Mirror Movements Research Articles

The impact of brain lesion characteristics and the corticospinal tract wiring on mirror movements in unilateral cerebral palsy

Mirror movements (MM) influence bimanual performance in children with unilateral cerebral palsy (uCP). Whilst MM are related to brain lesion characteristics and the corticospinal tract (CST) wiring pattern, the combined impact of these neurological factors remains unknown. Forty-nine children with uCP (mean age 10y6mo) performed a repetitive squeezing task to quantify similarity (MM-similarity) and strength (MM-intensity) of the MM activity. We used MRI data to evaluate lesion type (periventricular white matter, N = 30; cortico-subcortical, N = 19), extent of ipsilesional damage, presence of bilateral lesions, and damage to basal ganglia, thalamus and corpus callosum. The CST wiring was assessed with Transcranial Magnetic Stimulation (17 CSTcontralateral, 16 CSTipsilateral, 16 CSTbilateral). Data was analyzed with regression analyses. In the more-affected hand, MM-similarity and intensity were higher with CSTbilateral/ipsilateral. In the less-affected hand, MM-similarity was higher in children with (1) CSTcontra with CSC lesions, (2) CSTbilat/ipsi with PVL lesions and (3) CSTbilat/ipsi with unilateralized lesions. MM-intensity was higher with larger damage to the corpus callosum and unilateral lesions. A complex combination of neurological factors influences MM characteristics, and the mechanisms differ between hands.

Descriptive Study of Facial Motor Cocontractions During Voluntary Facial Movement in a Healthy Population: A New Hypothesis Contributing to Synkinesis.

Background: Motor overflow refers to involuntary movements that accompany voluntary movements in healthy individuals. This may have a role in synkinesis. Objective: To describe the frequency and magnitude of facial motor overflow in a healthy population. Methodology: Healthy participants performed unilateral facial movements: brow elevation, wink, snarl, and closed smile. Two reviewers analyzed the magnitude of each movement and cocontraction. Patterns of movements are described. Univariate analysis was used to assess the relationship between efficacy of unilateral facial control and the frequency and magnitude of cocontractions. Results: Eighty-nine participants completed the videos. Consensual mirror movements occurred in 96% of participants during unilateral eye closure and 86% during brow elevation. The most common associated movement was ipsilateral eye constriction occurring during snarl (90.1%). Improved unilateral facial control was associated with a decrease in frequency and magnitude of associated movements during brow elevation, wink, and snarl. Conclusion: This study showed stereotyped patterns of motor overflow in facial muscles that resemble those in synkinesis and become more evident as unilateral control of the face decreases.

Casimir-force-assisted ground-state cooling and macroscopic quantum coherence

We theoretically investigate the ground-state cooling and macroscopic quantum coherence of the mechanical motion in a hybrid optomechanical system with a movable cavity wall and a nearby oscillation nanosphere. In the study, the vacuum effect is used to realize a direct coupling between the movable cavity wall and the oscillation nanosphere, which plays a role in the energy transfer channel between them. We find that when the Casimir force between the mechanical oscillators is included, the ground-state cooling and the macroscopic quantum coherence of the oscillation nanosphere can be realized in a certain range of effective detuning and driving power. We discuss in detail the dependence of the quantum properties on the amplitude of Casimir force, the driving power, the optical effective detuning and the oscillation frequency of the movable mirror. The results suggest that the quantum phenomenon of a single nanosphere can be manipulated by coupling an optomechanical cavity to the nanosphere and therefore has a potential application in quantum optics and the utilization of vacuum force.

Dynamic spectral signatures of mirror movements in the sensorimotor functional connectivity network of patients with Kallmann syndrome.

