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Maze
Kinds of Maze Terms modified by Maze Selected AbstractsSurface Electrocardiographic Patterns and Electrophysiologic Characteristics of Atrial Flutter Following Modified Radiofrequency MAZE ProceduresJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2007JOSEPH G. AKAR M.D., Ph.D. Introduction: The radiofrequency MAZE is becoming a common adjunct to cardiac surgery in patients with atrial fibrillation. While a variety of postoperative arrhythmias have been described following the original Cox-MAZE III procedure, the electrophysiological characteristics and surgical substrate of post-radiofrequency MAZE flutter have not been correlated. We sought to determine the location, ECG patterns, and electrophysiological characteristics of post-radiofrequency MAZE atrial flutter. Methods: Nine consecutive patients with post-radiofrequency MAZE flutter presented for catheter ablation 9 ± 10 months after surgery. Results: Only one patient (11%) had an ECG appearance consistent with typical isthmus-dependent right atrial (RA) flutter. However, on electrophysiological study, 3/9 patients (33%) had typical right counter-clockwise flutter entrained from the cavo-tricuspid isthmus, despite description of surgical isthmus ablation. Six patients (67%) had left atrial (LA) circuits. These involved the mitral annulus in 5/6 cases (83%) despite description of surgical mitral isthmus ablation in the majority (60%). LA flutters had a shorter cycle length compared with RA flutters (253 ± 39 msec and 332 ± 63 msec respectively, P < 0.05). After a mean of 8 ± 4 months following ablation, 8/9 patients (89%) were in sinus rhythm. Conclusion: Up to one-third of post-radiofrequency MAZE circuits are typical isthmus-dependent RA flutters, despite a highly atypical surface ECG morphology. Therefore, diagnostic electrophysiological studies should commence with entrainment at the cavo-tricuspid isthmus in order to exclude typical flutter, regardless of the surface ECG appearance. Incomplete surgical lesions at the mitral and cavo-tricuspid isthmus likely predispose to the development of post-radiofrequency MAZE flutter. [source] Mild carbon monoxide exposure and auditory function in the developing ratJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003Janet E. Stockard-Sullivan Abstract We have examined the influence of chronic mild exposure to carbon monoxide (CO) on cognitive (learning) and auditory function in the developing rat. We have demonstrated that the auditory pathway is compromised at exposures less than 50 ppm, whereas learning was not influenced at 100 ppm. Artificially reared rat pups were exposed to CO during the brain growth spurt and onset of myelination. Spatial learning was assessed using the Morris Water Maze and three tests of auditory function: (1) auditory brainstem conduction times; (2) the amplitude of the eighth nerve's action potential; and (3) otoacoustic emissions carried out on rat pups (age 22, 24 days). The pups were gastrostomy-reared on a rat milk substitute and chronically exposed to CO at discrete concentrations in the range of 12,100 ppm from 6 days of age to post-weaning at 21,23 days of age. We found no difference in auditory brainstem conduction times at all CO concentrations in comparison to non-exposed controls. There was a difference in otoacoustic emissions for test and controls at CO concentrations of 50 ppm but not at lower concentrations. There was a consistent attenuation of the amplitude of the eighth nerve's action potential, even at the lowest CO exposure examined. The attenuation of the amplitude of the action potential of the eighth nerve at 50 ppm carbon monoxide exposure did not completely recover by 73 days of age. We conclude that prolonged mild exposure to carbon monoxide during development causes measurable functional changes at the level of the eighth cranial nerve. © 2003 Wiley-Liss, Inc. [source] Mobile phone exposure and spatial memoryBIOELECTROMAGNETICS, Issue 1 2009Clairy Wiholm Abstract Radiofrequency (RF) emission during mobile phone use has been suggested to impair cognitive functions, that is, working memory. This study investigated the effects of a 2,1/2 h RF exposure (884 MHz) on spatial memory and learning, using a double-blind repeated measures design. The exposure was designed to mimic that experienced during a real-life mobile phone conversation. The design maximized the exposure to the left hemisphere. The average exposure was peak spatial specific absorption rate (psSAR10g) of 1.4 W/kg. The primary outcome measure was a "virtual" spatial navigation task modeled after the commonly used and validated Morris Water Maze. The distance traveled on each trial and the amount of improvement across trials (i.e., learning) were used as dependent variables. The participants were daily mobile phone users, with and without symptoms attributed to regular mobile phone use. Results revealed a main effect of RF exposure and a significant RF exposure by group effect on distance traveled during the trials. The symptomatic group improved their performance during RF exposure while there was no such effect in the non-symptomatic group. Until this new finding is further investigated, we can only speculate about the cause. Bioelectromagnetics 30:59,65, 2009. © 2008 Wiley-Liss, Inc. [source] Flow-Based Automatic Generation of Hybrid Picture MazesCOMPUTER GRAPHICS FORUM, Issue 7 2009Fernando J. Wong Abstract A method for automatically generating a picture maze from two different images is introduced throughout this paper. The process begins with the extraction of salient contours and edge tangent flow information from the primary image in order to build the overall maze. Thus, mazes with passages flowing in the main edge directions and walls that effectively represent an abstract version of the primary image can be successfully created. Furthermore, our proposed approach makes possible the use of their solution path as a means of illustrating the main features of the secondary image, while attempting to keep its image motif concealed until the maze has been finally solved. The contour features and intensity of the secondary image are also incorporated into our method in order to determine the areas of the maze to be shaded by allowing the solution path to go through