Effects Of Disorientation Research Articles

Finding a goal on dry land and in the water: differential effects of disorientation on spatial learning

Two previous studies, Martin et al. (J. Exp. Psychol. Anim. Behav. Process. 23 (1997) 183) and Dudchenko et al. (J. Exp. Psychol. Anim. Behav. Process. 23 (1997) 194), report that, compared to non-disoriented controls, rats disoriented before testing were disrupted in their ability to learn the location of a goal on a dry radial-arm maze task, but that both groups learned at the same rate in the Morris water maze. However, the radial-arm maze task was much more difficult than the water maze. In the current set of experiments, we examined the performance of control and disoriented rats on more comparable dry land and water maze tasks. Compared to non-disoriented rats, rats that were disoriented before testing were significantly impaired in locating a goal in a circular dry arena, but not a water tank. The results constrain theoretical explanations for the differential effects of disorientation on different spatial tasks.

Updating egocentric representations in human navigation

Seven experiments tested whether human navigation depends on enduring representations, or on momentary egocentric representations that are updated as one moves. Human subjects pointed to unseen targets, either while remaining oriented or after they had been disoriented by self-rotation. Disorientation reduced not only the absolute accuracy of pointing to all objects (‘heading error’) but also the relative accuracy of pointing to different objects (‘configuration error’). A single light providing a directional cue reduced both heading and configuration errors if it was present throughout the experiment. If the light was present during learning and test but absent during the disorientation procedure, however, subjects showed low heading errors (indicating that they reoriented by the light) but high configuration errors (indicating that they failed to retrieve an accurate cognitive map of their surroundings). These findings provide evidence that object locations are represented egocentrically. Nevertheless, disorientation had little effect on the coherence of pointing to different room corners, suggesting both (a) that the disorientation effect on representations of object locations is not due to the experimental paradigm and (b) that room geometry is captured by an enduring representation. These findings cast doubt on the view that accurate navigation depends primarily on an enduring, observer-free cognitive map, for humans construct such a representation of extended surfaces but not of objects. Like insects, humans represent the egocentric distances and directions of objects and continuously update these representations as they move. The principal evolutionary advance in animal navigation may concern the number of unseen targets whose egocentric directions and distances can be represented and updated simultaneously, rather than a qualitative shift in navigation toward reliance on an allocentric map.

The combined effects of plane disorientation and foreshortening on picture naming: one manipulation or two?

Objects disoriented in plane away from the upright and objects rotated in depth producing foreshortening are harder to identify than canonical views. In Experiments 1 and 2, participants named pictures of familiar objects. There was no interaction between plane and depth rotation effects on initial presentation or after practice. Experiment 3 was a dual-task psychological refractory period study. Participants classified a high-low tone with a speeded keypress and then named a canonical, plane-rotated, or foreshortened view of an object. Naming was slower when the picture was presented 50 ms after the tone compared with 800 ms after the tone. Plane rotation effects were reduced (but not eliminated) at the short tone-picture stimulus onset asynchrony, but foreshortening effects were not reduced. The results implicate an early, prebottleneck locus for some processes compensating for plane rotation and a subsequent bottleneck or postbottleneck locus for compensation for foreshortening.

The combined effects of plane disorientation and foreshortening on picture naming: One manipulation or two?

The combined effects of plane disorientation and foreshortening on picture naming: One manipulation or two?

Disorientation combined with bilateral parietal cortex lesions causes path integration deficits in the water maze

The navigational abilities of rats were examined using the water maze after disorientation induced by rotation and/or swimming in darkness. Control and light-disoriented groups performed similarly, whereas the dark group and the dark-disoriented groups were initially much slower but improved to control levels. After receiving bilateral parietal lesions, multiple start position tests showed that both rotation groups were severely impaired in finding the hidden platform. The effects of disorientation induced by darkness and by rotation are therefore separable.

