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PubMed2002

Naive optics: understanding the geometry of mirror reflections.

Paper-and-pencil tasks showed that many university students believed that when laterally approaching a mirror, they would see a reflection in the mirror before it was geometrically possible. Participants failed to adequately factor in the observer's location in the room. However, when asked about the behavior of a ray of light, participants knew about the law of reflection. No differences between psychology and physics students were detected, suggesting that the phenomenon is widespread and refractory to training. The findings were replicated with observers making judgments about image locations in a real room using a pretend mirror. Possible heuristics about mirror reflection that might explain the data are discussed. Naive optics is a promising venue to further knowledge of how observers understand basic laws of physics.

Adolescent↗
PubMed1998

The mirror effect and attention-likelihood theory: a reflective analysis.

The mirror effect refers to findings from studies of recognition memory consistent with the idea that the underlying "strength" distributions are symmetric around their midpoint separating studied and nonstudied items. Attention-likelihood theory assumes underlying binomial distributions of marked features and claims that old-item differences result from differential attention across conditions during study. The symmetry arises because subjects use the likelihood ratio as the basis for decision. The author analyzes the model and argues that one of the main criticisms (the complexity of the likelihood-ratio decision rule) is unwarranted. A further analysis shows that other distributions (the Poisson and the hypergeometric) can also produce a mirror effect. Even with the binomial distribution, a variety of parameter values can produce a mirror effect, and with the right combination of parameter values, differential attention across conditions is not necessary for a mirror effect to occur.

Attention↗
PubMed1998

On the difference between strength-based and frequency-based mirror effects in recognition memory.

A mirror effect can be produced by manipulating word class (e.g., high vs. low frequency) or by manipulating strength (e.g., short vs. long study time). The results of 5 experiments reported here suggest that a strength-based mirror effect is caused by a shift in the location of the decision criterion, whereas a frequency-based mirror effect occurs although the criterion remains fixed with respect to word frequency. Evidence supporting these claims is provided by a series of studies in which high frequency (HF) words were differentially strengthened (and sometimes differentially colored) during list presentation. That manipulation increased the HF hit rate above that for low frequency (LF) words without selectively decreasing the HF false alarm rate, just as a fixed-criterion account of the word-frequency mirror effect predicts.

Adult↗
PubMed2000

Pixel switching of epitaxial Pd/YHx/CaF2 switchable mirrors

Exposure of rare-earth films to hydrogen can induce a metal-insulator transition, accompanied by pronounced optical changes. This 'switchable mirror' effect has received considerable attention from theoretical, experimental and technological points of view. Most systems use polycrystalline films, but the synthesis of yttrium-based epitaxial switchable mirrors has also been reported. The latter form an extended self-organized ridge network during initial hydrogen loading, which results in the creation of micrometre-sized triangular domains. Here we observe homogeneous and essentially independent optical switching of individual domains in epitaxial switchable mirrors during hydrogen absorption. The optical switching is accompanied by topographical changes as the domains sequentially expand and contract; the ridges block lateral hydrogen diffusion and serve as a microscopic lubricant for the domain oscillations. We observe the correlated changes in topology and optical properties using in situ atomic force and optical microscopy. Single-domain phase switching is not observed in polycrystalline films, which are optically homogeneous. The ability to generate a tunable, dense pattern of switchable pixels is of technological relevance for solid-state displays based on switchable mirrors.

Journal Article↗
PubMed2001

Light interference from single atoms and their mirror images.

A single atom emitting single photons is a fundamental source of light. But the characteristics of this light depend strongly on the environment of the atom. For example, if an atom is placed between two mirrors, both the total rate and the spectral composition of the spontaneous emission can be modified. Such effects have been observed using various systems: molecules deposited on mirrors, dye molecules in an optical cavity, an atom beam traversing a two-mirror optical resonator, single atoms traversing a microwave cavity and a single trapped electron. A related and equally fundamental phenomenon is the optical interaction between two atoms of the same kind when their separation is comparable to their emission wavelength. In this situation, light emitted by one atom may be reabsorbed by the other, leading to cooperative processes in the emission. Here we observe these phenomena with high visibility by using one or two single atom(s), a collimating lens and a mirror, and by recording the individual photons scattered by the atom(s). Our experiments highlight the intimate connection between one-atom and two-atom effects, and allow their continuous observation using the same apparatus.