them. Moreover, an experiment has been conducted to confirm that solution paths can be successfully hidden from the participants in the mazes generated using our method. [source] Mazes, Conflict, and Paradox: Tools for Understanding Chronic PainPAIN PRACTICE, Issue 3 2009Cary A. Brown PhD Abstract This article presents an argument for framing chronic pain within a complex adaptive systems (CAS) paradigm. The first aim of this article is to demonstrate how chronic pain can be framed as a CAS and how paradox, one of the core characteristics of a CAS, exists within the chronic pain experience. The second aim is to illustrate how paradox exists at multiple levels within the health care encounter and ongoing experience of chronic pain. Finally, the article will use the example of interactions at the patient/clinician level to illustrate how health care workers' efforts to deal with issues emergent from the range of paradoxes have for the most part been ineffective, and at times harmful, to persons experiencing chronic pain. This article uses the example of chronic pain to explore how the manner in which health care providers and patients recognize and deal with paradoxes can either worsen the pain experience or help generate creative new ways to manage the chronic pain condition. The CAS principles discussed in this article hold application across a range of chronic conditions for which a traditional biomedical paradigm proves insufficient. [source] Mazes and music: using perceptual processing to release verbal overshadowingAPPLIED COGNITIVE PSYCHOLOGY, Issue 8 2002Kimberly Finger Verbal overshadowing occurs when participants describe a previously viewed non-verbal stimulus such as a face prior to a recognition memory test. The results of numerous studies indicate that recognition accuracy is lower when participants describe the face or other non-verbal stimulus as compared to a no-description control condition. In the present two-experiment study, verbal overshadowing was alleviated when participants engaged in a non-verbal task that emphasized perceptual processing subsequent to describing the face but prior to the recognition memory test. In Experiments 1 and 2, participants viewed a face and then either described the face or completed a distractor task. Next, participants in Experiment 1 engaged in a perceptual task in the form of a series of mazes or a verbal task. Participants who described the face and completed the mazes experienced a release from verbal overshadowing as compared to participants who described the face and completed the verbal task. In Experiment 2, verbal overshadowing was alleviated when participants listened to instrumental music after describing the face, thus demonstrating that an auditory perceptual task can also release verbal overshadowing. The results of these two experiments provide support for a processing shift interpretation of verbal overshadowing. Furthermore, the results indicate this shift can be alleviated, and perceptual processing reinstated, by engaging in an unrelated perceptually oriented task such as completing a maze or listening to music. Copyright © 2002 John Wiley & Sons, Ltd. [source] Flow-Based Automatic Generation of Hybrid Picture MazesCOMPUTER GRAPHICS FORUM, Issue 7 2009Fernando J. Wong Abstract A method for automatically generating a picture maze from two different images is introduced throughout this paper. The process begins with the extraction of salient contours and edge tangent flow information from the primary image in order to build the overall maze. Thus, mazes with passages flowing in the main edge directions and walls that effectively represent an abstract version of the primary image can be successfully created. Furthermore, our proposed approach makes possible the use of their solution path as a means of illustrating the main features of the secondary image, while attempting to keep its image motif concealed until the maze has been finally solved. The contour features and intensity of the secondary image are also incorporated into our method in order to determine the areas of the maze to be shaded by allowing the solution path to go through them. Moreover, an experiment has been conducted to confirm that solution paths can be successfully hidden from the participants in the mazes generated using our method. [source] Designing mouse behavioral tasks relevant to autistic-like behaviors,DEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 4 2004Jacqueline N. Crawley Abstract The importance of genetic factors in autism has prompted the development of mutant mouse models to advance our understanding of biological mechanisms underlying autistic behaviors. Mouse models of human neuropsychiatric diseases are designed to optimize (1) face validity, i.e., resemblance to the human symptoms; (2) construct validity, i.e., similarity to the underlying causes of the disease; and (3) predictive validity, i.e., expected responses to treatments that are effective in the human disease. There is a growing need for mouse behavioral tasks with all three types of validity for modeling the symptoms of autism. We are in the process of designing a set of tasks with face validity for the defining features of autism: deficits in appropriate reciprocal social interactions, deficits in verbal social communication, and high levels of ritualistic repetitive behaviors. Social approach is tested in an automated three-chambered apparatus that offers the subject a choice between a familiar environment, a novel environment, and a novel environment containing a stranger mouse. Preference for social novelty is tested in the same apparatus, with a choice between the start chamber, the chamber containing a familiar mouse, and the chamber containing a stranger mouse. Social communication is evaluated by measuring the ultrasonic distress vocalizations emitted by infant mouse pups and the parental response of retrieving the pup to the nest. Resistance to change in ritualistic repetitive behaviors is modeled by forcing a change in habit, including reversal of the spatial location of a reinforcer in a T-maze task and in the Morris water maze. Mouse behavioral tasks that may model additional features of autism are discussed, including tasks relevant to anxiety, seizures, sleep disturbances, and sensory hypersensitivity. Applications