条件性味觉厌恶分化后臂旁核c-fos表达的变

以口内注入糖精或蔗糖溶液为条件刺激,腹腔内注射LiCl为非条件刺激,在大鼠形成条件性味觉厌恶后进行分化训练,观察味质和嗜好性对臂旁核各亚核c-fos表达的影响及其交互作用。结果表明：味质和嗜好性对背侧外侧亚核(dls)和腹侧外侧亚核(vls)的c-fos表达无影响;在内侧外侧亚核(ils)和外部内侧亚核(ems),蔗糖诱导的c-fos表达高于糖精,但在外部外侧亚核(els),糖精诱导的表达高于蔗糖;嗜好性刺激引起ils、中央外侧亚核(cls)和cms内c-fos高表达,厌恶性刺激引起ems和els内的高表达。在ils和cms嗜好性与味质的影响各自独立,在els和ems内嗜好性与味质的影响存在交互作用。提示PBN内存在味质辨别和报酬评价的代表区,两种代表区有交迭,ems和els对味质信息和报酬信息的整合有重要作用     

Reversal of Long-Delay Conditioned Taste Aversion Learning in Rats by Sex Hormone Manipulation

Conditioned taste aversion (CTA) learning is an adaptive, robust, well-established learning and memory paradigm. Strong taste aversions develop to the conditioned stimulus (CS = saccharin) despite long delays between exposure to the CS and unconditioned stimulus (US = LiCl). Rats display a sexually dimorphic pattern of long-delay CTA learning (Foy et al., 1996). The present study examines whether this sex difference is a result of activational or organizational hormone action, because here we implanted gonadectomized rats with their normal hormone replacements, or with opposing hormones prior to testing in a 4-hr delayed CTA learning task. We found that gonadally intact male rats displayed a more robust CTA response than intact female rats. Gonadectomy essentially eliminated this sex difference; gonadectomized males and gonadectomized females displayed similar CTA responses. In gonadectomized rats, when their normal sex hormones were replaced with implanted hormone pellets, the sex difference in CTA learning was reinstated. In contrast, when gonadectomized rats were implanted with opposing hormones, the sex difference was reversed. Gonadectomized female rats implanted with 5alpha-DHT pellets (metabolite of testosterone) displayed a stronger CTA response compared to gonadectomized males implanted with 17beta-estradiol pellets. Regardless of the original developmental hormonal environment, our study suggests that an activational manipulation of circulating hormones serves to significantly influence long-delay CTA learning in rats.     

味觉厌恶性条件反射建立后脑内c-Fos的表达

以新异味觉刺激糖精水的摄入为条件刺激,以腹腔注射环磷酰胺(CY,免疫抑制剂)或氯化锂(LiCl)为非条件刺激,分别使大鼠建立味觉厌恶性条件反射.在条件刺激日,糖精水在学习组大鼠下列脑区中诱发出密集的Fos表达下丘脑、杏仁核、边缘皮质等,而非学习组在这些区域中却没有或只有少量表达.另外,在丘脑前背侧核、扣带回、下丘脑外侧核、穹隆下器、压部后颗粒皮质、视上核,CY组的Fos表达明显多于LiCl组;而在伏核、杏仁基底外侧核、腹外侧隔核,LiCl组的Fos表达明显多于CY组,这种差异可能是两种药物的不同药理性质所致.     

Conditioned Inhibition of Cyclophosphamide-Induced Taste Aversion

Rats in an experimental group received trials during which 1 flavor (saccharin) was always followed by cyclophosphamide, an immunosuppressive drug, but another (vanilla) was not. An unconditioned stimulus-only group served as a control. Flavor-preference tests revealed that conditioned excitation and conditioned inhibition occurred in the conditioned group subjects but not in the control group subjects. This demonstration suggests that a conditioned inhibitor might be used to modify conditioned and unconditioned immune system functions, for example, natural killer-cell activity.     

Failure of Retrospective Inference in Rats' Taste Aversion

Three experiments explored the possibility of retrospective inference in the rat. Experiment 1 revealed that poisoning of an element of a taste compound after single compound poisoning enhanced aversion to the other element, and that presentation of an element without poison after the compound poisoning reduced aversion to the other element. These results were opposite to those predicted by retrospective inference. Experiment 2 eliminated some confounding variables and examined the effect of element poisoning after compound poisoning. The result again was opposite to what the retrospective view predicts. The results, however, accorded with the idea that within-compound learning was established during compound presentation, and subsequent poisoning or nonpoisoning of one element affected response to the other element via the within-compound learning. In Experiment 3, the possibility of within-compound learning was reduced by using sequential presentation of tastes, but there was no indication of retrospective inference even under this condition.     

Contextual Control of Running-Based Taste Aversion in Tats

The Psychological Record - The present study explored the contextual control of running-based taste aversion in rats by giving rats a salty solution in Context A followed by wheel running and the...     

