junior high school students, men and women, were exposed to the discriminative task, in which they had to press the number identifying the color in which the word was written on the screen. Order of the blocks did not affect interference indexes. Negative interferences correlated significantly with associated neutral words interference, but not with positive interference. It is concluded that the Stroop test for smoking risk assesses attentional bias related to smoking and to tobacco among adolescents, and that either order of block is equivalent for practical use.

Steady-state performance under both, Fixed-ratio and Fixed-interval reinforcement schedules generate a similar response pattern: a period with few or no responses, called postreinforcement pause (PRP), proportional to the interreinforcement interval (IRI). Because of this relationship, the IRI was considered as the determinant of the PRP, but the possibility exists that work time or delay to reinforcer are also involved. However, these variables are usually correlated, thus difficulting the evaluation of their relative contribution on the determination of the pause. To partially solve this problem, in the present experiment the contribution of the IRI and the reinforcer delay on the size of the pause was evaluated with a yoked procedure using Chained FR1-FTx and Conjunctive FR1-FTx reinforcement schedules. Results indicated that both IRI and delay to reinforcer were good predictors of the PRP value in steady state, and that the PRP in the Conjunctive schedule was temporally determined.

It is known that the 5-HT2C receptors are involved in the regulation of food intake. Nevertheless, the relative role of selective and nonselective 5-HT2C receptor antagonists in the control of feeding behavior remains uncertain. In the present study, we examined the effects of serotonin (5-HT) on the feeding behavior patterns of rats pretreated with RS-102221 (5-HT2C receptor selective antagonist) or cyproheptadine (5-HT2C/2A receptor antagonist). The drugs were injected into the paraventricular hypothalamus nucleus (PVN). The animals were maintained in a self-selection feeding paradigm and provided with freely available and separate sources of protein, carbohydrate, fat, and water. The rats were kept at 21 ± 1°C on a 12 h light and 12 h dark cycle. Our results indicate that more selective 5-HT2C antagonists induce a major blockade of the hypophagic effect produced by 5-HT in the PVN. Both, selective and nonselective 5-HT2C receptors have shown participation in feeding behavior, mainly in the expression of satiation.

Breast cancer prevalence in many developing nations such as those in Latin America continues to grow at a pace that deserves serious attention, since cancer accounts for high morbidity and mortality rates among relatively young women (LaVecchia & Bosetti, 2005). From a clinical standpoint, breast cancer patients suffer not only from the symptoms of cancer itself but from side-effects of invasive treatments (Burish, Shartner & Lyles, 1981; Donovan, Small, Andrykowski, Munster & Jacobsen, 2007; Falleti, Sanfilippo, Maruff, Weih, & Phillips, 2005). In addition to dealing with distress, the home-care component of breast cancer treatment demands complex routines and behaviors which patients with little or no schooling and other socioeconomic disadvantages have serious difficulty implementing. The purpose of the present study was to field test a behavioral self recording procedure with the first six patients who completed treatment, and to probe preliminary effects of a behavioral intervention to support healthcare and reduce distress. Results point toward a reliable, low-cost and practical recording system; as well as improvement in most behavioral and emotional categories for practically all participants.

The role of the stimulus correlated with extinction (S-) in observing-response procedures has been ambiguous. Although the S- is associated with extinction, some studies demonstrated that it effectively sustained observing behavior. To explore the conditions responsible for the S- to function as a conditioned reinforcer, the present experiment showed whether observing responses during an extinction component are controlled by the temporal contiguity between S- presentation and the reinforcement component. Presses on one lever were reinforced on a mixed schedule of reinforcement random-interval extinction. Pressing a second lever resulted in 5-s stimuli correlated with the components of the mixed schedule. For one group of three rats after observing responses were established, a no-consequence interval (NCI) was added between the end of the extinction component and the beginning of the reinforcement component. For other three rats the NCI was added between the end of the reinforcement component and the beginning of the extinction component. Observing responses during the extinction component decreased only when the NCI was added at the end of the extinction component. It was concluded that although the S- is nominally correlated with extinction it may function as a conditioned reinforcer because it is intermittently paired with the reinforcement component.

The present study systematically assessed the effects of two independent variables on response acquisition, delay duration and the number of sessions of non-contingent food delivery. Sixty naïve, male Wistar rats were exposed to an FT 60-s schedule for a different number of sessions (0, 1, 5, 15 or 30). Once exposure to non-contingent food delivery was over, subjects were exposed to one of four different Tandem FR 1, FT x-s schedule, for 10 sessions, where FT duration could be programmed at 10, 20, 40 or 60-s. Results showed evidence of response acquisition was more apparent in those groups where subjects were exposed to 1, 5 or 15 sessions of non-contingent food delivery; response acquisition was less evident in those groups exposed to 0 or 30 sessions of the FT 60-s schedule. In general, obtained reinforcement rate decreased as delay duration increased. Results were discussed in terms of how history effects may make it difficult to compare experimental findings; the discussion also centered on variables that could probably explain why reinforcement history affects response acquisition with delayed reinforcement.