Fuzzy management of user actions during hypermedia navigation

The recent dramatic advances in the field of multimedia systems has made pacticable the development of an Intelligent Tutoring Multimedia (ITM). In these systems are present hypertextual structures that belongs to the class hypermedia systems. ITM development involves the definition of a suitable navigation model in addition to the other modules of an Intelligent Tutoring System (ITS), i.e. Database module, User module, Interface module, Teaching module. The navigation module receives as inputs the state of the system and the user's current assessment and tries to optimize the fruition of the knowledge base. Moreover, this module is responsible for managing the effects of disorientation and cognitive overhead. In this paper we deal essentially with four topics: 1. (i) to define a fuzzy-based user model able to manage adequately the user's cognitive state, the orientation, and the cognitive overhead; 2. (ii) to introduce fuzzy tools within the navigation module in order to carry out moves on the grounds of meaningful data; 3. (iii) to define a set of functions that can dynamically infer new states concerning user's interests; 4. (iv) to classify the hypermedia actions according to their semantics.

The effects of disorientation on visual landmark control of head direction cell orientation.

Head direction (HD) and place cells were recorded in rats that had previously exhibited significant acquisition deficits on a radial arm maze task following disorientation treatment. In this study we determined whether this behavioral impairment was associated with a lack of landmark stimulus control over the preferred orientations of HD and place cells. Neurons were recorded as animals retrieved food pellets in a cylindrical apparatus containing a single cue card. Some of these HD cells were also recorded while animals explored an eight-arm radial maze in a similar cue-controlled environment. The stimulus control of the landmarks in each environment was assessed by rotating the landmark and examining the subsequent preferred orientations of HD and place cells. Animals underwent disorientation treatment before and after each recording session. Despite this disorientation, rotation of the cue card in the cylindrical apparatus resulted in a corresponding shift in the preferred orientations of HD and place cells in 13 of 15 and 7 of 7 recording sessions, respectively. On the radial arm maze, rotation of the landmark cue was associated with a corresponding shift in the HD cell's preferred orientation in 7 of 9 sessions. These results suggest that a visual landmark's stimulus control may not require a learned association between that landmark and an animal's stable experience in an environment. Furthermore, instability in the HD cell system is unlikely to account for the impaired performance of the disoriented animals in the radial arm maze. Rather, these impairments may be due to the animal's inability to utilize stable representations of the environment provided by HD and place cells.

Effects of repeated disorientation on the acquisition of spatial tasks in rats: dissociation between the appetitive radial arm maze and aversive water maze.

This study examined the effects of disorientation on the acquisition of different spatial reference memory tasks. In an appetitively motivated radial arm maze task in which 1 arm was consistently baited, rats that were disoriented before each trial were impaired in their ability to acquire the task relative to rats placed in a clear container and not disoriented. However, disoriented rats were able to learn a Morris water maze and a water version of the radial arm maze under similar training conditions, suggesting that the effects of disorientation may interact with the quality or quantity of motivation involved in a given task. These results suggest that appetitive and aversive spatial tasks are dissociable, and that any impairment that is due to disorientation is specific to the appetitive radial arm maze task.

Metastasis and neuroendocrine system in stressed mice.

The effects of experimental stressors have been examined for their differential effects on primary tumor growth and spontaneous lung metastasis in syngeneic mice bearing the weakly immunogenic tumor Lewis lung carcinoma. The effects caused by the early weaning, physical restraint and foot-shock are in general small, and affected by a high variability. On the contrary, spatial disorientation reproducibly causes a specific increase in tumor metastases. The effects of spatial disorientation are sensitive to the inhibition by treatment with bromocryptine and guanethidine, and particularly by a central and peripheral adrenergic neuron blocking agent reserpine. The use of different lighting conditions and assay of urinary melatonin excretion reveal an association between pineal gland function and effects of spatial disorientation on metastasis.

Can mental rotation occur before the dual-task bottleneck?

The effect of character disorientation on mirror-normal judgments was found to be partially attenuated with increasing task overlap with a preceding tone-frequency discrimination judgment. These results suggest that orientation-sensitive processing, used to prepare disoriented stimuli for mirror-normal discrimination, can be initiated and proceed in parallel with mental activities required for a tone-frequency discrimination task. The attenuation indicates that at least some of the orientation effect on mirror-normal discriminations has its locus prior to the dual-task processing bottleneck. The possibility that the partial attenuation of the orientation effect was due to attenuation of the effect of orientation on character identification, but not on the mental rotation required for mirror-normal judgments, was examined and rejected.