In Kallmann syndrome (KS), the peculiar phenomenon of bimanual synkinesis or mirror movement (MM) has been associated with a spectral shift, from lower to higher frequencies, of the resting-state fMRI signal of the large-scale sensorimotor brain network (SMN). To possibly determine whether a similar frequency specificity exists across different functional connectivity SMN states, and to capture spontaneous transitions between them, we investigated the dynamic spectral changes of the SMN functional connectivity in KS patients with and without MM symptom. Brain MRI data were acquired at 3 Tesla in 39 KS patients (32 without MM, KSMM-, seven with MM, KSMM+) and 26 age- and sex-matched healthy control (HC) individuals. The imaging protocol included 20-min rs-fMRI scans enabling detailed spectro-temporal analyses of large-scale functional connectivity brain networks. Group independent component analysis was used to extract the SMN. A sliding window approach was used to extract the dynamic spectral power of the SMN functional connectivity within the canonical physiological frequency range of slow rs-fMRI signal fluctuations (0.01–0.25 Hz). K-means clustering was used to determine (and count) the most recurrent dynamic states of the SMN and detect the number of transitions between them. Two most recurrent states were identified, for which the spectral power peaked at a relatively lower (state 1) and higher (state 2) frequency. Compared to KS patients without MM and HC subjects, the SMN of KS patients with MM displayed significantly larger spectral power changes in the slow 3 canonical sub-band (0.073–0.198 Hz) and significantly fewer transitions between state 1 (less recurrent) and state 2 (more recurrent). These findings demonstrate that the presence of MM in KS patients is associated with reduced spontaneous transitions of the SMN between dynamic functional connectivity states and a higher recurrence and an increased spectral power change of the high-frequency state. These results provide novel information about the large-scale brain functional dynamics that could help to understand the pathologic mechanisms of bimanual synkinesis in KS syndrome and, potentially, other neurological disorders where MM may also occur.

Motor organization of unilateral polymicrogyria associated with ipsilateral brainstem atrophy – a case report

BackgroundPolymicrogyria refers to the disruption of normal cerebral cortical development late in neuronal migration or in early cortical organization. Although patients with polymicrogyria feature relatively favorable motor outcomes, polymicrogyric lesions accompanied by extensive unilateral hemispheric atrophy and ipsilateral brainstem atrophy may induce poorer motor outcomes. This study is the first to employ transcranial magnetic stimulation (TMS) and diffusion tensor imaging (DTI) to characterize changes to motor organization and white matter tracts induced by polymicrogyria.Case presentationWe document a case of a 16-year-old female with left hemiplegic unilateral polymicrogyria associated with ipsilateral brainstem atrophy. Magnetic resonance imaging (MRI) of the brain revealed unilateral polymicrogyria to have affected anterior cortical areas, including the perisylvian region on the right side. The right halves of the brain and brainstem were significantly smaller than the left halves. Although our patient was found to exhibit cortical dysplasia of the right frontoparietal and sylvian fissure areas and a decreased number of fibers in the corticospinal tract (CST) of the affected side on DTI, the connectivity of the CST was preserved up to the motor cortex. We also measured the cross-sectional area of the CST at the level of the pons. In TMS, contralateral motor evoked potentials (MEPs) were evoked from both hands, but the ipsilateral MEPs were evoked only from the left hand. The left hand featured a long duration, polyphasic pattern of contralateral MEPs.Discussion and conclusionTMS revealed that the concurrent bilateral projections to the paretic hand from the affected and unaffected hemispheres and contralateral MEPs in the paretic hand were polyphasic, indicating delayed electrophysiological maturation or a pathologic condition of the corticospinal motor pathways. In DTI, the cross-sectional area of the CST at the level of the pons on the affected side was smaller than that on the unaffected side. These DTI findings reveal an inadequate CST volume. Despite extensive brain malformation and ipsilateral brainstem atrophy, our patient had less severe motor dysfunction and presented with involuntary mirror movements. Mirror movements in the paretic hand are considered to indicate ipsilateral corticospinal projections from the unaffected hemisphere and may suggest favorable motor outcomes in early brain injury.

Facilitative effects of use-dependent learning on interlimb transfer of visuomotor adaptation in a person with congenital mirror movements.

