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PubMed1991

Orientation discrimination in the cat: its cortical locus. I. Areas 17 and 18.

An elementary unit of visual pattern and form perception is thought to be the orientation of edges; this element has been studied extensively by neurophysiologists using oriented line segments or bars. These same stimuli have been used in the present study to measure threshold discriminations in cats before and after cortical lesions of areas 17 and/or 18. Control experiments showed that the discriminations were made by using a single cue, orientation, and that other stimulus parameters, width, length and contrast of the bar, were optimized. The extent of the lesions was evaluated anatomically from cell and fiber stained sections through cortex and thalamus, matched to retinotopic maps of Tusa et al. (Cortical Sensory Organization, Vol. 2, Humana Press, pp. 1-31, '81) and Sanderson (Journal of Comparative Neurology 143:101-118, '71), and physiologically from visual field position of receptive fields of cells recorded in areas neighboring the lesions. Lesions involving area 17 and large parts of area 18 produced a marked deficit in orientation discrimination which included a loss in retention, and after retraining a substantial increase in thresholds for up to 3 years when tested with long bars. There was no recovery of discrimination when the animals were tested with short bars. Lesions which involved area 17 plus small parts of 18, or lesions of areas 18 and 19, produced no retention deficit and resulted in an increase in thresholds only at low contrast and narrow width. These experiments revealed an excellent correlation between lesion locus and size and behavioral deficit. They indicate that the cortical representation of bar orientation used for discrimination is distributed within and across areas 17 and 18. The spread of the distribution depends on other stimulus parameters such as bar width and length. Furthermore the experiments show that neither the most narrowly tuned cells nor the X-cell system is required for fine orientation discrimination of a long bar.

Animals↗
PubMed1988

Unfamiliar environments impair information processing as measured by behavioral and cardiac orienting responses to auditory stimuli in preweanling and adult rats.

Placing animals in an unfamiliar environment triggers at least two major reactions: (1) a heightened state of arousal, fear, or distress and (2) a sharp increase in information processing as the animal attempts to learn about its new environment. These changes could have a profound effect on the way in which the animal reacts to the types of extraneous innocuous stimuli typically used to study learning and memory. For example, an increase in arousal or fear could either (1) make the animal more "attentive" to stimulus change resulting in a larger orienting response, or (2) produce a shift from orienting to defensive responding. Conversely, processing of the new stimuli present in the unfamiliar environment may make the animal less responsive to additional extrinsic stimulation. These possibilities were examined experimentally using both autonomic and behavioral measures of orienting and defensive responses. The results demonstrated that animals fail to exhibit either an orienting response or a defensive response to a novel auditory stimulus when they are first placed in an unfamiliar environment. With continued exposure to the test environment the orienting response appears and then shows a time-dependent increase in magnitude. This pattern of results was obtained in both preweaning and young adult rats. On the basis of additional research and analysis, it was concluded that a limitation in information processing capacity was the primary reason for the failure of the orienting response to occur when an animal is first placed in an unfamiliar test chamber.

Aging↗
PubMedDate not supplied

Nurses' assessment of patients' cognitive orientation in a rehabilitation setting.

Orientation is a critical determinant of a patient's neurological status and an indicator of change in condition during hospitalization. The ways rehabilitation nurses assess orientation and the manner in which findings are interpreted and reported can have significant implications for the care of neurologically compromised patients. This study used a questionnaire to examine how 52 nurses appraised and reported the results of orientation evaluations. Analyses produced descriptive statistics and correlational measures for determining nurses' tendencies and consistency in evaluating orientation. Most respondents, regardless of their education and experience, used a clinical interview, rather than psychometric tests, as a basis for forming opinions about orientation. Although most evaluations included assessments in terms of person, time, place, and circumstance, no consistent pattern emerged regarding questioning or in the ways results were reported. Findings revealed a significant lack of consensus in terms of assessing and reporting orientation results, which could reflect insufficient awareness about the importance of maintaining consistency in evaluations, the relevance of using standardized evaluations and comparing measures over time, and the necessity of agreeing on how to report cognitive disturbances.

Adult↗
PubMed1999

Neuronal mechanisms of perceptual learning: changes in human brain activity with training in orientation discrimination.

