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PubMed1981

Inhibition, disinhibition, and summation among orientation detectors in human vision.

A vertical test line viewed together with an oblique inducing line appears to be tilted in the opposite direction (orientation contrast); a similar effect results from adapting to an oblique line before presenting the test line (tilt after-effect). The error in perceived orientation caused by a clockwise tilted inducing line may be partially cancelled by a second clockwise tilted inducing line; likewise, adapting to a configuration of two clockwise orientations gives weaker tilt after-effects than adapting to the more effective of the two orientations alone. The angular functions of these "disinhibitory" effects mirror the angular functions of the principal effects. However, combining tilt after-effect and simultaneous contrast in a disinhibition design by having the subject first adapt to a clockwise orientation and then presenting the test line together with a clockwise inducing line results in partial summation rather than disinhibition. The results are consistent with Carpenter's and Blakemore's (1973) hypothesis that orientation contrast and the tilt after-effect are manifestations of cortical inhibition in a network of inhibitory, recurrent lateral connections between cortical orientation detectors. After-effects must be due to prolonged inhibition, probably caused by a sensitivity change in previously inhibited detectors.

Discrimination Learning↗
PubMed1981

Orienting behavior by rats with visual cortical and subcortical lesions.

The effect of visual cortical and subcortical lesions on orienting behavior was assessed bu examining the rats' ability to interrupt an ongoing response and perform appropriate head and postural adjustments to repeatedly presented auditory or apparently moving visual stimuli. Large lesions of the entire superior colliculus (SC) or the deep layers of the SC did not result in visual agnosia or the inability to perform the motor responses involved in orienting. Rather, the orienting response simply ws not emitted to visual stimuli that the intact rat treated as less salient, but was to those it treated as more salient. Lesions of either the superficial layers of the SC or visual cortex also did not completely prevent orienting to very salient, apparently moving visual stimuli, but did produce changes in the number of responses made to such stimuli and in the occurrence of other components of orienting behavior. It was suggested that the SC and visual cortex play a modulatory role in orienting behavior and that stimulus characteristics must be considered in the development of neuronal models of orienting behavior.

Animals↗
PubMed2001

Three-dimensional head and upper arm orientations during kinematically redundant movements and at rest.

The three rotational degrees of freedom of the head and the upper arm exceed the number needed in a two-dimensional (2-D) facing or pointing task, respectively. Previous studies reported a reduction of the number of degrees of freedom from three to two, with one degree of freedom being a unique function of the other two (Donders' law). This study investigated whether three-dimensional (3-D) orientations of the head and arm are the same at rest and during movement for corresponding pointing or facing directions. Two separate experiments were performed: one focused on head orientations, the other focused on upper arm orientations. We instructed subjects to direct the nose or to point the extended arm in the direction of targets, which appeared in a quasi-random order at 2-s intervals. The head and upper arm orientations at rest were described by a 2-D surface with a scatter less than 3 or 4 degrees, respectively. Both for the arm and the head, orientations started and ended near the 2-D surface, but for a number of the target pairs, the orientations deviated from those predicted by the 2-D surface during movement in a way that was consistent and reproducible for movements between each target pair. For upper arm movements, we often found that deviations of arm orientations from the 2-D surface increased with increasing movement velocity. Such a positive correlation between deviation and movement velocity was not found for head movements. These results clearly indicate violations of Donders' law during movement and argue against several models for movement control found in the literature.

Adult↗
PubMed2005

Spatial orientation of optokinetic nystagmus and ocular pursuit during orbital space flight.

