Reinforcement omission effects in rats with bilateral lesions in the substantia nigra pars compacta and ventral tegmental area

Reinforcement omission effects (ROEs) are characterized by higher response rates after reinforcement omission than after reinforcement delivery. This pattern of behavior is interpreted in terms of motivational and attentional processes. Recent studies from our laboratory have shown that the amygdala, nucleus accumbens, and medial prefrontal cortex are involved in ROE modulation. Also, the literature has demonstrated a role of other areas such as substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) in processes related to surprising events, such as prediction error and presentation or omission of an event (exteroceptive stimulus and reinforcement). Since these structures send projections to areas related to ROE modulation such as the amygdala, nucleus accumbens, and prefrontal cortex, the objective of the present study was to determine whether the SNc and VTA also integrate the circuit involved in ROE modulation. Rats were trained on a fixed-interval 12 s with limited-hold 6 s signaled schedule of reinforcement (Pre-lesion training). After acquisition of stable performance, the rats received bilateral neurotoxic lesions of the SNc (Experiment 1) and VTA (Experiment 2). Following postoperative recovery, the rats were submitted to two refresher sessions (Post-lesion training). Subsequently, the training was changed from a 100 to a 50% schedule of reinforcement (Post-lesion testing). In both experiments, the results showed that there was no difference in performance between sham rats and rats with bilateral lesions of the SNc or the VTA.

Renovación contextual de la distribución temporal del responder / Contextual Renewal of Temporal Patterns of Responding

Resumen Se ha reportado que en ciertos fenómenos (recuperación espontánea, readquisición, resurgencia y renovación contextual) es posible observar la recuperación de una respuesta previamente extinguida. La renovación contextual, se refiere a la reaparición de una respuesta extinguida que resulta de un cambio de contexto entre la fase de extinción y prueba. El propósito del presente trabajo consistió en evaluar la renovación contextual, atendiendo tanto a la distribución temporal del responder, como a la tasa de respuesta. Se encontró una recuperación de la tasa de respuesta, siendo un resultado consistente con los reportados en el área de renovación contextual. Además, se pudo identificar una renovación de la distribución temporal de respuesta. Los resultados se discuten reconociendo que la tasa y la distribución temporal constituyen dos dimensiones de la ejecución que son moduladas por los cambios de contexto.

Abstract It has been reported that in certain phenomena (spontaneous recovery, reacquisition, resurgence and contextual renewal) it is possible to observe the recovery of a previously extinguished response. Contextual renewal refers to the reappearance of an extinguished response that result from a change of context between the extinction and testing phase. The purpose of the present study was to evaluate contextual renewal, considering both the temporal distribution of the responses and the response rate. A recovery of the response rate was found, being a result consistent with those reported in the area of ​​contextual renewal. In addition, a renewal of the temporal distribution of the responses could be identified. The results are discussed by recognizing that rate and temporal distribution are two behavioral dimensions that are modulated by contextual changes.

Efeitos da consequência programada sobre a estabilidade da taxa de respostas em esquema F1 / Effects of the scheduled consequence on stability of response rate in F1

Estudos sugerem que a taxa de respostas de humanos em FI pode ser afetada pelo tipo de consequência programada. O objetivo foi verificar se diferentes consequências programadas para humanos respondendo em FI influenciariam o tempo necessário para atingir um critério de estabilidade quantitativo e se a estabilidade se manteria após ter sido atingida. Quinze universitários foram expostos a um FI 30 s por 10 horas (sessões de 30 min) em duas condições com consequências distintas para o responder (pontos vs. pontos trocados por dinheiro). Os resultados sugerem que a consequência programada não é suficiente para influenciar o tempo necessário para atingir o critério de estabilidade, embora pareça afetar a manutenção da estabilidade.

Studies suggest that the response rate of humans under FI may be affected by the type of reinforcer. The purpose of this study was to determine whether the type of scheduled consequence for humans under FI would affect the time required to reach a quantitative stability criterion and whether stability would be maintained after being reached. Fifteen college students were exposed to a FI 30 s for 10hours (30 min sessions) under two conditions with different consequences for responses (points vs. money). The results suggest that the type of reinforcer is not sufficient to affect the time required to reach the stability criterion, although its maintenance seems to be influenced by this variable.

Fixed-interval pause duration in chained fixed-ratio, fixed-interval schedules

Ten rats were submitted to chained fixed-ratio (FR), fixed-interval (FI) schedules of reinforcement. A FR schedule at one lever produced a discriminative stimulus associated with a FI 60-s schedule of primary reinforcement (water) at the second response lever. In Experiment 1, the FI schedule was kept constant while the FR requirement was changed from one to seven responses under five different experimental conditions for five rats. Increases in the FR requirement resulted in increases in post-reinforcement pauses but also decreases in pauses in the FI schedule. Using another five rats, Experiment 2 tested the hypothesis that short pauses in the FI schedule result from the use of the chained schedules procedure. Baseline was a FI 80-s schedule. In the second condition, chained FR 1 FI 80-s schedules were programmed. The third condition was a return to baseline. In baselines 1 and 2, the FI pause was compatible with the literature but decreased considerably when a chained schedule was used. The present results support the hypothesis that the time between primary reinforcement presentations dominates the control of FI pauses over control by the onset of a discriminative stimulus.

Optimization of Hospital Inventory Management of Expensive Drugs / 中国药房

OBJECTIVE:To scientifically establish the variety scope of expensive drugs and to reduce the stock level to a maximum degree under the premise of supply security. METHODS: The variety scope of expensive drugs was established by modified ABC (activity-based costing) analytical method,and the management on expensive drugs was carried out by fixed-quantity system (FQS) together with fixed-interval system (FIS). RESULTS: The practice of the optimized management effectively reduced the stock quantity of expensive drugs,increased the amount of money of 75 stocked drugs to 2.473 7 million yuan from 3.935 7 million yuan;the turnover rate rose from 238.36% to 461.86%,and the turnover days were decreased from 13.03 days to 8.29 days. CONCLUSION: Computer management in combination with the modified ABC analytical method together with FQS and FIS management led to an effective and accurate inventory management of expensive drugs,which then resulted in a speedy turnover rate,decreased fund occupying and lowered drug cost.

Lowering Inventory Cost of Chinese Patent Drugs by Means of Zero-Inventory-Ordering System / 中国药房

OBJECTIVE:To explore an effective,economical drug purchasing mode for hospital drug warehouse.METHODS:The inventory costs and stock turnover rates for the zero-inventory-ordering system and fixed-interval-ordering system once applied in the Chinese patent drug stockroom in our hospital were analyzed using the analytical method of stock turnover rate.RESULTS:The average inventory costs of 2 policies were 155 600 yuan and 103 800 yuan,respectively,and their average stock turnover rates were 199.23% and 301.16%,respectively.CONCLUSION:The zero-inventory-ordering system is more conducive to the reduction of inventory cost of stock drugs.