Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ORIENTATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,603 records · Page 89Linked to original sources
PubMed1990

Effects of element orientation on apparent motion perception.

We present an ambiguous motion paradigm that allows us to quantify the influence of aspects of form relevant to the perception of apparent motion. We report on the role of bar element orientation in motion paths. The effect of orientation differences between bar elements in a motion path is small with respect to the crucial role of the orientation of bar elements relative to motion direction. Motion perception between elements oriented along the motion direction dominates motion perception between elements oriented perpendicularly to motion direction. The perception of apparent motion is affected by bar length and width and is anisotropic.

Attention↗
PubMed1989

Visual orientation estimation.

A systematic error is reported in orientation estimation, in that on average, estimates are closer to the vertical axis than are the stimuli by up to 6 degrees. This systematic error results from a specific mechanism that may be related to depth perception, and that is avoided in certain circumstances or when other mechanisms take over. For example, the estimates of one observer who was a well-trained professional draughtsman did not show this systematic error. Furthermore, for all observers tested, estimation of clock time is not subject to the regular orientation estimation error. Rather, observers tend to estimate times as slightly further from the quarter hour than they really are. Orientation judgement channel capacity was also studied under various conditions. The number of discriminable orientations is far above the magic number "7" limit, reaching over 20 in optimal circumstances. The distribution of discriminable orientations is nonlinear, in that these are more closely packed about the horizontal and vertical axis than at the oblique.

Attention↗
PubMed1990

The processing of spatial frequency and orientation information.

Three identification experiments were completed to disambiguate the associations between spatial frequency and orientation information at the sensory, decisional, and response levels. The stimuli were gratings generated by crossing four levels each of spatial frequency and orientation. In Experiment 1, the subjects made a single identification response to the stimuli. In Experiment 2, two identification responses were made, one for the spatial frequency component and the other for the orientation component. In Experiment 3, the subjects identified either the spatial frequency or the orientation component in any block of trials. The data were confusion matrices, and an information-transmission approach was used to investigate the interactions in the system. The results show that although there were sensory associations, there were no interactions at the decisional level. Performance parity was found: there was no significant difference between the single- and double-judgment paradigms in terms of information transmitted. Overall, the results suggest that although spatial frequency and orientation information is coded jointly at the sensory level, subsequent processing is independent, with each dimension drawing upon different attentional resources.

Adult↗
PubMed1992

Absence of compensation and reasoning-like processes in the perception of orientation in depth.

When errors are present in the perceived depth between the parts of a physically stationary object, the object appears to rotate as the head is moved laterally (Gogel, 1980). This illusory rotation has been attributed either to compensation (Wallach, 1985, 1987) or to inferential-like processes (Rock, 1983). Alternatively, the perceived distances of and directions to the parts of the object are sufficient to explain the illusory perceived orientations and perceived rotations of the stimulus. This was examined in three experiments. In Experiment 1, a perceived illusory orientation of a stimulus object extended in depth was produced by misleading binocular disparity and was measured at two different lateral positions of the head under two conditions. In the static condition, the head was stationary at different times at each of the two measurement positions of the head. In the dynamic condition, continuous motion of the head occurred between these two positions. In Experiment 2, static and dynamic conditions of illusory stimulus orientation were observed with the head stationary. In Experiment 3, a perspective illusion instead of binocular disparity produced the errors in perceived depth. In no experiment did the perceived orientation of the object differ for the static and dynamic conditions. In the absence of head motion, neither compensatory nor inferential-like processes were available. It is concluded that these processes are not needed to explain either illusory or nonillusory perceptions of the orientation or rotation of stimuli viewed with a laterally moving head.

Adult↗
PubMed1992

Eigenvectors of the inertia tensor and perceiving the orientation of a hand-held object by dynamic touch.

