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PubMed1993

Mirror reversals: real and perceived.

A mirror optically reverses the axis perpendicular to its surface, but apparent reversals (eg right-left) can be seen parallel to the surface. This poses a perceptual problem which Ittelson, Mowafy, and Magid resolved by concluding that an object appears to differ from its mirror image by an apparent reversal along its axis of greatest symmetry. Three papers--two included in this discussion (by Haig and by Morris), and an earlier one by Gregory--that disagree with this conclusion are examined, and arguments advanced in them are shown to be unconvincing. The question of apparent mirror reversals is then discussed in more detail.

Attention↗
PubMed1993

Mirror image reversal: is what we see what we present?

Many psychological explanations have been advanced to explain left-right reversal in mirror images, but Gregory and Haig have each proposed a physical explanation for the reversal: the first is based upon the physical rotation used to present the surface of the object to the mirror, and the second on the classical optics of reflection. These physical explanations are considered together with an explanation based on object symmetry. The apparent reversal of directional coordinates (eg left and right) that occurs in the mirror images of most objects is distinguished from reversals achieved by physical or mental rotation. It is also distinguished from the object-image match that can be achieved by mental or physical rotation of some symmetrical objects. It is concluded that the left-right reversal is not specifically optical, but is determined by multiple factors, including object symmetry, the conventional and gravitational positioning of top and bottom and back and front, and our greater familiarity with right-left than with top-bottom or back-front reversals.

Attention↗
PubMed2005

Visual orientation in a mirror world tilted 90 degrees.

Previously, we showed that many supine observers in a furnished room tilted 90 degrees perceive themselves and the room as upright. We called this the "levitation illusion" because the arms feel weightless when held out from the body. We now report that a familiar scene viewed by supine observers through a mirror at 45 degrees appears vertical when, optically, it is horizontal and above the head. However, the body feels pitched upright only partially. This visual-righting effect, like the levitation illusion, is due to the polarity axis of the scene being accepted as vertical even in the presence of conflicting information from the gravity sense organs. In experiment 1 we tested the potency of objects containing either intrinsic polarity (due to familiar tops and bottoms) or extrinsic polarity (due to support relationships) to generate a visual-righting illusion. To almost all observers, a blank surface seen in the mirror appeared like a ceiling. A scene containing an object with intrinsic polarity, such as a chair or person, seen in the mirror appeared vertical to almost all observers. A scene containing a pair of objects with only extrinsic polarity, such as a ball on a shelf (but not a ball under a shelf), also appeared vertical to most observers. In experiment 2 we found that a polarised scene was more likely to produce a visual-righting illusion when it was arranged as a view through a window rather than as a picture inside a room.

Adolescent↗
PubMed2002

Learning, retention and generalization of a mirror tracing skill in Alzheimer's disease.

The present study examined the ability of 12 patients with probable Alzheimer's disease (AD) and 12 age- and education-matched normal control (NC) subjects to learn and retain the visuomotor skills necessary to efficiently trace a pattern (e.g., a 4- or 6-pointed star) seen only in mirror-reversed view. Those AD (N=6) and NC (N=7) subjects who were able to initially perform the basic mirror tracing task did not differ significantly in initial level of performance, learning over trials, retention of the skill over a 30-min delay interval, and generalization of the skill to a new figure or to the opposite direction of tracing. The AD patients who were unable to initially perform the mirror tracing task were significantly worse than those who could perform the task on several neuropsychological measures sensitive to deficits in problem solving and executive functions, but not on tests of global cognitive decline, memory, language, or visuoperceptual functioning. These results indicate that acquisition and retention of a complex visuomotor skill can proceed normally in the early stages of AD in those individuals who can initially perform the basic task, and that inability to perform the basic task may be related to the frontal lobe dysfunction that is often prominent in the disorder.

Aged↗
PubMed2000

Performance on a mirror-drawing task by non-right-handers.

Left-, mixed-, and right-handed (each n = 10, N = 30) adolescent boys who were classified on the basis of a hand preference inventory performed a mirror-drawing task with a bilateral transfer of a skill paradigm. Participants' hand preference and the magnitude of bilateral transfer of skill were assessed in terms of errors committed and time taken to complete the mirror-drawing task. Mixed-handed participants exhibited significantly less habit interference for mirror drawing, and they performed the task significantly faster than the left-handers did; the group difference was not significant for the frequency of errors committed. These groups did not differ in terms of the magnitude of bilateral transfer of skill; the trend, however, showed that the transfer of skill was minimum in mixed-handers. These findings extend the theory that mixed-handed participants' inability to transfer motor skill from one hand to the other could be attributable to their lack of a clear pattern of lateralization. Their ability to perform well either at initial or later trials may be a function of less interference from their normal motor habits.