It has been shown that use-dependent learning can facilitate interlimb transfer of motor learning in neurologically intact individuals. However, it is unknown whether it can also facilitate interlimb transfer in individuals with neurological impairment. In this case study, we examined the effect of use-dependent learning on interlimb transfer of visuomotor adaptation in a person with congenital mirror movements, DB, who showed no interlimb transfer in our previous studies (Bao, Morgan, Lei, & Wang, 2020; Javidialsaadi, & Wang, 2021). DB first performed reaching movements with the right arm repeatedly while adapting to a visuomotor rotation condition with the left arm (training session), and then adapted to the same rotation condition with the right arm (transfer session). DB's right arm performance in the transfer session was significantly better than that observed in our previous studies, indicating interlimb transfer of visuomotor adaptation. The percentage of transfer was over 90%, which is similar to that observed in healthy young adults previously. These findings suggest that interlimb transfer of visuomotor adaptation can occur by involving model-based learning, which is effector independent, and/or use-dependent (or model-free) learning, which is effector specific; and also that the relative contribution of use-dependent learning to interlimb transfer of visuomotor adaptation can be as large as that of model-based learning.

Brain lesion type, corticospinal tract organization, and task demands may be predictive of mirror movements and motor outcomes in children with unilateral cerebral palsy.

This commentary is on the original article by Kuo et al. on pages 264–273 of this issue.

Mirror movements and brain pathology in children with unilateral cerebral palsy.

We systematically examined the relationship between mirror movements and brain lesion type, corticospinal tract (CST) organization, and hand function to determine the relevance between mirror movements, brain lesion, the CST pattern, and hand function in children with unilateral cerebral palsy (CP). Forty-eight children (mean age 9y 9mo[SD 3y 3mo], range 6-18y; 30 males, 18 females) with unilateral CP participated. Mirror movements, brain lesion type, CST pattern identified by transcranial magnetic stimulation, and clinical outcomes were evaluated. Children performed four unilateral tasks: hand opening/closing, finger opposition, individuation, and finger 'walking'. Mirror movements induced in the contralateral hand were scored using standardized criteria (scores 0-4 using the Woods and Teuber scale). We found that children with periventricular lesion may have stronger mirror movement scores induced in either hand than those with middle cerebral artery lesion (more affected hand: p=0.02; less affected hand: p<0.01). The highest mirror movement score a child exhibits across the tested tasks (i.e. scores of 3-4 using the Woods and Teuber scoring criteria) may potentially be an indicator of an ipsilateral CST connectivity pattern (p=0.03). Significant correlations were observed between higher mirror movement scores when performing hand opening/closing as well as finger walking and better unimanual dexterity (Spearman's rank correlation coefficient rs =0.44, p=0.002; rs =0.46, p=0.002 respectively). Brain lesions may be predictive of the strength of mirror movements in either hand in children with unilateral CP. Our findings warrant further studies to extensively investigate the relationship between mirror movements and the underlying brain pathology. Brain lesion type may be predictive of mirror movement scores induced in either hand in children with unilateral cerebral palsy. The highest mirror movement score a child exhibits across the tested tasks may indicate corticospinal tract connectivity pattern in children with unilateral cerebral palsy.

Development of fast steerable launcher for ECRH system

Electron cyclotron resonance heating (ECRH) launcher is an electro-mechanical system mainly consisting of mirrors (flat and profiled), a steering mechanism, a vacuum barrier window and a UHV (Ultra High Vacuum) compatible gate valve which focuses and steers the ECRH beam into plasma. Presently, Steady-state Superconducting Tokamak (SST)-1 ECRH system has a 42 GHz Gyrotron capable of delivering 500 kW of RF power for the maximum duration of 500 ms. A new steerable ECRH launcher has been developed which can steer the EC beam along both poloidal and toroidal directions. The span of mirror movement in poloidal and toroidal directions is ±20° and ±50°, respectively. The poloidal motion of the mirror can be done in real-time during plasma operation and the mirror can be rotated by 20° in 100 ms. Two AC servo motors independently control the mirror movements through an assembly of motion feedthroughs, spur gears and mechanical linkages. The accuracy, repeatability and speed of both the motions have been measured under UHV in a specially designed vacuum chamber.

Amplification of mechanical quadratures using weak values

An interferometric arrangement is proposed in which the technique of weak value amplification is implemented in order to enlarge the effect of a single photon on the quadratures of a movable mirror of an optical cavity. The photon interacts weakly with the mirror via radiation pressure and is postselected in the dark port of the interferometer. The real and imaginary parts of weak values of angular momentum type photonic operators produce an amplification of the mirror quadratures, which is large as compared to the scenario in which all photons are taken into consideration, i.e. when no postselection is performed. The effect is studied both for a mirror initialized in a thermal and coherent states. For a thermal state, the weak value amplification effect is boosted with the number of particles of the mirror, which occurs due to the imaginary part of the weak values.