Subjects wielded an object, hidden from view, and reported the orientation in which the object was positioned in the hand. The object consisted of a stem with two branches forming a V attached perpendicularly to the stem's distal end. The branches were differentially weighted so that the same spatial orientation of the object was associated with different orientations of its principal (symmetry) axes or eigenvectors. Perceived orientation was found to be dependent on the eigenvectors of the object's inertia tensor, computed about the point of rotation in the wrist, rather than on its spatial orientation. The results underscore the significance of the inertia tensor to understanding the perception of spatial properties by dynamic touch.

Adult↗
PubMed2000

Rotating objects to determine orientation, not identity: evidence from a backward-masking/dual-task procedure.

The effects of picture-plane rotations on times taken to name familiar objects (RTs) may reflect a process of mental rotation to stored viewpoint-specific representations: the rotate-to-recognize hypothesis. Alternatively, mental rotation might be used after stored object representations are activated by a misoriented stimulus in order to verify a weak or distorted shape percept: the double-checking hypothesis. We tested these two accounts of rotation effects in object recognition by having subjects verify the orientations (to within 90 degrees) and basic-level names of 14-msec, backward-masked depictions of common objects. The stimulus-mask interval (SOA) varied from 14 to 41 msec, permitting interpolation of the SOA required for 75% accuracy (SOAc). Whereas the SOAc to verify orientation increased with rotation up to 180 degrees, the SOAc to verify identity was briefer and asymptoted at approximately 60 degrees. We therefore reject the rotate-to-recognize hypothesis, which implies that SOAc should increase steadily with rotation in both tasks. Instead, we suggest that upright and near-upright stimuli are matched by a fast direct process and that misoriented stimuli are matched at a featural level by a slightly slower view-independent process. We also suggest that rotation effects on RTs reflect a postrecognition stage of orientation verification: the rotate-to-orient hypothesis, a version of double-checking that also explains the well-known reduction in orientation effects on RTs when naming repeated objects.

Attention↗
PubMed1993

[Communication in problem solving by preschool children: effects of subject's familiarity with experimenter and task orientation of experimenter].

The purpose was to examine effects of subject's familiarity with experimenter, and the task orientation of experimenter towards preschool children's communication in a problem solving situation. After subjects were given one of three different information about a target card, they were asked to identify the target one. However, subjects were unable to identify the target one without questions. The main results were as follows: (1) 5-year-olds made more questions and chose the target more often than 4-year-olds, (2) High familiarity group made questions and chose the target more often than low one, (3) Task-oriented group made more questions and chose the target more often than non-oriented one, and (4) Interaction of familiarity and the task-orientation was not significant. These results suggested that familiarity and task-orientation affected rate of communication occurrence in problem solving by preschool children.

Child, Preschool↗
PubMed1997

[Does altruism reach beyond the in group?: a social orientation approach].

The experiment of this paper studied the role social orientation would play in double-dilemma situations. In a double-dilemma situation, social dilemmas exist both between and within groups; a cooperation choice at the within-groups level is considered a defection choice at the between-groups level, and vice versa. Using such a situation, whether "others" in other-orientedness are limited to those of the ingroup or include those of a competing group was examined. Each of 132 college students played both an ordinary social dilemma game and a double-dilemma game, with equivalent incentive structures. Subjects' social orientation was measured a few days after the experiment. Results indicated that other-oriented subjects thought only about ingroup members, and did not care much about the others. Furthermore, social orientation did not affect whether subjects acted similarly or differently for the two dilemma situations. Therefore, social orientation approach to intergroup conflicts apparently had its limitations.

Adult↗
PubMedDate not supplied

The effect of body orientation on a point-to-point movement in healthy elderly persons.

