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PubMed2000

Quantitative assessment of mirror movements in children and adolescents with hemiplegic cerebral palsy.

Mirror movements in individuals with hemiplegic cerebral palsy (CP) may result from a reorganization of the central sensorimotor system. Motor performances of both hands were measured to characterize mirror activity (or mirroring) and hand functions in 22 participants (6 to 18 years) with hemiplegic CP and in 17 control participants. During a unimanual repetitive squeezing task, contractions of the active hand and fingertip forces of the opposite hand were recorded simultaneously. In the control group, slight mirror activity (or mirroring) was found that decreased with age. In participants with CP, mirror activity was 15 times stronger than in the control group, and was found at all age levels. Mirroring was more prominent in the unaffected hand of the CP group. The amount of mirror activity was not related to the degree of hemiplegia, which was assessed with measures of spasticity, strength, and dexterity. Mirror movements disturbed functional bimanual skills, although to some extent they could be suppressed by voluntary effort.

Adolescent↗
PubMed2006

A role of the anti-angiogenic factor sVEGFR-1 in the 'mirror syndrome' (Ballantyne's syndrome).

BACKGROUND: 'Mirror syndrome' (Ballantyne's syndrome) refers to the association of fetal hydrops with placentomegaly and severe maternal edema. Preeclampsia occurs in approximately 50% of these cases. Soluble vascular endothelial growth factor receptor-1 (sVEGFR-1), an anti-angiogenic factor, has been implicated in the pathophysiology of preeclampsia (PE). OBJECTIVE: The objective of this study was to determine if the maternal plasma concentration of sVEGFR-1 is elevated in patients with mirror syndrome. STUDY DESIGN: This case-control study included patients with uncomplicated pregnancies (n = 40) and those with mirror syndrome (n = 4) matched for gestational age. Mirror syndrome was defined as fetal hydrops and severe maternal edema. Maternal plasma sVEGFR-1 concentrations were determined using specific enzyme-linked immunosorbent assays. Immunohistochemistry of sVEGFR-1 on villous trophoblasts was also performed in samples from one patient with mirror syndrome and compared with those from a patient with spontaneous preterm delivery matched for gestational age. Non-parametric statistics were used for analysis (p < 0.05). RESULTS: (1) The median maternal plasma concentration of sVEGFR-1 was significantly higher in patients with mirror syndrome than in the control group (median: 3974 pg/mL, range: 3083-10 780 vs. median: 824 pg/mL, range: 260-4712, respectively; p < 0.001). (2) All patients with mirror syndrome had sVEGFR-1 concentrations above the 95th percentile for gestational age. Syncytiotrophoblast, especially syncytial knots, showed strong staining with antibodies against sVEGFR-1 in placental samples from the patient with mirror syndrome, but not in those from the patient with spontaneous preterm delivery. CONCLUSION: High maternal plasma concentrations of sVEGFR-1 were observed in mirror syndrome. We propose that this anti-angiogenic factor may participate in the pathophysiology of this syndrome. Thus, maternal plasma determination of sVEGFR-1 may help to identify the hydropic fetus that places the mother at risk for preeclampsia.

Adult↗
PubMed2003

Abnormal cortex-muscle interactions in subjects with X-linked Kallmann's syndrome and mirror movements.

