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PubMed2004

Nature as a model for technical sensors.

Nature has developed a stunning diversity of sensory systems. Humans and many animals mainly rely on visual information. In addition, they may use acoustic, olfactory, and tactile cues for object detection and spatial orientation. Beyond these sensory systems a large variety of highly specialized sensors have evolved. For instance, some buprestid beetles use infrared organs for the detection of forest fires. The infrared sensors of boid and crotalid snakes are used for prey detection at night. For object detection and spatial orientation many species of nocturnal fish employ active electrolocation. This review describes certain aspects of the detection and processing of infrared and electrosensory information. We show that the study of natural exotic sensory systems can lead to discoveries that are useful for the construction of technical sensors and artificial control systems. Comparative studies of animal sensory systems have the power to uncover at least a small fraction of the gigantic untapped reservoir of natural solutions for perceptive problems.

Animals↗

PubMed1994

Psychopathology and cognitive decline in dementia.

This study investigated the correlation between the degree and quality of cognitive impairment and the presence and degree of severity of psychopathology. Sixty-four demented outpatients were rated for cognition by the Mental Status Questionnaire and for psychopathology by the BEHAVE-AD Reisberg questionnaire. A statistical analysis of the correlations between the cognitive and psychopathological parameters was performed. The study indicated a high rate of psychopathology (as high as 83% of the patients). No significant correlation was found between the cognitive grading score and the presence of psychopathology, except in the space of declined spatial orientation and the occurrence of hallucinations. Psychopathology is a common phenomenon occurring in the course of dementia in the form of Alzheimer's disease or multi-infarct dementia. There is a certain increase in the degree of psychopathology that correlated with cognitive impairment. The high correlation between impaired spatial orientation and the presence of hallucinations seems to point to a common neuropathological substrate.

Aged↗

PubMed2001

Background, but not foreground, spatial cues are taken as references for head direction responses by rat anterodorsal thalamus neurons.

Two populations of limbic neurons are likely neurophysiological substrates for cognitive operations required for spatial orientation and navigation: hippocampal pyramidal cells discharge selectively when the animal is in a certain place (the "firing field") in the environment, whereas head direction cells discharge when the animal orients its head in a specific, "preferred" direction. Cressant et al. (1997) showed that the firing fields of hippocampal place cells reorient relative to a group of three-dimensional objects only if these are at the periphery, but not the center of an enclosed platform. To test for corresponding responses in head direction cells, three objects were equally spaced along the periphery of a circular platform. Preferred directions were measured before and after the group of objects was rotated. (The rat was disoriented in total darkness between sessions). This was repeated in the presence or absence of a cylinder enclosing the platform. When the enclosure was present, the preferred directions of all 30 cells recorded shifted by the same angle as the objects. In the absence of the enclosure, the preferred directions did not follow the objects, remaining fixed relative to the room. These results provide a possible neurophysiological basis for observations from psychophysical experiments in humans that background, rather than foreground, cues are preferentially used for spatial orientation.

Animals↗

PubMed1991

Bacteriological composition and structure of granular sludge adapted to different substrates.

The bacteriological composition and ultrastructure of mesophilic granular methanogenic sludge from a large-scale Upflow Anaerobic Sludge Blanket reactor treating wastewater from a sugar plant and of sludge granules adapted to ethanol and propionate were studied by counting different bacterial groups and by immunocytochemical methods. Propionate-grown granular sludge consisted of two types of clusters, those of a rod-shaped bacterium immunologically related to Methanothrix soehngenii and those consisting of two different types of bacteria with a specific spatial orientation. One of these bacteria reacted with antiserum against Methanobrevibacter arboriphilus AZ, whereas the other is most likely a propionate-oxidizing bacterium immunologically unrelated to Syntrophobacter wolinii. Sludge granules obtained from the large-scale Upflow Anaerobic Sludge Blanket reactor and granules cultivated on ethanol did not show the typical spatial orientation of bacteria. Examination of the bacterial composition of the three types of granules by light and electron microscopy, the most-probable-number method, and by isolations showed that M. arboriphilus and M. soehngenii were the most abundant hydrogenotrophic and acetoclastic methanogens in propionate-grown sludge. Methanospirillum hungatei and Methanosarcina barkeri predominated in ethanol-grown granules, whereas many morphotypes of methanogens were abundant in granules from the full-scale reactor.

Ethanol↗

PubMedDate not supplied

The effects of prenatal stress on learning in rats in a Morris maze.

