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PubMed1998

Regions in the human brain activated by simultaneous orientation discrimination: a study with positron emission tomography.

In order to compare regional cerebral activity involved in simultaneous as opposed to successive orientation discrimination, we used positron emission tomography to measure regional cerebral blood flow, in two threefold sets of conditions, in a large number of subjects. The first such triad involved simultaneous orientation discrimination, orientation identification and detection, with all tasks using the same pair of gratings. The second triad consisted of successive orientation discrimination with its corresponding identification and detection tasks. Comparisons between tasks within each triad isolate attention to orientation and, respectively, spatial or temporal comparison. The subtraction of detection from simultaneous discrimination revealed activation of right fusiform, right lingual, left precentral, left cingulate and left temporal cortex, in addition to right insula, cerebellum and left thalamus. Only the fusiform, insular and precentral activations remained when the corresponding identification was subtracted from simultaneous discrimination. In contrast, most of the non-visual activation sites remained when simultaneous discrimination was compared with successive discrimination, which also revealed a left lingual activation. These experiments provide further evidence for task-dependent processing in the human visual system and suggest that the right fusiform cortex is involved in spatial as much as temporal comparisons.

Adult↗
PubMed1980

Spatial anisotropy in intramodal and cross-modal judgments of stimulus orientation: the stability of the oblique effect.

Visual and haptic judgments of stimulus orientation were examined intramodally and crossmodally by having subjects reproduced standard stimulus orientations simultaneously with their inspection or after a delay. For all conditions, an oblique effect was obtained, i.e. vertical and horizontal orientations were reproduced reliably more accurately than oblique orientations. Although intramodal differences were large, with haptic errors being greater than visual errors, cross-model differences were small. Furthermore, while for intramodal conditions simultaneous visual reproductions were reliably more accurate than delayed reproductions but haptic reproductions were more accurate when delayed, cross-modal errors were reliable greater with simultaneous reproductions, regardless of whether the standard orientation was visual or haptic. The modality differences reflect basic differences in stimulus information processing and the stability of the oblique effect across the experimental conditions suggests that perceptual spatial anisotropic effects are strongly influenced by experiential factors.

Female↗
PubMed1987

Effects of orientation-selective adaptation on the Zöllner illusion.

The model of inhibitory interaction between orientation detectors was examined by prolonged presentation of grating patterns (which was expected to induce orientation-selective adaptation) before measurement of the Zöllner illusion. Adaptation effects were measured under conditions which excluded intrusion by the tilt aftereffect. In experiment 1, illusion magnitude greatly decreased only when the orientation of the adapting grating was the same as that of the inducing lines, which confirmed the first prediction deduced from the model. There was no effect of adapting grating when it was oriented more than 20 degrees away from the inducing lines. In experiment 2, adaptation effects were selective not only to orientation but also to spatial frequency. In experiment 3 it was shown that illusion reduction was mediated neither by lowered apparent contrast of the inducing lines nor by retinal adaptation. The results are discussed with respect to the nature of adaptation and possible physiological correlates.

Adaptation, Ocular↗
PubMed1989

Pattern orientation, not motion, determines the two-dimensional tilt illusion.

In the usual tilt illusion (TI) configuration, an inducing stimulus which has a single orientation is used psychophysically to explore orientation analysis in the human visual system. Recently, this approach has been extended to the use of inducing stimuli which have two orientations. Such a two-dimensional (2-D) stimulus permits investigation of the low-level analysis of visual patterns. Prior experimentation has left it unclear whether it is the spatial or the motion properties of a moving crossed-grating plaid which determine two-dimensional tilt illusions (2-D TIs) because these two parameters previously were perfectly correlated. In the present experiments pattern orientation and motion were decoupled. It is shown that 2-D TIs are determined by the spatial properties of an inducing annulus and not by its motion properties. The results also support the existence of a mechanism which extracts axes of symmetry, and which is difficult to account for in terms of local cross-orientation domain inhibition.

Attention↗
PubMed1991

Comparison of contrast sensitivity functions across three orientations: implications for theory and testing.