of these tests include (1) behavioral phenotyping of transgenic and knockout mice with mutations in genes relevant to autism, (2) characterization of mutant mice derived from random chemical mutagenesis, (3) DNA microarray analyses of genes in inbred strains of mice that differ in social interaction, social communication and resistance to change in habit, and (4) evaluation of proposed therapeutics for the treatment of autism. Published 2004 Wiley-Liss, Inc. MRDD Research Reviews 2004;10:248,258. [source] Learning large-scale spatial relationships in a maze and effects of MK-801 on retrieval in the rhesus monkeyDEVELOPMENTAL NEUROBIOLOGY, Issue 13 2007Jian Hong Wang Abstract Monkeys have strong abilities to remember the visual properties of potential food sources for survival in the nature. The present study demonstrated the first observations of rhesus monkeys learning to solve complex spatial mazes in which routes were guided by visual cues. Three monkeys were trained in a maze (6 m × 6 m) included of four different mazes. We recorded the cue and cup errors, latencies, and pathway for each trial. The data showed that monkeys learned the target place after three days in the first maze and spent a shorter time in learning the following mazes. The maze was an efficient method to measure the ability and proceeding of spatial memory in monkeys. Moreover, working memory can also be tested by using the maze. MK-801 at 0.02 mg/kg but not at 0.005 mg/kg impaired monkeys' retrieval of spatial memory after they learned all four mazes. The present maze may provide an efficient method to help bridging the gap in cognition between nonhuman primates and humans, and in particular to gain insight into human cognitive function and dysfunction. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Attention-like processes underlying optomotor performance in a Drosophila choice mazeDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2007Bruno van Swinderen Abstract The authors present a novel paradigm for studying visual responses in Drosophila. An eight-level choice maze was found to reliably segregate fly populations according to their responses to moving stripes displayed on a computer screen. Visual responsiveness was robust in wild-type flies, and performance depended on salience effects such as stimulus color and speed. Analysis of individual fly choices in the maze revealed that stereotypy, or choice persistence, contributed significantly to a strain's performance. On the basis of these observations, the authors bred wild-type flies for divergent visual phenotypes by selecting individual flies displaying extreme stereotypy. Selected flies alternated less often in the sequential choice maze than unselected flies, showing that stereotypy could evolve across generations. The authors found that selection for increased stereotypy impaired flies' responsiveness to competing stimuli in tests for attention-like behavior in the maze. Visual selective attention was further investigated by electrophysiology, and it was found that increased stereotypy also impaired responsiveness to competing stimuli at the level of brain activity. Combined results present a comprehensive approach to studying visual responses in Drosophila, and show that behavioral performance involves attention-like processes that are variable among individuals and thus sensitive to artificial selection. © 2006 Wiley Periodicals, Inc. Develop Neurobiol 67: 129,145, 2007. [source] Spatial conditional discrimination learning in developing ratsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 2 2005Kevin L. Brown Abstract The present study established an effective procedure for studying spatial conditional discrimination learning in juvenile rats using a T-maze. Wire mesh located on the floor of the maze as well as a second, identical T-maze apparatus served as conditional cues which signaled whether a left or a right response would be rewarded. In Experiment 1, conditional discrimination was evident on Postnatal Day (PND) 30 when mesh,+,maze or maze-alone were the conditional cues, but not when mesh-alone was the cue. Experiment 2 confirmed that mesh-alone was sufficiently salient to support learning of a simple (nonconditional) discrimination. Its failure to serve as a conditional cue in Experiment 1 does not reflect its general ineffectiveness as a stimulus. Experiment 3 confirmed that the learning shown in Experiment 1 was indeed conditional in nature by comparing performance on conditional versus nonconditional versions of the task. Experiment 4 showed that PND19 and PND23 pups also were capable of performing the task when maze,+,mesh was the cue; however, the findings indicate that PND19 subjects do not use a conditional strategy to learn this task. The findings suggest postnatal ontogeny of conditional discrimination learning and underscore the importance of conditional cue salience, and of identifying task strategies, in developmental studies of conditional discrimination learning. © 2005 Wiley Periodicals, Inc. Dev Psychobiol 46: 97,110, 2005. [source] Contextual modulation of spatial discrimination reversal in developing ratsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2005Jerome H. Pagani Abstract Reversal of discrimination learning is influenced by manipulation of the training context. In adult and developing rats, contextual changes made between acquisition and reversal aid the learning of the new discrimination, possibly by serving to release proactive interference from the originally acquired discrimination (M. E. Bouton & D. C. Brooks, 1993; N. Spear, G. Smith, R. Bryan, & W. Gordon, 1980). The present study sought to examine this effect in an appetitive T-maze task, as a function of different contextual manipulations. Rats of three ages, Postnatal Day (PND) 19, PND23, and PND30, were tested for their ability to acquire and reverse a position habit in a T-maze. Contextual changes were made between acquisition and reversal sessions and consisted of one of three manipulations: (a) texture; the texture of the maze floor was changed via the addition or subtraction of wire mesh; (b) maze; subjects were reversed in a different maze that was identical in construction to the training maze, but differed in spatial location; (c) texture and maze; subjects were shifted to the new maze, the floor of which differed in texture from the training maze but was otherwise identical in construction. Results showed that the texture,maze combination was an effective aid to reversal learning at all ages tested. The texture alone, however, was not effective at any age. The maze alone also was an effective cue for reversal, but proved to have the greatest effect for PND30 subjects. During ontogeny, the contextual modulation of reversal learning is importantly influenced by the nature and the salience of the contextual cue. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 46: 36,46, 2005. [source] Role of oxytocin and vasopressin in the transitions of weaning in the ratDEVELOPMENTAL PSYCHOBIOLOGY, Issue 4 2004A. Kavushansky Abstract Sucklings (18-day-old) and weanlings (35-day-old) were injected icv with oxytocin or its antagonist (both 0.5 ,g/1 ,l), or vasopressin (1.0 ng/1 ,l) or its antagonist (100 ng/1 ,l), prior to 4-min observation in a behavioral maze with a sibling in one box and their anesthetized dam in the other. Oxytocin abolished nipple attachment in sucklings, decreased time spent with the dam, and increased self-grooming. The oxytocin antagonist had little influence on behavior. Vasopressin increased self-grooming while its antagonist reduced passive contact with the dam, increased active contact with her, and increased exploration and activity. We conclude that these neuropeptides have diverse roles during weaning, maintaining sucklings' behavior or promoting weaning, and subserving the transition from attachment to the dam to independence from her. We propose that these neurochemicals, and others, mediate the neural, affiliative, and affective changes of weaning, and that the term "weaning" should be understood to encompass these behavioral transitions. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 45: 231,238, 2004. [source] The novel nootropic compound DM232 (UNIFIRAM) ameliorates memory impairment in mice and ratsDRUG DEVELOPMENT RESEARCH, Issue 1 2002Carla Ghelardini Abstract The favorable pharmacological profile exhibited by piracetam stimulated the synthesis of related compounds potentially endowed with a higher nootropic potency. The antiamnesic and procognitive activity of DM232 (unifiram), a new compound structurally related to piracetam, was investigated. Mouse passive avoidance and rat Morris water maze and Social learning tests were employed. DM232 (0.001,1 mg kg,1 i.p. , 0.01,0.1 1 mg kg,1 p.o.) prevented amnesia induced by scopolamine (1.5 mg kg,1 i.p.), mecamylamine (20 mg kg,1 i.p.), baclofen (2 mg kg,1 i.p.), and clonidine (0.125 mg kg,1 i.p.). Furthermore, The antiamnesic effect of the investigated compound was comparable to that exerted by well-known nootropic drugs such as piracetam (30,100 mg kg,1 i.p.), aniracetam (100 mg kg,1 p.o.), rolipram (30 mg kg,1 p.o.), and nicotine (5 mg kg,1 i.p). DM232 (0.1 mg kg,1 i.p.) was also able to prevent amnesia induced by scopolamine (0.8 mg kg,1 i.p.) in the rat Morris watermaze test. In the rat social learning test, DM232 (0.1 mg kg,1 i.p.) injected in adults rats reduced the duration of active exploration of the familiar partner in the second session of the test. DM232, similarly to piracetam, reduced the duration of hypnosis induced by pentobarbital. At the highest effective doses, the investigated compound did not impair motor coordination (rota rod test), nor modified spontaneous (Animex). These results indicate DM232 (unifiram) as a novel cognition enhancer, strictly related to piracetam-like compounds, able to ameliorate memory impairment at doses about 1,000 times lower than the most active available nootropic compounds. Drug Dev. Res. 56:23,32, 2002. © 2002 Wiley-Liss, Inc. [source] Predictors of pharmacoresistant epilepsy: Pharmacoresistant rats differ from pharmacoresponsive rats in behavioral and cognitive abnormalities associated with experimentally induced epilepsyEPILEPSIA, Issue 10 2008Alexandra M. Gastens Summary Purpose:, Patients with intractable temporal lobe epilepsy (TLE) exhibit an increased risk of psychiatric comorbidity, including depression, anxiety, psychosis, and learning disorders. Furthermore, a history of psychiatric comorbidity has been suggested as a predictor of lack of response to therapy with antiepileptic drugs (AEDs) in patients with epilepsy. However, clinical studies on predictors of pharmacoresistant epilepsy are affected by several confounding variables, which may complicate conclusions. In the present study, we evaluated whether behavioral alterations in epileptic rats are different in AED nonresponders versus responders. Methods:, For this purpose, we used an animal model of TLE in which AED responders and nonresponders can be selected by prolonged treatment of epileptic rats with phenobarbital (PB). Behavioral and cognitive abnormalities were compared between responders and nonresponders as well as between epileptic rats and nonepileptic controls in a battery of tests. Results:, Fifteen epileptic rats with spontaneous recurrent seizures (SRS) either responding (11 rats) or not responding (4 rats) to PB were used for this study. The nonresponders differed markedly in behavioral and cognitive abnormalities from responders and nonepileptic controls in tests of anxiety (open field, elevated-plus maze test), behavioral hyperexcitability (approach-response, touch-response, pick-up tests), and learning and memory (Morris water maze). Discussion:, Our hypothesis that AED-resistant rats will show more severe behavioral and cognitive changes than AED-responsive rats was confirmed by the present experiments. The data substantiate that rodent models of TLE are useful to delineate predictors of pharmacoresistant epilepsy. [source] Seizures in the Developing Brain Cause Adverse Long-term Effects on Spatial Learning and AnxietyEPILEPSIA, Issue 12 2004Umit Sayin Summary:,Purpose: Seizures in the developing brain cause less macroscopic structural damage than do seizures in adulthood, but accumulating evidence shows that seizures early in life can be associated with persistent behavioral and cognitive impairments. We previously showed that long-term spatial memory in the eight-arm radial-arm maze was impaired in rats that experienced a single episode of kainic acid (KA)-induced status epilepticus during early development (postnatal days (P) 1,14). Here we extend those findings by using a set of behavioral paradigms that are sensitive to additional aspects of learning and behavior. Methods: On P1, P7, P14, or P24, rats underwent status epilepticus induced by intraperitoneal injections of age-specific doses of KA. In adulthood (P90,P100), the behavioral performance of these rats was compared with that of control rats that did not receive KA. A modified version of the radial-arm maze was used to assess short-term spatial memory; the Morris water maze was used to evaluate long-term spatial memory and retrieval; and the elevated plus maze was used to determine anxiety. Results: Compared with controls, rats with KA seizures at each tested age had impaired short-term spatial memory in the radial-arm maze (longer latency to criterion and more reference errors), deficient long-term spatial learning and retrieval in the water maze (longer escape latencies and memory for platform location), and a greater degree of anxiety in the elevated plus maze (greater time spent in open arms). Conclusions: These findings provide additional support for the concept that seizures early in life may be followed by life-long impairment of certain cognitive and behavioral functions. These results may have clinical implications, favoring early and aggressive control of seizures during development. [source] Pentylenetetrazol-induced Recurrent Seizures in Rat Pups: Time Course on Spatial Learning and Long-term EffectsEPILEPSIA, Issue 6 2002Li-Tung Huang Summary: ,Purpose: Recurrent seizures in infants are associated with a high incidence of neurocognitive deficits. Animal models have suggested that the immature brain is less vulnerable to seizure-induced injury than is that in adult animals. We studied the effects of recurrent neonatal seizures on cognitive tasks performed when the animals were in adolescence and adulthood. Methods: Seizures were induced by intraperitoneal injection of pentylenetetrazol (PTZ) for 5 consecutive days, starting from postnatal day 10 (P10). At P35 and P60, rats were tested for spatial memory by using the Morris water maze task. In adulthood, motor performance was examined by the Rotarod test, and activity level was assessed by the open field test. Seizure threshold was examined by inhalant flurothyl. To assess presence or absence of spontaneous seizures, rats were video recorded for 4 h/day for 10 consecutive days for the detection of spontaneous seizures. Finally, brains were examined for histologic evidence of injury with cresyl violet stain and Timm staining in the supragranular zone and CA3 pyramidal cell layers of the hippocampus. Results: PTZ-treated rats showed significant spatial deficits in the Morris water maze at both P35 and P60. There were no differences in seizure threshold, motor balance, or activity level during the open field test. Spontaneous seizures were not recorded in any rat. The cresyl violet stain showed no cell loss in either the control or experimental rats. PTZ-treated rats exhibited more Timm staining in the CA3 subfield. However, the control and experimental rats showed similar Timm staining within the supragranular zone. Conclusions: Our findings indicate that recurrent PTZ-induced seizures result in long-term cognitive deficits and morphologic changes in the developing brain. Furthermore, these cognitive deficits could be detected during pubescence. [source] Maze Learning and Recall in a Weakly Electric Fish, Mormyrus rume proboscirostris Boulenger (Mormyridae, Teleostei),ETHOLOGY, Issue 10 2010Alice G. Walton Mormyrus rume proboscirostris, African weakly electric fish, were trained to seek shelter in a meander maze, and following path acquisition released into the empty arena with all maze cues removed, either from the original start box or from a novel site (recall). We demonstrate that fish use their active electrosense, sight, and lateral line synergistically in maze acquisition and recall. In the presence of an electric roadmap consisting of an array of aluminum and Plexiglas objects, fish employed landmark orientation. But fish ignored visual markers and relied on internalized motor routines, which was inconsistent with evidence for cognitive mapping. [source] PRECLINICAL STUDY: Pentylenetetrazole-induced status epilepticus following training does not impair expression of morphine-induced conditioned place preferenceADDICTION BIOLOGY, Issue 2 2009Jie Zhang ABSTRACT Learning and memory play an important role in morphine addiction. Status epilepticus (SE) can impair the spatial and emotional learning and memory. However, little is known about the effects of SE on morphine-induced conditioned place preference (CPP). The present study was designed to investigate the effects of SE on morphine CPP, with food CPP being used as a control. The effects of SE on spatial memory in the Morris water maze (MWM) and Y-maze were investigated. SE was induced in adult mice using intraperitoneal injection of pentylenetetrazole; control mice received saline. The data indicated that SE had no effects on the formation of morphine CPP; however, the formation of food CPP was blocked by SE. Meanwhile, spatial memory assayed in the MWM and Y-maze was impaired by SE. In addition, the data demonstrated that SE did not cause a lasting disturbance of motor activity nor a change in the mice's appetite. These results suggested that although SE had no effects on morphine CPP, there was impaired food CPP and spatial memory in both the MWM and the Y-maze. The mechanisms underlying memory process of morphine CPP may be different from other types of memory. [source] Genetic reductions of ,-site amyloid precursor protein-cleaving enzyme 1 and amyloid-, ameliorate impairment of conditioned taste aversion memory in 5XFAD Alzheimer's disease model miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2010Latha Devi Abstract Although transgenic mouse models of Alzheimer's disease (AD) recapitulate amyloid-, (A,)-related pathologies and cognitive impairments, previous studies have mainly evaluated their hippocampus-dependent memory dysfunctions using behavioral tasks such as the water maze and fear conditioning. However, multiple memory systems become impaired in AD as the disease progresses and it is important to test whether other forms of memory are affected in AD models. This