Facilitation of acquisition and performance of operant and spatial learning tasks in self-stimulation experienced rats.

Adult male Wistar rats were implanted bilaterally with bipolar electrodes in substantia nigra-ventral tegmental area (SN-VTA) to experience intracranial self-stimulation (ICSS) for 15 min per day over a period of 10 days. These rats were then assessed for the acquisition and performance of the operant and the spatial learning tasks. ICSS experienced rats showed rapid acquisition of both the operant and the spatial learning tasks. Both the lever press performance for 7 sessions in the operant learning task and mean number of alternations per session in the spatial learning task were significantly higher (p?     

Effects of 3,3'-iminodipropionitrile on the peripheral structures of the rat visual system

Adult male Long-Evans rats received 3,3'-iminodipropionitrile (IDPN; 400 mg/kg i.p.) and were killed one day after one dose, or one, three, seven, thirty-five, or seventy day(s) following 3 consecutive daily doses for histological analysis of the eye. Histological alterations in visual structures were not observed before one day after the third dose of IDPN. Somato-dendritic swelling of cells in the inner nuclear (IN) layer was seen prior to retinal detachment (1 day after cessation of dosing) followed by progressive retinal degeneration (35 and 70 days). IDPN exposure resulted in opacification of the cornea and vascular hemorrhaging into the subretinal space (3 days) followed by complete detachment of the retina (7 days). The corneal opacification was transient and resolved by 14 days post-treatment. The retina underwent complete spontaneous reattachment between 35 and 70 days after IDPN administration. A subsequent experiment was performed to characterize the dose-response of IDPN on retinal histology, 2 weeks after the last dose (0, 100, 200, 400 mg/kg x 3 days). In the dose-response experiment, retinal detachment and degeneration in the IN layer were only apparent in the 400 mg/kg dose group. However, increased GFAP immunoreactivity in the retina was observed in the 200 mg/kg dose group without overt retinal pathology. Results indicate that the corneal opacification, vascular hemorrhaging, and detached retinae recovered in a time-dependant manner, while neurodegeneration of the visual retina was progressive, even after the retina had reattached. The present study indicates that this toxicant may have direct effects on both neural and non-neural structures, and characterizes the time-course and dose-response of histopathological changes in the retina.     

Effects of ketamine and L-glutamic acid diethyl ester on spatial and nonspatial learning tasks in rats

1. Current concepts in the regulation of atrial contractility by non-adrenergic non-cholinergic (NANC) sensory nerves are reviewed. 2. There is now evidence that in addition to sympathetic and parasympathetic innervation capsaicin-sensitive sensory nerves contribute to the local control of atrial contractility by releasing NANC transmitters, such as calcitonin gene-related peptide (CGRP). 3. Certain chemical and physical stimuli affect atrial contractility by inducing the release of CGRP from sensory nerves. In addition, as widely recognized for the sympathetic and vagal atrial innervation, NANC neurotransmission is under the inhibitory control of several endogenous modulators. 4. Cardioexcitatory actions of NANC neurotransmission on the atrial myocardium are considered. 5. Pharmacological modulation of NANC neurotransmission and functional evidence for cross-talk between NANC and sympathetic neurones are also discussed.     

Effects of repeated disorientation on the acquisition of spatial tasks in rats: Dissociation between the appetitive radial arm maze and aversive water maze.

This study examined the effects of disorientation on the acquisition of different spatial reference memory tasks. In an appetitively motivated radial arm maze task in which 1 arm was consistently baited, rats that were disoriented before each trial were impaired in their ability to acquire the task relative to rats placed in a clear container and not disoriented. However, disoriented rats were able to learn a Morris water maze and a water version of the radial arm maze under similar training conditions, suggesting that the effects of disorientation may interact with the quality or quantity of motivation involved in a given task. These results suggest that appetitive and aversive spatial tasks are dissociable, and that any impairment that is due to disorientation is specific to the appetitive radial arm maze task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of amygdaloid lesions on the performance of rats in four passive avoidance tasks

The blocking effect of apomorphine on the rise in striatal dopamine (DA) content, induced by 1-hydroxy-3-amino-pyrrolidone-2 (HA-966) was taken as a measure for the intrastriatal feedback inhibition of DA synthesis. The effects of cholinergic drugs on this feedback system were assessed in order to verify the hypothesis that this mechanism is mediated via an intrastriatal cholinergic link. We presumed that DA receptors were located on a cholinergic neuron, while the cholinergic terminals in turn made direct or indirect axon-axonal contact with the dopaminergic nigro-striatal pathway (N.S.P.). Although cholinergic agents could modify the effect of HA-966 on striatal DA content, it proved to be impossible to counteract the blocking effect of apomorphine with cholinergic drugs as was to be expected. Therefore we concluded that the effect of apomorphine was not brought about in the way which had been postulated.     