The offspring of female Wistar rats subjected to daily stress (they were placed in an unfamiliar social group for 1 h) during the last third of pregnancy were studied. The offspring of these females were tested for the ability to perform spatial orientation in a Morris water maze at the ages of two and four months. Prenatal stress had no effect on the ability of rats to learn in the Morris maze. However, two-month-old animals subjected to prenatal stress, unlike controls, demonstrated less flexibility in their behavioral strategy in solving the spatial orientation task. These animals were characterized by a clear tendency for their behavior to perseverate. By the age of four months, the differences between the control and prenatally stressed animals had disappeared.

Animals↗

PubMed2003

Tissue reaction to orthodontic tooth movement in different bone turnover conditions.

OBJECTIVES: To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states. DESIGN: 'Split mouth' design performing orthodontic tooth movement in 52, 6-month-old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University. EXPERIMENTAL VARIABLE: The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels. OUTCOME MEASURE: Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups. RESULTS: Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco-distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono-mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group. CONCLUSION: In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups.

Alveolar Process↗

PubMed1998

Differences in the iliolumbar ligament and the transverse process of the L5 vertebra in young white and black people.

The anatomy of the iliolumbar ligament (ILL) and the spatial orientation of the transverse process of the L5 vertebra were studied in 62 young black (n = 29) and white (n = 33) men and women during routine autopsy. The aim of the study was to determine possible racial differences in the structure and attachments of the iliolumbar ligament. The present study also investigated the spatial orientation of the transverse process of the L5 vertebra since the ILL has been reported to attach to the transverse process. The measurements of the iliolumbar ligament were carried out with a digital vernier caliper while the transverse process angles were measured with an adjustable protractor. The ligament in black people was made up of a single, markedly longer band compared to white people, where the ligament was made up of two shorter bands. The ILL measured 61.8 +/- 1.3 mm in black and 33.2 +/- 1.5 mm white men, and in black women 61.3 +/- 0.9 mm versus 32.2 +/- 1.2 mm in white women (p <0.01). Further, the ILL was markedly wider in black than white subjects (p <0.01). The horizontal and vertical angle also varied greatly between black and white subjects (p <0.01). These are previously unrecognized observations. Albeit unsubstantiated, these findings may have implications for understanding the etiology of various low back stress problems.

Adolescent↗

PubMed2000

Difference spatial distribution function analysis of aqueous solutions. IV. Hydration structure changes of ethylene glycol solutions throughout conformational change process from gGg' to tGg' conformers.

Monte Carlo (MC) simulations were carried out for an infinitely dilute aqueous solution of two stable conformers (gGg' and tGg') and of three conformations between gGg' and tGg' conformers of ethylene glycol (EG) at 298K. Based on the spatial distribution function (SDF) goo(x,y,z), obtained from the MC simulation in the above conformations in liquid water, the high distribution of hydration water molecules could be divided into hydrogen acceptor (HA), hydrogen donor (HD), MIX (overlapped distribution of HA and HD), and hydrophobic hydration (HH) regions. The spatial orientations of hydrogen-bonded water molecules were found to be of a linear type with a triple-layer structure in the HA region and HA part (in the MIX region), and double-layer structures in the HD region and HD part (in the MIX region). In addition, it was apparent that the spatial orientations of these water molecules were of the linear type throughout the conformational change process from gGg' to tGg' conformers in liquid water. From the difference SDF (DSDF), deltagoo(x,y, z), between the SDFs of two conformations, we concluded that the distribution of hydration water molecules in the HA and HD parts of the MIX region are governed by the competition of internal hydrogen bonds between the hydrogen atom and two lone-pair electrons on the oxygen atom of an EG molecule.

Algorithms↗

PubMed2006

Manual response preparation and saccade programming are linked to attention shifts: ERP evidence for covert attentional orienting and spatially specific modulations of visual processing.

The premotor theory of attention claims that attentional shifts are triggered during response programming, regardless of which response modality is involved. To investigate this claim, event-related brain potentials (ERPs) were recorded while participants covertly prepared a left or right response, as indicated by a precue presented at the beginning of each trial. Cues signalled a left or right eye movement in the saccade task, and a left or right manual response in the manual task. The cued response had to be executed or withheld following the presentation of a Go/Nogo stimulus. Although there were systematic differences between ERPs triggered during covert manual and saccade preparation, lateralised ERP components sensitive to the direction of a cued response were very similar for both tasks, and also similar to the components previously found during cued shifts of endogenous spatial attention. This is consistent with the claim that the control of attention and of covert response preparation are closely linked. N1 components triggered by task-irrelevant visual probes presented during the covert response preparation interval were enhanced when these probes were presented close to cued response hand in the manual task, and at the saccade target location in the saccade task. This demonstrates that both manual and saccade preparation result in spatially specific modulations of visual processing, in line with the predictions of the premotor theory.