Adolescent↗
PubMed1992

Some perceptual and cognitive factors in mirror tracing: their limits.

Three mirror tracing experiments were conducted to investigate the connection between perception and motor behavior. In the first experiment, some subjects traced a hex-maze, other subjects traced a hex-maze after observing a model trace, others traced a hex-maze after reading instructions on mirror images, and others traced a hex-maze after having observed a model and heard the instructions. There were no significant differences between the groups' error scores, but their time scores differed significantly, although not always in the predicted direction. In Experiment 2, the subjects were to trace selected letters of the alphabet. Error scores for the second experiment did not differ much from those for the first experiment. In Experiment 3, the experimenter gave each subject commands for the correct directions of movement, using the subject's body as a frame-of-reference. There was little improvement in motor performance. These results suggest that the visual information presented in the mirror captured the subjects' attention and blocked their motor tracing program.

Adult↗
PubMed1996

Handedness and performance variability as factors influencing mirror movement occurrence.

A finger flexion task was used to investigate the effect of hand preference and performance variability on intensity of mirror movement. Right- and left-handed subjects were asked to maintain target forces, with either their index or small finger, that represented 25, 50, or 75% of their maximum strength capacity for the active finger. Greater mirror movement occurred when the small finger was active, and where there was greater variability in task performance, while mirror movement intensity was less when the dominant hand and the index finger were active. These findings were consistent with the cortical activation explanation of motor overflow (Todor & Lazarus, 1986a), and suggest that task variability is an important factor influencing motor overflow production. It was concluded that, if performance variability reflects the efficiency of cortical activation underlying control of a voluntary task, then refined cortical control decreases the potential for motor overflow to occur. However, it is necessary to clarify the relationship between hand preference, performance variability, and motor overflow, perhaps by examining the neural pathways involved in motor overflow production.

Adult↗
PubMed1998

Surgical cleansing of varicose ulcers of the leg using a CO2 laser with rotating mirror scanner.

OBJECTIVE: Our purpose was to evaluate the effectiveness of cleansing by CO2 laser with a rotating mirror scanner in accelerating ulcer granulation and reducing sensitization, bleeding, and the need for painful medications. SUMMARY BACKGROUND DATA: Cleansing, the first step in treating phlebostatic ulcers, may be performed with a defocussed CO2 laser, but laser-to-target distance, technique, and duration of the procedure may vary. METHODS: We studied 20 patients, ages 38-85, with "common" phlebostatic ulcers showing a tendency not to granulate. The patients were divided into two groups by sex (7 females and 3 males) and by size of ulcer. The first group was treated using the CO2 laser and rotating mirror scanner; the second was treated surgically with scissors and tweezers. In both groups debridement was followed by mobile and fixed elastocompressing bandage, mobilization, and phlebotonics. Six patients in the first group and four in the second subsequently underwent short stripping to correct the incompetent saphenous circulation. RESULTS: Ulcer cleansing was achieved in all 20 cases. In the laser group, the treatment was well tolerated by 9 patients and granulation was achieved in 10 days on average; in the second group, cleansing was very painful in 5 cases and granulation was achieved in 25 days on average. Both groups had good cicatrization at 3 months after elastocompression, zinc dioxide medication, mobilization, and phlebotonics. The 6-month follow-up revealed only one recurrence--a small ulcer at a different location--in the first group and no cases of recurrence in the second. CONCLUSIONS: Cleansing by CO2 laser and rotating mirror scanner allows the acceleration of ulcer granulation and reduces sensitization, bleeding, and the need for painful and costly medications.

Aged↗
PubMed1989

Acute lymphoblastic leukemia-hand mirror variant. Analysis for endogenous retroviral antibodies in bone marrow plasma.

Two unusual cases of acute lymphoblastic leukemia-hand mirror variant (ALL-HMV) are presented. One patient demonstrated a mixed immunophenotype with HLA-DR, My7, transferrin receptor surface markers, and terminal deoxynucleotidyl transferase positivity. To the authors' knowledge, this is the first ALL-HMV reported with myeloid antigen. The patient died during induction and did not demonstrate the indolent course noted in the female subgroup with this disorder. The second case initially was not an ALL-HMV but presented as a non-T non-B ALL, and the patient had a relapse six years later with numerous hand mirror cells (HMCs). In the authors' experience, this is the first case of ALL that presented as a non-HMC and relapsed as an ALL-HMV. The patient's immunophenotype revealed he was HLA-DR, transferrin receptor, and TdT positive. Both patients' leukemic cells showed a diffuse granular periodic acid-Schiff on a clear background and acid phosphatase-positive pattern. Immunogenetics revealed a clonal rearrangement of one of the two Ig heavy chain loci in the one patient evaluated. Western blot analysis of the bone marrow plasma of both patients with ALL-HMV showed an increase of cross-reactive IgG to the envelope gp70 and IgM against the core p30 proteins of the baboon endogenous virus (BaEV) and simian sarcoma-associated virus (SSAV). Furthermore, their bone marrow plasma demonstrated IgM antibodies to the gp70 that were not present in any of the other non-hand mirror leukemic patients or the normal controls. These findings strengthen the concept that HMCs in ALL are formed in relation to an immunologic response to increased proteins related to BaEV and/or SSAV.

