Localisation de l'interférence forme/couleur au niveau perceptuel dans une tache de type Stroop avec des stimuli-dessins.

Four studies with 24 19–35 yr old French-speaking adults examined the localization of perceptual form–color interference in a Stroop task with drawings. Results indicate that the time required to name the color of an incongruently colored object, such as a blue banana, was significantly longer than that for a neutral object (a red book). The same effect was found for identifying the color of the ink in which the names of these observed objects were printed. However, there did not appear to be a common semantic component in the interference observed in the 2 tasks. Extended practice on the task with the names of incongruently colored objects did not transfer to the task with the drawings of the same objects. The time to discriminate the colors of 2 drawings of incongruently colored objects was significantly longer than that for 2 drawings of neutral objects, suggesting that a perceptual inhibition occurred for incongruently colored objects (objects for which color was normally an integral part of the stimulus) that created a delay in perceiving the object's color. This contextual interference may be the complementary phenomenon to the object superiority effect. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Firing properties of head direction cells in the rat anterior thalamic nucleus: dependence on vestibular input

Vestibular information influences spatial orientation and navigation in laboratory animals and humans. Neurons within the rat anterior thalamus encode the directional heading of the animal in absolute space. These neurons, referred to as head direction (HD) cells, fire selectively when the rat points its head in a specific direction in the horizontal plane with respect to the external laboratory reference frame. HD cells are thought to represent an essential component of a neural network that processes allocentric spatial information. The functional properties of HD cells may be dependent on vestibular input. Here, anterior thalamic HD cells were recorded before and after sodium arsanilate-induced vestibular system lesion. Vestibular lesions abolished the directional firing properties of HD cells. The time course of disruption in the directional firing properties paralleled the loss of vestibular function. Arsanilate-treated rats exhibited only minor changes in locomotor behavior, which were unlikely to account for the loss of direction-specific firing. Vestibular lesions also disrupted the influence of angular head velocity on anterior thalamic single-unit firing rates. Finally, a subset of anterior thalamic neurons recorded from vestibular-lesioned rats exhibited a pattern of intermittent firing bursts that were distinctly unrelated to HD. This novel anterior thalamic firing pattern has not been encountered in any vestibular-intact rat. These data suggest that: (1) the neural code for directional bearing is critically dependent on vestibular information; and (2) this loss of HD cell information may represent a neurobiological mechanism to account for the orientation and navigational deficits observed after vestibular dysfunction.     

Development of the use of sound in the search behavior of infants.

Investigated 48 7–9 mo olds' use of sound to guide their search behavior by presenting Ss with standard object-permanence tasks. The same tasks were then presented to Ss but an object was used that made sound as it was being hidden and continued to make sound from its hiding place. Ss were then presented with a task in which a sound-producing object was surreptitiously hidden and then sounded. Ss began to use sound to direct their search in Stage 4. The use of sound to locate the surreptitiously hidden sound-producing object appeared to come earlier than the use of sound to locate objects in displacement tasks; the use of sound to locate objects in displacement tasks was influenced by the complexity of the displacement. Results suggest that the role of sound in the construction of the object is a developing one that continues well into the 2nd yr of life. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterogeneity of growth hormone (GH)-producing cells in aging male rats: ultrastructure and GH gene expression in somatotrope subpopulations

Mammalian aging is characterized by a decline in the content and release of pituitary growth hormone (GH). However, few studies on the age-related changes in the population of GH-producing cells (somatotropes) have been carried out. We have investigated whether changes in number, ultrastructure and GH gene expression in subpopulations of somatotropes could explain the reduced GH release in aged rats. Three representative ages were studied: adult (5-month-old), old (19-month-old), and senescent (26-month-old) male rats. The total number of immunoreactive-GH cells per pituitary gland remained invariable to age. The separation of dispersed pituitary cells on a density gradient yielded two somatotrope subpopulations, of low density (LD) and high density (HD). Both subpopulations were equally represented in adults, whereas in old and senescent rats a predominance of LD-somatotropes was observed. Morphometric analysis showed that subpopulations exhibited storage and biosynthetic features inversely related. In LD-somatotropes, rough endoplasmic reticulum (RER) was more prominent but secretory granules (SG) were less abundant than in HD somatotropes. Concurrently, in situ hybridization for GH mRNA showed that GH gene expression was higher in LD-cells. Differences between subpopulations were essentially retained through the animals' lifespan, but small-sized SG, reduced RER, and low GH mRNA levels were inherent to aging both in LD- and in HD-somatotropes. The present findings demonstrate that the reduced content of pituitary GH in aged male rats is not due to a diminished number of GH-producing cells, but to the numerical predominance of scarcely granulated LD-somatotropes, combined with the decline in GH biosynthetic capacity observed in both subpopulations. In addition, age-related changes in ultrastructure and GH gene expression suggest a chronic inhibition of GH release and/or a weak stimulation of GH biosynthesis affecting both subpopulations.     