Adolescent↗

PubMed2003

The evolution of the cognitive map.

The hippocampal formation of mammals and birds mediates spatial orientation behaviors consistent with a map-like representation, which allows the navigator to construct a new route across unfamiliar terrain. This cognitive map thus appears to underlie long-distance navigation. Its mediation by the hippocampal formation and its presence in birds and mammals suggests that at least one function of the ancestral medial pallium was spatial navigation. Recent studies of the goldfish and certain reptile species have shown that the medial pallium homologue in these species can also play an important role in spatial orientation. It is not yet clear, however, whether one type of cognitive map is found in these groups or indeed in all vertebrates. To answer this question, we need a more precise definition of the map. The recently proposed parallel map theory of hippocampal function provides a new perspective on this question, by unpacking the mammalian cognitive map into two dissociable mapping processes, mediated by different hippocampal subfields. If the cognitive map of non-mammals is constructed in a similar manner, the parallel map theory may facilitate the analysis of homologies, both in behavior and in the function of medial pallium subareas.

Animals↗

PubMed1999

Polyethylene wear vector in vivo: a three-dimensional analysis using retrieved acetabular components and radiographs.

Polyethylene wear of the acetabular component can be described as one or more vectors. To help clarify the mechanisms of wear advancement in vivo, we used a combination of retrieved implants and radiographs to describe the three-dimensional wear vectors in total hip arthroplasty. The wear vectors in 41 retrieved implants from a single manufacturer were measured with use of the shadowgraph technique, and the spatial orientation of each implant was calculated from serial anteroposterior pelvic radiographs. On the basis of the combination of the wear vector in the implant and implant orientation in the pelvis, the wear vectors in vivo were determined. The mean wear vector was directed 8.1 degree lateral in the coronal plane and 4.1 degree posterior in the sagittal plane. The wear vectors in vivo showed a relatively wide range of directions, not necessarily coinciding with the commonly presumed resultant force in the hip. The wear vectors were not associated with the spatial orientation of the acetabular components, but cups with impingement demonstrated more anterior wear than did those without impingement. Our results suggest that the process of polyethylene wear is not as simple as previously described and that several factors influence advancement of wear in vivo.

Acetabulum↗

PubMed2001

Micropattern orientation and spatial localization.

A current, popular, theory of spatial localization holds that the visual system represents the location of simple objects by a single positional tag, the accuracy of which is largely independent of the internal properties of the object. We have already presented evidence of the limitations of such a view (Keeble & Hess (1998). Vision Research, 38, 827-840) in that 3-micropattern alignment performance was found to be dependent on the orientation of the micropatterns. We tested whether this was caused by a local anisotropy in positional coding by conducting 3-micropattern bisection experiments with varying patch orientation. No corresponding effect of patch orientation was found, implying a difference in the mechanisms used for the two tasks. In a further experiment we show that alignment task performance is very similar to the otherwise identical 2-patch orientation discrimination task. We conclude that the 3-micropattern alignment task is mediated by orientational mechanisms. We therefore present a 2nd-order orientation model for 3-patch alignment.

Anisotropy↗

PubMed1994

Are rostral and caudal parts of the hippocampus of the lizard Gekko gecko related to different types of behaviour?

Spatial orientation is an important function of the hippocampus. In reptiles the medial cortex is the equivalent of the mammalian hippocampus. In this study we compared the structure and connections of the hippocampus of ground-dwelling lizards with those of gekkonid lizards which are able to walk on vertical walls as well as on the ceiling. This last type of locomotor behaviour makes high demands on spatial orientation. It appeared that, in contrast to the ground-dwelling lizards, in geckos the small-celled part of the medial cortex can be divided into a rostral and a caudal part. The rostral part receives visual, auditory, vestibular and proprioceptive information from the dorsolateral thalamic nucleus. The caudal part is connected with the lateral cortex which is the recipient of olfactory information from the main olfactory bulb. Also the efferent connections of the rostral and caudal part of the small-celled part of the medial cortex to the septum, and via the septum to the preoptic and hypothalamic areas remain strictly separated. Since different behavioural aspects are localized in different preoptic and hypothalamic subdivisions it seems likely that the two parts of the hippocampus in gekkonid lizards serve different behavioural functions.