Journal Article↗
PubMed2006

The mirror neuron system and the consequences of its dysfunction.

The discovery of premotor and parietal cells known as mirror neurons in the macaque brain that fire not only when the animal is in action, but also when it observes others carrying out the same actions provides a plausible neurophysiological mechanism for a variety of important social behaviours, from imitation to empathy. Recent data also show that dysfunction of the mirror neuron system in humans might be a core deficit in autism, a socially isolating condition. Here, we review the neurophysiology of the mirror neuron system and its role in social cognition and discuss the clinical implications of mirror neuron dysfunction.

Animals↗
PubMed2002

Internally-referenced resonant mirror for chemical and biochemical sensing.

The resonant mirror sensor is a planar optical sensor platform that uses frustrated total internal reflection to couple light into and out of a leaky waveguiding layer. The evanescent wave associated with the dielectric structure is very sensitive to changes in surface refractive index caused by the binding of macromolecules to immobilised proteins or other biorecognition species such as antibodies. However, such variations can also be generated by variations in the bulk analyte solution, via changes in the composition or temperature. In the device described here, an additional buried resonant mirror layer is incorporated into the sensor structure generating an internal reference resonant mirror. The efficacy of this internal reference system is demonstrated in both chemical and immunological systems--as a pH sensor monitoring the absorption of an encapsulated sulfonephthalein dye, and as a refractive index sensor measuring the adsorption of anti-protein A and binding of its corresponding antigen. In both cases the internally referenced resonant mirror provides a means by which errors due to fluctuations in light intensity, temperature and bulk composition may be accounted for.

Adsorption↗
PubMed2003

A new mirrored laryngoscope.

A new laryngoscope has been designed, incorporating an adjustable mirror and a levered tip similar to the McCoy blade, in an attempt to bridge the gulf between simple direct laryngoscopy and fiberoptic laryngoscopy. Manual in-line neck stabilisation was used to simulate difficult laryngoscopy in 14 anaesthetised patients after full neuromuscular blockade. The best view at laryngoscopy was assessed using a standard Macintosh laryngsocope, a size 3 McCoy laryngoscope and the mirrored laryngoscope. The best laryngeal view obtained in all cases with the Macintosh blade was a grade 3. The mirrored laryngoscope improved this view in 10 cases (71%) compared with five cases (36%) with the McCoy laryngoscope (p = 0.005); in seven cases (50%), the view improved to a grade 1 compared with no cases when the McCoy was used (p = 0.02). We conclude that the mirrored laryngoscope offers considerable advantages over the Macintosh and the McCoy laryngoscopes in simulated difficult laryngoscopy, is simple to use and requires no special training.

Anesthesia, General↗
PubMed1991

The perception of mirror-reflected objects.

In what ways and under what conditions does an object appear to differ from its enantiomorph (its mirror reflection)? This 'mirror question' or its popular counterpart, "Why does a mirror reverse left and right but not up and down?" is frequently encountered, but an acceptable answer is not to be found in the literature. The question is approached as an experimental problem in visual psychophysics. A mirror optically reverses the axis perpendicular to its surface. What are the perceptual consequences of this stimulus transformation? This question is examined in four experiments by using stimuli of varying complexity and familiarity. Apparent reversals are demonstrated along right-left, front-back, top-bottom, and oblique axes, depending on the perceived asymmetries of the stimulus object. Perceived asymmetry is shown to depend both on structural asymmetries and on canonical axes and orientations defined by social convention. It is concluded that an object appears to differ from its enantiomorph by an apparent reversal along the axis of least perceived asymmetry. Implications for perceptual frames of reference and for the perception of symmetry are discussed.

Adult↗
PubMed2002

Mirror symmetry opposes splitting of chromatically homogeneous surfaces.