On Earth, eye velocity of horizontal optokinetic nystagmus (OKN) orients to gravito-inertial acceleration (GIA), the sum of linear accelerations acting on the head and body. We determined whether adaptation to micro-gravity altered this orientation and whether ocular pursuit exhibited similar properties. Eye movements of four astronauts were recorded with three-dimensional video-oculography. Optokinetic stimuli were stripes moving horizontally, vertically, and obliquely at 30 degrees/s. Ocular pursuit was produced by a spot moving horizontally or vertically at 20 degrees/s. Subjects were either stationary or were centrifuged during OKN with 1 or 0.5 g of interaural or dorsoventral centripetal linear acceleration. Average eye position during OKN (the beating field) moved into the quick-phase direction by 10 degrees during lateral and upward field movement in all conditions. The beating field did not shift up during downward OKN on Earth, but there was a strong upward movement of the beating field (9 degrees) during downward OKN in the absence of gravity; this likely represents an adaptation to the lack of a vertical 1-g bias in-flight. The horizontal OKN velocity axis tilted 9 degrees in the roll plane toward the GIA during interaural centrifugation, both on Earth and in space. During oblique OKN, the velocity vector tilted towards the GIA in the roll plane when there was a disparity between the direction of stripe motion and the GIA, but not when the two were aligned. In contrast, dorsoventral acceleration tilted the horizontal OKN velocity vector 6 degrees in pitch away from the GIA. Roll tilts of the horizontal OKN velocity vector toward the GIA during interaural centrifugation are consistent with the orientation properties of velocity storage, but pitch tilts away from the GIA when centrifuged while supine are not. We speculate that visual suppression during OKN may have caused the velocity vector to tilt away from the GIA during dorsoventral centrifugation. Vertical OKN and ocular pursuit did not exhibit orientation toward the GIA in any condition. Static full-body roll tilts and centrifugation generating an equivalent interaural acceleration produced the same tilts in the horizontal OKN velocity before and after flight. Thus, the magnitude of tilt in OKN velocity was dependent on the magnitude of interaural linear acceleration, rather than the tilt of the GIA with regard to the head. These results favor a 'filter' model of spatial orientation in which orienting eye movements are proportional to the magnitude of low frequency interaural linear acceleration, rather than models that postulate an internal representation of gravity as the basis for spatial orientation.

Acceleration↗
PubMed2006

Role of gravity-based information on the orientation and localization of the perceived body midline.

The present study focused on the influence of gravity-based information on the orientation and localization of the perceived body midline. The orientation was investigated by the rolling adjustment of a rod on the subjects' Z-axis and the localization by the horizontal adjustment of a visual dot as being straight ahead. Experiment 1 investigated the effect of the dissociation between the Z-axis and the direction of gravity by placing subjects in roll tilt and supine postures. In roll tilt, the perception of the body midline orientation was deviated in the direction of body tilt and the perception of its localization was deviated in the opposite direction. In the supine body orientation, estimates of the Z-axis and straight-ahead remained veridical as when the body was upright. Experiment 2 highlighted the relative importance of the otolithic and tactile information using diffuse pressure stimulation. The estimation of body midline orientation was modified contrarily to the estimation of its localization. Thus, subjects had no absolute representation of their egocentric space. The main hypothesis regarding the dissociation between the orientation and localization of the body midline may be related to a difference in the integration of sensory information. It can be suggested that the horizontal component of the vestibulo-ocular reflex (VOR) contributed to the perceived localization of the body midline, whereas its orientation was mainly influenced by tactile information.

Adult↗
PubMed2005

Orientation to solar radiation in black wildebeest (Connochaetes gnou).

We recorded the body axis orientation of free-living black wildebeest relative to incident solar radiation and wind. Observations were made on three consecutive days, on six occasions over the course of 1 year, in a treeless, predominantly cloudless habitat. Frequency of orientation parallel to incident solar radiation increased, and perpendicular to incident solar radiation decreased, as ambient dry-bulb temperature or solar radiation intensity increased, or wind speed decreased. We believe these changes were mediated via their effect on skin temperature. Parallel orientation behavior was more prominent when the wildebeest were standing without feeding than it was when they were feeding. We calculate that a black wildebeest adopting parallel orientation throughout the diurnal period would absorb 30% less radiant heat than the same animal adopting perpendicular orientation. Parallel orientation was reduced at times when water was freely available, possibly reflecting a shift from behavioral to autonomic thermoregulatory mechanisms. The use of orientation behavior by black wildebeest is well developed and forms part of the suite of adaptations that help them to maintain heat balance while living in a shadeless, often hot, environment.

Animals↗
PubMed1996

Muscle activity patterns altered during pedaling at different body orientations.

Gravity is a contributing force that is believed to influence strongly the control of limb movements since it affects sensory input and also contributes to task mechanics. By altering the relative contribution of gravitational force to the overall forces used to control pedaling at different body orientations, we tested the hypothesis that joint torque and muscle activation patterns would be modified to generate steady-state pedaling at altered body orientations. Eleven healthy subjects pedaled a modified ergometer at different body orientations (from horizontal to vertical), maintaining the same workload (80 J), cadence (60 rpm), and hip and knee kinematics. Pedal reaction forces and crank and pedal kinematics were measured and used to calculate joint torques and angles. EMG was recorded from four muscles (tibialis anterior, triceps surae, rectus femoris, biceps femoris). Measures of muscle activation (joint torque and EMG activity) showed strong dependence on body orientation, indicating that muscle activity is not fixed and is modified in response to altered body orientation. Simulations confirmed that, while joint torque changes were not necessary to pedal at different body orientations, observed changes were necessary to maintain consistent crank angular velocity profiles. Dependence of muscle activity on body orientation may be due to neural integration of sensory information with an internal model that includes characteristics of the endpoint, to produce consistent pedaling trajectories. Thus, both sensory consequences and mechanical aspects of gravitational forces are important determinants of locomotor tasks such as pedaling.

