Determinants of the perception of rotational motion: Orientation of the motion to the object and to the environment.

The results of two experiments suggest that strong constraints on the ability to imagine rotations extend to the perception of rotations. Participants viewed stereographic perspective views of rotating squares, regular polyhedra, and a variety of polyhedral generalized cones, and attempted to indicate the orientation of the axis and planes of rotation in terms of one of the 13 canonical directions in 3D space. When the axis and planes of a rotation were aligned with principal directions of the environment, participants could indicate the orientation of the motion well. When a rotation was oblique to the environment, the orientation of the object to the motion made a very large difference to performance. Participants were fast and accurate when the object was a generalized cone about the axis of rotation or was elongated along the axis. Variation of the amount of rotation and reflection symmetry of the object about the axis of rotation was not powerful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The transepicondylar axis approximates the optimal flexion axis of the knee

The traditional understanding of knee kinematics holds that no single fixed axis of rotation exists in the knee. In contrast, a recent hypothesis suggests that knee kinematics are better described simply as two simultaneous rotations occurring about fixed axes. Knee flexion and extension occurs about an optimal flexion axis fixed in the femur, whereas tibial internal and external rotations occur about a longitudinal rotation axis fixed in the tibia. No other translations or rotations exist. This hypothesis has been tested. Tibiofemoral kinematics were measured for 15 cadaveric knees undergoing a realistic loadbearing activity (simulated squatting). An optimization technique was used to identify the locations of the optimal flexion and longitudinal rotation axes such that simultaneous rotations about them could best represent the measured kinematics. The optimal flexion axis was compared with the transepicondylar axis defined by bony landmarks. The longitudinal rotation axis was found to pass through the medial joint compartment. The optimal flexion axis passed through the centers of the posterior femoral condyles. No significant difference was found between the optimal flexion and transepicondylar axes. To an average accuracy of better than 3.4 mm in translation, and 2.9 degrees in orientation, knee kinematics were represented successfully by simple rotations about the optimal flexion and longitudinal rotation axes. The optimal flexion axis is fixed in the femur and can be considered the true flexion axis of the knee. The transepicondylar axis axis, which is identified easily by palpation, closely approximates the optimal flexion axis.     

Development of three-dimensional form perception.

In 3 experiments with infants and one with adults we explored the generality, limitations, and informational bases of early form perception. In the infant studies we used a habituation-of-looking-time procedure and the method of Kellman (1984), in which responses to 3-dimensional (3-D) form were isolated by habituating 16-wk-old Ss to a single object in 2 different axes of rotation in depth, and testing afterward for dishabituation to the same object and to a different object in a novel axis of rotation. In Exp I, continuous optical transformations given by moving 16-wk-old observers around a stationary 3-D object specified 3-D form to infants. In Exp II, we found no evidence of 3-D form perception from multiple, stationary, binocular views of objects by 16- and 24-wk-olds. Exp IIIA indicated that perspective transformations of the bounding contours of an object, apart from surface information, can specify form at 16 wks. Exp IIIB provided a methodological check, showing that adult Ss could neither perceive 3-D forms from the static views of the objects in Exp IIIA nor match views of either object across different rotations by proximal stimulus similarities. The results identify continuous perspective transformations, given by object or observer movement, as the informational bases of early 3-D form perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceived orientation of axis of rotation in structure-from-motion

Perceived orientation of axis of rotation and accuracy in discriminating fixed-axis from nonfixed-axis rotations were investigated for orthographic projections of three-dimensional rotating objects. The principal findings were (a) the slant of the axis of rotation was systematically misperceived; (b) in both two-view and multiview displays, the perceived slant of the axis of rotation was well-predicted by the ratio between the deformation (a property of the first-order optic flow) and the component parallel to the image plane of the global velocity vector; (c) if this ratio was kept constant in each frame transition of the stimulus sequence (or it was varied), then the stimuli tended to be judged as fixed-axis rotations (or as nonfixed-axis rotations), regardless of whether they simulated a fixed-axis rotation or not; and (d) the tilt of the axis of rotation was perceived in two-view displays with a very small error.     

Perceived orientation of axis rotation in structure-from-motion.