study was designed to use conditioned taste aversion (CTA) and contextual fear conditioning paradigms to compare the phenotypes of hippocampus-independent and -dependent memory functions, respectively, in 5XFAD amyloid precursor protein/presenilin-1 transgenic mice that harbor five familial AD mutations. Although both types of memory were significantly impaired in 5XFAD mice, the onset of CTA memory deficits (,9 months of age) was delayed compared with that of contextual memory deficits (,6 months of age). Furthermore, 5XFAD mice that were genetically engineered to have reduced levels of ,-site amyloid precursor protein-cleaving enzyme 1 (BACE1) (BACE1+/,·5XFAD) exhibited improved CTA memory, which was equivalent to the performance of wild-type controls. Importantly, elevated levels of cerebral ,-secretase-cleaved C-terminal fragment (C99) and A, peptides in 5XFAD mice were significantly reduced in BACE1+/,·5XFAD mice. Furthermore, A, deposition in the insular cortex and basolateral amygdala, two brain regions that are critically involved in CTA performance, was also reduced in BACE1+/,·5XFAD compared with 5XFAD mice. Our findings indicate that the CTA paradigm is useful for evaluating a hippocampus-independent form of memory defect in AD model mice, which is sensitive to rescue by partial reductions of the ,-secretase BACE1 and consequently of cerebral A,. [source] Protein degradation, as with protein synthesis, is required during not only long-term spatial memory consolidation but also reconsolidationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008Julien Artinian Abstract The formation of long-term memory requires protein synthesis, particularly during initial memory consolidation. This process also seems to be dependant upon protein degradation, particularly degradation by the ubiquitin-proteasome system. The aim of this study was to investigate the temporal requirement of protein synthesis and degradation during the initial consolidation of allocentric spatial learning. As memory returns to a labile state during reactivation, we also focus on the role of protein synthesis and degradation during memory reconsolidation of this spatial learning. Male CD1 mice were submitted to massed training in the spatial version of the Morris water maze. At various time intervals after initial acquisition or after a reactivation trial taking place 24 h after acquisition, mice received an injection of either the protein synthesis inhibitor anisomycin or the protein degradation inhibitor lactacystin. This injection was performed into the hippocampal CA3 region, which is specifically implicated in the processing of spatial information. Results show that, in the CA3 hippocampal region, consolidation of an allocentric spatial learning task requires two waves of protein synthesis taking place immediately and 4 h after acquisition, whereas reconsolidation requires only the first wave. However, for protein degradation, both consolidation and reconsolidation require only one wave, taking place immediately after acquisition or reactivation, respectively. These findings suggest that protein degradation is a key step for memory reconsolidation, as for consolidation. Moreover, as protein synthesis-dependent reconsolidation occurred faster than consolidation, reconsolidation did not consist of a simple repetition of the initial consolidation. [source] Developmental neural plasticity and its cognitive benefits: olivocerebellar reinnervation compensates for spatial function in the cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Melina L. Willson Abstract The adult mammalian central nervous system displays limited reinnervation and recovery from trauma. However, during development, post-lesion plasticity may generate alternative paths, thus providing models to investigate reinnervation and repair. After unilateral transection of the neonatal rat olivocerebellar path (pedunculotomy), axons from the remaining inferior olive reinnervate the denervated hemicerebellum. Unfortunately, reinnervation to the cerebellar hemisphere is incomplete; therefore, its capacity to mediate hemispheric function (navigation) is unknown. We studied sensorimotor control and spatial cognition of rats with and without transcommissural reinnervation using simple (bridge and ladder) and complex (wire) locomotion tests and the Morris water maze (hidden, probe and cued paradigms). Although pedunculotomized animals completed locomotory tasks more slowly than controls, all groups performed equally in the cued maze, indicating that lesioned animals could orientate to and reach the platform. In animals pedunculotomized on day 3 (Px3), which develop olivocerebellar reinnervation, final spatial knowledge was as good as controls, although they learned more erratically, failing to retain all information from one day to the next. By contrast, animals pedunculotomized on day 11 (Px11), which do not develop reinnervation, did not learn the task, taking less direct routes and more time to reach the platform than controls. In the probe test, control and Px3, but not Px11, animals swam directly to the remembered location. Furthermore, the amount of transcommissural reinnervation to the denervated hemisphere correlated directly with spatial performance. These results show that transcommissural olivocerebellar reinnervation is associated with spatial learning, i.e. even partial circuit repair confers significant functional benefit. [source] Repeated withdrawal from ethanol spares contextual fear conditioning and spatial learning but impairs negative patterning and induces over-responding: evidence for effect on frontal cortical but not hippocampal function?