Interaction between the postsubiculum and anterior thalamus in the generation of head direction cell activity

Previous research has identified neurons in the postsubiculum (PoS) and anterior dorsal thalamic nucleus (AD) of the rat that discharge as a function of the animal's head direction. In addition, anatomical studies have shown that the AD and PoS are reciprocally connected with one another. The current study examined whether head direction (HD) cells in each of the two areas is dependent on input from the other structure. After both electrolytic or neurotoxic lesions of the AD, no cells were identified with direction-specific discharge in the PoS. In contrast, AD HD cell activity was still present after neurotoxic lesions to the PoS. However, AD HD cells in PoS-lesioned rats exhibited three important differences compared with AD HD cells in intact animals: (1) their directional firing range was significantly larger, (2) their firing predicted the animal's future head direction by a larger amount, and (3) their preferred firing direction was substantially less influenced by a prominent visual landmark within the recording environment. These results indicate that information critical for HD cell activity is conveyed in both directions between the AD and the PoS; whereas the AD is necessary for the presence of HD cell activity in the PoS, the PoS appears important in allowing visual landmarks to exert control over the preferred firing direction of AD HD cells. These findings have implications for several computational models that propose to account for the generation of the HD cell signal.     

An analysis of response, direction and place learning in an open field and T maze.

Rats were trained to locate food in a response, direction, or place problem on an open field located at 2 positions. In Experiment 1, both the response and direction groups solved the problem. The place group failed to solve the task in approximately 300 trials. Experiment 2 demonstrated that rats need distinguishable start points to solve a place problem when neither a response nor a direction solution is available. Findings from Experiment 3 suggest that a combination of path traveled and distinct cues help to differentiate start points. Experiment 4 replicated the findings using a T maze. These results suggest 'place' solutions are difficult for rats. The data are discussed with respect to conditional learning and modem spatial mapping theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Angular velocity and head direction signals recorded from the dorsal tegmental nucleus of gudden in the rat: Implications for path integration in the head direction cell circuit.

When a rat navigates through space, head direction (HD) cells provide an ongoing signal of the rat's directional heading. It is thought that these cells rely, in part, on angular path integration of the rat's head movements. This integration requires that the HD cell system receive information about angular head movements and that this information be combined with the current directional signal, to generate the next "predicted" direction. Recent data suggest that the dorsal tegmental nucleus (DTN) may play a critical role in helping to generate the HD cell signal. To test this, recordings were made from cells in the DTN in freely moving rats. The following cell types were found: (a) "classic" HD cells, (b) angular velocity cells, and (c) cells that fired as a function of both head direction and angular velocity. Thus, DTN cells exhibit firing characteristics that are critical to the neural circuit hypothesized for generation of the HD cell signal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the behavioral significance of head direction cells: Neural and behavioral dynamics during spatial memory tasks.

Current theories assume that rats use the directional information reflected by head direction (HD) cells when performing spatial tasks. This assumption was assessed by monitoring anterior thalamic HD cell activity and relating it to the S's (female rats) behavioral response on 2 spatial memory tasks and tested either reference memory or working memory. In both tasks, there was a significant number of trials where there was not a tight coupling between the preferred firing direction of HD cells and the direction of the behavioral response. In addition, it was possible to intentionally change the preferred direction of HD cells without affecting performance accuracy. An additional experiment showed that manipulations that affected internal, but not external, cues impaired performance on the reference memory task. These findings suggest that HD cell activity was not consistently guiding Ss' behavior on these 2 spatial tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inflammation-induced Fos protein expression in the rat spinal cord is enhanced following dorsolateral or ventrolateral funiculus lesions

Previous studies have shown an enhanced expression of Fos protein-like immunoreactivity in the lumbar spinal cord of rats with complete spinal transection following persistent hindpaw inflammation. To further locate the spinal pathways responsible for these effects, we compared the inflammation-evoked Fos expression in rats with bilateral lesions of the dorsolateral (DLFX) or ventrolateral (VLFX) funiculus, and with rats with a sham operation. The results indicate that the number of Fos-labeled neurons was significantly increased in all laminae of the dorsal horn ipsilateral to the inflamed hindpaw and in contralateral deep dorsal horn in both DLFX and VLFX rats compared to sham-operated rats. Moreover, when comparing DLFX and VLFX rats, in the ipsilateral spinal cord, DLFX resulted in more Fos expression in the deep dorsal horn; in contrast, a larger number of Fos-labeled cells in superficial laminae was observed in VLFX rats. These results suggest that modulatory systems, which descend in both DLF and VLF pathways, mediate the enhanced net descending nociceptive inhibition after persistent inflammation, although the supraspinal sites of origin of each pathway are likely functionally diverse.     