Perceived orientation of axis of rotation and accuracy in discriminating fixed-axis from nonfixed-axis rotations were investigated for orthographic projections of three-dimensional rotating objects. The principal findings were (1) the slant of the axis of rotation was systematically misperceived; (2) in both two-view and multiview displays, the perceived slant of the axis of rotation was well-predicted by the ratio between the deformation (a property of the first-order optic flow) and the component parallel to the image plane of the global velocity vector; (3) if this ratio was kept constant in each frame transition of the stimulus sequence (or it was varied), then the stimuli tended to be judged as fixed-axis rotations (or as nonfixed-axis rotations), regardless of whether they simulated a fixed-axis rotation or not; and (4) the tilt of the axis of rotation was perceived in two-view displays with a very small error. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Myosin head configuration in relaxed fish muscle: resting state myosin heads must swing axially by up to 150 A or turn upside down to reach rigor

The arrangement and shape of myosin heads in relaxed muscle have been determined by analysis of low-angle X-ray diffraction data from a very highly ordered vertebrate muscle in bony fish. This reveals the arrangement and interactions between the two heads of the same myosin molecule, the shape of the resting myosin head (M.ADP.Pi) assuming a putative hinge between the myosin catalytic domain and the light chain binding-domain, and the way that the actin-binding sites on myosin are arrayed around the actin filaments in the bony fish muscle A-band cell unit. The results are discussed in terms of possible force-generating mechanisms. Changes in myosin head shape or tilt have been implicated in the mechanism of force generation. The myosin head arrangement, including perturbations from perfect helical symmetry, has all heads oriented roughly the same way up (there is only a small range of rotations around the head long axis). X-ray data do not define the absolute polarity of the myosin head array. The resting head rotation is either similar to (65 degrees difference) or opposite to (115 degrees difference) the rotation in the rigor state. If the rotations are similar, probably the more likely possibility, then the average relative axial displacement of the inner and outer ends of the heads from the resting state to rigor is about 140 to 150 A. If (less likely) the resting head rotation is opposite to rigor, then the heads would need to turn over (i.e. rotate about 115 degrees around their own long axes) and the mean relative axial displacement from relaxed to rigor would only be 20 to 30 A.     

Updating displays after imagined object and viewer rotations.

Six experiments compared spatial updating of an array after imagined rotations of the array versus viewer. Participants responded faster and made fewer errors in viewer tasks than in array tasks while positioned outside (Experiment 1) or inside (Experiment 2) the array. An apparent array advantage for updating objects rather than locations was attributable to participants imagining translations of single objects rather than rotations of the array (Experiment 3). Superior viewer performance persisted when the array was reduced to 1 object (Experiment 4); however, an object with a familiar configuration improved object performance somewhat (Experiment 5). Object performance reached near-viewer levels when rotations included haptic information for the turning object. The researchers discuss these findings in terms of the relative differences in which the human cognitive system transforms the spatial reference frames corresponding to each imagined rotation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oculomotor control of primary eye position discriminates between translation and tilt

We have previously shown that fast phase axis orientation and primary eye position in rhesus monkeys are dynamically controlled by otolith signals during head rotations that involve a reorientation of the head relative to gravity. Because of the inherent ambiguity associated with primary otolith afferent coding of linear accelerations during head translation and tilts, a similar organization might also underlie the vestibulo-ocular reflex (VOR) during translation. The ability of the oculomotor system to correctly distinguish translational accelerations from gravity in the dynamic control of primary eye position has been investigated here by comparing the eye movements elicited by sinusoidal lateral and fore-aft oscillations (0.5 Hz +/- 40 cm, equivalent to +/- 0.4 g) with those during yaw rotations (180 degrees/s) about a vertically tilted axis (23.6 degrees). We found a significant modulation of primary eye position as a function of linear acceleration (gravity) during rotation but not during lateral and fore-aft translation. This modulation was enhanced during the initial phase of rotation when there was concomitant semicircular canal input. These findings suggest that control of primary eye position and fast phase axis orientation in the VOR are based on central vestibular mechanisms that discriminate between gravity and translational head acceleration.     

Detection of information specifying the motion of objects by 3- and 5-month-old infants.