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006Gilyana G. Borlikova Abstract Repeated exposure of rats to withdrawal from chronic ethanol reduces hippocampal long-term potentiation and gives rise to epileptiform-like activity in hippocampus. We investigated whether such withdrawal experience also affects learning in tasks thought to be sensitive to hippocampal damage. Rats fed an ethanol-containing diet for 24 days with two intermediate 3-day withdrawal episodes, resulting in intakes of 13,14 g/kg ethanol per day, showed impaired negative patterning discrimination compared with controls and animals that had continuous 24-day ethanol treatment, but did not differ from these animals in the degree of contextual freezing 24 h after training or in spatial learning in the Barnes maze. Repeatedly withdrawn animals also showed increased numbers of responses in the period immediately before reinforcement became available in an operant task employing a fixed-interval schedule although overall temporal organization of responding was unimpaired. Thus, in our model of repeated withdrawal from ethanol, previously observed changes in hippocampal function did not manifest at the behavioural level in the tests employed. The deficit seen after repeated withdrawal in the negative patterning discrimination and over-responding in the fixed-interval paradigm might be related to the changes in the functioning of the cortex after withdrawal. [source] The role of the medial caudate nucleus, but not the hippocampus, in a matching-to sample task for a motor responseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2006Raymond P. Kesner Abstract A delayed-match-to-sample task was used to assess memory for motor responses in rats with control, hippocampus, or medial caudate nucleus (MCN) lesions. All testing was conducted on a cheeseboard maze in complete darkness using an infrared camera. A start box was positioned in the centre of the maze facing a randomly determined direction on each trial. On the sample phase, a phosphorescent object was randomly positioned to cover a baited food well in one of five equally spaced positions around the circumference of the maze forming a 180-degree arc 60 cm from the box. The rat had to displace the object to receive food and return to the start box. The box was then rotated to face a different direction. An identical baited phosphorescent object was placed in the same position relative to the start box. A second identical object was positioned to cover a different unbaited well. On the choice phase, the rat must remember the motor response made on the sample phase and make the same motor response on the choice phase to receive a reward. Hippocampus lesioned and control rats improved as a function of increased angle separation used to separate the correct object from the foil (45, 90, 135, and 180 degrees) and matched the performance of controls. However, rats with MCN lesions were impaired across all separations. Results suggest that the MCN, but not the hippocampus, supports working memory and/or a process aimed at reducing interference for motor response selection based on vector angle information. [source] Enhancement of learning behaviour by a potent nitric oxide-guanylate cyclase activator YC-1EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2005Wei-Lin Chien Abstract Memory is one of the most fundamental mental processes, and various approaches have been used to understand the mechanisms underlying this process. Nitric oxide (NO), cGMP and protein kinase G (PKG) are involved in the modulation of synaptic plasticity in various brain regions. YC-1, which is a benzylindazole derivative, greatly potentiated the response of soluble guanylate cyclase to NO (up to several hundreds fold). We have previously shown that YC-1 markedly enhances long-term potentiation in hippocampal and amygdala slices via NO-cGMP-PKG-dependent pathway. We here further investigated whether YC-1 promotes learning behaviour in Morris water maze and avoidance tests. It was found that YC-1 shortened the escape latency in the task of water maze, increased and decreased the retention scores in passive and active avoidance task, respectively. Administration of YC-1 30 min after foot-shock stimulation did not significantly affect retention scores in response to passive avoidance test. Administration of scopolamine, a muscarinic antagonist, markedly impaired the memory acquisition. Pretreatment of YC-1 inhibited the scopolamine-induced learning deficit. The enhancement of learning behaviour by YC-1 was antagonized by intracerebroventricular injection of NOS inhibitor L-NAME and PKG inhibitors of KT5823 and Rp-8-Br-PET-cGMPS, indicating that NO-cGMP-PKG pathway is also involved in the learning enhancement action of YC-1. YC-1 is thus a good drug candidate for the improvement of learning and memory. [source] Genetic ablation of the mammillary bodies in the Foxb1 mutant mouse leads to selective deficit of spatial working memoryEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2005Konstantin Radyushkin Abstract Mammillary bodies and the mammillothalamic tract are parts of a classic neural circuitry that has been implicated in severe memory disturbances accompanying Korsakoff's syndrome. However, the specific role of mammillary bodies in memory functions remains controversial, often being considered as just an extension of the hippocampal memory system. To study this issue we used mutant mice with a targeted mutation in the transcription factor gene Foxb1. These mice suffer perinatal degeneration of the medial and most of the lateral mammillary nuclei, as well as of the mammillothalamic bundle. Foxb1 mutant mice showed no deficits in such hippocampal-dependent tasks as contextual fear conditioning and social transmission of food preference. They were also not impaired in the spatial reference memory test in the radial arm maze. However, Foxb1 mutants showed deficits in the task for spatial navigation within the Barnes maze. Furthermore, they showed impairments in spatial working memory tasks such as the spontaneous alternation and the working memory test in the radial arm maze. Thus, our behavioural analysis of Foxb1 mutants suggests that the medial mammillary nuclei and mammillothalamic tract play a role in a specific subset of spatial tasks, which require combined use of both spatial and working memory functions. Therefore, the mammillary bodies and the mammillothalamic tract may form an important route through which the working memory circuitry receives spatial information from the hippocampus. [source] Sexually dimorphic effects of hippocampal cholinergic deafferentation in ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2004Zachariah Jonasson Abstract To determine whether the basal forebrain-hippocampal cholinergic system supports sexually dimorphic functionality, male and female Long-Evans rats were given either selective medial septum/vertical limb of the diagonal band (MS/VDB) cholinergic