X-linked Kallmann's (XKS) subjects, who display mirror movements, have abnormal corticospinal tracts which innervate motoneurons of the left and right distal muscles of the upper limb. The size of the abnormal ipsilateral projection is variable. We have used coherence and cumulant analysis between EEG and first dorsal interosseous muscle (1DI) EMG to explore mechanisms underlying mirror movements in three XKS subjects. Results are compared with those of three normal subjects. We argue that significant coherence is functionally relevant when associated with a negative cumulant at an appropriate lag. Given this, normal subjects showed coherence at approximately 22 Hz between the EEG recorded over the sensori-motor cortex contralateral to the voluntarily moved hand and the 1DI EMG of this hand. No significant coherence was seen between 1DI EMG and the sensori-motor cortex ipsilateral to the muscle activity. In contrast, two of the XKS subjects (K2 and K4) had significant coherence at 22 Hz, together with a negative cumulant at an appropriate lag, between the ipsilateral cortical EEG and the 1DI EMG of the voluntarily activated hand. This implies that activity in the abnormal ipsilateral corticospinal projection can contribute to the voluntary drive. For these two subjects, the ipsilateral corticospinal projection was greater than the contralateral projection, as revealed using magnetic brain stimulation. In one of these subjects, K4, significant 22 Hz coherence and negative cumulant was also seen between the EMG of the voluntarily activated hand and the cortex contralateral to this hand. In the third subject, K4a, coherence and negative cumulant was detected between the EMG of the voluntary side and the cortical activity contralateral to this hand. The contralateral cortico spinal projection of this subject was greater than the ipsilateral projection. Regarding the mirroring hand of the XKS subjects, coherence (with negative cumulant at an appropriate lag) was seen in all three subjects between the EMG recorded from the mirroring hand and cortical EEG ipsilateral to this hand. This provides evidence that activity in the aberrant ipsilateral projection is involved in producing the drive that results in mirror movements. In one subject, K4, coherence and negative cumulant was also seen between the EMG of the mirroring hand and motor cortical activity contralateral to this hand. Thus, in this subject, activity in the corticospinal projection contralateral to the mirroring hand also contributed to the mirror movements. In conclusion, this study has provided further evidence that the 22 Hz coherence seen between EEG and EMG is dependent upon corticospinal activity and has furthered our understanding of mechanisms underlying mirror movements.

Adult↗
PubMed2006

Mirror writing: neurological reflections on an unusual phenomenon.

Mirror writing is an unusual script, in which the writing runs in the opposite direction to normal, with individual letters reversed, so that it is most easily read using a mirror. This writing is seen in healthy individuals; it is also associated with various focal lesions that most commonly involve the left hemisphere, as well as with certain diffuse cerebral disorders. Mirror writing is nearly always undertaken with the left hand, and left-handers, and those whose languages are written leftwards, have an unusual facility for this writing. Concerning possible underlying processes, the implications of using the left hand when writing are considered first. Motor pathways that may be important, the surrogate model of bimanual mirror movements and the contribution of the corpus callosum are then discussed. The reasons why left-handed writing is mirrored, and the factors that tend to inhibit mirroring, are outlined. After commenting on mirrored motor and visual engrams, the possibility that the right hemisphere may play an important part is entertained, and Leonardo da Vinci's unique, habitual mirror writing proves to be of unexpected relevance. Further investigations, ranging from epidemiological to functional imaging studies, may provide valuable insights into mirror writing.

Adult↗
PubMed1980

Mirror pecking and timeout under a multiple fixed-ratio schedule of food delivery.

Pigeons were trained to peck a key under a multiple fixed-ratio 25 fixed-ratio 175 schedule of food presentation. In the first condition, either a mirror or the opportunity to produce a 30-second timeout were available. In a second condition, mirror and timeout availability were reversed for the two groups. Following a return to the initial condition, mirror and timeout keys were presented together for all birds. Mirror and timeout responses occurred predominantly in the pause in the larger fixed-ratio component, regardless of whether the opportunities for the two responses were available singly or together. Mirror responding occurred in a greater proportion of the pauses than did timeouts. When the opportunities for both mirror pecking and timeout were available concurrently, they occurred with probabilities similar to those under the single conditions. Within the pause itself, mirror responses most frequently occurred immediately after reinforcement. Timeouts occurred most frequently toward the end of the pause, and some timeouts occurred in the early part of the run. Longer preratio pausing occurred in the larger fixed-ratio component in the conditions in which the mirror was present, whether or not any mirror pecks were recorded.

Journal Article↗
PubMed1993

[A modified Macintosh blade for difficult intubation. The mirror blade].