The contrast sensitivity functions of a large group of observers (N = 71) were determined for three orientations of test gratings: vertical, oblique, and horizontal. Comparison of group means indicated that, consistent with previous findings for the 'oblique effect', sensitivity was poorer for the oblique orientation-but only for the mid-high spatial frequencies. Correlation analyses indicated that contrast sensitivity for a particular spatial frequency at a given orientation was highly correlated with contrast sensitivity for that same frequency at the other two orientations. Factor analysis of the intercorrelations revealed two strong factors, a low frequency factor, and a mid-high frequency factor. Results are discussed in terms of: (a) the implications for contrast-sensitivity testing across orientations, (b) the basis for the oblique effect, and (c) a different type of evidence for a dichotomy among spatial-frequency channels that may reflect the distinction between X cells and Y cells or between the parvocellular and magnocellular systems.

Adult↗
PubMed2003

Visual and haptic matching of perceived orientations of lines.

In this study we investigated the perception and production of line orientations in a vertical plane. Previous studies have shown that systematic errors are made when participants have to match oblique orientations visually and haptically. Differences in the setup for visual and haptic matching did not allow for a quantitative comparison of the errors. To investigate whether matching errors are the same for different modalities, we asked participants to match a visually presented orientation visually, haptically with visual feedback, and haptically without visual feedback. The matching errors were the same in all three matching conditions. Horizontal and vertical orientations were matched correctly, but systematic errors were made for the oblique orientations. The errors depended on the viewing position from which the stimuli were seen, and on the distance of the stimulus from the observer.

Feedback, Psychological↗
PubMed2003

Reference frames for orientation anisotropies in face recognition and biological-motion perception.

Both face recognition and biological-motion perception are strongly orientation-dependent. Recognition performance decreases if the stimuli are rotated with respect to their normal upright orientation. Here, the question whether this effect operates in egocentric coordinates or in environmental coordinates is examined. In addition to the use of rotated stimuli the observers were also rotated and tested both with a same-different face-recognition task and with a biological-motion detection task. A strong orientation effect was found that depended only on the stimulus orientation relative to the observer. This result clearly indicates that orientation effects in both stimulus domains operate in an egocentric frame of reference. This finding is discussed in terms of the particular requirement of extracting sophisticated information for social recognition and communication from faces and biological motion.

Analysis of Variance↗
PubMed2004

Visual perception of orientation is categorical near vertical and continuous near horizontal.

Four experiments were conducted to examine whether visual-orientation information is perceived categorically. In experiments 1 and 3, adult participants sorted oriented line stimuli into broad oblique and narrow vertical or horizontal categories. Experiments 2 and 4 showed that categorical discrimination of orientation occurred only near the vertical-oblique boundary. The data indicate that there is categorical perception near vertical and more continuous perception near horizontal. The results are relevant to the debate over whether categorical perception is derived from perceptual structure, verbal coding, or within-task learning. In addition, the asymmetrical perception of orientation around vertical and horizontal is consistent with the possibility that there may be differences in the functional significance of orientation near the two main axes.

Adult↗
PubMed2006

Orientation selectivity in visual cortex by fluctuation-controlled criticality.

Within a large-scale neuronal network model of macaque primary visual cortex, we examined how intrinsic dynamic fluctuations in synaptic currents modify the effect of strong recurrent excitation on orientation selectivity. Previously, we showed that, using a strong network inhibition countered by feedforward and recurrent excitation, the cortical model reproduced many observed properties of simple and complex cells. However, that network's complex cells were poorly selective for orientation, and increasing cortical self-excitation led to network instabilities and unrealistically high firing rates. Here, we show that a sparsity of connections in the network produces large, intrinsic fluctuations in the cortico-cortical conductances that can stabilize the network and that there is a critical level of fluctuations (controllable by sparsity) that allows strong cortical gain and the emergence of orientation-selective complex cells. The resultant sparse network also shows near contrast invariance in its selectivity and, in agreement with recent experiments, has extracellular tuning properties that are similar in pinwheel center and iso-orientation regions, whereas intracellular conductances show positional dependencies. Varying the strength of synaptic fluctuations by adjusting the sparsity of network connectivity, we identified a transition between the dynamics of bistability and without bistability. In a network with strong recurrent excitation, this transition is characterized by a near hysteretic behavior and a rapid rise of network firing rates as the synaptic drive or stimulus input is increased. We discuss the connection between this transition and orientation selectivity in our model of primary visual cortex.

Animals↗
PubMed1990

Orientation discrimination in the cat: a distributed function.