lesions using the neurotoxin 192 IgG-saporin or a control surgery and then postoperatively tested in a set of standard spatial learning tasks in the Morris water maze. Lesions were highly specific and effective as confirmed by both choline acetyltransferase/parvalbumin immunostaining and acetylcholinesterase histochemistry. Female controls performed worse than male controls in place learning and MS/VDB lesions failed to impair spatial learning in male rats, both consistent with previous findings. In female rats, MS/VDB cholinergic lesions facilitated spatial reference learning. A subsequent test of learning strategy in the water maze revealed a female bias for a response, relative to a spatial, strategy; MS/VDB cholinergic lesions enhanced the use of a spatial strategy in both sexes, but only significantly so in males. Together, these results indicate a sexually dimorphic function associated with MS/VDB-hippocampal cholinergic inputs. In female rats, these neurons appear to support sex-specific spatial learning processes. [source] Mice with astrocyte-directed inactivation of connexin43 exhibit increased exploratory behaviour, impaired motor capacities, and changes in brain acetylcholine levelsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2003Christian Frisch Abstract Gap junctions mediate communication between many cell types in the brain. Gap junction channels are composed of membrane-spanning connexin (Cx) proteins, allowing the cell-to-cell passage of small ions and metabolites. Cx43 is the main constituent of the brain-spanning astrocytic gap junctional network, controlling activity-related changes in ion and glutamate concentrations as well as metabolic processes. In astrocytes, deletion of Cx43-coding DNA led to attenuated gap junctional coupling and impaired propagation of calcium waves, known to influence neuronal activity. Investigation of the role of Cx43 in behaviour has been impossible so far, due to postnatal lethality of its general deletion. Recently, we have shown that deletion of Cx30, which is also expressed by astrocytes, affects exploration, emotionality, and neurochemistry in the mouse. In the present study, we investigated the effects of the astrocyte-directed inactivation of Cx43 on mouse behaviour and brain neurochemistry. Deletion of Cx43 in astrocytes increased exploratory activity without influencing habituation. In the open field, but not in the elevated plus-maze, an anxiolytic-like effect was observed. Rotarod performance was initially impaired, but reached control level after further training. In the water maze, Cx43 deficient mice showed a steeper learning course, although final performance was similar between groups. Cx43 inactivation in astrocytes increased acetylcholine content in the frontal cortex of water maze-trained animals. Results are discussed in terms of altered communication between astrocytes and neurons, possible compensation processes, and differential effects of Cx30- and astrocyte-specific Cx43 deletion. [source] Rapid reversal of stress induced loss of synapses in CA3 of rat hippocampus following water maze trainingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Carmen Sandi Abstract The impact was examined of exposing rats to two life experiences of a very different nature (stress and learning) on synaptic structures in hippocampal area CA3. Rats were subjected to either (i) chronic restraint stress for 21 days, and/or (ii) spatial training in a Morris water maze. At the behavioural level, restraint stress induced an impairment of acquisition of the spatial response. Moreover, restraint stress and water maze training had contrasting impacts on CA3 synaptic morphometry. Chronic stress induced a loss of simple asymmetric synapses [those with an unperforated postsynaptic density (PSD)], whilst water maze learning reversed this effect, promoting a rapid recovery of stress-induced synaptic loss within 2,3 days following stress. In addition, in unstressed animals a correlation was found between learning efficiency and the density of synapses with an unperforated PSD: the better the performance in the water maze, the lower the synaptic density. Water maze training increased the number of perforated synapses (those with a segmented PSD) in CA3, both in stressed and, more notably, in unstressed rats. The distinct effects of stress and learning on CA3 synapses reported here provide a neuroanatomical basis for the reported divergent effects of these experiences on hippocampal synaptic activity, i.e. stress as a suppressor and learning as a promoter of synaptic plasticity. [source] Sex differences in anxiety, sensorimotor gating and expression of the ,4 subunit of the GABAA receptor in the amygdala after progesterone withdrawalEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003M. Gulinello Abstract In a progesterone withdrawal (PWD) model of premenstrual anxiety, we have previously demonstrated that increased hippocampal expression of the ,4 subunit of the GABAA receptor (GABAA -R) is closely associated with higher anxiety levels in the elevated plus maze. However, several studies indicate that sex differences in regulation of the GABAA -R in specific brain regions may be an important factor in the observed gender differences in mood disorders. Thus, we investigated possible sex differences in GABAA -R subunit expression and anxiety during PWD. To this end, we utilized the acoustic startle response (ASR) to assess anxiety levels in male and female rats undergoing PWD as the ASR is also applicable to the assessment of human anxiety responses. We also investigated GABAA -R ,4 subunit expression in the amygdala, as the amygdala directly regulates the primary startle circuit. Female rats exhibited a greater ASR during PWD than controls, indicating higher levels of anxiety and arousal. In contrast, male rats undergoing PWD did not demonstrate an increased ASR. The sex differences in the ASR were paralleled by sex differences in the expression of the GABAA -R ,4 subunit in the amygdala such that ,4 subunit expression was up-regulated in females during PWD whereas ,4 levels in males undergoing PWD were not altered relative to controls. These findings might have implications regarding gender differences in human mood disorders and the aetiology of premenstrual anxiety. [source] | |||||||||||||||||||