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PubMed2001

A particular difficulty in discriminating between mirror images.

We investigated the selective impairment of mirror image discrimination in a patient with bilateral parieto-occipital lesions (FIM). We report a difficulty with the discrimination between mirror images more selective than has been previously reported (Turnbull OH, McCarthy RA. Failure to discriminate between mirror-image objects: a case of viewpoint-independent object recognition? Neurocase 1996;2:63). FIM was asked to judge, in five same/different experiments, whether pairs of simultaneously presented line drawings of objects were identical. FIM demonstrated only a minor impairment in discriminating between orientations in the picture plane but was at chance in making discrimination between mirror images. An experiment with normal observers established that our results were not due to differences in task difficulty. Two further experiments investigated the effects of rotation on the discrimination of letters and geometric shapes. FIM's impairment extended to geometric shapes but not to letters. These results would be consistent with the preservation of an abstract representation for object recognition that did not code the difference between mirror image views.

Adult↗
PubMed2003

Impaired mirror-image imitation in Asperger and high-functioning autistic subjects.

Imitation is crucial for proper development of social and communicative skills. Here, we argue that, based on an error analysis of a behavioral imitation task, adult Asperger and high-functioning autistic subjects suffer from an intriguing deficit of imitation: they lack the natural preference for imitation in a mirror-image fashion. The imitation task consisted of a simple movement sequence of putting a pen with the left or right hand into a green or a blue cup using one of two possible grips. The subjects were asked to imitate the experimenter's hand movements either using the crossed hand (e.g., the subject's right hand corresponding to the experimenter's right hand) for imitation or to imitate as if looking in a mirror (e.g., the subject's left hand corresponding to the experimenter's right hand). When people normally view other persons face-to-face, they prefer to imitate as in a mirror, and observation of mirror-image-like movements speeds up performance in nonimitative tasks. However, our autistic subjects, defective in social cognition, did not profit from mirror-image movements of others. These results provide a new insight into the difficulties that autistic subjects face in viewing and understanding actions of others.

Adult↗
PubMed1992

Subjective memorability and the mirror effect.

The mirror effect refers to the common finding that hit and false alarm rates on a recognition test are inversely related. The present research investigated the generality of the mirror effect (to rare words) and tested whether the effect might be grounded in accurate estimates of word memorability. The first 2 experiments showed that although high- and low-frequency words exhibit a mirror effect, rare words do not. Furthermore, contrary to expectations, Ss consistently (and mistakenly) predicted that memorability was directly correlated with frequency of usage. These findings weight against the idea that the mirror effect arises because of a S's ability to reject low-frequency lures on the grounds that such words would have been remembered had they appeared previously. Instead, the rejection of lures from different frequency categories may be determined by their semantic or phonemic overlap with list targets, and an analysis along these lines may help to explain why rare words constitute an exception to the otherwise ubiquitous mirror effect.

Adult↗
PubMed2002

A reexamination of stimulus-frequency effects in recognition: two mirrors for low- and high-frequency pseudowords.

The word-frequency mirror effect (more hits and fewer false alarms for low-frequency than for high-frequency words) has intrigued memory researchers, and multiple accounts have been offered to explain the result. In this study, participants were differentially familiarized to various pseudowords in a familiarization phase that spanned multiple weeks. Recognition tests given during the first week of familiarization replicated a result of W. T. Maddox and W. K. Estes (1997) that failed to show the classic word-frequency mirror effect for pseudowords; however, recognition tests given toward the end of training showed the classic mirror pattern. In addition, a stimulus-frequency mirror effect for "remember" vs. "know" judgments was obtained. These data are consistent with an account of the mirror effect that posits the involvement of dual processes for episodic recognition.

Attention↗
PubMed1993

Intact acquisition and long-term retention of mirror-tracing skill in Alzheimer's disease and in global amnesia.

