5HT antagonists attenuate MK801-impaired radial arm maze performance in rats

Glutamatergic hypofunction occurs in Alzheimer's disease (AD). MK801, a noncompetitive blocker of glutamate N-methyl-D-aspartate receptors, was used to disrupt the cognitive performance of rats trained on a delayed nonmatching to sample radial maze task. Drugs which act by blocking serotonin (5-HT) receptors were evaluated for their ability to reduce the cognitive impairment produced by MK801. Specifically, WAY-100635, a selective 5-HT1A receptor antagonist, buspirone, a 5-HT1A partial agonist, ritanserin, a 5-HT2 antagonist, and ondansetron, a 5-HT3 antagonist, were assessed. In addition, the muscarinic agonist arecoline was evaluated for its potential cognitive benefit in this model. It was found that WAY-100635 significantly reduced the cognitive impairment induced by MK801. Treatment with single doses of ritanserin, ondansetron, or arecoline in combination with MK801 did not result in a cognitive impairment, indicating that these drugs attenuated the MK801 impairment. The combination of buspirone and MK801 resulted in an inability of the animals to complete the task. These results suggest that interactions between 5-HT and glutamate may mediate the beneficial effects of reducing cognitive impairment and that 5-HT antagonists, especially selective 5-HT1A antagonists, may be useful in treating AD. Further, it is indicated that the MK801 model of cognitive impairment may add to the armamentarium of tools available to predict treatment efficacy in AD.     

MK-801与环境线索交互作用对吗啡行为敏感化的影响

为探讨MK-801与环境线索交互作用对吗啡诱导行为敏感化的影响,将42只大鼠随机分为对照组,MK-801组,吗啡组（匹配和非匹配）和MK-801+吗啡组（匹配和非匹配）。行为敏感化模型建立分为发展期,戒断期和表达期三个阶段。实验结果发现：同时给予MK-801（0.1mg·kg-1）会促进吗啡（5mg·kg-1）诱导大鼠行为敏感化的发展,而且会使MK-801成为大鼠行为敏感化表达所必需的条件性刺激。MK-801的内部线索作用过强,从而削弱了环境的外部线索作用。研究结果表明：MK-801对吗啡诱导行为敏感化的影响存在状态依赖（state-dependency）现象,提示在NMDA受体与行为敏感化关系的研究中应考虑选择刺激特性更小的药物     

Effects of olfactory bulbectomy on social behavior of male guinea pigs (Cavia procellus)

Effects of olfactory bulbectomy on social behavior in male guinea pigs were studied. Both brief-exposure pairing techniques and a group-living observation period were employed to test for disruption. During short-term testing sessions bulbectomized animals courted females less than but mounted them as frequently as control subjects. While the groups did not differ in fighting behavior during short-term tests, control subjects scent-marked more frequently. Subsequently, animals were observed as same-treatment pairs living continuously with females, and behavior was sampled over a 3-wk period. Under these conditions bulbectomized males, unlike controls, failed to form dominance orders, exhibited virtually no intermale aggressive activity, had markedly depressed sexual activity, and scent-marked rarely. It is concluded that olfactory bulbectomy profoundly alters the behavior of male domestic guinea pigs and that hose alterations are most evident when experimental subjects are observed in a species-typical group-living environment.     

Identity matching-to-sample with olfactory stimuli in rats

Identity matching-to-sample has been difficult to demonstrate in rats, but most studies have used visual stimuli. There is evidence that rats can acquire complex forms of olfactory stimulus control, and the present study explored the possibility that identity matching might be facilitated in rats if olfactory stimuli were used. Four rats were trained on an identity match-to-sample procedure with odorants mixed in cups of sand as stimuli. Digging in the sample cup produced two comparison cups, and digging in the comparison cup that contained the same scent as the sample was reinforced. When criterion accuracy levels were reached, novel stimuli were added to the baseline training regimen. All 4 rats reached terminal performance of above 90% correct matching with more than 20 different baseline stimuli and matched novel stimulus combinations with above-chance accuracy; 3 of the 4 rats matched novel stimuli at levels significantly above chance. Accurate matching performance was demonstrated both with 2- and 3-comparison procedures. These results suggest that generalized matching-to-sample can be observed in rats when olfactory stimuli are used and, furthermore, that multiple-exemplar training may be important for its emergence.     

Effects of spatial food distribution on search behavior in rats (Rattus norvegicus)

To analyze how search strategies are adapted according to the geometric distribution of food sources, the authors submitted rats to a search task in which they had to explore 9 food trays in an open field and avoid visiting already-depleted trays. Trays were spatially arranged in 4 independent configurations: a cross, a 3 x 3 matrix, 3 clusters of 3 trays each, and a random configuration. Rats exhibited differential search efficiency as a specific effect of the susceptibility of the configurations to being explored in a principled way: crosses were first, matrices or clusters were in the middle, and random configurations were last. Although no exhaustive searches or highly principled patterns were observed in any of the configurations, performances improved as the sessions went by. Thus, structural affordances of the environment influence the construction not only of search strategies but also of information linked to where the reward is.     

