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PubMed2006

Errors in judging information about reflections in mirrors.

We investigated people's perception and knowledge of planar mirror reflections. People were accurate at deciding when they could first see their reflection as they approached a mirror from the side, but only if their reflection was visible. Most people stopped too early if the mirror was covered up. People also overestimated the size of the reflection of their face on the surface of a mirror if they were shown a covered mirror. Their accuracy improved somewhat if their reflection was visible but, unlike the first task, they still made striking errors. Perceptual feedback thus improved performance at predicting the behaviour of mirror reflections in both tasks but failed to eliminate errors in the second task. The overestimation of reflection size was not face-specific as it generalised to novel stimuli (paper ellipses) and it was found with both a matching response and for verbal size estimations. The early error in the first task appears to be due to an inaccurate belief that can be overridden by perceptual feedback. The overestimation in the second task is primarily caused by a powerful size-constancy effect.

Adolescent↗

PubMed1996

Self-recognition and abstraction abilities in the common chimpanzee studied with distorting mirrors.

The reactions of chimpanzees to regular mirrors and the results of the standard Gallup mark test have been well documented. In addition to using the mark test to demonstrate self-recognition in a regular mirror, we exposed six female chimpanzees to mirrors that produced distorted or multiplied self-images. Their reactions to their self-images, in terms of mirror-guided self-referenced behaviors, indicated that correct assessment of the source of the mirror image was made by each subject in each of the mirrors. Recognition of a distorted self-image implies an ability for abstraction in the subjects in that the distortion must be rationalized before self-recognition occurs. The implications of these results in terms of illuminating the relative importance of feature and contingency of movement cues to self-recognition are discussed.

Animals↗

PubMed1990

Infant social behavior in front of a mirror and in front of a familiar and an unfamiliar peer.

In this study, we explored the differences in infant social behaviors in front of the mirror and in front of a familiar and an unfamiliar peer. We assumed that infant social behaviors in front of the mirror constitute mainly an exploration of the mirror image characteristics. Our observations were videotaped and coded according to definitions of social behavior in infant-infant situations. The results obtained indicate that 6- to 13-month-old infants display significantly more frequent social behaviors in front of a mirror than in front of a familiar or an unfamiliar peer. These behaviors are characterized by tactile contact with the mirror surface, adapting the hand to this surface, and very frequent coordinated social behaviors. This pattern of social behaviors in front of the mirror is discussed and linked to the exploration of distinctive characteristics of the self-reflected image such as perfect synchronicity of movement and two-dimensionality.

Body Image↗

PubMed2002

Reflective mirrors: perspective-taking in autoscopic phenomena.

INTRODUCTION: ''Autoscopic phenomena refer to different illusory reduplications of one's own body and self. This article proposes a phenomenological differentiation of autoscopic reduplication into three distinct classes, i.e., autoscopic hallucinations, heautoscopy, and out-of-body experiences (OBEs). METHOD: Published cases are analysed with special emphasis on the subject's point of view from which the reduplication is observed. RESULTS: In an autoscopic hallucination the observer's perspective is clearly body-centred, and the visual image of one's own body appears as a mirror reversal. Heautoscopy (i.e., the encounter with an alter ego or doppelgänger), is defined as a reduplication not only of bodily appearance, but also of aspects of one's psychological self. The observer's perspective may alternate between egocentric and ''alter-ego-centred''. As a consequence of the projection of bodily feelings into the doppelgänger (implying a mental rotation of one's own body along the vertical axis), original and reduplicated bodies are not mirror images of one another. This also holds for OBEs, where one's self is not reduplicated but appears to be completely dissociated from the body and observing it from a location in extracorporeal space. It is argued that perspective-taking in a spatial sense may be meaningfully related to perspective-taking in a psychological sense. The mirror in the autoscopic hallucination is a ''cognitively nonreflective mirror'' (Jean Cocteau), both spatially and psychologically. The reflective abilities of the heautoscopic mirror are better developed, yet frequent shifts in the observer's spatial perspective render the nature of psychological interactions between self and alter ego highly unpredictable. The doppelgänger may serve a transitivistic (i.e., own suffering is transferred to the alter ego) or aggressive function when this behaviour is directed against a patient. The mirror in an OBE is always reflective: It allows the self to view both space and one's psychological state from a detached but stable perspective. CONCLUSIONS: Spatial perspective-taking should be more thoroughly assessed in patients reporting autoscopic phenomena. By elucidating the interactions between spatial phenomenology and psychological function, we may gain important insights into the relationships between the self, its body, and phenomenal space.