Adult↗
PubMed1986

Dimensional salience and speeded sorting of orientation by kindergarten and fourth-grade children.

Perceptual sensitivity and cognitive processing hypotheses relating to orientation perception in kindergarten and fourth-grade children were tested. Assessment of dimensional salience for orientation and form revealed that subjects at both grade levels identified geometric figures as being alike on the basis of form regardless of orientation condition. The effects of dimensional salience and orientation condition on speeded sorting were then investigated. Kindergarten results supported the cognitive processing prediction that orientation sorting times would vary as a function of orientation condition, but no differences were obtained for the fourth-grade subjects. In addition, the results indicated a substantial improvement in kindergarten performance when sorting on the basis of form as compared with orientation. Dimensional salience had much less effect on fourth-grade sorting times.

Attention↗
PubMed1993

Orientation identification at different background levels: its precision and distortions.

Orientation identification was studied at high (1000 td) and low (1 td) background illuminations. The subject had to estimate in degrees the orientation of a line presented in one of 18 orientations, 10 deg apart. Unlike other spatial discriminations, the precision of orientation judgments was not significantly impaired at low background if a suprathreshold stimulation was used. However, our earlier data showed that the identification at threshold was deteriorated at low background level. Different mechanisms of threshold and suprathreshold identification were suggested. The mechanism of suprathreshold identification was thought to contribute to the stability of the orientation perception during adaptation. The deviations of the subjective estimates from real orientations were also studied. The bias of perceived orientation toward the vertical increased at low background. This bias remained the same in egocentric coordinates, when the subjects were in supine position.

Contrast Sensitivity↗
PubMed1996

Lateralization of brain mechanisms underlying automatic and controlled forms of spatial orienting of attention.

Unilateral Spatial Neglect (USN) can be considered as a defect in spatial orienting of attention toward the half space contralateral to the damaged hemisphere. Since the classical work of Brain, W.R. Brain 64:224-272 (1941), several authors have emphasized that this defect is definitely more frequent and severe in patients with right brain damage, but the reason for this hemispheric asymmetry has remained controversial. Several investigations conducted with different experimental paradigms in different laboratories have shown that only automatic orienting of attention toward stimuli arising in the half space contralateral to the damaged hemisphere is disrupted in USN, whereas controlled, volitional orienting can be more or less completely spared. The hypothesis that at the level of the right hemisphere, spatial orienting of attention may be mainly prompted by automatic mechanisms may, therefore, be advanced. By contrast, the left hemisphere might play a leading role in mechanisms underlying volitional orienting of attention. According to this model, recovery from USN could be due to substitution of the lost automatic orienting mechanisms with the spread volitional orienting mechanisms subserved by the intact left hemisphere.

Attention↗
PubMed1990

Tangential intracortical pathways and the development of iso-orientation bands in cat striate cortex.

Evidence is accumulating that tangential connections are a prominent feature of cortical organization. In the mammalian visual cortex, these connections appear to be related to columnar systems and theoretical considerations have suggested that they contribute to the development of regularly spaced orientation columns. We tested this assumption and examined whether early cortical lesions affected the formation and layout of the pattern of iso-orientation bands. In the striate cortex of 2-week-old kittens, tangential fiber paths were disrupted unilaterally along the representation of the horizontal meridian either by cuts, or by suction or by implanting pieces of Teflon. At this age, tangential fibers are still growing, orientation selectivity is only poorly developed and 2-deoxyglucose mapping does not yet reveal orientation columns. When the kittens were 7-10 weeks old, the organization of orientation bands was studied with the 2-deoxyglucose technique in flat-mounts of both visual cortices. In addition, kittens from the same litters as the experimental animals, having received the same lesions at the same postnatal day were subjected to neuroanatomical experiments to assess the effect of the lesion on the tangential fibers. These investigations revealed that a small fraction of tangential fibers had grown across the lesion when no mechanical barrier was implanted while disruption of tangential connections was complete in cases who had received Teflon implants. Apart from minor irregularities that were confined to the vicinity of the lesion, the 2-deoxyglucose experiments showed no differences in the pattern of orientation bands between the lesioned and intact hemispheres. In both, the bands extended throughout all cortical layers and their main trajectories were orthogonal to the representation of the vertical meridian. We conclude that at least from two weeks of age onwards, intracortical tangential connections are not necessary for the development of the regular pattern of iso-orientation bands in the striate cortex of cats.