Effects of subchronic administration of gammahydroxybutyrate (GHB) on spatial working memory in rats

GHB, a popularly known drug as "liquid ecstasy", is a substance with abuse potential. Among the possible described side-effects after the continued consumption of GHB are amnesia and deterioration of memory. Likewise, recent studies indicate the existence of neurotoxicity in certain brain regions after its prolonged treatment. The aim of this study was to examine the effect of the subchronic administration of GHB (10 and 100 mg/kg) on spatial memory and sensoriomotor reflexes in male rats, using the Morris water maze and a battery of sensoriomotor tests, respectively. The results indicated that animals treated with GHB (10 mg/kg) showed a greater latency of escape during the phase of acquisition in the days first and third of tests, as compared with the control group (p<0.05), as well as a deterioration of grasping reflex with the two doses of GHB (p<0.01). Numerous studies indicated that the medial prefrontal cortex is a crucial neuronal substrate in the working memory and grasping reflex modulation. These results suggest that prolonged administration of GHB could alter structure and/or function of the medial prefrontal cortex, as well as its interconnections with other brain regions involved in the evaluated cognitive and neurological processes.     

Effects of reading span and textual coherence on rapid-sequential reading

Subjects’ Comprehension and Memory of Conventional Presentations (Pages) And Rapid, Serial Visual Presentations (Rsvps) Of Text Were Investigated With A Statement-Recognition Test. Texts Were Presented With Sentences in An Intact Or A Scrambled Order At Rates Of 300 And 600 Words Per Minute (Wpm). Subjects’ Memory for Text Meaning And Surface Structure Was Better In 300-Than In 600-Wpm Conditions, And Subjects Retained More Textual Meaning From Coherent than Incoherent Texts Regardless of Display Rates. These Findings Are Inconsistent With the Idea That Rapid Reading Disrupts the Intersentence Integration Processes of Comprehension, but are Consistent With The Hypothesis of Consolidation Limitation: Furthermore, Subjects Were Separated Into Two Groups Based on Their Performance on the Reading Span Test of Daneman And Carpenter (1980). Low-Span Subjects Retained Significantly Less Text Meaning than High-Span Subjects with Pages, But They Did Almost As Well With RSVPs. This Interaction Suggests that the RSVP Technique Could Be Useful For Improving the Reading Abilities of Less Efficient Readers.     

Interspecific aggression and reactivity in rats: Effects of selective raphe lesions and additional olfactory bulb ablation

Large depletion of brain 5 HT has been shown to induce mouse-killing behavior in the rat. Selective lesions of the raphe nuclei have been investigated in order to determine whether the various components of the 5 HT system exert some specific control over this aggressive behavior. Electrolytic lesions of the dorsal or the median raphe nucleus do not induce mouse killing, whereas combined lesions of these nuclei elicit this behavior in about 40% of naive rats. Consequently, it appears that serotonergic neurons originating in the dorsal and median raphe nuclei work synergistically in mediating inhibitory control over mouse-killing behavior. Loco-motor activity is increased in novel environments by each of the selective lesions and to a larger extent by combined raphe lesions; 24 hours activity in resting conditions is unchanged during the light period, and increased during the dark period of the daily cycle by the various lesions. As it has been shown previously that hyper-activity in response to novelty following raphe lesions is not directly related to the 5 HT decrease in the brain, it appears that interspecific aggression and motor responsiveness must not be dependent on the same neural substrate within the raphe nuclei. The raphe lesions do not facilitate the elicitation of mouse killing by further olfactory bulb ablations, in contrast to earlier results where bulbectomy facilitated the induction of this behavior by raphe lesions.     

Effects of anesthetic agents on socially transmitted olfactory memories in mice

Mice can learn a food preference from odor cues transmitted on the breath of a conspecific, even if the “demonstrator” is anesthetized. To our knowledge there are no studies examining the effect of anesthetizing the “observer” on development of memory for socially transmitted food preferences (STFP). In Experiment 1 we found that 2–4 month-old F2 C57Bl/6x129sv male and female mice demonstrated a STFP after a 5 min exposure to an anesthetized demonstrator mouse when tested 24 h later. In Experiment 2, observer mice anesthetized with Sagatal (60 mg/kg) prior to the “social interaction” preferentially avoided the cued food when tested 24 h later. This aversion was not due to any overt aversive effects of this dose of Sagatal because mice that ate the food and were then anesthetized, or could only smell the food for 5 min while anesthetized, showed no preference or aversion. In a third experiment we found that the Sagatal-induced aversion was not a general property of anesthesia because there were varied results produced by observer mice treated with anesthetic drugs with different mechanisms of action. Vetalar (200 mg/kg) and Rompun (10 mg/kg) treated animals ate similar amounts of cued and non-cued food at test, indicating an absence of learning. Hypnorm (0.5 ml/kg) treated animals showed a preference for the cued food whereas those treated with Hypnovel (2.5 ml/kg) showed an aversion to the cued food. These results show that the food aversion observed with Sagatal is not a general property of anesthetic agents, but appears to be restricted to those acting primarily on the GABAergic system. Thus, we have shown that under certain conditions it is possible for an anesthetized observer mouse to learn a preference or aversion of a socially-linked olfactory cue.     