Journal Article↗

PubMed1978

American Burkitt's lymphoma-hand-mirror variant. A detailed investigation of cytologic, ultrastructural, and immunologic features.

Previous studies of patients with lymphoid malignancies have suggested a relationship between survival and the presence of more than 40% hard-mirror cells in the bone marrow. This report represents the first detailed study of a patient with American Burkitt's lymphoma with numerous hand-mirror cells in the bone marrow during the course of the disease. The Burkitt cells were atypical because of their hand-mirror configuration in the bone marrow, the presence of cytoplasmic glycogen, the finding of an IgG surface marker, and a strongly positive acid phosphatase staining reaction. The presence of increased numbers of hand-mirror forms in the bone marrow during the course of the patient's illness may have clinical significance, because they were replaced by non-hand-mirror Burkitt cells in the terminal phase. More reports and investigations of patients with large numbers of hand-mirror forms in the bone marrow are needed to elucidate the full significance of this unusual cellular phenomenon.

Adult↗

PubMed1979

Acute lymphoblastic leukemia, hand-mirror variant. A detailed ultrastructural study.

The hand-mirror cell in acute lymphoblastic leukemia may have important immunologic, pathogenic, and prognostic implications. To learn more about this cell, a detailed ultrastructural analysis was performed. Fifty electronmicrographs of lymphoblasts from an untreated patient with acute lymphoblastic leukemia with numerous hand-mirror cells in the bone marrow were compared with 60 electronmicrographs of lymphoblasts from six patients with classic acute lymphoblastic leukemia. The unique qualitative ultrastructural features of the hand-mirror cells were the presence of undamaged mitochondria and uropods (handles) with terminal microspikes containing circular organized arrangement of 50-A microfilaments. Quantitative differences between hand-mirror cells and lymphoblasts were observed in nuclear perimeters (P less than 0.0001), nuclear lengths (P less than 0.001), cytoplasmic lengths (P less than 0.0002), nuclear-cytoplasmic length ratios (P less than 0.0001), and numbers of mitochondria (P less than 0.002). These findings indicate that hand-mirror cells contain ultrastructural components that are related to cell motility and the immunologic process. These results are significant in that the hand-mirror cells may be associated with an immunologic mechanism that is involved in leukemogenesis.

Cell Nucleolus↗

PubMed2006

Functions of the mirror neuron system: implications for neurorehabilitation.

Mirror neurons discharge during the execution of hand object-directed actions and during the observation of the same actions performed by other individuals. These neurons were first identified in the ventral premotor cortex (area F5) and later on in the inferior parietal lobule of monkey brain, thus constituting the mirror neuron system. More recently, mirror neurons for mouth object-directed actions have also been found in the monkey. Several pieces of experimental data demonstrate that a mirror neuron system devoted to hand, mouth, and foot actions is also present in humans. In the present paper we review the experimental evidence on the role of the mirror neuron system in action understanding, imitation learning of novel complex actions, and internal rehearsal (motor imagery) of actions. On the basis of features of the mirror neuron system and its role in action understanding and imitation, we discuss the possible use of action observation and imitation as an approach for systematic training in the rehabilitation of patients with motor impairment of the upper limb after stroke.

Animals↗

PubMed1996

Synaesthesia in phantom limbs induced with mirrors.