OBJECTIVE: Upper limb retraining during the early phases of neurological rehabilitation often involves having individuals practice reaching in body orientations that reduce the effect of gravity on various joint motions (e.g., shoulder flexion, elbow extension). However, the efficacy of these training techniques has not been determined. The purpose of this study was to determine the effects of reducing gravity through a change in body orientation from sitting to side-lying on the kinematics of a point-to-point movement in healthy elderly persons. METHOD: Nine healthy, right-hand-dominant women 62 to 66 years of age pointed to a target in two different body orientations-sitting and side-lying. A 2-dimensional kinematic analysis of the movement was performed to compare the trajectory of the hand and the interjoint coordination under the two conditions. RESULTS: Regardless of body orientation relative to gravity, participants produced straight hand paths and smooth, bell-shaped velocity profiles. However, they moved slower in side-lying, and the pattern of interjoint coordination varied. The shoulder and elbow moved less, whereas the scapula made a greater contribution to the overall movement. Furthermore, the temporal coordination of the joints was modified as a consequence of body position. CONCLUSION: The results indicate that point-to-point arm movements made against gravity differ from those made in a gravity-reduced plane, particularly at the joint level, illustrating that movement organization is sensitive to this contextual difference. The effect of minimizing gravity on upper limb movement needs to be explored in patient populations to determine whether training patients in gravity-reduced orientations is efficacious.

Aged↗
PubMed1976

Use of a problem-oriented dental record in undergraduate dental education.

This paper describes how the concepts and methods of problem-orientation have been applied in the clinical education of dental students. It makes the point that the problem-oriented dental record is only one part of a complete system which has five interrelated components. The problem-oriented dental record is discussed in detail, and the paper includes examples of all four sections of the record. All sections of the record are interrelated, and the steps in identifying and resolving problems follow a logical sequence: (1) collect the data base, (2) write the cue list, (3) write the problem list, (4) write the initial plan, (5) write the final plan, and (6) record progress. The problem-oriented dental record is seen as a tool for patient care, audit, and education. The main advantage lies in the way information is organized and recorded. The record is highly communicative and permits everyone involved an opportunity to relate the data collected to the problem list and to the decisions made regarding how problems will be resolved. The record and the systems were borrowed from Weed and are being adapted for use in dentistry. Although still in the trial stages, this system has proven to have many more advantages than other record-keeping systems and is invaluable as a tool for education. In the future we plan to use computers to help store and retrieve data from these records. We anticipate that a dental education built on this record will have a lasting impact on the graduates' approach to patient care. This should result in a graduate who is conversant with medical colleagues and systematic in the collection of data, listing of problems, and resolution of patient problems. Finally, we believe that the problem-oriented dental record is also a good tool to help the dental graduate become more empathetic with patients and more aware of their total health needs. The record provides a mechanism for recording physical and emotional information as well as the oral status.

Dental Records↗
PubMed2000

Binocular cross-orientation suppression in the primary visual cortex (V1) of infant rhesus monkeys.

PURPOSE: To better understand the course of cortical maturation during early development, the phenomenon of binocular cross-orientation suppression in neurons of the primary visual cortex (V1) in young infant monkeys was investigated. METHODS: Extracellular single-unit recordings were made in anesthetized and paralyzed monkeys ranging in age between 6 days and 8 weeks. Orthogonally oriented, dichoptic sine-wave gratings were used as visual stimuli. RESULTS: V1 neurons in young infant monkeys showed a higher prevalence and greater magnitude of binocular cross-orientation suppression than in adult monkeys. Binocular suppression decreased and reached an adult level between 4 and 8 weeks of age, the presumed onset-age for stereopsis in monkeys. CONCLUSIONS: During the first 4 weeks of life, the functional connections that are necessary for initiating binocular cross-orientation suppression exist in the monkey primary visual cortex. This finding is consistent with the view that before the abrupt onset of stereopsis, human infants may detect the differences between interocularly iso-oriented gratings and orthogonal gratings.

Aging↗
PubMed1975

[Shape and orientation of nuclei of embryonal fibroblast-like cells cultured on substrates with ordered relief].