Difficult intubations can occur in cases of anatomical or physiological abnormalities of the face and neck. They are frequently predictable when specific signs are evident preoperatively. There are still occasional unexpected difficulties during conventional laryngoscopy when common blades like the Macintosh and Foregger types are used. During the past 5 decades several authors have proposed many types of laryngoscopes and blades differing in length and shape, as well as various accessories such as guide-wires, prisms, and mirrors. METHOD. We modified a size 3 Macintosh blade by adding a mirror placed tangential to the external curve near the apex. This configuration allows both conventional direct visualisation of the vocal cords and non-direct viewing through the mirror. Insertion of the tube is facilitated using a specially shaped guide-wire. RESULTS. This equipment was used for orotracheal intubation in 20 patients with different degrees of direct laryngeal visibility prior to otolaryngologic endoscopy and surgery under general anaesthesia. Both methods of larynx visualisation were performed and compared. In 1 patient the mirror was not useful because it became fogged. In all the others we could avoid this problem by warming the blade in water. Only in 1 other case was the conventional view better and intubation seemed to be easier than when the mirror was used. In 15 patients the vocal cords were visualised better with the mirror, and intubation was performed by means of the guide-wire with the non-direct technique. In 2 of these cases difficult direct laryngoscopy of grades 3 and 4 according to the Cormack and Lehane classification was found. Four patients were difficult to intubate and neither type of laryngoscopy was ideal. It is notable that a satisfactory view was achieved in the mirror with much less effort. In particular, there was no need to introduce the blade as deeply or raise its apex as much as is usually done. CONCLUSION. The mirror-blade is a suitable device for management of unexpected difficult intubations. Because of its dual availability, it offers both direct and non-direct visualisation of the larynx. Handling of this mirror-blade can be practised extensively, which allows integration of this equipment in the "failed intubation drill". This should be an integral part of the teaching and training of anaesthesia personnel.

Adult↗
PubMed1998

Responses of gibbons (Hylobates lar) to their mirror images.

Nine gibbons (Hylobates lar) and one gibbon-siamang crossbreed were observed during exposure to their mirror images over two 30 minute baseline condition periods (mirror off) and four 30 minute treatment condition periods (mirror on). Greater frequencies and durations of gazing at the mirror and mirror-contingent behaviors were noted during the reflective conditions than for nonreflective conditions. Despite two subjects' apparent use of the mirror to view body parts otherwise not visible to them, no subjects passed a modified mark test. One subject exhibited limited aggressive displays toward the mirror, but no subjects exhibited abnormal behaviors in the presence of the mirror. The results expand on and confirm similar findings by Lethmate and Dücker [Zeitschrift fur Tierpsychologie 33:248-269, 1973].

Animals↗
PubMed1997

Function and mechanism of mirror-image ambiguity in bumblebees

This study investigated the function and mechanism underlying a previously documented 'mirror-image ambiguity' (i.e. the mirror image of a pattern is treated as similar to the original stimulus) in foraging bumblebees, Bombus impatiensArtificial flowers were constructed so that the mirror image of a petal configuration was different from the left-right reversal of that configuration. Bees were first trained to discriminate between rewarding and unrewarding artificial flowers that differed only in their configuration of four differently patterned petals. On subsequent choice tests between two empty flowers, the bees chose the rewarding configuration (S+) over the unrewarding one (S-), over the mirror image and over the left-right reversal. In the critical test conditions, the bees failed to choose the mirror image over a novel petal configuration, but they chose the left-right reversal over the novel configuration (78% of the time). A mirror-image mental transformation was ruled out as a mechanism underlying mirror-image ambiguity. The notion that mirror-image ambiguity has general functional significance (e.g. is a by-product of the symmetry of the nervous system) received no support. The results favour a specific mechanism tied to a specific function: a left-right transposition of a floral pattern, which would enable foraging bees to recognize vertically symmetrical flowers that were partially occluded at the time of learning.

Journal Article↗
PubMed1980

Design of mirror systems for commercial vehicles.

This paper describes a computer aided design project for the evaluation of alternative mirror systems for a range of commercial vehicles. Computer modelling of mirror systems introduces the ergonomics parameters into the design programme at an early stage. The flexibility of computer modelling allows a far greater range of designs to be evaluated. The problems can be studied and resolved before producing a series of mirror designs to be evaluated by more conventional techniques on prototype vehicles. Mirrors designed in this way are less likely to require major redesign. Compliance with the legislative requirements of mirror design was a major consideration. Attempts were also made to optimise mirror systems for a range of cabs basing the evaluations on ergonomic as well as legislative criteria. Additionally, consideration was given to the use of mirrors for viewing trailer swing, passenger exit surveillance (for public service vehicles) and the viewing of objects close to high cabs. SAMMIE (System for Aiding Man-Machine Interaction Evaluation), a computer-aided workplace and work task design system, was used to model the vehicles and to produce the required mirror views on a computer graphics terminal.

Journal Article↗
PubMed2005

[Complex polydactyly of the limbs: mirror foot. Report of two cases and review of literature].