Using 15O-water 3D positron emission tomography, regional cerebral blood flow was measured twice in six human subjects: before and after extensive training in orientation discrimination. In each session subjects performed two orientation discrimination tasks, during which they discriminated the orientation of a grating at either the trained or untrained reference orientation, and a control task, during which they detected a randomly textured pattern. By comparing the discrimination to the detection tasks, we observed a main effect of task bilaterally in the posterior occipital cortex, extending into the left posterior fusiform gyrus and the right inferior occipital gyrus, bilaterally in the intraparietal sulcus, as well as in the cerebellum, thalamus, and brainstem. When we compared the activation pattern before and after the training period, all the changes observed were activity decreases. The nonspecific changes, which were not related to the orientation used during the training, were situated in the cerebellum and bilaterally in the extrastriate visual cortex. The orientation-specific changes, on the other hand, were restricted to the striate and extrastriate visual cortex, more precisely the right calcarine sulcus, the left lingual gyrus, the left middle occipital, and the right inferior occipital gyrus. These findings confirm our hypothesis concerning the existence of learning related changes at early levels of visual processing in human adults and suggest that mechanisms resulting in neuronal activity decreases might be involved in the present kind of learning.

Adult↗
PubMed1991

Ecological causes and consequences of bird orientation.

An advanced orientation capability offers possibilities for birds to optimize movement patterns in a wide variety of ecological situations. The adaptive significance of various patterns of angular dispersion and of orientation responses to topography and sociality are elucidated. The orientation capacity is characterized by flexibility, exemplified by reorientation, promoting safety and restoration of fat reserves during migration. There are also limitations to the orientation process, leading to costs of migration through mis- or disorientation, and to constraints on the evolution of routes and timing of migratory flights. Young migrants may acquire an erroneous compass sense, and misorient several thousands of kilometers off their normal course. Widespread and dense fog of long duration causes disorientation and mortality among land birds migrating over the sea. Orientational constraints in the evolution of migration routes may be most easily disclosed at high geographic and magnetic latitudes. Here the birds are faced with special difficulties in using their celestial as well as their magnetic compasses. The sun compass could be used for great circle orientation, but observed spring flight trajectories of high-arctic waders and geese seem to conform with rhumbline routes.

Animals↗
PubMed1993

Wavelength-dependent effects of light on magnetic compass orientation in Drosophila melanogaster.

1. Wildtype Oregon-R Drosophila melanogaster were trained in the ambient magnetic field to a horizontal gradient of 365 nm light emanating from one of the 4 cardinal compass directions and were subsequently tested in a visually-symmetrical, radial 8-arm maze in which the magnetic field alignment could be varied. When tested under 365 nm light, flies exhibited consistent magnetic compass orientation in the direction from which light had emanated in training. 2. When the data were analyzed by sex, males exhibited a strong and consistent magnetic compass response while females were randomly oriented with respect to the magnetic field. 3. When tested under 500 nm light of the same quantal flux, females were again randomly oriented with respect to the magnetic field, while males exhibited a 90 degree clockwise shift in magnetic compass orientation relative to the trained direction. 4. This wavelength-dependent shift in the direction of magnetic compass orientation suggests that Drosophila may utilize a light-dependent magnetic compass similar to that demonstrated previously in an amphibian. However, the data do not exclude the alternative hypothesis that a change in the wavelength of light has a non-specific effect on the flies' behavior, i.e., causing the flies to exhibit a different form of magnetic orientation behavior.

Animals↗
PubMed1993

Orientational influences of layer V of visual area 18 upon cells in layer V of area 17 in the cat cortex.

We examined the orientation tuning curves of 86 cells located in layer V of area 17, before, during, and after focal blockade of a small (300-microns diameter) region of near-retinotopic register in layer V of area 18 of quantitatively established orientation preference. Such focal blockade revealed three distinct populations of area 17 layer V cells-cells with decreased responses to stimuli of some orientations (21%), cells with increased responses to stimuli of some orientations (43%), and cells unaffected by the focal blockade (36%). These effects were clearcut, reproducible, and generally directly related to the known receptive field properties of the cell recorded in area 18 at the center of the zone of blockade. These effects were also analyzed in terms of alterations in orientation bandwidth in the cells in area 17 as a result of the blockade-bandwidth increases (22%) and decreases (24%) were found; however, these changes were essentially unrelated to the measured receptive field properties. Inhibitory and excitatory effects were most pronounced when the regions in areas 17 and 18 were of like ocular dominance and were of similar orientation preference. Inhibitory effects (suggesting a normally excitatory input) were most dependent upon the similarity of receptive fields; excitatory effects (suggesting a normally inhibitory input) were less heavily dependent.