Animals↗

PubMed2000

Biomechanical study of a computer simulated reconstruction of the anterior cruciate ligament (ACL).

UNLABELLED: The purpose of the study was to use a computer simulation of various surgical techniques for reconstruction of the anterior cruciate ligament (ACL) to study graft biomechanics. To ensure the normal function of the cruciate ligament and, consequently, normal kinematics of the knee joint, the complex structure of the normal ACL must be built into the graft. METHODS: First the ACL was modeled and then a reconstruction of the ACL was simulated on a computer model of the cadaveric knee. Biomechanical patterns of the ACL and the modeled grafts in different spatial orientations and positions of the femoral attachments were studied. Isometricity of the peripheral and central fibers of the ACL and grafts was measured and the average fiber length change and isometric pattern of fibers in the graft were compared. RESULTS: None of the ACL fibers is isometric and fiber length change varies with individual fibers of the original ligament or graft. The average length change of graft fibers depends on the position of the femoral attachment in the sagittal plane. It is smaller in anterior positions in relation to the geometric center of the femoral origin of the ACL, and larger in posterior positions. The isometric pattern of fibers in the graft in isometric orientations resembles most closely the pattern of the original ACL. CONCLUSIONS: A computer simulation of various surgical techniques of reconstruction of the ACL can be successfully used for the study of biomechanics. The most significant kinematic characteristics of the ACL is gradual recruitment of graft fibers during knee extension, which can be defined as the pattern of isometricity. The isometric pattern of the graft is primarily influenced by spatial orientation.

Anterior Cruciate Ligament↗

PubMedDate not supplied

Interactions of aryloxyphenoxypropionic acids with sensitive and resistant acetyl-coenzyme a carboxylase by homology modeling and molecular dynamic simulations.

Acetyl-coenzyme A carboxylase (ACCase) has been identified as one of the most important targets of herbicides. In the present study, we constructed homology models of the carboxyl-transferase (CT) domain of ACCase from sensitive and resistant foxtail and used these models as templates to study the molecular mechanism of herbicide resistance and stereochemistry-activity relationships of aryloxyphenoxypropionates (APPs). In the homology modeling structures, the dimer of the CT domain was formed by the side-to-side arrangement of the two monomers, in such a way that the N domain of one molecule is placed next to the C domain of the other. The dimeric association of sensitive foxtail CT was found to differ from that of resistant foxtail CT, and the spatial orientation of two key residues, Leu-695 and Ile-695, in these dimers also differed. The mutation of Ile to Leu may perturb the conformation of the dimeric interface, which may account for the molecular mechanism of herbicide resistance. Further docking analysis indicated that the binding model of high-active compounds is similar to that in the crystal structure of the enzyme-ligand complex. The different spatial orientations of ester groups of the isomers of APPs may explain the stereochemistry-activity relationship. Ser-698 formed a H-bonding interaction with all of the docked ligands, while Tyr-728 formed a pi-pi stacking interaction with some of the APPs. These findings may enhance our understanding of the molecular mechanism of herbicide resistance and stereochemistry-activity relationships, which may provide a new starting point for the identification of more potent inhibitors against both sensitive and resistant ACCase.

Acetyl-CoA Carboxylase↗

PubMedDate not supplied

Functional heterogeneity in cingulate cortex: the anterior executive and posterior evaluative regions.

The cingulate gyrus is a major part of the "anatomical limbic system" and, according to classic accounts, is involved in emotion. This view is oversimplified in light of recent clinical and experimental findings that cingulate cortex participates not only in emotion but also in sensory, motor, and cognitive processes. Anterior cingulate cortex, consisting of areas 25 and 24, has been implicated in visceromotor, skeletomotor, and endocrine outflow. These processes include responses to painful stimuli, maternal behavior, vocalization, and attention to action. Since all of these activities have an affective component, it is likely that connections with the amygdala are critical for them. In contrast, posterior cingulate cortex, consisting of areas 29, 30, 23, and 31, contains neurons that monitor eye movements and respond to sensory stimuli. Ablation studies suggest that this region is involved in spatial orientation and memory. It is likely that connections between posterior cingulate and parahippocampal cortices contribute to these processes. We conclude that there is a fundamental dichotomy between the functions of anterior and posterior cingulate cortices. The anterior cortex subserves primarily executive functions related to the emotional control of visceral, skeletal, and endocrine outflow. The posterior cortex subserves evaluative functions such as monitoring sensory events and the organism's own behavior in the service of spatial orientation and memory.