Polydactyly is the most common congenital limb anomaly occurring both as an isolated defect or as part of a syndrome. However mirror foot is an exceptional abnormality (14 cases reported). The authors describe two sporadic cases of mirror foot. The first case presents a mirror polydactyly of the left foot, an hexadactyly of the right foot and a central polysyndactyly of both hands. The second case presents a mirror polydactyly of both feet. Mirror foot is a very rare defect. Both sporadic and familiar cases have been reported. This malformation can affect one or both feet. Some cases are associated with other congenital anomalies. The definition of mirror foot is warying according to the authors and the review of literature shows an important variability in the patterns of mirror polydactyly. Mirror duplication of hands and feet result of aberrant positioning of the zone of polarizing activity in relation to the apical ectodermal ridge during limb bud development. Different genes encoding limb pattern have been described.

Abnormalities, Multiple↗
PubMed2004

Reactions of capuchin monkeys (Cebus apella) to multiple mirrors.

This study attempted a new manipulation to prompt mirror self-recognition in a monkey species through simultaneous exposure to two mirrors. Four capuchin monkeys (Cebus apella) were exposed to one large and one small mirror object with different reflective or configurational properties, which was thought to deepen their understanding of mirrors. The monkeys predominantly engaged in looking behaviours towards the large mirror, which decreased over sessions. There was also an increase in looking behaviours towards the small mirror object when it reflected an undistorted image compared to the control condition. No instances of self-directed responses, oblique looks or manipulations of both mirror objects in combination were observed. The results confirm and expand on previous reports of failure to find evidence of mirror self-recognition in monkeys.

Animals↗
PubMed2006

Mirror neurons and imitation: a computationally guided review.

Neurophysiology reveals the properties of individual mirror neurons in the macaque while brain imaging reveals the presence of 'mirror systems' (not individual neurons) in the human. Current conceptual models attribute high level functions such as action understanding, imitation, and language to mirror neurons. However, only the first of these three functions is well-developed in monkeys. We thus distinguish current opinions (conceptual models) on mirror neuron function from more detailed computational models. We assess the strengths and weaknesses of current computational models in addressing the data and speculations on mirror neurons (macaque) and mirror systems (human). In particular, our mirror neuron system (MNS), mental state inference (MSI) and modular selection and identification for control (MOSAIC) models are analyzed in more detail. Conceptual models often overlook the computational requirements for posited functions, while too many computational models adopt the erroneous hypothesis that mirror neurons are interchangeable with imitation ability. Our meta-analysis underlines the gap between conceptual and computational models and points out the research effort required from both sides to reduce this gap.

Animals↗
PubMed2004

One good turn deserves another: an event-related brain potential study of rotated mirror-normal letter discriminations.

The time to decide if a letter is normal or backwards (mirror-reversed) increases as the letter is rotated away from the upright. It is widely accepted that this increase in time reflects the mental rotation of the stimulus to the upright orientation in order to determine the mirror-normal status of the stimulus. Although response times tend to be longer for mirrored stimuli than for normal stimuli, the difference is constant across orientation. Little work has been focused on why mirror-image stimuli produce longer response times than normal stimuli. This study examines the question of whether or not mirrored stimuli are rotated in the picture plane at the same time as normal stimuli, and if so, why response times to mirrored stimuli are longer than that for normal stimuli. Both the behavioural and electrophysiological findings suggest that the mirrored stimuli are not only rotated in the picture plane, but that they are subsequently rotated to the normal view. It is this additional rotation that produces, at least in part, the delayed response times for mirror-image stimuli.

Adult↗
PubMed2006

Mirror movements following cortical resection of polymicrogyria in a child with intractable epilepsy.

Mirror movements may be congenital or acquired. There are few reports of acquired mirror movements in pediatric patients. Further, mirror movements in children with epilepsy have rarely been reported. A 9-year old male, with intractable partial epilepsy resulting from polymicrogyria of the right hemisphere, underwent cortical resection of the right frontotemporoparietal region for a malformation of cortical development. He developed left hemiplegia and mirror movements in the left hand in the postoperative period. Four months after surgery, he remained seizure-free with mild residual left-sided hemiplegia and persistent mirror movements. Mechanisms postulated for mirror movements include aberrant pyramidal tract development and transcallosal inhibitory pathways. The latter mechanism might have contributed to the mirror movements observed in this child. This study is the first report of mirror movements following focal cortical resection for intractable epilepsy due to polymicrogyria.

Cerebral Cortex↗
PubMed1999

Can mirrors alleviate visual hemineglect?