Effects of intracisternal 6-hydroxydopamine treatment on acquisition and performance of rats in a double T-maze.

136 male Sprague-Dawley rats in 4 experiments were subjected to various treatments with 6-hydroxydopamine (6-OHDA) to produce decrements in brain catecholamine content either before or after learning to respond in an appetitively motivated double –T maze task. Intracisternal injections of 6-OHDA not only impaired acquisition of the required behavioral response but also decreased performance of Ss which had previously acquired the task. Although reduced food consumption found in 6-OHDA-treated Ss may contribute to the observed deficits in –T maze responding, the behavioral deficit produced by 6-OHDA injection did not seem to be due only to a simple decrease in food intake. The decrements in acquisition and performance were clearly related to amount of central catecholamine depletion produced by 6-OHDA treatment. Further analysis suggested that the behavioral deficits were more related to the reductions in dopamine than they were to the depletion of brain norepinephrine. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial hippocampal inactivation: Effects on spatial memory performance in aged and young rats.

Changes in anatomical or functional connectivity during normal aging are thought to contribute to cognitive alterations over the lifespan. Neural network theories predict that synaptic loss in an aging brain could place the organism near the point of dysfunction in the nonlinear curve defining neural compromise versus performance. The present experiments examined whether aged rats are closer to this point of behavioral dysfunction by reversibly inactivating one or both hippocampal hemispheres. As expected, bilateral tetracaine inactivation of the hippocampus disrupted spatial memory in both age groups. Unilateral left hippocampal inactivation significantly increased errors only in aged rats; however, unilateral inactivation of the right hippocampus had no effect. The present outcome could reflect more extensive synaptic dysfunction in the aged right hippocampus or a greater involvement of the left hippocampus in spatial working memory problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Loss of the thalamic nuclei for "head direction" impairs performance on spatial memory tasks in rats.

This study sought to characterize the effects of removing the nuclei of primary importance in relaying the thalamic head direction signal to the hippocampal formation (the anterior dorsal [AD] and lateral dorsal [LD] nuclei) on the performance of a variety of spatial and nonspatial tasks. The results indicate that combined excitotoxic lesions of the AD and LD nuclei produce marked deficits on a variety of spatial tasks. These tasks included T-maze alternation and the ability to locate a hidden platform set at a fixed distance and fixed direction from a beacon in a Morris water maze. Although object recognition appeared unaffected, marked impairments were found in the ability to detect when an object was placed in a novel position (object-in-place memory). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions of the associative parietal cortex on the acquisition and use of spatial memory in egocentric and allocentric navigation tasks in the rat.

It has been hypothesized that the rat associative parietal cortex (APC) is involved in the association between visuospatial and locomotion-generated (kinesthetic) information. To study the kinesthetic component, APC-lesioned and control rats were trained in total darkness to reach a submerged platform in the Morris water maze. In the egocentric task, the relative position of the starting point and the platform was constant all over training. Parietal rats have been found impaired in acquisition and to a less extent in retention of this task. In the allocentric task, rats were then trained in the standard version of the navigation task. A mild deficit was observed in acquisition of this task because the APC-lesioned rats displayed longer escape latencies but control-like search patterns. These results suggest that the APC is involved in the coding of kinesthetic information that plays an important role in place navigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amnesia for discrete events in rats with fornicotomies: Effects of interference on spatial alternation performance.

12 male hooded Long-Evans rats were divided into groups for either a control operation or a lesion of the fimbria-fornix. Ss were trained in several versions of a barpress, spatial alternation task. In free operant conditions across 5 experiments, Ss with fimbria-fornix lesions showed adequate alternation performance when the bars were relatively separated by placement either at the ends of an alley or at the ends of the arms of a T-maze, but they were impaired when bars were adjacent. Lesioned Ss also failed to alternate after interpolation of either baffles or a 10-sec delay in the stem, both of which resulted in intervening turning responses before each choice. Results are accounted for by a failure to discriminate memories of relevant, discrete events from those of similar, intervening events. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Glutamatergic influences on the nucleus paragigantocellularis: Contribution to performance in avoidance and spatial memory tasks.