The ability of patients with Alzheimer's disease (AD) or global amnesia (AMN) to acquire skill for tracing a pattern seen in mirror-reversed view and to retain that skill over 24-h intervals was examined. Both patient groups had poor recall and recognition of their mirror-tracing experience, but they acquired and retained mirror-tracing skill as well as normal control subjects. One AMN patient (H.M.) retained the skill over a year-long interval. Furthermore, the patients transferred their skill normally to an alternate pattern. These results indicate that the memory system underlying mirror-tracing skill learning is separable from medial-temporal structures compromised in AMN and AD and from neocortical areas compromised in AD. Brain regions relatively spared in early AD, such as the basal ganglia or cerebellum, may mediate critical aspects of the learning of novel sensorimotor associations that underlie skilled mirror tracing.

Aged↗
PubMed2000

Observations on the behavior of gibbons (Hylobates leucogenys, H. gabriellae, and H. lar) in the presence of mirrors.

Three captive gibbons (Hylobates leucogenys, H. gabriellae, and H. lar) were videotaped in the course of longitudinal exposure to mirrors introduced into their familiar cage or island housing situation. The gibbons, which differed in age, sex, species, and rearing condition, exhibited great individual differences in their behavioral reactions to mirrors, spanning from a minimal reaction dominated by social responses to a dramatic sequence of progressive behavioral change that featured a variety of contingency testing behaviors and included mirror-mediated, self-directed behavior. Additional information on the mirror competence of gibbons was provided by modified mark tests and a hidden object task. The results are discussed in relation to current criteria for self-recognition in primates and factors involved in individual and species differences in reactions to mirror exposure.

Animals↗
PubMed2000

Doppler mirror image artifacts mimicking mitral regurgitation in patients with mechanical bileaflet mitral valve prostheses.

AIMS: To characterize the origin and mechanisms of generation of Doppler mirror images in the left atrium observed in patients with mechanical bileaflet mitral valve prosthesis. We hypothesized that these systolic colour Doppler images are artifactual and generated by reflection of the left ventricular outflow tract flow at the leaflet of the mitral valve prosthesis. METHODS AND RESULTS: Fifty patients with mechanical bileaflet mitral valves were prospectively examined by means of transthoracic Doppler-echocardiography. From different apical views, the left atrium was carefully interrogated for systolic colour flow signals, which were further analysed by pulsed wave Doppler. In all patients, a systolic colour Doppler signal was detected in the left atrium. Pulsed wave Doppler analysis revealed a low velocity signal (= mirror image) corresponding to the shape and duration of the left ventricular outflow tract signal. The peak velocities of these mirror images, however, were consistently lower than the velocities obtained from the left ventricular outflow tract. In addition, if paravalvular mitral valve leakage was present, a high velocity signal identical to the duration of mitral regurgitation time was detected outside the ring of the prosthesis. CONCLUSIONS: Mirror image artifacts mimicking mitral regurgitation occur in patients with mechanical mitral valves prosthesis. As mirror image artifacts can be specifically identified by analysis of shape. velocity, and duration of pulsed wave Doppler spectra, their identification will help to avoid misinterpretation of both spectral and colour Doppler signals in patients with prosthetic mitral valves.

Aged↗
PubMed1991

Mirror-reversal phenomena in the cutaneous perception and writing of children.

When a letter is drawn on the forehead, it is perceived cutaneously as a mirror reversal of the experimenter-defined stimulus. An analogous mirror-reversal phenomenon is found in motor behaviour; eg, writing on the downward-facing horizontal surface of a table. We examined these mirror-reversal phenomena in tasks, performed by 4-year-old and 8-year-old children, involving cutaneous perception and motor-production. The children's tendencies toward mirror reversal in the two tasks varied with the orientation and position of the surface, but were similar to those of sighted and blind adult subjects. In addition, mirror reversal was independent of the left-right indifference often observed in young children in writing or visual-matching tasks. The implications of these findings are discussed in the context of a body schema used to guide sensorimotor functions.

Attention↗
PubMed2001

The use of mirrors during an assembly task: a study of ergonomics and productivity.