Animals↗
PubMed1993

Transformations between visual and kinesthetic coordinate systems in reaches to remembered object locations and orientations.

The abilities of human subjects to perform reach and grasp movements to remembered locations/orientations of a cylindrical object were studied under four conditions: (1) visual presentation of the object-reach with vision allowed; (2) visual presentation-reach while blindfolded; (3) kinesthetic presentation of the object-reach while blindfolded and (4) kinesthetic presentation-reach with vision. The results showed that subjects were very accurate in locating the object in the purely kinesthetic condition and that directional errors were low in all four conditions; but, predictable errors in reach distance occurred in conditions 1,2, and 4. The pattern of these distance errors was similar to that identified in previous research using a pointing task to a small target (i.e., overshoots of close targets, undershoots of far targets). The observation that the pattern of distance errors in condition 4 was similar to that of conditions 1 and 2 suggests that subjects transform kinesthetically defined hand locations into a visual coordinate system when vision is available during upper limb motion to a remembered kinesthetic target. The differences in orientation of the upper limb between target and reach positions in condition 3 were similar in magnitude to the errors associated with kinesthetic perceptions of arm and hand orientations in three-dimensional space reported in previous studies. However, fingertip location was specified with greater accuracy than the orientation of upper limb segments. This was apparently accomplished by compensation of variations in shoulder (arm) angles with oppositely directed variations in elbow joint angles. Subjects were also able to transform visually perceived object orientation into an appropriate hand orientation for grasp, as indicated by the relation between hand roll angle and object orientation (elevation angle). The implications of these results for control of upper limb motion to external targets are discussed.

Adolescent↗
PubMed1993

The influence of stimulus orientation on the vertex positive scalp potential evoked by faces.

The scalp-recorded "vertex-positive peak" (VPP) evoked by images of faces in humans has previously been shown to be delayed when an originally upright stimulus is inverted or rotated by 90 degrees (Jeffreys 1989a). This paper describes a study of the effects on this scalp potential of smaller face orientation changes (15 degrees increments). The results showed that, under normal viewing conditions of clearly defined facial images, the VPP latency, which was minimal for face orientations within 15 degrees of the vertical (0 degree), increased almost linearly for incremental rotations from 15 up to 90 degrees, but was relatively unchanged or decreased slightly for further rotations from 90 up to 180 degrees. Similar results were observed for clockwise and anticlockwise rotations, and for different facial representations. These stimulus orientation changes did not change the latency of simultaneously recorded, pattern-specific potentials recorded from occipital scalp locations; nor did they greatly affect the VPP amplitude. By contrast, rotations of "Mooney figure" stimuli away from the vertical produced concurrent reductions in both the perception of a face and the amplitude of the evoked VPP. Experiments in which the orientation of both the stimulus face and the subject's head were varied further showed that minimal latency VPP responses were evoked for parallel stimulus and viewing orientations. The speed of response is thus determined by the orientation of the subtended retinal image.

Adult↗
PubMed1995

Perception of arm orientation in three-dimensional space.