Stimulation of the locus coeruleus (LC) and the subsequent release of norepinephrine contribute to memory consolidation processes. Excitatory input to the LC is derived primarily from neurons in the nucleus paragigantocellularis (PGi). The authors examined the effects of activating the pathway between PGi and the LC on memory. Rats received vehicle or the excitatory amino acid glutamate (25, 50, or 100 nmol/0.5 μl) into PGi after training in an inhibitory avoidance (IA) or delayed matching-to-sample (DMS) task. Rats given the 100-nmol dose had significantly longer retention latencies on a 48-hr IA retention test. Rats treated with the 50- or 100-nmol dose made significantly more correct responses than controls on an 18-hr DMS retention test. Results suggest that encoding and storage of memory for emotional and spatial events may be enhanced by activation of neuronal circuits afferent to the LC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repeated spatial acquisition: Effects of NMDA antagonists and morphine.

Effects of morphine and 2 N-methyl-D-aspartate (NMDA) receptor antagonists, phencyclidine and LY235959, were studied using a within-subject, repeated-acquisition/performance procedure adapted to the Morris Swim Task. In the performance component, subjects swam to a hidden platform that was always in the same location in the pool. In the acquisition component, the platform was moved to a different place for each session. Baseline training produced rapid and direct swims to the platform in the performance component and steep within-session learning curves in the acquisition component. All 3 compounds increased swim distances, escape latencies, and slowed swim speed in a dose-dependent manner, but only morphine consistently produced selective impairments on acquisition. NMDA antagonists generally affected acquisition only at doses that also disrupted performance, although phencyclidine produced selective effects in some animals. These outcomes were different than those from studies of response chains in primates, suggesting that task and species variables may be important determinants of drug effects on acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of scopolamine on spatial double alternation in rats.

Developed and tested a method for training spatial double alternation in 3 experiments, with a total of 4 male albino Wistar rats and 10 male albino Sprague-Dawley rats. Responding on different components of the sequence was controlled by different interoceptive and exteroceptive stimuli. This base line was used to compare the effects of scopolamine (.25-1 mg/kg) on the 2 sorts of cued responding in the same S. The 2 types of response did not differ appreciably in susceptibility to disruption by scopolamine. An analysis of errors showed that both switching and perseverative errors were increased by scopolamine, and that no lever preferences developed. An analysis of the various response sequences shows that in the same S, the probability of some sequences decreased consistently with increasing dose level, some sequences increased, and others showed an inverted -shaped function. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Altered performance of reelin-receptor ApoER2 deficient mice on spatial tasks using the Barnes maze.

The apolipoprotein E receptor 2 (ApoER2), expressed predominantly in forebrain regions including the hippocampus, is 1 of 2 receptors for the extracellular matrix protein reelin, which is critical for cortical development. Previous studies of ApoER2 mutant mice have indicated deficits in synaptic plasticity and learning. The current authors assessed learning and memory of ApoER2 knockout and wild-type mice on the Barnes circular maze. Mice were trained in this task for 22 days, followed by memory recall and reversal tests. ApoER2 knockout mice were initially slower to complete the task, but by Day 22 they were more accurate than wild-type mice on several indices. There were no differences in memory assessed by the recall task, but ApoER2 knockout mice performed significantly worse on the memory reversal task. ApoER2 knockout mice also displayed altered use of specific search strategies and relationship of these strategies to errors made on the maze. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of orienting tasks on the recall and recognition performance of subjects differing in age.

Investigated the recall and recognition performance of 498 adults in 3 age groups (20–39, 40–59, and 60–80 yrs) following different orienting-task requirements. It was demonstrated that young and old adults are differentially affected by task requirements. The youngest group was disproportionately benefited by an orienting task that involved semantic processing. Results support the notion of an age-related processing deficit. (3 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The behavioral syndrome caused by 3,3'-iminodipropionitrile and related nitriles in the rat is associated with degeneration of the vestibular sensory hair cells

Animals exposed to 3,3'-iminodipropionitrile (IDPN) or to several similar nitriles develop a permanent syndrome of behavioral abnormalities. The present work addressed the hypothesis that this syndrome is caused by a toxic effect of these nitriles on the peripheral vestibular system. Male Long-Evans rats were given acute doses of IDPN (0, 200, 400, 600, or 1000 mg/kg, ip) and assessed for a number of behaviors indicative of vestibular function at postdosing times ranging from 1 day to 9 weeks. The pathological effects of IDPN on the morphology of the vestibular sensory epithelia were studied by scanning electron microscopy at 1,2,4, and 21 days after exposure. The behavioral study revealed dose-dependent deficits in vestibular function after IDPN. Alterations in vestibular morphology occurred at the same doses of IDPN that induced behavioral changes (400-1000 mg/kg). The pathological alterations after IDPN consisted of degeneration of the vestibular sensory hair cells, and no hair cells remained in the vestibular receptors 3 weeks after the 1000 mg/kg dose. A good correlation was also found for the time-course characteristics of the behavioral and the morphopathological effects of IDPN. The vestibular sensory epithelia displayed a regional pattern of differential sensitivity to the toxic effect of IDPN. Both intraepithelial and interepithelial differences in sensitivity were found. Crotonitrile (250 mg/kg, ip), which induces the same behavioral syndrome, was found to induce also degeneration of the vestibular hair cells. We conclude that IDPN and the similar nitriles that cause the same behavioral abnormalities are toxic to the peripheral vestibular system.     