Industrial assembly tasks often require awkward, sustained neck and/or shoulder postures that can lead to increased musculoskeletal discomfort and reduced productivity. The aim of this study was to investigate the effects of mirror and periscope visual aids as ergonomic interventions designed to eliminate awkward postures of the cervicobrachial region during assembly tasks. Participants simulated a simple assembly task by using a cordless screwdriver to drive screws into a pre-tapped aluminium block. Trials of 15 min were run for each of four distinct assembly workstation configurations: industry standard (in-line screwdriver, work at elbow height, no visual aid); pistol grip (pistol grip screwdriver, work at shoulder height, no visual aid); mirror (in-line screwdriver, work at elbow height, single mirror visual aid); and periscope (in-line screwdriver, work at elbow height, two-mirror visual aid system). Muscular activity, discomfort, body posture, productivity and operator subjective assessment were recorded to determine the effects of the visual aid interventions. The results show that when comparing the interventions to the industry standard condition, there was a 45% reduction in average cervical erector spinae activity, a 90% reduction in average neck flexion angle and a 72% reduction in neck discomfort with the interventions. When comparing these interventions to the pistol grip condition there was an 80% reduction in activity of the dominant side deltoid, a 92% reduction in shoulder flexion angle and an 81% decrease in shoulder discomfort with the interventions. Productivity was greatest in the industry standard configuration followed by the pistol grip (9% lower), the periscope (13% lower) and the mirror (23% lower) configurations. A follow-up study that compared the productivity of the periscope configuration with that of the industry standard configuration showed that within a 4-h work period this productivity differential decreased by over 33%.

Adult↗
PubMed2006

Effect of retention interval on the simultaneous cognate-noncognate and remember-know mirror effects.

Recognition memory for Spanish-Catalan cognate and noncognate words was tested at retention intervals of 30 minutes, 3 days, and 7 days using a remember/know response procedure. We observed a clear mirror effect for the cognate-noncognate stimulus class and a remember-know response categorisation at the immediate retention interval. However, the cognate and noncognate mirror was still observed at 3 and 7 days, whereas the remember-know mirror disappeared at both retention intervals. Also, we ran a repeated testing condition to be able to carry out a sequential item analysis and observe the fate of the original remember and know responses 3 or 7 days later. The analysis supported the idea that there was a loss of contextual information that was at the root of the disappearance of the remember-know mirror effect. These results provide support to the idea that it is the imbalance between recollection and familiarity that is the most likely cause of the mirror effect.

Association↗
PubMed2003

Image converter eliminates mirror imaging during laparoscopy.

BACKGROUND AND PURPOSE: In laparoscopy, the term "mirror imaging" is used to describe a visual illusion resulting in paradoxical movements when a surgeon is positioned opposite the laparoscope. Mirror imaging is a common problem, creating difficulty in ergonomics and task performance. We introduce the use of a video image converter box (IC box) to overcome mirror imaging. The IC box converts the analog signal to a digital one, performs image rotation or inversion or both, and then reproduces an analog signal for monitor viewing. A laboratory study evaluated whether the IC box could improve performance during laparoscopic tasks. MATERIALS AND METHODS: Fourteen laparoscopic surgeons (10 novice and 4 experienced) completed three laparoscopic tasks while positioned opposite the camera and experiencing mirror imaging: (1). suture cutting; (2). multiple transfers of a piece of foam; and (3). multiple transfers of a pinto bean. Participants were timed during each test both with and without the use of the IC box. RESULTS: All surgeons completed each task faster using the IC box (P < 0.015). On average, use of the IC box allowed subjects to complete assignments in less than one-third the time needed without the IC box. In Task 3, requiring multiple transfers of a small bean, all participants using the IC box completed the task. However, without the box, only 1 of 14 participants accomplished the goal in the allotted time. CONCLUSION: Use of the IC box eliminates mirror imaging and improves performance and efficiency during laparoscopic tasks. The box would significantly benefit surgeons positioned opposite the camera during laparoscopic surgery.

Clinical Competence↗
PubMed1980

Hand-mirror cell leukemia. Report of nine cases and a review of the literature.