Effect of disorientation on visual analysis, familiarity decision and semantic decision on faces

The disproportionate effect of vertical inversion on the processing of faces has often been interpreted as indicating differences in perceptive strategies between upright and inverted faces. If this is true, then the mathematical relation between the performance and the angular deviation would not be a linear function. Thirty subjects processed faces shown under 10 angular deviations from upright (0 deg) to upside-down (180 deg) in steps of 20 degrees, in a random design. Three cognitive levels (a between-subject factor) were tested, namely, gender classification of unfamiliar faces, familiarity decision on famous vs. unknown faces, and semantic decision (occupation) on famous faces, with 480 items per subject and task. We found no sign of a change of processing strategies for the upright vs. inverted presentations: a clear linear function emerged. However, the nature of the task could influence the effect of the angular deviation on the performance. Results suggest that, up to now, there is no definite proof of qualitatively different mechanisms underlying the processing of upright and inverted faces, respectively.

Influence of Photoisomerization of Azobenzene Derivatives in Polymeric Thin Films on Second Harmonic Generation: Towards Applications in Molecular Optoelectronics

Under visible irradiation with polarized light, polymethylmethacrylate (PMMA) films doped or functionalized with Disperse Red One (DR1) exhibit dichroism and birefringence. Both effects are due to the reversible trans-cis photoisomerization. This reaction is also responsible for the photoinduced decrease of the second harmonic generation (SHG) signal measured on these materials previously oriented by Corona poling above the T g of the polymer. This decrease is totally irreversible in the functionalized polymer whereas partly reversible in the doped one, and its intensity is strongly polarization sensitive. The irreversible component can be interpreted as the effect of disorientation and the reversible one (in the doped polymer) as a pure effect of the photochemical reaction

Orientation-invariant transfer of training in the identification of rotated natural objects.

The effects of stimulus orientation on naming were examined in two experiments in which subjects identified line drawings of natural objects following practice with the objects at the same or different orientations. Half the rotated objects were viewed in the orientation that matched the earlier presentations, and half were viewed at an orientation that mismatched the earlier presentations. Systematic effects of orientation on naming time were found during the early presentations. These effects were reduced during later presentations, and the size of this reduction did not depend on the orientation in which the object had been seen originally. The results are consistent with a dual-systems model of object identification in which initially large effects of disorientation are the result of a normalization process such as mental rotation, and in which attenuation of the effects is due to a shift from the normalization system to a feature/part-based system.

Categorization of disoriented faces in the cerebral hemispheres of normal and commissurotomized subjects.

We examined the capacity of the cerebral hemispheres to process faces that deviate from canonical perspective. In Experiment 1, normal Ss performed a gender categorization of faces presented at varying angular orientations in the left visual field (LVF) or right visual field (RVF). Orientation affected processing speed, more so in the RVF than in the LVF. The function relating reaction times to disorientation of the faces was approximately monotonic and reflected the increased difficulty in extracting relevant configurational information as the faces were rotated from canonical perspective. In Experiment 2, 3 commissurotomized Ss performed the same task. They responded above chance in the 2 visual fields, and the pattern of their results was similar to that obtained with the normal Ss, but the effect of disorientation was considerably more pronounced. It is suggested that the right hemisphere contribution becomes more critical the further the visual pattern departs from conventional view. Issues regarding the specification of processes correcting for disorientation and comparison of normal and commissurotomized Ss are discussed.

Establishing global and local correspondence between successive stimuli: The holistic nature of backward alignment.

Reflection decisions on alphanumeric characters display systemic effects of disorientation, suggesting that subjects mentally rotate the stimulus to the upright (the uprighting process). However, response time also increases with increasing angular disparity between the current and preceding orientations. This occurs only when the current stimulus is brought into congruence with the preceding one (the backward alignment process). In the present study, we examined the hypothesis that the transformation that occurs in backward alignment in holistic even in tasks in which the uprighting process is likely to be piecemeal. Evidence supporting this hypothesis is presented on the basis of tasks requiring either classification of numbers (Experiments 1 and 3) and words (Experiment 2), or mirror image discrimination on letter pairs (Experiment 4). The results indicated that backward alignment establishes global correspondence between successive stimuli and is indifferent to local correspondence at the level of the constituent elements. The establishment of this global correspondence decreases with the number of elements in the stimulus (Experiment 5), but its effects are still observed for four-letter strings (Experiment 6).