Cats were trained to make fine orientation discriminations with stimuli similar to those used in physiological experiments--narrow, light bars 12 degrees long--before and after various combinations of lesions of areas 17 and 18. Discrimination thresholds were measured at different contrast levels and different bar widths, both pre- and postoperatively, for up to 1.5 years after the lesion. For high contrast stimuli, lesions restricted to area 17 or area 18 had little effect, but those lesions involving area 17 and a substantial part of area 18 raised thresholds. In the latter case there was a relationship between the amount of area 18 spared and the bar width at which discrimination was impaired. At low contrast deficits were seen only for narrow widths. These results lead to the following conclusions. (i) Orientation discrimination is a function distributed within and across areas 17 and 18. (ii) How this function is distributed in this cortex depends on stimulus width. (iii) The X system does not carry the signal necessary for orientation discrimination. (iv) Cells most narrowly tuned for orientation, which reside in the part of area 17 subserving central vision, do not determine the orientation discrimination threshold.

Animals↗
PubMed1992

Relationships between orientation-preference pinwheels, cytochrome oxidase blobs, and ocular-dominance columns in primate striate cortex.

The relationships between cytochrome oxidase blobs, ocular-dominance columns, and iso-orientation domains, subsystems underlying visual perception, were explored in primary visual cortex of macaque monkey. High-resolution maps of these three subsystems were acquired. Optical imaging based on activity-dependent intrinsic signals revealed that the most prominent organizational feature of orientation preference was a radial arrangement, forming a pinwheel-like structure surrounding a singularity point. More than 80% of these pinwheels were centered along the midline of ocular-dominance columns. The iso-orientation contours of adjacent pinwheels crossed borders of ocular-dominance columns at approximately right angles. Pinwheels with the same or opposite directions of orientation-preference change were smoothly connected with each other. On the average, all orientations were equally represented. In exactly the same cortical area, the cytochrome oxidase blobs, thought to be involved in color processing, were also mapped, using cytochrome oxidase histology. Like the centers of pinwheels, the centers of blobs also lie along the midline of ocular-dominance columns. However, the centers of pinwheels did not coincide with the centers of blobs; these two subsystems are spatially independent. "Hypercolumn" modules, each including two complete pinwheels in two adjacent columns of complementary ocularity, as well as portions of a few blobs, were frequently found but did not seem to be the primary unit of cortical organization. An alternative to hypercolumns is proposed.

Animals↗
PubMed1983

Psychological sexual identity and hemispheric orientation.

The study examines gender and psychological sexual identity as alternative bases for the development of hemispheric orientation. Hypotheses anticipated that females place greater reliance upon right hemisphere functions, such as imagery and emotion, whereas males place more emphasis upon left hemisphere functions, such as logical reasoning. This was extended to an examination of the roles of masculinity and femininity within genders upon hemispheric orientation. With a sample of 219 male and 221 female adults, it was found that the male-left hemisphere orientation/female-right hemisphere orientation dichotomy was supported in part. However, this relationship appears to be moderated by a second dimension: females appear more internally oriented, males more externally oriented.

Adult↗
PubMed1992

Orienting task effects on memory for presentation modality in children, young adults, and older adults.

Children (7 to 10 years), young adults (17 to 24 years), and older adults (55 to 77 years) were asked to learn three lists of words that were of mixed modality (half the words were visual, and half the words were auditory). With one list the subjects were asked a semantic orienting question; with another, a nonsemantic orienting question; and with a third, no orienting question. Half the subjects in each age group were also asked to remember the presentation modality of each word. Older adults remembered less information about modality than children and young adults did, and the variation in the type of orienting question--or the lack of one--affected modality identification. However, there was no Orienting Task x Age interaction for modality identification. The results of this study suggest that encoding modality information does not take place automatically--in any age group--but that explanations focusing on encoding strategies and effort are not likely to account for older adults' difficulties in remembering presentation modality.

Adolescent↗
PubMed1998

Dual-task results and the lateralization of spatial orientation: artifact of test selection?

An investigation was conducted to identify the degree to which results regarding the lateralization of spatial orientation among men and women are artifacts of test selection. A dual-task design was used to study possible lateralization differences, providing baseline and dual-task measures of spatial-orientation performance, right- and left-hand tapping, and vocalization of "cat, dog, horse." The Guilford-Zimmerman Test (Guilford & Zimmerman, 1953), the Eliot-Price Test (Eliot & Price, 1976), and the Stumpf-Fay Cube Perspectives Test (Stumpf & Fay, 1983) were the three spatial-orientation tests used to investigate possible artifacts of test selection. Twenty-eight right-handed male and 39 right-handed female undergraduates completed random baseline and dual-task sessions. Analyses indicated no significant sex-related differences in spatial-orientation ability for all three tests. Furthermore, there was no evidence of differential lateralization of spatial orientation between the sexes.