Effects of lexical competition on immediate memory span for spoken words

Current theories and models of the structural organization of verbal short-term memory are primarily based on evidence obtained from manipulations of features inherent in the short-term traces of the presented stimuli, such as phonological similarity. In the present study, we investigated whether properties of the stimuli that are not inherent in the short-term traces of spoken words would affect performance in an immediate memory span task. We studied the lexical neighbourhood properties of the stimulus items, which are based on the structure and organization of words in the mental lexicon. The experiments manipulated lexical competition by varying the phonological neighbourhood structure (i.e., neighbourhood density and neighbourhood frequency) of the words on a test list while controlling for word frequency and intra-set phonological similarity (family size). Immediate memory span for spoken words was measured under repeated and nonrepeated sampling procedures. The results demonstrated that lexical competition only emerged when a nonrepeated sampling procedure was used and the participants had to access new words from their lexicons. These findings were not dependent on individual differences in short-term memory capacity. Additional results showed that the lexical competition effects did not interact with proactive interference. Analyses of error patterns indicated that item-type errors, but not positional errors, were influenced by the lexical attributes of the stimulus items. These results complement and extend previous findings that have argued for separate contributions of long-term knowledge and short-term memory rehearsal processes in immediate verbal serial recall tasks.     

Effects of poisoning on predatory and ingestive behavior toward artificial prey in rats (Rattus norvegicus)

Ingestion of novel prey by vertebrate predators that is followed by illness typically decreases the predators' eating the prey more readily than their pursuing or killing it. We used artificial prey-food items (rolling ball bearings that predicted food pellets) to model and extend this finding in laboratory rats. During daily experimental sessions presentations of a novel bearing-food combination were intermixed with presentations of a familiar bearing-food combination. The poisoned animals received lithium chloride injections after each session. Experiment 1a showed that: (a) Poisoning markedly decreased ingestion of the novel food without decreasing the frequency of contact (nose, seize, carry, or chew) with the novel bearing predicting that food. (b) However, poisoning did significantly decrease the average duration of contact with the novel bearing. (c) Poisoning did not decrease behavior toward the familiar food and bearing. Experiment 1b showed that after moderate exposure to pairings of the novel food and bearing, poisoning decreased behavior toward both novel and familiar food and bearings. The results indicate that important aspects of predation can be simulated and examined in the laboratory by using artificial prey-food items. These results also support the conclusions that predatory behavior and ingestion reflect separable modes of behavior and that the presence of novel prey interferes with the generalization of poisoning effects to familiar prey.     

Effects of word frequency and age of acquisition on short-term memory span

The experiments reported examine the effects of two highly related variables, word frequency and age of acquisition, on short-term memory span. Short-term memory span and speech rate were measured for sets of words which independently manipulated frequency and age of acquisition. It was found that frequency had a considerable effect on short-term memory span, which was not mediated by speech rate differences—although frequency did affect speech rate in one experiment. For age of acquisition, this situation was reversed; there was a small but significant effect of age of acquisition on speech rate, but no effect on memory span. This occurred despite results confirming that the stimuli used in the experiments produce an effect of age of acquisition on word naming. The results are discussed in terms of a two-component view of performance on short-term memory tasks.     

Matching- and nonmatching-to-sample concept learning in rats using olfactory stimuli

Previous research has shown that rats can learn matching-to-sample relations with olfactory stimuli; however, the specific characteristics of this relational control are unclear. In Experiment 1, 6 rats were trained to either match or nonmatch to sample in a modified operant chamber using common household spices as olfactory stimuli. After matching or nonmatching training with 10 exemplars, the contingencies were reversed with five new stimuli such that subjects trained on matching were shifted to nonmatching and vice versa. Following these reversed contingencies, the effects of the original training persisted for many trials with new exemplars. In Experiment 2, 9 rats were trained with matching procedures in an arena that provided for 18 different spatial locations for comparison stimuli. Five subjects were trained with differential reinforcement outcomes and 4 with only one type of reinforcer. Differential outcomes and multiple exemplars facilitated learning, and there was strong evidence for generalization to new stimuli for most rats that acquired several conditional discriminations. Performances with novel samples were generally above chance, but rarely reached the high levels obtained during baseline with well-trained stimulus relations. However, taken together, the data from the two experiments extend previous work, show that rats can learn both match and nonmatch relations with different experimental protocols, and demonstrate generalization to novel sample stimuli.     

An investigation on the olfactory capabilities of domestic dogs (Canis lupus familiaris)

Animal Cognition - The extraordinary olfactory capabilities in detection and rescue dogs are well-known. However, the olfactory performance varies by breed and search environment (Jezierski...