Effects of Cerebroventricle Administration of Acidic Fibroblast Growth Factor on Conditioned Taste Aversion Learning in Rats

Wistar strain rats were given acidic fibroblast growth factor (aFGF) or denatured aFGF into their cerebroventricle before taste aversion conditioning for saccharin solution. Animals administrated with aFGF showed significantly lower aversion threshold for saccharin at the 1st day and preference ratios for saccharin vs distilled water at the 4th, 6th, and 7th day after the conditioning than those administered with denatured aFGF. These results suggests that aFGF in the cerebrospinal fluid facilitates acquisition of the conditioned taste aversion learning.     

Does Conspecific Fighting Yield Conditioned Taste Aversion in Rats?

Running in an activity wheel yields conditioned aversion to a taste solution consumed before the running, but its underlying physiological mechanism is unknown. According to the claim that energy expenditure or general stress caused by physical exercise is a critical factor for this taste-aversion learning, not only running but also other stressful exercises should yield conditioned aversion to the paired taste. This prediction was disconfirmed in two experiments, because stressful conspecific fighting did not work as an effective agent to establish taste aversion in rats.

     

Facilitation of Sodium Aversion Learning in Sodium-Deprived Rats

Two experiments with rats explored the effects of sodium deprivation induced by furosemide injections upon acquisition of taste aversion to sodium chloride (NaCl). In Experiment 1, rats under either sodium deprivation or a balanced nutrition condition were given access to a limited amount of NaCl solution prior to poisoning. When all rats were tested under sodium repletion, the previously sodium-deprived rats consumed less NaCl than did the nondeprived rats. This finding was replicated in Experiment 2A in which ingestion of a compound solution of NaCl and hydrochloric acid (HCl) was followed by poisoning. Consumption of HCl, however, showed the opposite pattern: the sodium-deprived rats drank more HCl than did the nondeprived rats, a result that was replicated in Experiment 2B. These results suggest that sodium deprivation strengthens the salience of NaCl, thereby facilitating acquisition of aversion to this taste and strongly overshadowing that to a simultaneously presented taste.     

Taste Aversion Learning Based on Swimming and Lithium Chloride Injection in Rats: Implications From Cross-familiarization Tests and Stimulus Selectivity1

In rats, swimming causes avoidance of the taste solution consumed immediately before the swimming. Several lines of research have shown that this taste avoidance reflects Pavlovian conditioned aversion based on correlations between the taste and swimming-induced nausea. The present research compared swimming-based taste aversion learning (TAL) with conventional TAL based on nausea-inducing lithium chloride (LiCl). By exploiting cross-familiarization techniques, Experiments 1A and 1B suggested that different physiological states are induced by swimming and LiCl. This claim was supported by Experiment 2, which reports stimulus selectivity in saccharin and sucrose aversions based on swimming and LiCl.     

Facilitation and Retardation of Flavour Aversion Conditioning Following prior Exposure to the CS

Two sets of experiments on flavour aversion conditioning in rats examined the effects of the following factors: the nature of the flavour serving as the conditioned stimulus (CS), which was either a compound of monsodium glutamate, sucrose and quinine, or an elemental flavour, either sucrose or dilute acid; the amount of the CS rats consumed on a single conditioning trial-4 ml or 1 ml; and whether rats had been pre-exposed to the CS before this conditioning trial. There were three main findings. First, conditioning to an elemental CS was unaffected by the amount consumed on the conditioning trial, but conditioning to 1 ml of the compound CS was poorer than to 4 ml. Second, pre-exposure produced a latent inhibition effect if the CS was an elemental flavour, or if rats were allowed to drink 4 ml of the compound solution on their conditioning trial. But, third, pre-exposure facilitated conditioning in rats given only 1 ml of the compound solution as their CS.     

Augmentation: Synergistic Conditioning in Taste-Aversion Learning

Recent work in taste-aversion learning has revealed a new phenomenon in classical conditioning. When a preconditioned gustatory cue (taste or odor) is conditioned in compound with a second gustatory cue, conditioning to the second cue is augmented. This enhanced conditioning of the second cue is noteworthy because studies with other forms of classical conditioning have shown blocked conditioning to the second cue. This new phenomenon has been termed augmentation , and it has implications for the study of taste and odor interactions, formal models of learning, and clinical interventions with cancer patients.     

Rapid, Labile, and Protein Synthesis– Independent Short-Term Memory in Conditioned Taste Aversion