Amidines↗
PubMed1983

Meridional variations in the line orientation discrimination of the cat.

Cat's differential orientation thresholds were measured with single lines presented in succession. Differential orientation thresholds measured at horizontal or vertical orientations were smaller (median 2.9 degrees) than those measured at oblique orientation (median 4.7 degrees). Replications of the experiments showed that the oblique effect was stable over a period of 2 years. Using the same behavioral methods grating acuity was measured and did not show an oblique effect. These behavioral observations are compared with the physiological data on orientation specificity of area 17 cells. This comparison suggests that the most likely explanation of the meridional variation in orientation discrimination is the meridional variation in orientation preference of area 17 S cells.

Animals↗
PubMed1985

Vasopressin and ACTH analogs affect orienting but not activity in rabbits.

Two experiments were conducted in which albino rabbits were tested for cardiac Orienting Reflexes to novel tones and open field locomotor activity in a novel environment. In Experiment I subcutaneous doses of desglycinamide-arginine8-vasopressin (DGAVP; 25 micrograms/kg) and ACTH fragment 4-10 (250 micrograms/kg) altered tonic heart rate but did not affect bradycardiac Orienting Reflexes, activity, habituation or retention of habituation. In Experiment II a lower dose of DGAVP (5 micrograms/kg) enhanced the magnitude of cardiac orienting reflexes when administered 60 min before an initial orienting test. Both DGAVP and a lower dose of ACTH4-10 (50 micrograms/kg) administered before the first orienting test enhanced cardiac orienting and delayed habituation during a second (retention) test conducted following saline treatment; neither peptide had any effect on orienting when administered before the retention test. The lower doses of the peptides also failed to affect activity, habituation of activity or retention of habituation. These data suggest that low doses of DGAVP and ACTH4-10 affect stimulus processing and attention, but not more generalized responses to environmental novelty, in rabbits.

Adrenocorticotropic Hormone↗
PubMed2006

Customer orientation among employees in public administration: a transnational, longitudinal study.

The relation between ergonomic principles and quality management initiatives, both, in the private and public sector, has received increasing attention in the recent years. Customer orientation among employees is not only an important quality principle, but also an essential prerequisite for customer satisfaction, especially in service organizations. In this context, the objective of introducing new public management (NPM) in public-service organizations is to increase customer orientation among employees who are at the forefront of service providing. In this study, we developed a short scale to measure perceived customer orientation. In two separate longitudinal studies carried out in Austria and the US, we analyzed changes in customer orientation resulting from the introduction of NPM. In both organizations, we observed a significant increase in customer orientation. Perceived customer orientation was related to job characteristics, organizational characteristics and employee quality of working life. Creating positive influences on these characteristics within the framework of an organizational change process has positive effects on employee customer orientation.

Austria↗
PubMed2006

Automatic attention orienting by social and symbolic cues activates different neural networks: an fMRI study.

Visual attention can be automatically re-oriented by another person's non-predictive gaze as well as by symbolic arrow cues. We investigated whether the shifts of attention triggered by biologically relevant gaze cues and biologically non-relevant arrow cues rely on the same neural systems by comparing the effects of gaze-cued and arrow-cued orienting on blood oxygenation level-dependent (BOLD) signal in humans. Participants detected laterally presented reaction signals preceded by centrally presented non-predictive gaze and arrow cues. Directional gaze cues and arrow cues were presented in separate blocks. Furthermore, two separate control blocks were run in which non-directional cues (straight gaze or segment of a line) were used. The BOLD signals during the control blocks were subtracted from those during the respective blocks with directional cues. Behavioral data showed that, for both cue types, reaction times were shorter on congruent than incongruent trials. Imaging data revealed three foci of activation for gaze-cued orienting: in the left inferior occipital gyrus and right medial and inferior occipital gyri. For arrow-cued orienting, a much more extensive network was activated. There were large postcentral activations bilaterally including areas in the medial/inferior occipital gyri and medial temporal gyri and in the left intraparietal area. Interestingly, arrow cuing also activated the right frontal eye field and supplementary eye field. The results suggest that attention orienting by gaze cues and attention orienting by arrow cues are not supported by the same cortical network and that attention orienting by symbolic arrow cues relies on mechanisms associated with voluntary shifts of attention.

Adult↗
PubMed2004

Orientation bias of the extraclassical receptive field of the relay cells in the cat's dorsal lateral geniculate nucleus.