Adult↗
PubMed1991

Congenital mirror movements. Abnormal organization of motor pathways in two patients.

We studied 2 patients with congenital mirror movements by means of various neurophysiological and metabolic techniques, including mapping of motor evoked potentials to transcranial electrical and magnetic stimulation, premovement and somatosensory evoked potentials, kinematics of voluntary movements, muscle reflexes, and positron emission tomography (PET). Abnormalities in maps of motor and premovement potentials and in PET scans were consistent with a bilateral representation of hand muscles in the motor cortex, the existence of physiologically active connections capable of conducting fast efferent volleys from the motor cortex to ipsilateral muscles, the presence of mirror EMG activity in either hand with intended voluntary movement of the other hand, the absence of mirrored EMG responses from wrist flexors and extensors to mechanical perturbation of the contralateral wrist, and normal scalp distribution of somatosensory evoked potentials to right and left median nerve stimulation. Our findings are consistent with aberrant organization of motor representation areas and corticospinal pathways with ipsilateral as well as contralateral control of voluntary movement.

Adult↗
PubMed1997

Mirror movements in X-linked Kallmann's syndrome. I. A neurophysiological study.

Possible mechanisms underlying the pathological mirror movements that are seen in the majority of patients with X-linked Kallmann's syndrome have been investigated using neurophysiological techniques. An EMG was recorded from the first dorsal interosseous muscle (1DI) during voluntary self-paced abduction of one indexed finger; EMG activity could also be recorded simultaneously from the contralateral 1DI. There was no significant difference between the time of onset of the bursts of voluntary and involuntary mirroring EMG. Focal magnetic stimulation of the hand area of the motor cortex revealed the presence of fast conducting bilateral corticospinal projections from each motor cortex in all subjects. However, both inter- and intra-subject differences exist when considering the ratio of ipsilaterally to contralaterally projecting axons. Cross-correlation analysis of multi-unit EMGs recorded during simultaneous voluntary sustained activation of homologous left and right pairs of distal upper limb muscles was performed. A short duration central peak was seen in the cross-correlograms indicating the presence of a common drive to left and right homologous motor neuron pools. This common drive may result from the synchronous activation of intermingled ipsilaterally and contralaterally projecting corticospinal neurons in the motor cortex. Cutaneomuscular reflexes were recorded from the 1DI following stimulation of the digital nerves of the index finger. Typically each reflex comprises spinal and longer latency trans-cortical components. In these subjects, the long latency components of the reflex response could, in addition, be recorded from the 1DI of the non-stimulated side. We conclude that these subject have a novel ipsilateral at least in part, for the pathological mirroring.

Adolescent↗
PubMed2003

Pure agnosia for mirror stimuli after right inferior parietal lesion.

This study reports the experimental investigation of G.R., a patient suffering from a highly specific disorder in discriminating mirror stimuli following a right temporoparietal cerebrovascular accident. G.R. showed intact perceptual, attentional, mnestic, linguistic and executive abilities. Object recognition was accurate even under unusual viewing conditions. He was highly accurate in defining the canonical orientation of common objects and in discriminating misoriented objects among identical distracters. However, he was severely impaired in tasks requiring mirror-stimulus discrimination, a deficit that persisted even when the object's coordinates were systematically misaligned with respect to his body. The disorder was also dependent upon the frame of reference (allocentric versus egocentric) activated on the basis of task demands. These results demonstrate the existence of a highly specific disorder in discriminating mirror stimuli defined in object-based coordinates, suggesting a failure in processing the directionality of an object's intrinsic x-axis.

Aged↗
PubMed2006

Regional specificity of format-specific priming effects in mirror word reading using functional magnetic resonance imaging.

The speed and accuracy with which subjects can read words is enhanced or "primed" by a prior presentation of the same words. Moreover, priming effects are generally larger when the physical form of the words is maintained from the first to the second presentation. We investigated the neural basis of format-specific priming in a mirror word-reading task using event-related functional magnetic resonance imaging (fMRI). Participants read words that were presented either in mirror-image (M) orientation or in normal (N) orientation and were repeated either in the same or the alternate orientation, creating 4 study-test conditions, N-N, M-N, N-M, and M-M. Priming of N words resulted in reductions in fMRI signal in multiple brain regions, even though reading times (RTs) were unchanged. Priming of M words showed a pattern of RTs consistent with format-specific priming, with greater reductions when the prime matched the form of the test word. Priming-related reductions in fMRI activity were evident in all regions involved in mirror-image reading, regardless of the orientation of the prime. Importantly, reductions in several posterior regions, including fusiform, superior parietal, and superior temporal regions were also format specific. That is, signal reductions in these regions were greatest when the visual form of the prime and target matched (M-M compared with N-M). The results indicate that, although there are global neural priming effects due to stimulus repetition, it is also possible to identify regional brain changes that are sensitive to the specific perceptual overlap of primes and targets.