Although there is a vast clinical literature on phantom limbs, there have been no experimental studies on the effects of visual input on phantom sensations. We introduce an inexpensive new device--a 'virtual reality box'--to resurrect the phantom visually to study inter-sensory effects. A mirror is placed vertically on the table so that the mirror reflection of the patient's intact had is 'superimposed' on the felt position of the phantom. We used this procedure on ten patients and found the following results. 1. In six patients, when the normal hand was moved, so that the phantom was perceived to move in the mirror, it was also felt to move; i.e. kinesthetic sensations emerged in the phantom. In D.S. this effect occurred even though he had never experienced any movements in the phantom for ten years before we tested him. He found the return of sensations very enjoyable. 2. Repeated practice led to a permanent 'disappearance' of the phantom arm in patient D.S. and the hand became telescoped into the stump near the shoulder. 3. Using an optical trick, impossible postures--e.g. extreme hyperextension of the fingers--could be induced visually in the phantom. In one case this was felt as a transient 'painful tug' in the phantom. 4. Five patients experienced involuntary painful 'clenching spasms' in the phantom hand and in four of them the spasms were relieved when the mirror was used to facilitate 'opening' of the phantom hand; opening was not possible without the mirror. 5. In three patients, touching the normal hand evoked precisely localized touch sensations in the phantom. Interestingly, the referral was especially pronounced when the patients actually 'saw' their phantom being touched in the mirror. Indeed, in a fourth patient (R.L.) the referral occurred only if he saw his phantom being touched: a curious form of synaesthesia. These experiments lend themselves readily to imaging studies using PET and fMRI. Taken collectively, they suggest that there is a considerable amount of latent plasticity even in the adult human brain. For example, precisely organized new pathways, bridging the two cerebral hemispheres, can emerge in less than three weeks. Furthermore, there must be a great deal of back and forth interaction between vision and touch, so that the strictly modular, hierarchical model of the brain that is currently in vogue needs to be replaced with a more dynamic, interactive model, in which 're-entrant' signalling plays the main role.

Adult↗

PubMed2005

Adenoid size assessment: a comparison of palpation, nasendoscopy and mirror examination.

OBJECTIVES: To compare the digital, mirror and nasendoscopic assessment of adenoid size and posterior choanal obstruction in patients undergoing adenoidectomy. DESIGN: Prospective, blinded study. SETTING: Otorhinolaryngology department at a London teaching hospital. PARTICIPANTS: Twenty-eight consecutive patients undergoing adenoidectomy in conjunction with tonsillectomy or myringotomy under general anaesthesia, aged 17 months to 16 years. MAIN OUTCOME MEASURES: Adenoid size and postnasal space obstruction as assessed by digital examination, nasendoscopy and trans-oral mirror visualization. These examination methods were each compared with each other. RESULTS: Nasendoscopy and mirror examination correlated well (Spearman's R(S) = 0.71, P < 0.0001) but Passing and Bablock regression analysis demonstrated that mirror examination consistently underestimated the degree of choanal obstruction in comparison with nasendoscopy. There was no significant correlation between nasendoscopy and palpation (R(S) = 0.26, P = 0.17) and only a moderate correlation between mirror examination and palpation (R(S) = 0.46, P = 0.014). CONCLUSION: If nasendoscopy is considered the gold standard, then palpation is a poor measure of adenoid hypertrophy and mirror examination consistently underestimates choanal occlusion.

Adenoidectomy↗

PubMedDate not supplied

Morphology and development of mirror-image doublets of Stylonychia mytilus.

This paper describes the cortical anatomy and development of mirror-image doublets of Stylonychia mytilus, analyzed using the protargol technique. The reversed, or "left-handed" (LH) component of these doublets is a mirror image of the normal or "right handed" (RH) component with regard to the arrangement of cortical structures. The mirror-image patterning is imperfect, however, as the individual ciliary structures of the LH component all are of normal internal asymmetry, and the orientation of membranelles is inverted. Certain structures that would be expected to form near the line of symmetry are absent. During cell division and cortical reorganization, ciliary primordia arise and become arranged in a mirror-image pattern that is more perfect than that exhibited by the mature structures. Deviations from a mirror-image pattern appear at late stages when organelle sets differentiate within ciliary primordia: for example, the membranelle set differentiates within the oral primordium of the LH component in a sequence that is an inversion rather than a mirror image of the corresponding sequence of the RH component. This mixed control of oral development by different cortical "informational systems" accounts for some of the characteristic abnormalities of the mature oral structures of the LH component.

Animals↗

PubMed2006

Complex visual hallucination and mirror sign in posterior cortical atrophy.