058 Hypogonadotropic hypogonadism: Phenotypic variations in a series of adolescent patients

Objective: There is a relatively broad spectrum of clinical expression that can occur in idiopathic hypogonadotropic hypogonadism (IHH), ranging from a complete absence of sexual development to partial completion of puberty that does not subsequently progress. Midline defects (i.e., cleft lip/palate), anosmia/hyposmia, unilateral renal agenesis, bimanual synkinesia (or mirror movements), syndactyly or other skeletal abnormalities, hearing loss and dental agenesis have been linked to the condition. Although usually sporadic in nature, a number of familial cases have been reported. Our aim was to identify features suggestive of a syndromic condition, as well as family history in girls with IHH.

Macroscopic Mechanical Entanglement Stability in Two Distant Dissipative Optomechanical Systems

AbstractA theoretical scheme for the stable entanglement generation of two remote mechanical modes is introduced. Two identical optomechanical systems, each constituting a single‐mode optical field as well as a qubit and a moveable mirror driven by an external pump field, are considered. To make the model more realistic, atomic, photonic, and phononic dissipations are considered. The time‐dependent state of each subsystem is obtained, analytically. Then, by an appropriate Bell‐state measurement (BSM) on the state of the whole system (first approach), the entanglement of two mechanical modes is created. As a second parallel approach, appropriate atomic measurement is applied after the BSM. According to these numerical simulations via concurrence, the noteworthy features are as follows. There exists optimum value of photon–phonon coupling strength for obtaining the steady‐state entanglement; by choosing appropriate values of dissipation, photon–phonon coupling, and pump amplitude, a significant degree and stable entanglement between the two mechanical modes are accessible. The present scheme opens new practical perspectives in constructing stable entanglement between two remote mechanical modes and can be helpful to realize quantum memories for quantum information processing and establishing long‐distance quantum communication networks.

Wavelength measurement of a Helium-Neon laser using a Michelson-type amplitude division interferometer

This paper describes a way to experimentally calculate the wavelength of the light emitted by a Helium-Neon laser, model HNLS008R, which according to its technical manual has 0.8 mW of power and wavelength 632.8 nm. The experiment is based on Michelson's light interference theory, which consists of using a light source that illuminates a beam splitter, which allows dividing the light wave into two paths, one is directed towards a fixed mirror and the other towards a mobile mirror, these optical elements allow reflecting the light with the same angle of incidence producing a superposition of waves in the form of circular finges. When the movable mirror moves about its optical axis, a movement in the fringes of the order of half a wavelength is observed. The equations governing the behavior of the interference fringes in the experiment are also described and the expression to calculate experimentally the wavelength as a function of the number of fringes, the displacement of the moving mirror and the wavelength of the source under test is obtained. Finally, the experimental results are compared with the technical data provided by the manual of the device, concluding that the laser still conserves a stability in the wavelength, so it is still reliable to be used in optical experimental arrangements.

Effects of a three-level laser on mechanical squeezing in a doubly resonant optomechanical cavity coupled to biased noise fluctuations

We address the behavior of squeezing in two movable mirrors coupled to a pumped correlated emission laser inside a doubly resonant optomechanical driven cavity in the presence of biased noise fluctuations. Aiming at generating controllable and robust mechanical squeezing that can be utilized in making the quantum features of radiation in the cavity accessible for application, we explore mechanical squeezing that can be induced as a result of the transfer of coherent superposition. We found that a coupled mechanical oscillator mode exhibits squeezing in the good cavity limit and adiabatic regime. It is also shown that the degree of mechanical squeezing is robust for large amplitudes of atomic pumping until maximum squeezing is achieved but weakens afterwards. The squeezing turns out to be powerful mainly for strong atom-field coupling, large atomic injection rates, and intense biased noise fluctuations. In light of the observed possibility of controlling the realizable degree of squeezing, we hope and expect that the considered system could be employed in applications such as quantum metrology.

Mirror movements after bimanual intensive therapy in children with unilateral cerebral palsy: A randomized controlled trial.