Chromatically homogeneous surfaces can be seen as single figures but also as two or more overlapping figures. Local factors such as relatability have been proposed in order to explain perception of two or more figures (Kellman and Shipley, 1991 Cognitive Psychology 23 141-221). However, even when these factors are at work, there are conditions favouring the perception of a single figure, which have not been explored so far. Here we propose that one such factor is the mirror symmetry of the surface. Three experiments were designed to test: (a) the main hypothesis, that mirror symmetry enhances perception of a single figure; (b) the role of orientation; (c) the effect of the number of axes of symmetry. The results show that (i) there is a good general correlation between mirror symmetry and perception of a single figure; (ii) vertical and horizontal axes of symmetry are the most effective; and (iii) the more axes of symmetry a surface has, the more likely is the perception of a single figure. These results suggest that mirror symmetry is an important factor in the perception of chromatically homogeneous displays. Some explanations are discussed, particularly one based on the rejection-of-coincidence principle [Rock, 1983 The Logic of Perception (Cambridge, MA: MIT Press)], and a version of the minimum principle in which the strength of the global solution depends on symmetry, whereas the strength of the splitting solution depends on the strength of local factors. In brief, global and local factors compete in determining the perceptual outcome in chromatically homogeneous surfaces.

Depth Perception↗
PubMed2003

The Venus effect: people's understanding of mirror reflections in paintings.

We propose the term 'Venus effect' for a common phenomenon in picture perception. It occurs when a picture shows an actor and a mirror that are not placed along the observer's line of sight, for instance a Venus admiring herself in a small mirror, and when the actor's reflection in the mirror is visible to the observer. In this situation, observers tend to report, incorrectly, that Venus is also seeing herself in the mirror in the same location as the observer. We discuss this using famous paintings as examples.

Adult↗
PubMed2001

Mirror self-recognition in the bottlenose dolphin: a case of cognitive convergence.

The ability to recognize oneself in a mirror is an exceedingly rare capacity in the animal kingdom. To date, only humans and great apes have shown convincing evidence of mirror self-recognition. Two dolphins were exposed to reflective surfaces, and both demonstrated responses consistent with the use of the mirror to investigate marked parts of the body. This ability to use a mirror to inspect parts of the body is a striking example of evolutionary convergence with great apes and humans.

Animals↗
PubMed2006

The neuroscience of observing consciousness & mirror neurons in therapeutic hypnosis.

Neuroscience documents the activity of "mirror neurons" in the human brain as a mechanism whereby we experience empathy and recognize the intentions of others by observing their behavior and automatically matching their brain activity. This neural basis of empathy finds support in research on dysfunctions in the mirror systems of humans with autism and fMRI research on normal subjects designed to assess intentionality, emotions, and complex cognition. Such empathy research now appears to be consistent with the historical and research literature on hypnotic induction, rapport, and many of the classical phenomena of suggestion. A preliminary outline of how mirror neurons may function as a rapport zone mediating between observing consciousness, the gene expression/protein synthesis cycle, and brain plasticity in therapeutic hypnosis and psychosomatic medicine is proposed. Brain plasticity is generalized in the theory, research, and practice of utilizing mirror neurons as an explanatory framework in developing and training new skill sets for facilitating an activity-dependent approach to creative problem solving, mind-body healing, and rehabilitation with therapeutic hypnosis.

Brain↗
PubMed1991

Mirror phenomena in language and nonverbal activities--a case report.

A case is described of a 38-year-old, left-handed female who demonstrated mirror phenomena for both language and non-motor, nonverbal material. She mirror-wrote with her left hand with normal right-hand writing. Mirror-reading as well as object and spatial reversals were revealed. These data are consistent with bilateral representation of visual engrams, with one hemisphere containing a mirror-reversed representation of the other.

Adult↗
PubMedDate not supplied

Mirror treatment of lower limb phantom pain: a case study.

PURPOSE: Phantom limb pain (PLP) can be an enduring and distressing experience for people with amputations. Previous research has shown that 'mirror treatment' can reduce PLP for some people who have an upper limb amputation, and that it can increase a sense of motor control over the phantom in people with lower limb amputations who are not reporting PLP. There has been no previous report of therapeutic 'mirror treatment' for lower-limb phantom pain. METHOD: We present the first case study of the use of 'mirror treatment' in a person with a lower limb amputation who was reporting PLP at the time of treatment. RESULTS: During the intervention there was a significant reduction in his PLP, an increase in sense of motor control over the phantom and a change in aspects of the phantom limb that was experienced. CONCLUSION: This case study, conducted in a conventional clinical setting, supports the potential of 'mirror treatment' for PLP in people with a lower limb amputation.