Embryo fibroblasts of hamster, rat, mouse, and were cultured 24 hrs on polyvinylchloride plates with regular relief of grooves with cylindric surfaces in between. Most cells were accumulated on the middle part of spaces between the grooves, their nuclei were elongated and oriented in the direction of grooves. Nuclear elongation was assessed quantitatively by the ratio of long to short nuclear axes. Contact orientation was measured as deviation of the long nuclear axes from the grooves direction. Both contact orientation and elongation considered respectively as "orientation reaction" is maximal and the "form reaction", increased with increasing cylinder curvature (i. e. when the radii diminished from 333 to 61 mcm). Both reactions are well expressed in cultures of the human and (less distinctly) the rat cells. In murine cells, the "orientation reaction" is maximal and the "form reaction" is weak while for the hamster cells the opposite is true. Therefore, both types of reaction seem to be independent characteristics of cells.

Animals↗
PubMedDate not supplied

Modeling corticofugal feedback and the sensitivity of lateral geniculate neurons to orientation discontinuity.

We model feedback from primary visual cortex to the dorsal lateral geniculate nucleus (dLGN). This feedback makes dLGN neurons sensitive to orientation discontinuity (Sillito et al., 1993; Cudeiro & Sillito, 1996). In the model, each dLGN neuron receives retinotopic input driven by layer 6 cortical neurons in a full set of orientation columns. Excitation is monosynaptic, while inhibition is through perigeniculate neurons and dLGN interneurons. The stimulus consists of drifting gratings,k one within and the other outside a circular region centered over the receptive field of the model dLGN relay neuron we study. They appear as a single grating when they are aligned with equal contrast. The model reproduces experimental results showing an increasing inhibitory effect of feedback on the firing rate of dLGN neurons as the two gratings move towards the aligned position. Moreover, enhancement of dLGN cell center-surround antagonism by feedback is revealed by measuring the responses to drifting gratings inside a circular window, as a function of window radius. This effect is related to the observed length tuning of dLGN cells. Sensitivity to orientation discontinuity could be mediated in the model by feedback from either simple or complex cells. The model puts constraints on the feedback synaptic footprint and shows that its elongated shape does not play a crucial role in sensitivity to orientation discontinuity. The inhibitory component of feedback must predominate overall, but the feedback signal from a cortical neuron to a dLGN neuron with the same or nearby receptive-field center can be dominated by excitation. Predictions of the model include (1) robust stimuli for layer 6 cortical neurons give pronounced nonlinearities in the responses of dLGN neurons; (2) the sensitivity to orientation discontinuity at low contrast is twice that at high contrast.

Animals↗
PubMedDate not supplied

Temporal-frequency tuning of cross-orientation suppression in the cat striate cortex.

A sinusoidal mask grating oriented orthogonally to and superimposed onto an optimally oriented base grating reduces a cortical neuron's response amplitude. The spatial selectivity of cross-orientation suppression (XOR) has been described, so for this paper we investigated the temporal properties of XOR. We recorded from single striate cortical neurons (n = 72) in anesthetized and paralyzed cats. After quantifying the spatial and temporal characteristics of each cell's excitatory response to a base grating, we measured the temporal-frequency tuning of XOR by systematically varying the temporal frequency of a mask grating placed at a null orientation outside of the cell's excitatory orientation domain. The average preferred temporal frequency of the excitatory response of the neurons in our sample was 3.8 (+/- 1.5 S.D.) Hz. The average cutoff frequency for the sample was 16.3 (+/- 1.7) Hz. The average preferred temporal frequency (7.0 +/- 2.6 Hz) and cutoff frequency (20.4 +/- 6.9 Hz) of the XOR were significantly higher. The differences averaged 1.1 (+/- 0.6) octaves for the peaks and 0.3 (+/- 0.4) octaves for the cutoffs. The XOR mechanism's preference for high temporal frequencies suggests a possible extrastriate origin for the effect and could help explain the low-pass temporal-frequency response profile displayed by most striate cortical neurons.