The purpose of this investigation was to determine the preferred coordinate system for perception of arm (humerus) orientation in three-dimensional space. Perception of arm orientation relative to trunk-fixed versus earth-fixed axes were compared in seven human subjects. The experimenter first moved the subject's trunk and arm into a target configuration (in which the arm's orientation relative to the trunk and/or earth was perceived and memorized by the subject) and then moved the trunk and arm to a new configuration. The blindfolded subject then attempted to reproduce the target orientation of their arm relative to either the trunk (i.e., reproduce shoulder angles--intrinsic kinesthetic coordinate system) or earth-fixed axes (extrinsic kinesthetic coordinate system). Perceptual errors were similar for both shoulder (arm relative to trunk) and extrinsic (arm relative to earth) angles. However, elevation angles were perceived with greater accuracy than yaw angles in the two coordinate systems. Also, perceptual errors for arm yaw angles in the extrinsic kinesthetic coordinate system task were better predicted from changes in trunk orientation than the errors for other angles. Furthermore, four subjects matched arm yaw angle relative to the trunk-fixed axis more accurately than to the earth-fixed axis in the extrinsic coordinate system task. These results suggests a bias toward perception of yaw angles relative to trunk-fixed axes (i.e., in an intrinsic coordinate system). These data suggest that the preferred coordinate system for kinesthetic perception of arm orientation is probably fixed in the trunk.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Orientation bias of cat dorsal lateral geniculate cells: directional analysis of the major axis of the receptive field centre.

The receptive field centre of cells in the dorsal lateral geniculate nucleus were mapped as iso-sensitivity contours. 94% of the cells were found to have elliptical centres, and analysis of the major axis orientation showed that 29% and 59% of units had their major axis oriented within +/- 20 degrees of the radial and horizontal directions, respectively. The data for Y-cells showed a greater dispersion in their orientation biases (R = 0.57) compared with X-cells (R = 0.79). Nevertheless, a horizontal orientation bias was found in both classes of cells: 47% of Y-cells and 73% of X-cells. In addition, an examination of the major axis orientations was undertaken for cells with receptive field centres located along the radial direction of 35 degrees below the horizontal meridian. In this 35 degree Radial Group a horizontal bias was also confirmed. Analysis of the dispersion of major axis orientations with eccentricity from the area centralis showed a statistically significant decrease in scatter and, hence, indicated an increase in the horizontal bias with eccentricity.

Animals↗
PubMed1978

Orientation tuning of cells in areas 17 and 18 of the cat's visual cortex.

Sharpness and symmetry of orientation tuning were quantitatively investigated and compared in ninety-seven cells from areas 17 and 18 of the lightly-anaesthetised feline visual cortex. Halfwidths of orientation tuning at half-height ranged between 5 degrees and 73 degrees for long stimuli, with an extreme exception at 111 degrees (excluding untuned cells). There was a tendency for cells in area 18 to be more broadly tuned than those in area 17, due largely to the relatively sharp tuning of area 17 simple cells. Confirming previous work, simple cells were more sharply tuned than complex cells in area 17. In area 18, there was no clear distinction in sharpness of tuning between complex type 1 cells (equated with area 17 simple cells), complex type 2 cells (equated with area 17 complex cells), or hypercomplex cells. Approximately 60% of cells in both areas were asymmetrically tuned for orientation: ratios of half-widths to either side of the optimal orientation ranged from 1.0-3.0, exceptionally 5.8. Asymmetry of tuning was more marked in area 18 than in area 17, except that area 18 complex type 2 cells as a group were relatively symmetrically tuned for orientation. Occasional cells with different preferred orientations for opposite directions of motion, for each peak of a bimodal response to a single direction, or for each half of the receptive field were also observed. The latter are described in the following paper.

Animals↗
PubMed2000

Gravity-independent orientation of honeycomb cells.

Honey bees have long been assumed to build their comb with the cells in either of two preferred orientations with respect to gravity ("vertical" or "horizontal"). I show here that these typical cell orientations in fact derive from substrate orientation and a simple building rule, rather than the influence of gravity itself. When bees were induced to build comb on substrates at four different orientations with respect to gravity, they always made cells with one vertex pointing directly toward the substrate. This produced horizontal and vertical cells on vertical and horizontal substrates, respectively, but yielded intermediate orientations on oblique substrates. The apparent preference for vertical and horizontal cells may simply reflect substrate orientation in the rectilinear hives from which cell measurements have been taken.

Animals↗
PubMed2002

Effects of inertial load and cervical-spine orientation on a head-tracking task in the alert cat.