Two studies investigated the ability of 56 3.5- and 5-mo-olds to recognize and discriminate among different motions of rigid objects. In each study, Ss were habituated to 1 of 2 motions made by several different objects. After reaching criterion, they were tested with a novel object making the familiar motion and a novel one. At 5 mo, Ss discriminated (a) the translation of an object from rotation plus translation, (b) translation alone from rotation alone, (c) full rotation on the vertical axis from oscillation on the vertical axis, and (d) rotation to the left and rotation to the right. At 3.5 mo, Ss responded differently only in the 1st case, and it was less clear that they were discriminating on the basis of motion. Three additional studies, with 64 5-mo-olds, suggested that texture on the surface of the object and the projected contour were both important to the discrimination of the different motions. Results are discussed in terms of disruptions in the optic array. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transient hemifacial spasm associated with subarachnoid brainstem cysticercosis: a case report

The vestibulo-ocular reflex (VOR) and angular displacement perception were measured in 25 healthy humans in darkness before and after exposure to incoherent visual-vestibular stimulation (VVS): 45 min of repeated passive 180 degrees whole-body rotations around the vertical axis concurrent with only 90 degrees rotation in a visual virtual square room. Large inter-individual variability was observed for both VOR gain and turning estimates. The individual VOR gains were not correlated with perceived angles of rotation either before or after VVS. After VVS, the angular displacement perception decreased by 24+/-16% while the VOR gain did not change significantly. The results suggest that adaptive plasticity in turning perception and adaptive plasticity in VOR might be independent of one another.     

Spatial coordination by descending vestibular signals. 2. Response properties of medial and lateral vestibulospinal tract neurons in alert and decerebrate cats

Spatial response properties of medial (MVST) and lateral (LVST) vestibulospinal tract neurons were studied in alert and decerebrate cats during sinusoidal angular rotations of the whole body in the horizontal and many vertical planes. Of 220 vestibulospinal neurons with activity modulated during 0.5-Hz sinusoidal rotations, 200 neurons exhibited response gains that varied as a cosine function of stimulus orientation and phases that were near head velocity for rotation planes far from the minimum response plane. A maximum activation direction vector (MAD), which represents the axis and direction of rotation that maximally excites the neuron, was calculated for these neurons. Spatial properties of secondary MVST neurons in alert and decerebrate animals were similar. The responses of 88 of 134 neurons (66%) could be accounted for by input from one semicircular canal pair. Of these, 84 had responses consistent with excitation from the ipsilateral canal of the pair (13 horizontal, 27 anterior, 44 posterior) and 4 with excitation from the contralateral horizontal canal. The responses of the remaining 46 (34%) neurons suggested convergent inputs. The activity of 38 of these was significantly modulated by both horizontal and vertical rotations. Twelve neurons (9%) had responses that were consistent with input from both vertical canal pairs, including 9 cells with MADs near the roll axis. Thirty-two secondary MVST neurons (24%) had type II yaw and/or roll responses. The spatial response properties of 18 secondary LVST neurons, all studied in decerebrate animals, were different from those of secondary MVST neurons. Sixteen neurons (89%) had type II yaw and/or roll responses, and 12 (67%) appeared to receive convergent canal pair input. Convergent input was more common on higher-order vestibulospinal neurons than on secondary neurons. These results suggest that MVST and LVST neurons and previously reported vestibulo-ocular neurons transmit functionally different signals. LVST neurons, particularly those with MADs close to the roll axis, may be involved in the vestibular-limb reflex. The combination of vertical and ipsilateral horizontal canal input on many secondary MVST neurons suggests a contribution to the vestibulocollic reflex. However, in contrast to most neck muscles, very few neurons had maximum vertical responses near pitch.     

Spatial memory during progressive disorientation.