OBJECTIVE: In posterior cortical atrophy (PCA), visual hallucinations are rare symptoms and mirror sign has not been described. METHOD: Single case report. RESULTS: We reported a 60-year-old woman with PCA who reported complex visual hallucinations, such as a man walking in her room, and mirror sign, which was the perception of a stranger staring at her when she looked into a mirror. She could not recognize images of herself in the mirror correctly, although she could recognize that a person standing next to her and the images of that person reflected in the mirror were the same person. CONCLUSION: Early complex visual hallucinations in this patient appeared to be more characteristic of dementia with Lewy body than Alzheimer's disease (AD). It is hard to explain mirror sign in this patient as being because of either prosopagnosia, Balint's syndrome or advanced AD. This patient may have other underlying cognitive dysfunction.

Agnosia↗

PubMed2001

Ocular responses to head rotations during mirror viewing.

The gain of the human vestibuloocular reflex (VOR) is influenced by the proximity of the object of regard. In six human subjects, we measured the eye rotations induced by passive, sinusoidal, horizontal head rotations at 2.0 Hz during binocular fixation of a stationary far target at 7 m; a stationary target close to the subject's near point of fixation (<15 cm); and the bridge of the subject's own nose, viewed through a mirror positioned so that, for each subject, the angle of vergence was similar to that during viewing of the near target. The median gain of compensatory eye movements for the group of subjects during far viewing was 0.99 (range 0.80-1.04), during near viewing was 1.21 (range 0.88-1.47), and during mirror viewing was 0.85 (range 0.71-1.01). The gain during near and mirror viewing was significantly different for each subject (P < 0.001) even though the vergence angles were similar. The lower gain values during mirror viewing can be attributed to the geometric relationship between the head rotation, the position of the eyes in the head, and the movement of the subject's virtual image in the mirror. To determine whether visually mediated eye movements were responsible for the observed gain values, we conducted a control experiment in which subjects were rotated using a sum-of-sines stimulus that minimized the effects of predictive visual tracking; differences of gain values between near- and mirror-viewing conditions were similar to those during rotation at 2 Hz. We conclude that, in these experiments, target proximity and vergence angle were not the key determinants of gain of the visuo-vestibular response during head rotation while viewing a near target but that contextual cues from motion vision were more important in generating the appropriate response.

Adult↗

PubMed1978

Mirror movements after childhood hemiparesis.

Mirror movements are normal in childhood and may persist to a later age following early brain lesions. We studied these movements in patients with childhood hemiparesis at different ages. The earlier the lesions, the more the mirror movements persisted. More mirror movement persisted in the nonparetic hand than in the paretic one. Complete paralysis of either hand tended to abolish all mirror movements in both hands. The task eliciting the most mirror movement was one that may come under ipsilateral control following contralateral damage. The greater persistence of mirror movements after earlier lesions appears to be an indicator of more extensive compensatory motor system reorganization that takes place after damage to a less mature nervous system.

Adolescent↗

PubMed1999

Kallmann's syndrome: mirror movements associated with bilateral corticospinal tract hypertrophy.

OBJECTIVE: To investigate the etiology of mirror movements in patients with X-linked Kallmann's syndrome (xKS) through statistical analysis of pooled white matter data from structural MR images. BACKGROUND: Mirror movements occur in 85% of xKS patients. Previous electrophysiologic studies have suggested an abnormal ipsilateral corticospinal tract projection in xKS patients exhibiting mirror movements. However, an alternative hypothesis has proposed a functional lack of transcallosal inhibitory fibers. METHODS: T1-weighted brain scans were normalized into stereotaxic space with segregation of gray and white matter to allow comparison of pooled white matter data on a voxel-by-voxel basis using SPM-96 software. Nine xKS patients were compared with two age-matched groups of nonmirroring individuals: nine patients with autosomal Kallmann's syndrome (aKS) and nine age-matched normal (healthy) men. RESULTS: Hypertrophy of the corpus callosum was found in both Kallmann's syndrome groups: the anterior and midsection in xKS, and the genu and posterior section in aKS. Bilateral hypertrophy of the corticospinal tract was found only in the group of xKS patients exhibiting mirror movements. SPM analysis was validated by an independent region of interest analysis of corpus callosum size. CONCLUSION: Although morphometry on its own cannot determine the cause of mirror movements, the specific finding of a hypertrophied corticospinal tract in xKS is consistent with electrophysiologic evidence suggesting that mirror movements in xKS result from abnormal development of the ipsilateral corticospinal tract fibers.