Short-term memory is a rapid, labile, and protein-synthesis-independent phase of memory. The existence of short-term memory in conditioned taste aversion (CTA) learning has not been demonstrated formally. To determine the earliest time at which a CTA is expressed, we measured intraoral intake of sucrose at 15 min, 1 hr, 6 hr, or 48 h after contingent pairing of an intraoral infusion of 5% sucrose (6.6 ml over 6 min) and toxic lithium chloride injection (76 mg/kg). Rats were implanted with intraoral catheters to allow presentation of taste solutions at arbitrary times. Intraoral intake was measured under conditions of long-delay, single-trial learning typical of CTA. Rats decreased intraoral intake of sucrose at 15 min after contingent pairing of sucrose and LiCl, but not after noncontingent LiCl or sucrose. Thus CTA learning can be expressed rapidly. To determine if short-term CTA memory is labile and decays in the absence of long-term memory, we measured intraoral intake of sucrose after pairing sucrose with low doses of LiCl. Rats received an intraoral infusion of 5% sucrose (6 ml/6 min); 30 min later LiCl was injected at three different doses (19, 38, or 76 mg/kg). A second intraoral infusion of sucrose was administered 15 min, 1 hr, 3 hr, 4.5 hr, 6 hr, or 48 hr later. The formation of long-term CTA memory was dependent on the dose of LiCl paired with sucrose during acquisition. Low doses of LiCl induced a CTA that decayed within 6 hr after pairing. Central administration of the protein synthesis inhibitor cycloheximide prior to LiCl injection blocked long-term CTA expression at 6 and 48 hr, but not short-term CTA expression at 1 hr. Thus, short-term memory for CTA learning exists that is acquired rapidly and independent of protein synthesis, but labile in the absence of long-term memory formation.     

The Role of Mediated Conditioning in Acquired Equivalence

In Experiment 1 rats received initial training in which delivery of a sucrose pellet was signalled by an auditory cue. This cue was then paired with shock in a second phase of training. In a test the rats showed an unwillingness to perform an instrumental response that yielded the sucrose pellet. This was interpreted as indicating that the associatively activated representation of the pellet had acquired aversive properties during the shock-reinforced stage of training. Experiment 2 replicated this mediated conditioning effect making use of a Phase 1 training procedure, modelled on that used by Honey and Hall (1989) to demonstrate acquired equivalence of cues, in which two auditory cues were each used to signal sucrose pellets. A further test revealed that this training resulted in enhanced generalization between these two cues. It was argued that this effect is mediated by the conditioned aversive properties of the common associate of the two auditory cues.     

条件联结觉察在评价性条件反射中的作用

评价性条件反射(Evaluative Conditioning, EC)指通过将一个中性刺激和一个情绪性刺激重复配对, 使中性刺激获得情绪性刺激的情感性评价。条件联结觉察(Contingency Awareness)指被试觉察到中性刺激和情绪性刺激的配对规律。当前, 条件联结觉察在EC中的作用尚存争议。一些研究证明, 条件联结觉察独立于EC, 甚至阻碍了EC; 另一些研究则表明, 条件联结觉察促进EC的发生; 还有些研究发现条件联结觉察在EC中的作用受其他变量的调节。因此, 在将来的研究中, 需发展出更准确的觉察测量、检验其他变量的调节作用、加强多感觉通道的EC研究、探索EC的加工机制。     

A Role for the Human Amygdala in Recognizing Emotional Arousal From Unpleasant Stimuli

Functional neuroimaging and lesion-based neuropsychological experiments have demonstrated the human amygdala's role in recognition of certain emotions signaled by sensory stimuli, notably, fear and anger in facial expressions. We examined recognition of two emotional dimensions, arousal and valence, in a rare subject with complete, bilateral damage restricted to the amygdala. Recognition of emotional arousal was impaired for facial expressions, words, and sentences that depicted unpleasant emotions, especially in regard to fear and anger. However, recognition of emotional valence was normal. The findings suggest that the amygdala plays a critical role in knowledge concerning the arousal of negative emotions, a function that may explain the impaired recognition of fear and anger in patients with bilateral amygdala damage, and one that is consistent with the amygdala's role in processing stimuli related to threat and danger.     

Lesions in the Central Nucleus of the Amygdala: Discriminative Avoidance Learning, Discriminative Approach Learning, and Cingulothalamic Training-Induced Neuronal Activity

The amygdala is critically involved in discriminative avoidance learning. Large lesions of the amygdala block discriminative avoidance learning and abolish cingulothalamic training-induced neuronal activity. These results indicated that amygdalar processing is critical for cingulothalamic plasticity. The larger lesions did not allow differentiation of the specific functioning of various amygdalar nuclei. Anatomical analysis showed that damage in the central (CE) nucleus of the amygdala was correlated with the severity of the behavioral deficit. The present study was carried out to determine whether smaller lesions, centered in the CE nucleus, would impair discriminative avoidance learning and block cingulothalamic plasticity. In addition, the possible role of the CE nucleus in appetitively motivated discriminative approach learning was examined for the first time. New Zealand White rabbits with CE nuclear lesions were first trained in the discriminative approach task. After attaining asymptotic performance, discriminative avoidance training sessions were alternated with continuing approach training sessions, one session each day. The rabbits with lesions were severely impaired in avoidance learning but showed no impairment of approach learning. Surprisingly, the attenuating effects of the lesions on cingulothalamic training-induced neuronal activity were more prevalent during approach learning than during avoidance learning. These results indicated that avoidance learning can be impaired by lesions centered in the CE nucleus that leave cingulothalamic plasticity largely intact and that the CE nucleus is involved in extra-cingulothalamic learning processes.