Human spatial representations of object locations in a room-sized environment were probed for evidence that the object locations were encoded relative not just to the observer (egocentrically) but also to each other (allocentrically). Participants learned the locations of 4 objects and then were blindfolded and either (a) underwent a succession of 70° and 200° whole-body rotations or (b) were fully disoriented and then underwent a similar sequence of 70° and 200° rotations. After each rotation, participants pointed to the objects without vision. Analyses of the pointing errors suggest that as participants lost orientation, represented object directions generally "drifted" off of their true directions as an ensemble, not in random, unrelated directions. This is interpreted as evidence that object-to-object (allocentric) relationships play a large part in the human spatial updating system. However, there was also some evidence that represented object directions occasionally drifted off of their true directions independently of one another, suggesting a lack of allocentric influence. Implications regarding the interplay of egocentric and allocentric information are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. I. Linear acceleration responses during off-vertical axis rotation

1. The dynamic properties of otolith-ocular reflexes elicited by sinusoidal linear acceleration along the three cardinal head axes were studied during off-vertical axis rotations in rhesus monkeys. As the head rotates in space at constant velocity about an off-vertical axis, otolith-ocular reflexes are elicited in response to the sinusoidally varying linear acceleration (gravity) components along the interaural, nasooccipital, or vertical head axis. Because the frequency of these sinusoidal stimuli is proportional to the velocity of rotation, rotation at low and moderately fast speeds allows the study of the mid-and low-frequency dynamics of these otolith-ocular reflexes. 2. Animals were rotated in complete darkness in the yaw, pitch, and roll planes at velocities ranging between 7.4 and 184 degrees/s. Accordingly, otolith-ocular reflexes (manifested as sinusoidal modulations in eye position and/or slow-phase eye velocity) were quantitatively studied for stimulus frequencies ranging between 0.02 and 0.51 Hz. During yaw and roll rotation, torsional, vertical, and horizontal slow-phase eye velocity was sinusoidally modulated as a function of head position. The amplitudes of these responses were symmetric for rotations in opposite directions. In contrast, mainly vertical slow-phase eye velocity was modulated during pitch rotation. This modulation was asymmetric for rotations in opposite direction. 3. Each of these response components in a given rotation plane could be associated with an otolith-ocular response vector whose sensitivity, temporal phase, and spatial orientation were estimated on the basis of the amplitude and phase of sinusoidal modulations during both directions of rotation. Based on this analysis, which was performed either for slow-phase eye velocity alone or for total eye excursion (including both slow and fast eye movements), two distinct response patterns were observed: 1) response vectors with pronounced dynamics and spatial/temporal properties that could be characterized as the low-frequency range of "translational" otolith-ocular reflexes; and 2) response vectors associated with an eye position modulation in phase with head position ("tilt" otolith-ocular reflexes). 4. The responses associated with two otolith-ocular vectors with pronounced dynamics consisted of horizontal eye movements evoked as a function of gravity along the interaural axis and vertical eye movements elicited as a function of gravity along the vertical head axis. Both responses were characterized by a slow-phase eye velocity sensitivity that increased three- to five-fold and large phase changes of approximately 100-180 degrees between 0.02 and 0.51 Hz. These dynamic properties could suggest nontraditional temporal processing in utriculoocular and sacculoocular pathways, possibly involving spatiotemporal otolith-ocular interactions. 5. The two otolith-ocular vectors associated with eye position responses in phase with head position (tilt otolith-ocular reflexes) consisted of torsional eye movements in response to gravity along the interaural axis, and vertical eye movements in response to gravity along the nasooccipital head axis. These otolith-ocular responses did not result from an otolithic effect on slow eye movements alone. Particularly at high frequencies (i.e., high speed rotations), saccades were responsible for most of the modulation of torsional and vertical eye position, which was relatively large (on average +/- 8-10 degrees/g) and remained independent of frequency. Such reflex dynamics can be simulated by a direct coupling of primary otolith afferent inputs to the oculomotor plant. (ABSTRACT TRUNCATED)     

Seeing things from a different angle: The pigeon's recognition of single geons rotated in depth.

In 2 experiments involving computer-rendered versions of single shapes or "geons," the extent to which depth rotation affects the visual discrimination performance of pigeons in both go/no-go and forced-choice tasks was documented. The pigeons were able to recognize geons at most rotations in depth; however, the pigeons' recognition performance was better at the training view than at most other views. Aspects of these results are both consistent with and problematic for object-centered and viewer-centered theories of object recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition blindness for rotated objects.