The spatial properties of the extraclassical receptive fields (ECRF) of neurons responding to a stimulus restricted to it and its interaction with the classical receptive field (CRF) in visual information processing were investigated in 74 relay cells in the dorsal lateral geniculate nucleus (LGNd) of anesthetized cats. The results demonstrate that the ECRF of most relay cells in the LGNd responded preferentially to a grating stimulus of low spatial frequency through a mechanism of spatial summation. These biased cells showed a significant orientation bias which was relatively smaller than that of the CRF. The preferred orientations of the ECRF were not correlated with those of the CRF in most relay cells. The orientation biased ECRFs and CRFs interacted with each other in a non-linear way, resulting in a great diversity of response properties. Overall, the CRF played a more significant role than the ECRF in determining a cell's orientation bias and preferred orientation. The ECRF mostly showed a modulatory role mainly in suppressing and/or in partially facilitating the neural response to stimulation in the CRF although in some cases, the ECRF did determine a cell's responsiveness and orientation sensitivity. These results suggest that the ECRF might contribute to the ability of the LGNd neurons to detect some complex features such as texture segmentation and provide a subcortical contribution to the integrative field of visual cortical cells through receiving inputs from retinal ganglion cells with similar orientation biased extended surrounds [Neuroscience 98 (2000) 207].

Action Potentials↗
PubMed2004

Polarizational colours could help polarization-dependent colour vision systems to discriminate between shiny and matt surfaces, but cannot unambiguously code surface orientation.

It was hypothesized that egg-laying Papilio butterflies could use polarizational colours as a cue to detect leaf orientation and to discriminate between shiny and matt leaves. These hypotheses would be supported if the following general questions were answered positively: (1) Can surface orientation be unambiguously coded by the polarizational colours perceived by polarization-sensitive colour vision systems? (2) Are the changes in the polarizational colours due to retinal rotation significantly different between shiny and matt surfaces? Using video polarimetry, we measured the reflection-polarizational characteristics of a shiny green hemisphere in the red, green and blue spectral ranges for different solar elevations and directions of view with respect to the solar azimuth as well as for sunlit and shady circumstances under clear skies. The continuously curving hemisphere models numerous differently oriented surfaces. Using the polarization- and colour-sensitive retina model developed earlier, we computed the polarizational colours of the hemisphere, and investigated the correlation between colours and local surface orientation. We also calculated the maximal changes of the polarizational colours of shiny and matt hemispheres induced by rotation of the retina. We found that a surface with any orientation can possess almost any polarizational colour under any illumination condition. Consequently, polarizational colours cannot unambiguously code surface orientation. Polarization sensitivity is even disadvantageous for the detection of surface orientation by means of colours. On the other hand, the colour changes due to retinal rotation can be significantly larger for shiny surfaces than for matt ones. Thus, polarizational colours could help discrimination between shiny and matt surfaces. The physical and perceptional reasons for these findings are explained in detail. Our results and conclusions are of general importance for polarization-dependent colour vision systems.

Animals↗
PubMed1996

Orientation in the acute and chronic stroke patient: impact on ADL and social activities. The Copenhagen Stroke Study.

OBJECTIVES: To determine the influence of initially lowered orientation on rehabilitation outcome in stroke patients, and how decreased orientation 6 months after stroke influences ADL and social activities. DESIGN: Prospective, consecutive, and community based. SETTING: A stroke unit receiving all acute stroke patients from a well-defined catchment area. All stages of rehabilitation were completed within the unit. PATIENTS: 524 patients with acute stroke. MAIN OUTCOME MEASURES: Basic ADL assessed by the Barthel Index (BI) at discharge; discharge placement; higher level ADL and social functions assessed by the Frenchay Activity Index(FAI) at a 6-month follow-up. RESULTS: The independent influence of orientation in acute stroke on rehabilitation outcome was analyzed with multiple linear and logistic regression models, using initial stroke severity (Scandinavian Neurologic Stroke Scale), initial BI, age, sex, comorbidity, prior stroke, and marital status as covariates. A one-point decrease in orientation decreased BI with 9 points (coefficient b=8.66, SE(b)=1.02,p<.0001) and reduced the likelihood (1.49, 95% CI: 1.05 to 2.11) of discharge to independent living (b=.40, SE(b)=.18,p=.026). Follow-up examinations 6 month poststroke showed that decreased orientation at this point still exerted a marked, negative influence on ADL and social functions (BI: coefficient b=12.06, SE(b)=1.95,p<.0001; FAI: coefficient b=6.28, SE(b)=1.42,p<.0001). CONCLUSION: The level of orientation influences basic ADL and higher level ADL and social activities in acute as well as chronic stroke. This finding suggests that rehabilitation of memory and attention might be relevant in stroke patients with impaired orientation.

Activities of Daily Living↗