Amygdala↗

PubMed1995

Alterations in the immunoreactivity for muscarinic acetylcholine receptors and colocalized PKC gamma in mouse hippocampus induced by spatial discrimination learning.

This study describes changes in the immunoreactivity for muscarinic acetylcholine receptors (mAChRs) in the hippocampus of mice in relation to spatial discrimination behavior, employing the monoclonal antibody M35 raised against purified bovine mAChR protein. Performance in a hole board in which the animals learned the pattern of 4 baited holes out of 16 holes served as the measure of spatial discrimination learning and memory. Twenty-six adult male house mice were used, divided into four groups. Three groups served as various controls: group N (naive; blank controls); group H (habituated; animals were introduced to the hole board with all holes baited for 5 consecutive days), and group P (pseudo-trained; the animals were admitted to the hole board for 13 consecutive days with all holes baited). The T group (trained) was subjected to the hole board for 5 consecutive habituation days with all holes baited (similar to the H and P groups), followed by 8 successive training days with only four holes baited in a fixed pattern. During the 8 training days, the T group gradually acquired a pattern to visit the baited holes, whereas the P group continued visiting holes in a random fashion. The mice were killed 24 h after the last behavioral session. All principal cells in teh cornu ammonis (CA) and dentate gyrus (DG) of the habituated animals revealed increased levels of mAChR immunoreactivity (mAChR-ir) over the naive mice. A minor increase in mAChR-ir was found in the apical dendrites of the CA1 pyramidal cells. Pseudotraining resulted in a CA1-CA2 region with a low level of mAChR-ir, resembling naive animals, whereas the trained mice showed a further increase in mAChR-ir in the CA1-CA2 pyramidal cell bodies and apical dendrites. Optical density measures of the mAChR-ir in the CA1 region revealed a significant (P < 0.05) increase in the pyramidal cell bodies of the H and T group over the N and P group, and a significant (P < 0.05) increase in the apical dendrites of the T group over all other groups. In contrast to the CA1-CA2 region, both pseudotrained and trained mice revealed high mAChR staining in the CA3-CA4 region and the DG. These results indicate that prolonged exposure to the hole board is sufficient for an enhanced mAChR-ir in the CA3-CA4 and DG, whereas the increase in CA1-CA2 pyramidal cells is a training-specific feature related to spatial orientation. Nonpyramidal neurons within the CA1-CA2 region with enhanced mAChR-ir in the pyramidal cells, however, revealed a decreased level of mAChR-ir. The opposing effect of pyramidal and nonpyramidal cells suggests a shift in the excitability of the hippocampal microcircuitry. Previously we demonstrated an increase and redistribution of hippocampal protein kinase C gamma-immunoreactivity (PKC gamma-ir) induced by hole board learning in mice (Van der Zee et al., 1992, J Neurosci 12:4808-4815). Immunofluorescence double-labeling experiments conducted in the present study in naive and trained animals revealed that the principal cells and DG interneurons co-express mAChRs and PKC gamma, and that the immunoreactivity for both markers increased in relation to spatial orientation within these neurons. The mAChR-positive nonpyramidal cells of the CA1-CA2 region were devoid of PKC gamma and revealed an opposite training-induced effect. These results suggest that the postsynaptic changes in mAChR- and PKC gamma-ir reflect functional alterations of the hippocampal formation induced by spatial learning.

Animals↗

PubMed2000

[Planning and performance of orthopedic surgery with the help of individual templates].

Operational interventions can be planned and simulated accurately with the help of a three-dimensional reconstruction of the anatomical bone structures, created from the tomographic data of a patient. Computer-assisted navigation systems or robotic systems can assist the intraoperative realization of the planned intervention and may support the spatial orientation within the operational field. As an inexpensive alternative without the high excessive technical workload on the physicians or the surgical personnel, individual templates were developed in the Helmholtz Institute Aachen. In this approach the negative three-dimensional bone surface, known exactly from the 3D-reconstruction of the patient's bone by the planning system DISOS, is milled into a small cubic block of polycarbonate. During the intervention, the template serves as a reference for the spatial orientation and as a tool-guide for cutting or milling of the bone according to the previous planning. Clinical and experimental studies have shown that operation times as well as intraoperative X-ray times can be shortened by the use of individual templates, while preserving the task sequence of the conventional operation procedures.

Arthroplasty, Replacement, Hip↗