Persistence of colchicine resistance in Ehrlich-Lettré ascites tumors and cell strains

The effect of colchicine on mitoses of mutant HD33 Ehrlich-Lett?e ascites cells growing in vivo and in vitro was studied. HD33 mouse ascites tumors are colchicine-resistant. The LD50 of colchicine in mice bearing HD33 ascites tumors was 1.4 mg/kg body weight (b.w.), but a single dose of 3.33 mg colchicine/kg b.w. failed to suppress the anaphase of HD33 tumor mitoses for 24 h. No change in the level of colchicine resistance was observed after 269 weekly transplantations of HD33 ascites tumors without colchicine. In suspension culture, growth of HD33 ascites cells ceased at 1.5 x 10(-6) M colchicine. 10(-5) M colchicine suppressed the anaphase of HD33 mitoses and produced typical C-mitoses within one hour. The same effects on mitoses of colchicine sensitive Ehrlich ascites cells in vitro were achieved with 10(-6) M colchicine. In HD33 ascites cell cultures grown without colchicine, only a slight increase in colchicine sensitivity was registered after 5 years. Parallel cultures were propagated for the same period in the presence of 10(-7) M colchicine (HD33C ascites cells) without detectable growth alterations; the resistance level increased slightly. The limit of 10(-6) M colchicine was tolerated by the ascites cells in permanent culture without growth reduction (HD33CS ascites cells). 3H-colchicine binding studies suggest a permeability barrier of the plasma membrane as a mechanism of genetically fixed resistance.     

A general rule for the relationship between hydrophobic effect and conformational stability of a protein: stability and structure of a series of hydrophobic mutants of human lysozyme

Previous research has shown that head direction (HD) cells in both the anterior dorsal thalamus (ADN) and the postsubiculum (PoS) in rats discharge in relation to familiar, visual landmarks in the environment. This study assessed whether PoS and ADN HD cells would be similarly responsive to nonvisual or unfamiliar environmental cues. After visual input was eliminated by blindfolding the rats, HD cells maintained direction-specific discharge, but their preferred firing directions became less stable. In addition, rotations of the behavioral apparatus indicated that some nonvisual cues (presumably tactile, olfactory, or both) exerted above chance stimulus control over a cell's preferred firing direction. However, a prominent auditory cue was not effective in exerting stimulus control over a cell's preferred direction. HD cell activity also was assessed after rotation of a novel visual cue exposed to the rat for 1, 3, or 8 min. An 8-min exposure was enough time for a novel visual cue to gain control over a cell's preferred direction, whereas an exposure of 1 or 3 min led to control in only about half the sessions. These latter results indicate that HD cells rely on a rapid learning mechanism to develop associations with landmark cues.     

Cue control and head direction cells.

Previous research has shown that head direction (HD) cells in both the anterior dorsal thalamus (ADN) and the postsubiculum (PoS) in rats discharge in relation to familiar, visual landmarks in the environment. This study assessed whether PoS and ADN HD cells would be similarly responsive to nonvisual or unfamiliar environmental cues. After visual input was eliminated by blindfolding the rats, HD cells maintained direction-specific discharge, but their preferred firing directions became less stable. In addition, rotations of the behavioral apparatus indicated that some nonvisual cues (presumably tactile, olfactory, or both) exerted above chance stimulus control over a cell's preferred firing direction. However, a prominent auditory cue was not effective in exerting stimulus control over a cell's preferred direction. HD cell activity also was assessed after rotation of a novel visual cue exposed to the rat for 1, 3, or 8 min. An 8-min exposure was enough time for a novel visual cue to gain control over a cell's preferred direction, whereas an exposure of 1 or 3 min led to control in only about half the sessions. These latter results indicate that HD cells rely on a rapid learning mechanism to develop associations with landmark cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Roles of COX-1 and COX-2 in gastrointestinal pathophysiology