Oriented molecule beams: Focusing and orientation of t-butyl iodide with analysis by polarized laser photofragmentation

The tert-butyl iodide molecule is readily focused with the electrostatic hexapole, via its first-order Stark effect as a pseudo-symmetric top. The pulsed, seeded supersonic focused beam, characterized by 〈cos θ〉=Vth/ V0 (where θ is the angle between the molecular dipole axis μ and the electric field E; ±V0 the hexapole ‘‘rod voltage,’’ and Vth the so-called threshold voltage), passes into a small homogeneous electric field in which it is oriented. The degree of laboratory orientation achieved is measured using the method of linearly polarized laser-induced photofragmentation [S. R. Gandhi, T. J. Curtiss, and R. B. Bernstein, Phys. Rev. Lett. 59, 2951 (1987)], operating (at three laser wavelengths) on the I(2P3/2) and I(2P1/2) as well as the t-C4H9 radical photofragments. The results show that the oriented beam molecules of t-butyl iodide (at a rotational temperature near 15 K) have a higher degree of orientation than the prototype CH3I molecules (JKM state-selected and focused similarly), explainable by the greater importance of the so-called hyperfine disorientation effect for the prolate symmetric top (CH3I) than for the t-C4H9I. For the latter, orientations with photofragment up–down asymmetry ratios as large as a factor of 10 can be achieved, suggesting that t-C4H9I is an excellent candidate reagent for reactive asymmetry studies.

Oriented molecule beams: Focusing and orientation of t-butyl bromide with analysis by polarized laser photofragmentation

Tert-butyl bromide is photodissociated at 277.3 nm (in the tail of the first absorption continuum). Both fragments, i.e., the t-butyl radical and the Br(2P1/2) atom, are detected by laser MPI-TOF mass spectrometry. Seeded, supersonic beams of this pseudosymmetric top molecule are readily focusable and orientable (via its first-order Stark effect) using the electrostatic hexapole lens. The linearly polarized laser-induced photofragmentation technique reveals unusually high degrees of orientation, significantly greater than that for t-C4H9I, due to the less serious hyperfine disorientation effect for the Br- (vs I-) containing molecule. Thus t-C4H9Br is an excellent candidate reagent for reactive asymmetry scattering studies of the steric effect via the oriented molecule beam method.

Reading rotated words.

Hebrew-speaking students performed lexical decisions on Hebrew letter strings that appeared at different orientations. Response times evidenced a strong interaction between string length and orientation. At angular deviations of less than 60 degrees from the upright, neither orientation nor string length had any effect, suggesting that words were directly, and probably holistically, recognized. The results for the 60 degrees deviation, while also exhibiting no effects of word length, yielded slower response times, suggesting a holistic rectification process. For deviations between 60 degrees and 120 degrees, the effects of disorientation increased sharply with increasing string length, suggesting piecemeal processing that may be due to the utilization of reading units smaller than the whole word or to piecemeal rectification. In this region, stimulus disorientation appears to impair word recognition by disrupting transgraphemic information rather than by interfering with letter identification. Extreme disorientations, 120 degrees or more, exhibited no further impairment with increased disorientation, and all evidenced strong and similar length effects, suggesting letter-by-letter reading. The implications of the results for the reading of normal and transformed text are discussed.

Recognition of inverted photographs of faces by children and adults.

Inverted black-white photographs of the faces of highly familiar peers (classmates, fraternity brothers, etc.) were presented to 350 Ss ranging from 3 to 20 years of age. In an untimed test session, S tried to identify the person in the inverted photograph. Success in this task was positively correlated with age up to approximately 14 years, but performance deteriorated after this age; college-age Ss and preschool Ss' performances were approximately equal. This finding contrasts with the current view that the effects of disorientation on perception becomes less potent with age. A cognitive explanation is offered for the early rise in the performance curve; the subsequent reduction in level of performance is attributed to rigidity of the perceptual mechanism as a function of overlearning of a mono-oriented configuration.

The effect of disorientation on the intensity distribution of non-crystalline fibres. I. Theory

The intensity function in reciprocal space is derived for the case of non-crystalline fibres with a Gaussian distribution of orientations. An expression is found relating the observed intensity function with the weighted integral along a circle of the intensity derived from the molecular structure factor. From this result in the case where the layer-line width is very small a correction factor may be derived which, if applied to the observed intensity, yields the intensity which would be obtained from a perfectly orientated fibre. The general problem of correcting for disorientation can only be treated by a numerical deconvolution procedure.