To investigate potential changes in mirror movements after Hand and Arm Bimanual Intensive Therapy Including Lower Extremity (HABIT-ILE) training in children with unilateral cerebral palsy (CP). Thirty-one children with unilateral CP (mean age 9 years 4 months, SD 4 years 3 months; range 5 years 4 months-17 years 3 months; 14 females, 17 males) were randomized to either a control or treatment group. After allocation, children were assessed three times: before (T1, baseline) and after (T2) a 2-week interval and again at 3 months after T1 (T3) as follow-up. Between T1 and T2, the treatment group received 90 hours of HABIT-ILE training, while the control group continued their customary treatment. Mirror movements were assessed in all children using the Woods and Teuber Scale, as well as the Assisting Hand Assessment, Pediatric Evaluation of Disability Inventory, and Canadian Occupational Performance Measure. Repeated measures analysis of variance indicated a significant decrease in mirror movements in the more-affected (mean difference=0.97; 95% confidence interval [CI]=0.51-1.42; p < 0.001) and less-affected (mean difference=0.71; 95% CI=0.37-1.0; p < 0.001) hands of children after HABIT-ILE; these improvements were maintained at the 3-month follow-up. Moreover, the mirror movement changes observed at the second assessment (T2) were inversely correlated with changes in the assessment of activities of daily living, especially in the less-affected hand. HABIT-ILE decreased the intensity of mirror movements in a group of children with CP. Furthermore, mirror movement changes were associated with bimanual performance and activities of daily living in these children. The intensity of mirror movements decreased in both hands after 2 weeks of Hand and Arm Bimanual Intensive Therapy Including Lower Extremity (HABIT-ILE) training. Mirror movement changes were maintained at the 3-month follow-up after HABIT-ILE. Mirror movement changes were associated with improvements in bimanual performance and activities of daily living.

Dynamics of an atomic system associated with a cavity-optomechanical system

This paper introduces the effective Hamiltonian of two two-level atoms inside a cavity with a movable mirror. The temporal evolution of the output density state that includes the interaction between movable mirror, atoms, and field is obtained. The dynamical properties of the quantum correlations of the system are studied via l1-norm of coherence, Entanglement of Formation (EoF) and Bell non-locality. The results shown that the phenomena of coherence, and non-locality are approached to the degree of entanglement as the initial atomic state is set in an excited state. However, different chaotic behavior is generated for the coherence at the initially mixed state. Overall, the temporal evolution of entanglement is an intermediate correlation that lies in between coherence and normalized Bell non-locality.

Improving the Stochastic Feedback Cooling of a Mechanical Oscillator Using a Degenerate Parametric Amplifier

Cooling of a macroscopic mechanical resonator to extremely low temperatures is a necessary condition to observe a variety of macroscopic quantum phenomena. Here, we study the stochastic feedback cooling of a mechanical resonator in an optomechanical system with a degenerate optical parametric amplifier (OPA). In the bad-cavity limit, we find that the OPA can enhance the cooling of the movable mirror in the stochastic feedback cooling scheme. The movable mirror can be cooled from 132 mK to 0.033 mK, which is lower than that without the OPA by a factor of about 5.

Two‐Photon Nanomachining of a Micromechanically Enhanced Optical Cavity Sensor on an Optical Fiber Tip

Herein, a two‐photon nanostructuring process that is employed to monolithically integrate dynamic three‐dimensional (3D) micromechanical features into Fabry–Pérot cavity (FPC) sensors on an optical fiber tip is demonstrated. These features represent a breakthrough in the integration and fabrication capabilities of micro optomechanical devices and systems. The demonstrated dynamic optical surface enables directional thin‐film deposition onto obscured areas. The rotation of the dynamically movable mirror to deposit a thin reflective coating onto the inner surfaces of a FPC with curved geometry is leveraged. The reflective coating in conjunction with the dynamically rotatable mirror greatly improves the quality factor of the FPC and enables a new class of highly integrated multipurpose sensor systems. A unique open cavity geometry on an optical fiber tip is used to demonstrate temperature and refractive index sensing with sensitivities of 2045 ± 39 nm/RIU and 366 ± 22 pm °C−1, respectively. A gold reflective coating sputtered onto the inner surfaces of the FPC improves the quality factors of the cavity by more than 800%. This technology presents a path forward for utilizing 3D design freedom in micromechanically enhanced optical systems to facilitate versatile processing and advantageous geometries beyond the current state of the art.