We studied 40 cases of Hodgkin's disease (HD) from Costa Rica for evidence of Epstein-Barr virus (EBV) in the Reed-Sternberg and Hodgkin (RS-H) cells. We also compared the epidemiologic features of these patients with previous reports of HD in industrialized and developing nations. Because Costa Ricans enjoy a relatively higher standard of living than the residents of other developing Central American nations yet live in the same general geographic region and are genetically similar, we believed that this comparison might shed additional light on the hypothesis that the prevalence of EBV in HD and the epidemiologic factors of HD are influenced by socioeconomic factors. In 16 (40%) of 40 cases, immunohistochemical studies demonstrated that the RS-H cells were positive for EBV latent membrane protein (LMP), including 1 case of lymphocytic depletion analyzed, 12 (86%) of 14 cases of mixed cellularity, and 3 (15%) of 20 cases of nodular sclerosis. All five cases of lymphocytic predominance were negative. In the 16 EBV LMP-positive cases, polymerase chain reaction studies revealed that the virus was type A in 12 cases and type B in 4 cases. Nodular sclerosis was the most common type of HD, accounting for 20 cases (50%), followed by mixed cellularity, with 14 cases (35%). The relatively low prevalence of EBV in the RS-H cells of HD and the high incidence of nodular sclerosis in Costa Rica are similar to industrialized nations and are unlike HD in neighboring Central American countries. These findings further support the hypothesis that the prevalence of EBV in HD and the epidemiologic features of HD are most closely linked with socioeconomic conditions, and geographic location or ethnic heritage are of relatively less importance.     

Sex Differences in the Behavioral Response to Spatial and Object Novelty in Adult C57BL/6 Mice.

The present studies examined sex differences in object localization and recognition in C57BL/6 mice. Experiment 1 measured responses to spatial novelty (object displacement) and object novelty (object substitution). Males strongly preferred displaced and substituted objects over unchanged objects, whereas females showed a preference in only 1 measure of object novelty. Experiment 2 further examined object recognition by presenting mice with 2 identical objects, followed 24 hr or 7 days later by testing with a familiar and a novel object. After 24 hr, males preferentially explored the novel object, whereas females exhibited no such preference. Neither sex displayed a preference for the novel object after 7 days. The data suggest that male mice are superior to females at localizing and recognizing objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular analysis of the IgH gene in 212 cases of Hodgkin's disease: correlation of IgH clonality with the histologic and the immunocytochemical features

The aims of this study are to evaluate the frequency of clonal immunoglobulin heavy chain gene rearrangements in paraffin-embedded samples of Hodgkin's disease (HD) with use of the polymerase chain reaction method and to correlate the molecular findings with the histologic and immunocytochemical features. DNA extracts from paraffin-embedded sections from 212 HD samples were used for amplification of the IgH gene by use of framework 2 and framework 3 region primers. Immunohistochemical studies were performed on paraffin sections by use of monoclonal antibodies for CD20 and latent membrane protein-1 and polyclonal antibody for CD3. With use of both primer combinations, monoclonality was detected in 18.7% of lymphocyte-predominant HD cases and in 32.2% of classical HD cases. These results suggest that immunoglobulin heavy chain gene clonal rearrangements are relatively frequent in classical HD. In addition, the statistical analyses of the genotypic and immunocytochemical data revealed that the detection of B-cell populations is significantly associated with the expression of CD20 on HRS cells. There was, however, no correlation between the histologic subtype, the percentage of HRS cells, the presence of latent membrane protein-1 expression, and the molecular analysis results.     

Intraosseous device of perfusion. Apropos of 3 cases before hospitalization]

Hodgkin's disease (HD) has seldom been reported after transplantation. Epstein-Barr virus (EBV) is present in about 50% of Reed-Sternberg cells in HD developing in immunocompetent individuals, but is more frequently found in HD of acquired immune deficiency syndrome patients. We report 7 cases of HD that occurred in transplant recipients. Clinical and pathological data and studies of EBV reveal specific features of HD after transplantation. Six patients received kidney transplants and 1 patient received combined kidney and pancreas transplantation. Immunosuppressive therapy consisted of cyclosporine, steroids, azathioprine, and antilymphocyte globulins. One patient received, in addition, anti-CD3 mAb therapy and an EBV+ B cell lymphoma developed. Retrospective EBV serological data from patients were collected. Tumors were classified according to pathology. EBV studies were conducted by immunohistochemical methods with monoclonal antibodies to EBV-latent membrane protein (LMP) or EBV-nuclear antigen 2 (EBNA2), and by in situ hybridization for latent nuclear EBV-early RNAs (EBERs). The mean lapse of time between transplantation and HD was 49 months. Six patients presented with enlarged lymph nodes and 1 patient presented with liver involvement. HD was classified as IA in 2 patients, IIA in 3 patients, IIIB in 1 patient, and IVB in 1 patient. Four patients had primary EBV infection after graft, before HD, and the others reactivated latent EBV infection. Histological subtypes were mixed cellularity in 6 cases and lymphocytic depletion in 1 case. Latent EBV infection was detected with EBERs in all tumors. Reed-Sternberg cells expressed LMP, and were negative for EBNA2 expression. Six patients were treated: 2 patients at stage I received radiotherapy, and relapsed within 1 year with a more advanced stage of HD; chemotherapy was indicated as primary therapy in 5 patients, and as salvage therapy in 2 patients; it was associated with radiotherapy in 4 patients. Immunosuppressive therapy was reduced in all patients. Four patients were alive and in complete remission 18, 25, 31, and 67 months after chemotherapy, with a functioning graft in 3 patients. Two patients died of infection. Mixed cellularity is the most frequent histological subtype observed in HD occurring in transplant patients. EBV is present in all Reed-Sternberg cells. Posttransplant HD shows similarities with human immunodeficiency virus-associated HD. These facts argue for a role of EBV infection and immunosuppression in the progression of HD after transplantation.     