Adult↗
PubMed1990

Recovery of orientation following closed-head injury.

The pattern of recovery of orientation to person, place, and time was investigated in 84 patients who were initially disoriented while hospitalized on the neurosurgery service after sustaining a closed-head injury (CHI) of varying severity. Results of daily administration of the Galveston Orientation and Amnesia Test revealed that the most common sequence of recovery of orientation was person, place, and time: accounting for about 70% of the patients. Return of orientation to time preceded reorientation to place in 13% of the patients while other orderings of reorientation were present in 11% of the cases. Temporal disorientation was initially characterized by backward displacement of the date from the actual date in 68% of the patients. The magnitude of this displacement progressively shrank as the patients became more oriented. Patients who exhibited the greatest backward displacement of the date had more severe and persistent impaired consciousness, were older and had longer durations of posttraumatic amnesia. These data support Ribot's hypothesis that older memories are relatively resistant to cerebral insult.

Amnesia, Retrograde↗
PubMed1991

Value orientations: a description of teachers' goals for student learning.

This study examined the extent to which physical educators made consistent decisions regarding goals for student learning within five educational value orientations. The research examined value orientations within hypothetical educational situations as represented by a paper and pencil inventory. Ninety physical educators in three school districts in the midwest completed the Value Orientation Inventory (VOI). Total scores from each value orientation on the VOI were converted to T-scores and used to divide teachers into two groups representing high and low priority categories. Chi-square tests were used to examine the data by gender, teaching level, and teacher's years of experience. Results indicated that 97% of the physical educators made consistent curricular and instructional decisions within one or more of the value orientations. There were no significant differences based on gender, level, or teaching experience.

Attitude↗
PubMed1989

Thermal and physiological changes in rats exposed to CW and pulsed 2.8 GHz radiofrequency radiation in E and H orientations.

Ketamine-anesthetized Sprague-Dawley rats were exposed in both E and H orientations to far-field 2.8 GHz continuous-wave (CW) and pulsed (0.5 microseconds, 500 pps) radiofrequency radiation (RFR) at equivalent whole-body average specific absorption rates (SAR) of approximately 14 W/kg. Intermittent irradiation was performed in all four exposure conditions, in the same animal, to repeatedly increase colonic temperature from 38.5 to 39.5 degrees C. Tympanic, subcutaneous (sides toward and away from RF sources), colonic, and tail temperatures, electrocardiogram, arterial blood pressure, and respiratory rate were continuously recorded. The results revealed no significant difference between the thermal effects of CW and pulsed RFR exposure. The results did show significant differences between the thermal effects of E- and H-orientation exposure. H-orientation irradiation produced significantly faster colonic temperature increases and, with the exception of the tail, produced significantly greater localized heating in the anesthetized rat, and higher local SAR in rat carcasses than did E-orientation exposure. Under all exposure conditions, heart rate and blood pressure increased significantly during irradiation and returned to baseline when exposure was discontinued. Respiratory rate remained unchanged during irradiation. There were no significant differences between the effects of E- and H-orientation exposure, or between CW and pulsed irradiation, upon heart rate, blood pressure, and respiratory rate.

Animals↗
PubMed2006

The neural correlates of human working memory for haptically explored object orientations.

Skillful object manipulation requires that haptically explored spatial object characteristics like orientation be adequately represented in working memory. In the current functional magnetic resonance imaging study, healthy right-handed participants explored a bar-shaped reference object with the left hand, memorizing its orientation. After a variable delay (0.5, 5, or 10 s), participants used their right hand to match the orientation by rotating a second, identical object. In the first seconds of the delay, right sensorimotor cortex was active, whereas clusters in left anterior prefrontal cortex (aPFC) (Brodmann area 10) became dominant 2 s after the end of exploration, showing sustained activity for several seconds. In contrast, left parieto-occipital cortex was involved toward the end of the delay interval. Our results indicate that a dynamic network of brain areas subserves hapticospatial information processing in the delay between haptic stimulus exploration and orientation matching. We propose that haptic sensory traces, maintained in contralateral sensorimotor cortex, are transformed into more abstract hapticospatial representations in the early delay stages. Maintenance of these representations engages aPFC and parieto-occipital cortex. Whereas aPFC possibly integrates spatial and motor components of hapticospatial working memory, parieto-occipital cortex might be involved in orientation imagery, supporting working memory, and the preparation of haptic matching.

Adult↗