Following right hemisphere stroke, many patients display an indifference to objects and events in the left side of the world ('neglect'). Here, we describe a new technique that might help accelerate recovery from neglect. The patient sits at a table and a mirror is propped vertically on the patient's right side in the parasagittal plane, so that when the patient rotates his head rightward and looks into the mirror, he sees the neglected side of the world reflected in the mirror. Our question was: since the sensory information was now coming from the non-neglected left side, would this somehow make him overcome the neglect? In pilot experiments, two types of responses were seen: (a) In one subset of patients the presence of the mirror seemed to enhance the patients' awareness of the neglected field, so that they reached correctly for an object that was shown in the neglected field. Will repeated practice with this task accelerate recovery from neglect? (b) The second group of patients kept reaching into the mirror to grasp the reflection or kept groping behind the mirror ('mirror agnosia'). If the mirror was placed in the coronal position and the object placed behind their head, then some of these patients (from group B) reached correctly for the object. Quite apart from its obvious theoretical implications, we believe this technique might provide a new approach for the treatment of visual hemineglect.

Brain↗
PubMed2000

Essential role of the right superior parietal cortex in Japanese kana mirror reading: An fMRI study.

Functional magnetic resonance imaging (fMRI) was used to investigate the neural substrates responsible for Japanese kana mirror reading. Japanese kana words, arranged vertically from top to bottom, were used in the mirror reading task in 10 normal right-handed Japanese adults. Since both mirror-reversed and normally oriented kana items are read in the same (top to bottom) direction, it was possible to minimize the oculomotor effects which often occur in the process of mirror reading of alphabetical language. By using the SPM96 random effect analysis method, a significant increase in the blood oxygen level-dependent signal during mirror reading relative to normal reading was detected in multiple brain regions, including the bilateral superior occipital gyri, bilateral middle occipital gyri corresponding to Brodmann area (BA) 18/19, bilateral lingual gyri (BA 19), left inferior occipital gyrus (BA 18), left inferior temporal cortex (BA 37), bilateral fusiform gyri (BA 19), right superior parietal cortex (SPC) (BA 7), left inferior frontal gyrus (BA 44/45) and an inferior part of the left BA 6. In addition to these cortical regions, the right caudate nucleus and right cerebellum were also activated. The activation found in the right SPC and the left inferior temporal region is consistent with the hypothesis that mirror reading involves both the dorsal visuospatial and ventral object recognition pathways. In particular, a significant correlation was found between the fMRI signal change in the right SPC and the behavioural performance (error index) in the task. This may reflect increased demand on the right SPC for the spatial transformation which is required for the accurate recognition of mirror-reversed kana items. This relationship between the haemodynamic response in a specific brain area and the behavioural data provides new evidence for the essential role of the right SPC in Japanese kana mirror reading.

Adult↗
PubMed1996

The mirror as a therapeutic tool for patients with dementia.

The aim of the study was to examine changes in patient behavior that occurred as a consequence of looking in a mirror. How do dementia patients relate to their image in the mirror? Is the use of the mirror effective in raising levels of self-awareness, calmness and satisfaction? The survey was carried out on 100 patients suffering from dementia: 67 women and 33 men aged between 67 and 85. The findings showed that most responses to looking in the mirror were positive and raised the patients' awareness regarding self-care. In a small number of patients, looking into the mirror aroused feelings of anger or despair, followed by relief and calmness. Findings indicated that the use of mirrors enabled nurses and caregivers to communicate better with patients. Most patients appeared to benefit in various ways from looking into the mirrors. The staff felt that use of mirrors was an inexpensive and efficient therapeutic tool for improving care of demented aged patients.

Aged↗
PubMed2003

Cryogenic optical testing of sandwich-type silicon carbide mirrors.

The experimental cryogenic performance of 160-mm-diameter silicon carbide (SiC) mirrors, one of which, a 700-mm-diameter mirror, is to be used as a primary mirror of the Japanese Infrared Astronomical Satellite ASTRO-F, is described. The mirrors are made from a sandwich-type SiC material that comprises a light porous core and a dense chemical-vapor-deposited coat of SiC. Three mirrors were manufactured consecutively, and changes in their surface contours related to temperature were measured with an interferometer when the mirrors were placed in a liquid-helium cryostat. Owing to significant improvements in manufacturing, the third SiC mirror showed only slight deformation as the temperature decreased from 300 to 6 K, which indicates high thermal strain homogeneity for a well-controlled sandwich-type SiC mirror.

Journal Article↗