Repetition blindness (RB) is the finding that observers often miss the repetition of an item within a rapid stream of words or objects. Recent studies have shown that RB for objects is largely unaffected by variations in viewpoint between the repeated items. In 5 experiments, we tested RB under different axes of rotation, with different types of stimuli (line drawings and shaded images, intact and split), using both novel and familiar objects. Although RB was largely viewpoint invariant, in most experiments, RB was reduced for small (0°) and large (180°) viewpoint differences relative to intermediate rotations. However, these deviations from invariance were eliminated when object images were split, breaking the holistic coherence of the object. These findings suggest that RB is due mainly to the activation of object representations from local diagnostic features, but can be modulated by priming on the basis of view similarity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rotated object identification with and without orientation cues.

The time to name two-dimensional line drawings of objects increases linearly for object rotations between 00 and 1200 from the upright. Several theories attribute these effects of orientation to finding the top or the top-bottom axis of objects. By this account, prior knowledge of the location of the top or the top-bottom axis of objects should diminish effects of object orientation when they are named. When this hypothesis was tested by cuing the top or the top-bottom axis, no reduction in the effects of orientation on object naming was found. This result is inconsistent with effects of orientation on object naming being due to finding the top or the top-bottom axis. Instead, the top may be found prior to rotational normalization of the object image. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Convergence of ampullar and macular inputs on vestibular nuclei unit of the rat

181 vestibular nucleus neurons were examined for their responsiveness to rotation about the vertical axis and static tilts in roll and pitch planes in the rat. 68 of these units were sensitive to rotation and tilts (canal-otolith cells). In other words, 41.0% of the neurons responded to rotation (68/166). There was no significant difference in percentage of canal-otolith cells in type I and II neurons, which were 48.6% and 37.0% respectively. Vertical axis rotation when the head was tilted produced a simultaneous stimulation of the canal and otoliths. Using this stimulus method, the bias effect was observed in 72.5% of the canal-otolith cells (29/40). Furthermore, since vertical axis rotation with the head tilted elicited vertical canal responses, the rate of ampullary convergence was estimated by analysing response profiles obtained such rotations. The results obtained in the rat were compared with those in other species.     

CD40 and its crucial role as a member of the TNFR family

The remarkable accuracy with which healthy subjects can monitor their orientation while walking in darkness has been attributed to a process whereby awareness of orientation is automatically updated by information derived from active locomotion. The aim of this study was, first, to determine the contribution of vestibular information to the perception of orientation without vision, by comparing the accuracy of judgments of orientation following passive (seated) rotation about an earth-vertical axis with those following active (locomotor) rotation. The second aim was to assess whether monitoring orientation is indeed automatic, or whether it requires some degree of mental effort. This was evaluated by assessing whether accuracy in monitoring multiple passive or active rotations was affected by asking subjects to perform a mental task (that is, counting backwards) during rotation. The results indicated that although reliance on the primarily vestibular information available during passive rotation enabled subjects to accurately monitor single turns of up to 180 degrees, subjects were able to judge orientation after multiple turns more accurately after active rotation than after passive rotation, owing to the additional sensorimotor feedback gained from active locomotion. Accuracy in judging orientation was substantially impaired by backwards counting during both passive and active locomotion. This finding confirms that monitoring orientation during multiple turns in darkness necessitates central processing and adds to the growing body of evidence for the influence of mental activity on the perception and control of orientation.     

The effect of distinctive parts on recognition of depth-rotated objects by pigeons (Columba livia) and humans.

To explore whether effects observed in human object recognition represent fundamental properties of visual perception that are general across species, the authors trained pigeons (Columba livia) and humans to discriminate between pictures of 3-dimensional objects that differed in shape. Novel pictures of the depth-rotated objects were then tested for recognition. Across conditions, the object pairs contained either 0, 1, 3, or 5 distinctive pails. Pigeons showed viewpoint dependence in all object-part conditions, and their performance declined systematically with degree of rotation from the nearest training view. Humans showed viewpoint invariance for novel rotations between the training views but viewpoint dependence for novel rotations outside the training views. For humans, but not pigeons, viewpoint dependence was weakest in the 1-part condition. The authors discuss the results in terms of structural and multiple-view models of object recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)