Adult↗
PubMed2006

A mirror in the mind: a case of visual allaesthesia in homonymous hemianopia.

We report the case of a 61-year-old female patient with intracranial bleeding in left parietal and parieto-temporal regions and a history of epilepsy and migraine. MR images showed lesions of the optic radiation, but primary visual cortical areas were intact. Perimetric testing revealed an incomplete right hemianopia. The patient claimed that visual percepts from her intact field were projected as "mirror images" into the hemianopic field. The illusory images were weak and sometimes difficult to detect, but focusing spatial attention on the "mirror" image increased its saliency. Drawings the patient made of her pseudo-hallucinations revealed that the illusions were lateral transpositions instead of mirror images of real objects. The illusions were tilted in clockwise direction and were never colored, although color discrimination was unimpaired in the patient's left hemifield. We quantified the characteristics of the pseudohallucinations in several experiments: The patient was asked to adjust the position, rotation angle, and size of a white test card in her blind field so that it corresponded with the illusory projection of a card of standard size and position that was presented in the intact field. The test card was compressed in horizontal size by 20% and positioned 17 degrees visual angle to the right of the standard, shifted 1.5 degrees upward or downward, and rotated in clockwise direction by 22.6 degrees on average. Large objects in the intact field were projected incompletely into the blind area. Our patient's symptoms are similar to those reported in earlier case studies of visual allaesthesia. We hypothesize that the "mirror image" is induced by sparse input from contralesional V1 via the corpus callosum upstream of the lesion site and a lack of inhibition or hyperexcitability of ipsilesional early visual areas after deafferentation. The rotation of the illusions may be induced by the parietal lesions causing faulty co-ordinate computations, e.g., an inability to integrate visual and otholitic input.

Female↗
PubMed1992

Hand mirror variant of adult acute lymphoblastic leukemia. Evidence for a mixed leukemia.

Blast cells from a female patient with acute lymphoblastic leukemia-hand mirror variant were examined using various techniques, including light and ultrastructural morphologic examination, cytochemical analysis, surface antigen characterization, cytogenetic analysis, and gene rearrangement studies. The blast cells were found to be pre-B cells (CD19+ and Tdt+) that also expressed the myeloid antigens CD13 and CD33 and demonstrated a heavy chain immunoglobulin gene rearrangement. Cytogenetic studies revealed a t(11;19) translocation previously described in biphenotypic leukemias. A subset of acute lymphoblastic leukemia-hand mirror cells has been previously defined and includes predominately female patients with an indolent course. The authors' findings place this case, a mixed leukemia, within that subgroup. The possibility of mixed lineage should be considered in future cases of hand mirror variants of adult acute lymphoblastic leukemia. Furthermore, hand mirror morphologic features in any case of acute leukemia should alert the hematopathologist/hematologist to the possibility of mixed lineage.

Adult↗
PubMed1997

Mirror movements in X-linked Kallmann's syndrome. II. A PET study.

To investigate the mechanism of mirror movements seen in X-linked Kallmann's syndrome, we measured changes of regional cerebral blood flow with H2 15O-PET. We studied six right-handed Kallmann male subjects and six matched, right-handed control subjects during an externally paced finger opposition task. The analyses were done both on a single subject and a group basis. The Kallmann group showed a strong primary motor cortex (M1) activation contralateral to the voluntarily moved hand, but there was also a significant degree of M1 activation ipsilateral to the voluntarily moved hand, i.e. contralateral to the mirroring hand. However, when comparing contralateral to ipsilateral M1 activation, the M1 activation contralateral to the voluntarily moved hand was significantly stronger. In the controls, significant increases in rCBF were seen in the contralateral M1 during voluntary movement of either hand; a small ipsilateral M1 activation was found in two out of six normal subjects when they moved their left hand. In a second experiment it was shown that, in two out of two Kallmann subjects, passive movements of the right hand resulted in left M1 activation that was similar to the activation in the left M1 when subjects made mirror movements with their right hand. This suggests, but does not prove, that the small but significant activation of the ipsilateral M1 in Kallmann's subjects may be due to sensory feedback from the involuntarily mirroring hand.

Adolescent↗