Simultaneous video-fluoroscopic and neck muscle EMG data were recorded from one cat performing +/-15 degrees sinusoidal (0.25 Hz) head-tracking movements in the sagittal plane in a standing body posture with two initial neck orientations and four inertial loads. Radio-opaque markers were inserted into the anterior/posterior and lateral aspects of the occipital ridge and C(1)-C(7) to measure vertebral displacement. Kinematic data were analyzed, and a computer model was applied to the data to characterize the limits of movement in the cervical spine and to estimate the moment arms of the neck muscles at different orientations of head-neck movement. For each initial neck orientation, the cat utilized a distinct set of vertebral alignments, relative joint movements, and muscle-activation patterns to achieve the same movement outcome. As inertial load increased, vertebral alignments and relative joint movements were constant with a vertically oriented neck but differed when the neck was more horizontally oriented. Different muscle-activation patterns were used to maintain the same kinematic pattern with increased inertial loads. Some muscle EMG response gains (rectus capitis major and splenius capitis) increased with increasing mass, while others (biventer cervicis and occipitoscapularis) demonstrated an initial increase and then a plateau. EMG phases were not affected by changing the mass of the system but were affected by changing neck orientation. The model predicted that muscle moment arms would vary little for the different vertebral alignments, suggesting a robust biomechanical system minimally compensates for small changes in task geometry.

Animals↗
PubMed2005

The attentional mechanism of temporal orienting: determinants and attributes.

A review of traditional research on preparation and foreperiod has identified strategic (endogenous) and automatic (exogenous) factors probably involved in endogenous temporal-orienting experiments, such as the type of task, the way by which temporal expectancy is manipulated, the probability of target occurrence and automatic sequential effects, yet their combined impact had not been investigated. These factors were manipulated within the same temporal-orienting procedure, in which a temporal cue indicated that the target could appear after an interval of either 400 or 1,400 ms. We observed faster reaction times for validly versus invalidly cued targets, that is, endogenous temporal-orienting effects. The main results were that the probability of target occurrence (catch-trial proportion) modulated temporal orienting, such that the attentional effects at the short interval were independent of catch trials, whereas at the long interval the effects were only observed when catch trials were present. In contrast, the interval duration of the previous trial (i.e., exogenous sequential effects) did not influence endogenous temporal orienting. A flexible and endogenous mechanism of attentional orienting in time can account for these results. Despite the contribution of other factors, the use of predictive temporal cues was sufficient to yield attentional facilitation based on temporal expectancy.

Attention↗
PubMed1998

Spatial coding of eye movements relative to perceived earth and head orientations during static roll tilt.

This purpose of this study was to examine the spatial coding of eye movements during static roll tilt (up to +/-45 degrees) relative to perceived earth and head orientations. Binocular videographic recordings obtained in darkness from eight subjects allowed us to quantify the mean deviations in gaze trajectories along both horizontal and vertical coordinates relative to the true earth and head orientations. We found that both variability and curvature of gaze trajectories increased with roll tilt. The trajectories of eye movements made along the perceived earth-horizontal (PEH) were more accurate than movements along the perceived head-horizontal (PHH). The trajectories of both PEH and PHH saccades tended to deviate in the same direction as the head tilt. The deviations in gaze trajectories along the perceived earth-vertical (PEV) and perceived head-vertical (PHV) were both similar to the PHH orientation, except that saccades along the PEV deviated in the opposite direction relative to the head tilt. The magnitude of deviations along the PEV, PHH, and PHV corresponded to perceptual overestimations of roll tilt obtained from verbal reports. Both PEV gaze trajectories and perceptual estimates of tilt orientation were different following clockwise rather than counterclockwise tilt rotation; however, the PEH gaze trajectories were less affected by the direction of tilt rotation. Our results suggest that errors in gaze trajectories along PEV and perceived head orientations increase during roll tilt in a similar way to perceptual errors of tilt orientation. Although PEH and PEV gaze trajectories became nonorthogonal during roll tilt, we conclude that the spatial coding of eye movements during roll tilt is overall more accurate for the perceived earth reference frame than for the perceived head reference frame.

Adult↗
PubMed1998

Disorders of visuospatial orientation in the frontal plane in patients with visual neglect following right or left parietal lesions.