Multiphoton Nanosculpting of Optical Resonant and Nonresonant Microsensors on Fiber Tips.

This work presents a multiphoton nanosculpting process that is employed to fabricate three-dimensional (3D) mechanically assisted optical resonant and nonresonant microsensors on fiber tips. The resonant microsensor consists of a complex 3D optical cavity design with submicron resolution and advanced micromechanical features including a hinged, multipositional mirror, a 3D spring body to displace this mirror without deforming it, and adhesive-retaining features for sealing the cavity. These features represent a breakthrough in the integration and fabrication capabilities of micro-optomechanical systems. The demonstrated dynamic optical surface enables directional thin-film deposition onto obscured areas. We leverage the rotation of the dynamically movable mirror to deposit a thin reflective coating onto the inner surfaces of a Fabry–Pérot cavity (FPC) with curved geometry. The reflective coating in conjunction with the dynamically rotatable mirror greatly improves the quality factor of the FPC and enables a new class of highly integrated multipurpose sensor systems. A unique spring body FPC on an optical fiber tip is used to demonstrate pressure sensing with a sensitivity of 38 ± 7 pm/kPa over a range of −80 to 345 kPa. The nonresonant microsensor consists of microblades that spin in response to an incident flow. Light exiting the core of the optical fiber is reflected back into the fiber core at a flow-dependent rate as the blades pass by. The fiber tip flow sensor operates successfully over a range of 9–25 LPM using nitrogen gas and achieves a linear response of 706 ± 43 reflections/LPM over a range of 10.9–12 LPM. The nanostructuring technology presented in this work offers a path forward for utilizing 3D design freedom in micromechanically enhanced optical and optofluidic systems to facilitate versatile processing and advantageous geometries beyond the current state-of-the-art.

409 Diffusion MRI to investigate atypical corticospinal tract microstructure and motor impairments in hemiplegic cerebral palsy

OBJECTIVES/GOALS: Hemiplegic cerebral palsy (HCP) limits the functional ability of one side of the body, but motor impairments are very heterogeneous among children with this diagnosis. The purpose of this study was to evaluate the CST using DTI and tractography analyses as it relates to quantitative measures of the severity of weakness and mirror movements in HCP. METHODS/STUDY POPULATION: Preliminary results include five participants with HCP (2M, 16±7.8 years) and six controls (2M, 12±3.5 years). DTI data were collected using a spin-echo echo-planar imaging sequence with diffusion weighting of b=1000 s/mm2 in 60 different directions and 8 scans without diffusion weighting (b=0 s/mm2). Images were processed with steps of brain extraction, denoising, motion and eddy current correction, and fit with tensors to generate maps of diffusivity metrics. Anatomical landmarks were used to guide probabilistic tractography of the CST for analyses in both the lesioned and non-lesioned hemispheres. To quantify grasp weakness and mirroring severity, participants completed a bilateral assessment of grip strength using handheld force measurement devices and custom MATLAB data acquisition software. RESULTS/ANTICIPATED RESULTS: DTI is a feasible method to evaluate CST microstructure in HCP and typically developing pediatric participants. Spearman correlation analyses, using age and sex as covariates, revealed that for the lesioned hemisphere CST, there were significant positive correlations between grasp weakness severity and mean diffusivity (MD) (Ï=0.66, p=0.038) and between grasp weakness severity and axial diffusivity (AD) (Ï =0.68, p=0.030). There was not a significant correlation between grasp weakness severity and fractional anisotropy (FA) (Ï =-0.47, p=0.166). For the non-lesioned hemisphere CST, there was a significant positive correlation between mirroring severity and radial diffusivity (RD) (Ï =0.70, p=0.023). There was not a significant correlation between mirror movement severity and FA (Ï =-0.41, p=0.2361). DISCUSSION/SIGNIFICANCE: The correlations demonstrated here show a potential relationship between CST microstructure and the severity of hand impairments in HCP. While these relationships between CST diffusivity properties and hand function are preliminary, they provide the first steps to better understand underlying neural mechanisms for motor impairments in HCP.