Adult↗
PubMed2006

Motivation modulates the activity of the human mirror-neuron system.

It is not known whether the mirror-neuron system is modulated by motivation, such as hunger. In this study, 2 groups of healthy participants underwent 2 functional magnetic resonance imaging scanning sessions separated by 1.5 h interval. During each session, participants were presented with video clips of another person grasping objects or grasping food. The first session was conducted after participants from group 1 had fasted. Then these participants were allowed to eat and were scanned again. Participants from group 2 had a meal before the first session. Food-related stimuli elicited specific hemodynamic response in the parahippocampal gyrus, orbitofrontal cortex, and amygdala, when participants were in a hungry state as compared with a satiated state. In addition, regions that belong to the mirror-neuron system, including the inferior frontal gyrus, and the posterior parietal cortex showed greater response when participants were hungry. Increased activity was also detected in the extrastriate body area. A positive correlation was observed between the self-report ratings of hunger and the hemodynamic activity in the inferior frontal gyrus as well as in the amygdala. Our results suggest that motivation to eat modulates the neural activity in the mirror-neuron system, facilitating the preparation or the intention to act.

Adult↗
PubMed1992

Self-recognition in Alzheimer's disease: a mirror and video study.

Twenty-nine subjects with Senile Dementia of the Alzheimer Type (SDAT) were tested for self-recognition when confronted with their reflection in a mirror and with a noncontingent video image. All subjects at stage 5 (moderately severe cognitive decline) on the Global Deterioration Scale (GDS) showed self-recognition in the mirror condition, whereas 25% of GDS stage 6 subjects (severe cognitive decline) did not self-recognize. Only seven subjects showed signs of self-recognition on video (six at GDS 5, one at GDS 6). The results confirm two hypotheses: the first, based on studies with infants, is that contingency cues in the mirror condition facilitate self-recognition; the second is that SDAT patients may show "regression" of at least some cognitive functions.

Aged↗
PubMed1992

Synthesis and properties of mirror-image DNA.

We have investigated the conformations of the hexadeoxyribonucleotide, L-d(CGCGCG) composed of L-deoxyribose, the mirror image molecule of natural D-deoxyribose. In this paper, we report the synthesis of four L-deoxynucleosides and the L-oligonucleotide-ethidium bromide interactions. The L-deoxyribose synthon 9 was synthesized from L-arabinose with an over all yield of 28.5% via the Barton-McCombie reaction. The L-deoxynucleosides were obtained by a glycosylation of appropriate nucleobase derivatives with the 1-chloro sugar 9. After derivatization to nucleoside phosphoramidites, L-deoxycytidine and L-deoxyguanosine were incorporated into a hexadeoxynucleotide, L-d(CGCGCG) by a solid-phase beta-cyanoethylphosphoramidite method. This L-hexanucleotide was resistant to digestion with nuclease P1. The conformations of L-d(CGCGCG) were an exact mirror image of that of the corresponding natural one as described previously, and the conformations of the L-d(CGCGCG)-ethidium bromide complex were also the mirror images of those of the D-d(CGCGCG)-ethidium bromide complex under both low and high salt conditions. These results suggest that ethidium bromide prefers not a right-handed helical sense, but the base-base stacking geometry of the B-form rather than that of the Z-form. Thus, L-DNA would be a useful tool for studying DNA-drug interactions.

Chromatography, High Pressure Liquid↗
PubMed2006

Modulation of the mirror system by social relevance.

When we observe the actions of others, certain areas of the brain are activated in a similar manner as to when we perform the same actions ourselves. This 'mirror system' includes areas in the ventral premotor cortex and the inferior parietal lobule. Experimental studies suggest that action observation automatically elicits activity in the observer, which precisely mirrors the activity observed. In this case we would expect this activity to be independent of observer's viewpoint. Here we use whole-head magnetoencephalography (MEG) to record cortical activity of human subjects whilst they watched a series of videos of an actor making a movement recorded from different viewpoints. We show that one cortical response to action observation (oscillatory activity in the 7-12 Hz frequency range) is modulated by the relationship between the observer and the actor. We suggest that this modulation reflects a mechanism that filters information into the 'mirror system', allowing only socially relevant information to pass.

Adult↗