Combined blockade of serotonergic and muscarinic transmission disrupts the anterior thalamic head direction signal.

Head direction (HD) cells have been speculated to be part of a network mediating navigational behavior. Previous work has shown that combined administration of serotonergic and muscarinic antagonists eliminates hippocampal theta activity and produces navigational deficits more severe than blockade of either neurotransmitter system alone. The authors sought to assess this effect on the directional characteristics of HD cells. HD cells were recorded from the anterior dorsal thalamus of Long-Evans rats before and after administration of the serotonergic antagonist methiothepin, the muscarinic antagonist scopolamine, both drugs, or saline. Combined drug administration produced HD cells with preferred directions that drifted within recording sessions. In addition, cells showed shifts in the preferred directions at the start of a session relative to the position of the major landmarks, suggesting that combined drug administration led to deficits in landmark control of the HD system. Single drug exposures to methiothepin or scopolamine did not noticeably affect the directional characteristics of HD cells. This finding that navigation-impairing drugs can disrupt the HD signal provides further evidence that this network plays an important role in navigational behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preferential use of the landmark navigational system by head direction cells in rats.

Previous studies have identified a population of cells recorded in the postsubiculum and the anterior thalamic nucleus (ATN) that discharge as a function of an animal's head direction (HD) in the horizontal plane. The present experiments monitored HD cell activity when rats were confronted with a situation in which directional information from internal sensory sources (e.g., proprioceptive, vestibular, or motor efference copy) conflicted with directional information derived from familiar, external landmarks. Results showed that when a salient, familiar cue was reintroduced to rat's environment into a position that conflicted with the cell's current firing direction, HD cells in both the ATN and the postsubiculum shifted their preferred direction to reflect their originally established orientation with this cue. This finding suggests that sensory inputs onto HD cells from external landmark cues are capable of overriding spatial information developed through internal sensory cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of combined lesions of the subicular complex and the entorhinal cortex on two forms of spatial navigation in the water maze.

The role of the subicular complex and entorhinal cortex (SUB–EC) in spatial learning was examined in 2 water maze experiments. In Experiment 1, rats had to locate a hidden platform that was always a fixed distance and direction from an intramaze landmark. Each day, the landmark and platform were moved to a new location. Both control and SUB–EC-lesioned rats learned to locate the platform equally readily during training. However, the control group was impaired in locating the platform when the visual extramaze cues were concealed, whereas the lesioned group was unaffected by this manipulation. In Experiment 2, the lesioned rats were impaired in finding a hidden platform that was in a fixed place in the water maze and showed no evidence of having learned its location in a probe test. These results suggest that damage to the SUB–EC impairs the integration of geometric information but spares a more general navigational-directional strategy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expression and loss of the transferrin receptor in growing and differentiating HD3 cells

During induced differentiation and maturation of HD3 cells (a chicken erythroblast cell line infected with a temperature-sensitive mutant of the avian erythroblastosis virus), the levels of transferrin receptor (TFR) and nucleoside transporter increase. Both these activities increase before elevated levels of hemoglobin are detected. Shortly after induction, as cellular TFR levels rise, a native-size TFR is detected in the cell-free culture medium, associated with an exosome fraction (100,000 xg pellet). Nucleoside transporter (measured as NBMPR-binding activity) is not increased in this pellet with induction. Previous studies have suggested that exosome formation in peripheral reticulocytes may be a significant route for loss of specific membrane proteins (Johnstone et al., 1991). Although the present experiments in HD3 cells do not address the quantitative importance of exosome formation, the studies suggest that exosome formation is an early event in commitment to the red cell lineage and is not a phenomenon restricted to the terminal stages of red cell maturation.