Animals↗
PubMed2003

Cooperation between area 17 neuron pairs enhances fine discrimination of orientation.

We examined 66 complex cells in area 17 of cats that were paralyzed and anesthetized with propofol and N2O. We studied changes in ensemble responses for small (<10 degrees ) and large (>10 degrees ) differences in orientation. Examination of temporal resolution and discharge history revealed advantages in discrimination from both dependent (e.g., synchronization) and independent (e.g., bursting) interspike interval properties. For 27 pairs of neurons, we found that the average cooperation (the advantage gained from the joint activity) was 57.6% for fine discrimination of orientation but <5% for gross discrimination. Dependency (probabilistic quantification of the interaction between the cells) was measured between 29 pairs of neurons while varying orientation. On average, the dependency tuning for orientation was 35.5% narrower than the average firing rate tuning. The changes in dependency around the peak orientation (at which the firing rate remains relatively constant) lead to substantial cooperation that can improve discrimination in this region. The narrow tuning of dependency and the cooperation provide evidence to support a population-encoding scheme that is based on biologically plausible mechanisms and that could account for hyperacuities.

Action Potentials↗
PubMed2003

Orientation-specific adaptation in human visual cortex.

Nearly all methods for analyzing and interpreting functional magnetic resonance imaging (fMRI) data assume that the fMRI signal behaves in an approximately linear manner. However, it has been shown that the mean fMRI response to a pair of briefly presented visual stimuli is significantly smaller than would be expected from the response to a single stimulus. This smaller response could be the result of either a nonlinearity in the fMRI signal or neuronal adaptation. We tested the neuronal adaptation hypothesis by measuring the fMRI response to sequential pairs of sinusoidal gratings that had either the same or orthogonal orientation. The adaptation hypothesis predicts that brain areas with orientation-selective neurons should show a more linear response when the stimulus pair is orthogonal than when the pair is identical. Our results show no orientation-specific adaptation effects in primary visual cortex (V1) but increasing effects along the hierarchy of visual areas (V2, V3, and V4V). A psychophysical contrast detection experiment, using similar oriented gratings as adapters, shows evidence of orientation-specific adaptation in the visual system. These results have implications for the interpretation of rapid event-related fMRI experiments, as well as for recently developed methods that use adaptation as a tool to measure the response properties of underlying neuronal subpopulations.

Adaptation, Physiological↗
PubMed1990

Retrosplenial cortex: possible role in habituation of the orienting response.

A patient with a unilateral lesion that included the retrosplenial area had a propensity to attend to contralateral stimuli. To determine whether the retrosplenial-area lesion was inducing this defect, unilateral retrosplenial lesions were produced in rats by surgical aspiration. Animals were assessed preoperatively and postoperatively for orientation and habituation to bilateral simultaneous stimulation in 3 sensory modalities: visual, tactile, and auditory. At each session, the orientation test was terminated upon completion of 5 trials per modality, and the habituation test ended after 4 consecutive response failures or upon completion of 15 trials per modality. Postoperatively, contralateral orientation was not significantly different from ipsilateral orientation, suggesting that there was no neglect. However, there was a significant delay in habituation to contralateral stimulation in postoperative weeks 2 and 3-5. Our results suggest that rats with retrosplenial area lesions have normal orientation but fail to habituate to contralateral stimuli.

Acoustic Stimulation↗
PubMed1977

The family-oriented medical record.

The usual form of the Problem-Oriented Medical Record is primarily focused on the individual, and thus has serious deficiencies for the family-oriented physician. This paper presents a practical, office-tested medical charting system that incorporates features of the Problem-Oriented Medical Record and allows the recording of aspects of the family situation that are of particular importance to the family physician. The essential features of the chart are described and the special features, advantages, and disadvantages are discussed. This record has been developed to avoid the gaps that appear when attempts are made to use individually-oriented record systems in a family-oriented practice.

Child↗