Firing characteristics of deep layer neurons in prefrontal cortex in rats performing spatial working memory tasks

Single cells were recorded with 'tetrodes' in regions of the rat medial prefrontal cortex, including those which are targets of hippocampal afferents, while rats were performing three different behavioral tasks: (i) an eight-arm radial maze, spatial working memory task, (ii) a figure-eight track, delayed spatial alternation task, and (iii) a random food search task in a square chamber. Among 187 recorded units, very few exhibited any evidence of place-specific firing on any of the behavioral tasks, except to the extent that different spatial locations were related to distinct phases of the task. Furthermore, no prefrontal unit showed unambiguous spatially dependent delay activity that might mediate working memory for spatial locations. Rather, the cells exhibited diverse correlates that were generally associated with the behavioral requirements of performing the task. This included firing related to intertrial intervals, onset or end of trials, selection of specific arms on the eight-arm radial maze, delay periods, approach to or departure from goals, and selection of paths on the figure-eight track. Although a small number of cells showed similar behavioral correlates across tasks, the majority of cells showed no consistent correlate when recorded across multiple tasks. Furthermore, some units did not exhibit altered firing patterns in any of the three tasks, while others showed changes in firing that were not consistently related to specific behaviors or task components. These results are in agreement with previous lesion and behavioral studies in rats that suggest a prefrontal cortical role in encoding 'rules' (i.e. structural features) or behavioral sequences within a task but not in encoding allocentric spatial information. Given that the hippocampal projection to this cortical region is capable of undergoing LTP, our data lead to the hypothesis that the role of this projection is not to impose spatial representations upon prefrontal activity, but to provide a mechanism for learning the spatial context in which particular behaviors are appropriate.     

Effects of hypothermia on the acquisition of conditioned taste aversion in rats.

Analyzed the mechanism of conditioned taste aversion (CTA) by subjecting 131 male and hooded rats in 5 experiments to reduced body temperature during various phases of CTA acquisition. A 15-min access to .1% saccharin served as the CS, and an ip injection of LiCl (.15 M, 4% of body weight) given 30 min later served as the UCS. Hypothermia (cooling to 20-22°C colonic temperature) alone or combined with anesthesia (Nembutal 20 or 40 mg/kg) did not prevent CTA acquisition when applied during the CS-UCS interval. Hypothermia induced immediately after LiCl administration to anesthetized or unanesthetized Ss failed to disrupt CTA or to increase neophobic rejection of saccharin. On the other hand, hypothermic Ss were not able to form the short-term gustatory trace when the CS (2% saccharin, 1% of body weight) was injected ip, although this procedure yielded significant CTA in euthermic Ss. It is concluded that the most vulnerable link of CTA acquisition is the formation of the short-term gustatory trace. Persistence of the short-term trace, its association with poisoning, and consolidation of the permanent CTA engram are accomplished by mechanisms that are resistant to hypothermia and/or anesthesia. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of age and naturally occurring experience on spatial visualization performance.

A questionnaire designed to assess experience with activities presumed to require spatial visualization abilities, and psychometric tests of these abilities, were administered to 383 adults ranging from 20 to 83 years of age. Although research participants varied considerably in the amount of self-reported experience, statistical control of experience resulted in relatively modest attenuations of the relations between age and spatial visualization performance. These findings seem inconsistent with a strong disuse interpretation of cognitive aging phenomena and suggest that at least some age-related differences in cognitive functioning are independent of the amount of experience with relevant activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Baseline EEG asymmetries and performance on neuropsychological tasks

Thirty-two participants were tested for both resting electroencephalography (EEG) and neuropsychological function. Eight one-minute trials of resting EEG were recorded from 14 channels referenced to linked ears, which was rederived to an average reference. Neuropsychological tasks included Verbal Fluency, the Tower of London, and Corsi's Recurring Blocks. Asymmetries in EEG alpha activity were correlated with performance on these tasks. Similar patterns were obtained for delta and theta bands. Factor analyses of resting EEG asymmetries over particular regions suggested that asymmetries over anterior scalp regions may be partly independent from those over posterior scalp regions. These results support the notions that resting EEG asymmetries are specified by multiple mechanisms along the rostral/caudal plane, and that these asymmetries predict task performance in a manner consistent with lesion and neuroimaging studies.