In order to determine the significance of 40% or more leukemic cells in hand-mirror configuration in the bone marrow (hand-mirror cell leukemia), eight of 34 cases of acute lymphoblastic leukemia and one of 17 cases of acute myeloblastic leukemia were collected from a six-year period. Five of the eight patients who had acute lymphoblastic leukemia were children; the remaining patients were less than 40 years of age. Females outnumbered males two to one. Cytochemical and electron-microscopic studies were performed for three cases. The clinical presentations were similar to those of patients without the hand-mirror cell variant, except for a high incidence of central nervous system relapses (over 50% of patients) despite prophylaxis. When compared with patients with acute leukemia in equivalent age and morphologic categories, adults with the hand-mirror cell variant had a similar, but not better, prognosis, while children with the variant had a poorer prognosis. Additional studies must be performed to determine whether the hand-mirror cell variant warrants separation from other forms of acute leukemia.

Adult↗
PubMed2001

Characterizing the neural mechanisms of skill learning and repetition priming: evidence from mirror reading.

The changes in brain activity related to skill learning and repetition priming in a mirror-reading task were examined using functional MRI. Subjects exhibited significant learning across five training sessions and this learning generalized significantly to different spatial transformations (inverted-mirror reversed text and normal letters spelled backwards). Mirror reading, compared with reading normal text, was associated with extensive activation in occipital, temporal, parietal and frontal regions. Learning to read mirror-reversed (MR) text was associated with increased activation in left inferior temporal, striatal, left inferior prefrontal and right cerebellar regions and with decreased activity in the left hippocampus and left cerebellum. Short-term repetition priming was associated with reduced activity in many of the regions active during mirror reading and extensive item-specific practice (long-term repetition priming) resulted in a virtual elimination of activity in those regions. Short- and long-term repetition priming thus appeared to rely upon common neural mechanisms. Nearly all of the regions exhibiting significant learning-related changes also exhibited increased repetition priming effects, suggesting common neural substrates for priming and skill learning in this task. Comparison of MR items with other spatially transformed typographies showed that the learning-related changes were general to all of the spatial transformations. The results confirm the importance of striatofrontal neural networks for the acquisition of skills, and suggest that skill learning and repetition priming may have common substrates within a particular task.

Adult↗
PubMed2002

Endotracheal intubation with a gum-elastic bougie in unanticipated difficult direct laryngoscopy: comparison of a blind technique versus indirect laryngoscopy with a laryngeal mirror.

UNLABELLED: We evaluated the efficacy of intubation over a gum-elastic bougie by using either a blind technique or indirect laryngoscopy with a laryngeal mirror in patients with unexpected difficult direct laryngoscopy. In a prospective study, 60 consecutive patients with an unexpected Grade III or IV direct laryngoscopy were randomly allocated for intubation with a gum-elastic bougie either blindly (Group 1) or by indirect laryngoscopy with a laryngeal mirror (Group 2). We evaluated the failure rate of each method of intubation, complications related to either method, and the time required for intubation. Out of 725 patients evaluated over a 2-mo period, 60 patients (8.3%) had a Grade III laryngoscopy, and 30 of these were randomized into each group. There were 8 failed intubations in Group 1 compared with 1 failed intubation in Group 2 (P < 0.05). All eight failures in the blind intubation group ended with esophageal intubation. No additional complications were noted in either group. The time required for endotracheal intubation with each group was not significantly different (45 +/- 10 s versus 44 +/- 11 s). We conclude that intubation with a gum-elastic bougie had a lower failure rate using indirect laryngoscopy with a laryngeal mirror than a traditional blind technique. IMPLICATIONS: We evaluated the efficacy of intubation over a gum-elastic bougie by using either a blind technique or a laryngeal mirror. Intubation with a gum-elastic bougie had a lower failure rate using indirect laryngoscopy with a laryngeal mirror (P < 0.05) than a traditional blind technique.

Aged↗
PubMed2000

Perception of mirror symmetry reveals long-range interactions between orientation-selective cortical filters.