Adult↗

PubMed2006

Wolter type I x-ray focusing mirror using multilayer coatings.

A multilayer coating is a useful addition to a mirror in the x-ray region and has been applied to normal incidence mirrors used with soft x rays. When a multilayer coating is used on grazing incidence optics, higher performance can be achieved than without it. Cr/Sc multilayers coated on a Wolter type I mirror substrate for a soft x-ray microscope are considered. The reflectivity and effective solid angle are calculated for Wolter type I mirrors with uniform and laterally graded multilayer coatings. The laterally graded multilayer mirror showed superior x-ray performance, and the multilayer tolerances were relaxed. This multilayer mirror could be especially useful in the soft x-ray microscope intended for biological applications.

Journal Article↗

PubMed2003

Effect of teaching with mirrors on ballet dance performance.

This study assessed the effect of mirrors on the dance performance of beginning college ballet students in the classroom setting, using an evaluation methodology developed for this study. 13 women enrolled in one ballet class were taught using mirrors, 14 women in a second beginning ballet class were taught without mirrors. Both classes were taught by the same instructor. All students were videotaped performing the same adagio and grand allegro phrase during Weeks 5 and 14 of the 14-wk. term. At the end of the semester two ballet teachers viewed the videotapes for both classes. One evaluator was the instructor, and the other was a blind reviewer who had no knowledge of which was the mirror and nonmirror class during the evaluation process. They were instructed to choose a score for each dancer with anchors of 1: low skill and 5: high skill for both the adagio and allegro phrases. High interrater reliability was noted for both the adagio and allegro phrase data. In the nonmirror class, there was a significant increase in adagio scores, but no significant increases in adagio and allegro scores for the mirror class. These results suggest that the use of the mirror in a ballet classroom may negatively affect skill acquisition of the dancer.

Adult↗

PubMed2001

The variance theory of the mirror effect in recognition memory.

The mirror effect refers to a rather general empirical finding showing that, for two classes of stimuli, the class with the higher hit rates also has a lower false alarm rate. In this article, a parsimonious theory is proposed to account for the mirror effect regarding, specifically, high- and low-frequency items and the associated receiver-operating curves. The theory is implemented in a recurrent network in which one layer represents items and the other represents contexts. It is shown that the frequency mirror effect is found in this simple network if the decision is based on counting the number of active nodes in such a way that performance is optimal or near optimal. The optimal performance requires that the number of active nodes is low, only nodes active in the encoded representation are counted, the activation threshold is set between the old and the new distributions, and normalization is based on the variance of the input. Owing to the interference caused by encoding the to-be-recognized item in several preexperimental contexts, the variance of the input to the context layer is greater for high- than for low-frequency items, which yields lower hit rates and higher false alarm rates for high- than for low-frequency items. Although initially the theory was proposed to account for the mirror effect with respect to word frequency, subsequent simulations have shown that the theory also accounts for strength-based mirror effects within a list and between lists. In this case, consistent with experimental data, the variance theory suggests that focusing attention to the more difficult class within a list affects the hit rate, but not the false alarm rate and not the standard deviations of the underlying density, leading to no mirror effect.

Adult↗

PubMed2004

When mirrors lie: "visual capture" of arm position impairs reaching performance.

If we stand at a mirror's edge, we can see one half of our body reflected in the mirror, as if it were the other half of our body, seen "through" the mirror. We used this mirror illusion to examine the effect of conflicts between visually and proprioceptively specified arm positions on subsequent reaching movements made with the unseen right arm. When participants viewed their static left arm in the mirror (i.e., as if it were their right arm), subsequent right-arm reaching movements were affected significantly more when there was conflict between the apparent visual and the proprioceptively specified right-arm positions than when there was no conflict. This result demonstrates that visual capture of arm position can occur when individual body parts are viewed in the mirror and that this capture has a measurable effect on subsequent reaching movements made with an unseen arm. The result has implications for how the brain represents the body across different sensory modalities.

Adult↗