Current models of spatial neglect focus on deficits in the patients' horizontal or midsagittal plane. However, other evidence suggests that patients with temporo-parietal lesions centered on the parieto-insular-vestibular cortex show disturbed spatial perception of the subjective visual vertical and oblique orientation discrimination in another spatial plane, the frontal plane. As the relationship between neglect and spatial orientation deficits is unclear, we examined how patients with and without visual neglect perform visuospatial tasks in the roll plane and how their performance is related to neglect. Thirteen patients with predominantly right parietal lesions and left-sided neglect, 14 control patients without neglect after right-hemispheric cerebral lesions (RBD-controls), 11 patients without neglect after left-hemispheric lesions (LBD-controls), 3 patients with right-sided neglect after left parietal lesions, and 12 normal subjects were investigated. Constant errors and difference thresholds were measured with a PC-based system when the subjects had to adjust a luminous line to their subjective visual vertical, subjective visual horizontal, and in relation to an obliquely oriented reference line. Subjects were oriented with their head and body earth-vertical while sitting in a chair in total darkness. Patients with left-sided as well as those with right-sided neglect showed a significant, in most cases contraversive, tilt of the three spatial orientations (about 5 degrees counterclockwise in the left neglect group and 5.5 degrees-8.5 degrees clockwise in the right neglect group). In contrast, the two patient groups without neglect as well as the normal subjects showed nearly perfect visuospatial judgements with constant errors of less than 0.8 degrees . Difference thresholds were significantly elevated in patients with left neglect and in two of three patients with right-sided neglect, whereas normal control subjects and both control patient groups without neglect performed indistinguishably, having thresholds of one-tenth of those of the neglect patients. Tilt of all three spatial axes was significantly related to the severity of neglect (mean r for unsigned errors, 0.74; for difference thresholds, 0.40), indicating a significant contribution to the symptomatology of left and right spatial neglect. These results indicate a close although not necessarily causal link between spatial orientation deficits in the frontal plane and hemispatial neglect in patients with left or right parietal lesions, surpassing the well-documented impairments of these patients in the horizontal plane.

Adult↗
PubMed2005

Orientation of human semicircular canals measured by three-dimensional multiplanar CT reconstruction.

Analysis of vestibulo-ocular reflex experiments requires knowledge of the absolute orientations (with respect to skull landmarks) of semicircular canals (SCC). Data relating SCC orientations to accessible skull landmarks in humans are sparse, apart from a classic study of 10 skulls, which concluded that the horizontal and anterior SCC are not mutually orthogonal (111 +/- 7.6 degrees). Multiple studies of isolated labyrinths have shown the inter-SCC angles are close to 90 degrees. We hypothesized that a larger sample would yield mean absolute SCC orientations closer to the mutual orthogonality demonstrated for isolated labyrinths. We measured canal orientations with respect to accessible skull landmarks using 3-D multiplanar reconstructions of computerized tomography scans of the temporal bones of 22 human subjects. Images were acquired with 0.5-mm thickness and reconstructed with in-plane resolution of 234 microm. There was no significant difference between the left and a mirror image of the right (p > 0.57 on multiway ANOVA of orientation vector coefficients), so data were pooled for the 44 labyrinths. The angle between the anterior and posterior SCC was 94.0 +/- 4.0 degrees (mean +/- SD). The angle between the anterior and horizontal SCC was 90.6 +/- 6.2 degrees. The angle between the horizontal and posterior SCC was 90.4 +/- 4.9 degrees. The direction angles between a vector normal to the left horizontal SCC and the positive Reid's stereotaxic X (+nasal), Y (+left), and Z (+superior) axes were 108.7 +/- 7.5 degrees, 92.2 +/- 5.7 degrees, and 19.9 +/- 7.0 degrees, respectively. The angles between a vector normal to the left anterior SCC and the positive Reid's stereotaxic X, Y, and Z axes were 125.9 +/- 5.2 degrees, 38.4 +/- 5.1 degrees, and 100.1 +/- 6.2 degrees, respectively. The angles between a vector normal to the left posterior SCC and the positive Reid's stereotaxic X, Y, and Z axes were 133.6 +/- 5.3 degrees, 131.5 +/- 5.1 degrees, and 105.6 +/- 6.6 degrees, respectively. The mean anterior SCC-contralateral posterior SCC angle was 15.3 +/- 7.2 degrees. The absolute orientations of human SCC are more nearly orthogonal than previously reported.

Adult↗