We investigated perceptual interactions between orientation selective cortical filters using a task in which the observer was to detect mirror symmetry in briefly flashed visual patterns composed of oriented Gabor elements. On each trial, the Gabor patches were randomly placed in one half of the stimulus region, and symmetry was generated by reflecting the positions of the patch centers across the vertical axis. A prespecified proportion of patches were in mirror symmetrical positions with the remaining patches placed at random positions. The perception of mirror symmetry was measured for three stimulus conditions: (1) same orientation (i.e. all the local Gabor elements were either vertical or horizontal), (2) mixed matching (i.e. the orientations could be randomly both vertical and horizontal with the constraint that the orientations in a mirror symmetrical pair were matching), and (3) mixed opposing (i.e. the orientations were both vertical and horizontal, but in a mirror symmetrical pair they were always orthogonal). We found that the perception of global symmetry was poorer (thresholds were elevated) when the local orientations of feature pairs were orthogonal than when they were matched. This result is consistent with the properties of the neurons in the corpus callosum, which selectively interconnect cortical filters with identical orientation specificity.

Brain Mapping↗
PubMed2006

History of mirrors dating back 8000 years.

PURPOSE: The purpose of this study is to consider the ancient history and early development of mirrors, because mirrors played a key role in refraction and magnification for an extended period of time before the invention of spectacles, including broad use in Roman times. FINDINGS: The earliest known manufactured mirrors (approximately 8000 years old) have been found in Anatolia (south central modern-day Turkey). These were made from obsidian (volcanic glass), had a convex surface and remarkably good optical quality. Mirrors from more recent periods have been found both in Egypt and Mesopotamia and still later in China and in the New World. In each of these areas, mirrors were in use by approximately 2000 BC or 4000 years ago.

History, Ancient↗
PubMed2006

Second-harmonic generation in doubly resonant microcavities with periodic dielectric mirrors.

Strong enhancement of second-harmonic generation (SHG) is expected in one-dimensional microcavities when double resonance for the pump and the harmonic fields, as well as phase matching, are achieved. The realization of a doubly resonant microcavity with dielectric mirrors made of nonbirefringent materials is difficult because of the refractive index dispersion of the constituent media. Here we present a powerful method, based on photonic crystal concepts like gap maps and their generalization to defect modes, for the design of doubly resonant microcavities with periodic dielectric mirrors. The material dispersion is compensated by using the angle of incidence as a tuning parameter, thanks to the polarization splitting of cavity modes. The cavity enhancement of SHG increases exponentially with the number of periods in the dielectric mirrors and can be much larger than in single-resonant microcavities with comparable (or even larger) quality factors. The roles of phase delay and of thin versus thick configurations in the dielectric mirrors, of the growth orientation, and of the polarization degrees of freedom in achieving double resonance with phase matching are discussed. Significant examples of doubly resonant SHG with high conversion efficiency are given for Al0.25Ga0.75As cavities with Al0.4Ga0.6As/Alox (oxidized AlAs) mirrors.

Journal Article↗
PubMed1999

Experiences and expectations of a novel X-ray microsource with focusing mirror. I.

Data are presented from a novel microfocus X-ray generator installed with a choice of ellipsoidal specularly reflecting mirrors. Diffraction data from proteins show the useful flux from this low-power device to be approaching equivalence with that from many far more powerful generators. Intensity measurements show that for small crystals the brilliance is now restricted by the performance of the mirror, which appears to be limited by imperfections in the figure of its surface rather than by a low reflectivity. Suitable choices of ellipsoidal mirror enable the size and divergence of the X-ray beam to be altered readily to match the different requirements of successive samples and appropriate designs are proposed. Alternative types of mirror are expected to be advantageous, especially for the smallest crystals. For crystals of sizes 300 microm or less, which need a small well collimated beam with low divergence, the output from this X-ray tube running at 24 W provides a usable flux similar to that available from rotating-anode generators. The relative performance of this tube and mirror combination becomes increasingly advantageous with the study of ever-smaller crystals.

Crystallography, X-Ray↗