New Framework for Understanding Cross-Brain Coherence in Functional Near-Infrared Spectroscopy (fNIRS) Hyperscanning Studies

Despite the growing body of functional near-infrared spectroscopy (fNIRS) hyperscanning studies, the assessment of coupling between two neural signals using wavelet transform coherence (WTC) seems to ignore the directionality of the interaction. The field is currently lacking a framework that allows researchers to determine whether a high coherence value obtained using a WTC function reflects in-phase synchronization (i.e., neural activation is seen in both members of the dyad at the same time), lagged synchronization (i.e., neural activation is seen in one member of the dyad prior to the other member), or anti-phase synchronization (i.e., neural activation is increased in one member of the dyad and decreased in the other). To address this need, a complementary and more sensitive approach for analyzing the phase coherence of two neural signals is proposed in this work. The toolbox allows investigators to estimate the coupling directionality by classifying the phase angle values obtained using traditional WTC into in-phase synchronization, lagged synchronization, and anti-phase synchronization. The toolbox also allows researchers to assess how the dynamics of interactions develop and change throughout the task. Using this novel WTC approach and the toolbox will advance our understanding of complex social interactions through their uses in fNIRS hyperscanning studies.

Peroneal muscle response to single-leg drop-jump and unexpected leg-drop in young and middle-aged adults before and after one session of neuromuscular training

BACKGROUND

Changes in neuromuscular ability in middle age (MA) may lead to deterioration of postural control. The aim of this study was to investigate the anticipatory response of the peroneus longus muscle (PL) to landing after a single-leg drop-jump (SLDJ), and its postural response after an unexpected leg-drop in MA and young adults. A second aim was to investigate the influence of neuromuscular training on PL postural responses in both age groups.

METHODS

Twenty-six healthy MA (55.3 ± 4 years) and 26 healthy young adults (26.3 ± 3.6 years) participated in the study. Assessments were performed before (T0) and after (T1) PL EMG biofeedback (BF) neuromuscular training. Subjects performed SLDJ, and PL EMG activity in preparation for landing (% of flight time) was calculated. To measure PL time to activation onset and time to peak activation in response to an unexpected leg-drop, subjects stood on a customized trapdoor device that produced a sudden 30° ankle inversion.

RESULTS

Before training, the MA group showed significantly shorter PL activity in preparation for landing compared to the young adults (25.0% vs. 30.0%, p = 0.016), while after training there was no difference between the groups (28.0% vs. 29.0%, p = 0.387). There were no differences between groups in peroneal activity after the unexpected leg-drop before and after training.

CONCLUSIONS

Our results suggest that automatic anticipatory peroneal postural responses are decreased at MA, whereas reflexive postural responses appear to be intact in this age group. A short PL EMG-BF neuromuscular training may have an immediate positive effect on PL muscle activity at MA. This should encourage the development of specific interventions to ensure better postural control in this group.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05006547.

Young, but not in the dark-The influence of reduced lighting on gait stability in middle-aged adults

BACKGROUND

The aim of this study was to investigate the effects of walking in reduced lighting with or without performing a secondary cognitive task on gait dynamics in middle-aged adults and to compare them with young and old adults.

METHODS

Twenty young (age 28.8±4.1), 20 middle-aged (age 50.2±4.4), and 19 elderly (age 70.7±4.2) subjects participated in the study. Subjects walked on an instrumented treadmill at a self-determined pace under four conditions in randomized order: (1) walking in usual lighting (1000 lumens); (2) walking in near-darkness (5 lumens); (3) walking in usual lighting with a serial-7 subtraction dual-task; and (4) walking in near-darkness with a serial-7 subtraction dual-task. Variability in stride time and variability in the trajectory of the center of pressure in the sagittal and frontal planes (anterior/posterior and lateral variability) were measured. Repeated measures ANOVA and planned comparisons were used to determine the effects of age, lighting conditions, and cognitive task on each gait outcome.

RESULTS

Under usual lighting, stride time variability and anterior/posterior variability of the middle-aged subjects were similar to those of the young and lower than those of the old. The lateral variability of the middle-aged subjects was higher than that of young adults under both lighting conditions. Similar to the older adults, the middle-aged participants increased their stride time variability when walking in near-darkness, but they were the only ones to exhibit increased lateral variability and anterior/posterior variability in near-darkness. Young adult gait was not affected by lighting, and concurrent performance of a cognitive task while walking did not affect gait stability in all groups under any of the lighting conditions.

CONCLUSIONS

Gait stability decreases in middle age when walking in the dark. Recognition of functional deficits in middle age could promote appropriate interventions to optimize aging and reduce fall risk.

Can stabilization analysis following a single leg drop jump be compared between young and middle-aged adults

We aimed to verify whether the computational approaches previously proposed to analyze stability after a single-leg drop-jump (SLDJ) could be applied to a population of middle-aged adults. Fifteen middle-aged (56.4 ± 4.6 years) and 15 young adults (26.7 ± 3.9 years) performed five SLDJs. Stabilization measurements included (1) time to stabilization (TTS) based on vertical ground reaction force (GRF) (TTSv) and a fixed stabilization threshold; (2) TTS based on medio-lateral GRF (TTSml) using five different methods to preprocess the signal and stabilization threshold; (3) early medio-lateral stabilization- the averaged absolute values of the GRF in 0.2-1.4 s post-landing; (4) late medio-lateral stabilization - the averaged absolute values of the GRF at 1 s-5 s after landing. TTSv showed longer TTS values in middle-aged participants. In addition, middle-aged adults showed greater sway in late stabilization. However, TTSml values varied considerably between calculation methods, and early stabilization showed no significant differences between groups except in the first 0.2 s after landing. The results of the current study suggest that TTS calculations are sensitive to signal and threshold selection, and to the processing method. Calculations based on a fixed threshold are more appropriate for studying dynamic postural stability in middle age. With appropriate method selection, a decreased stabilizing performance can be demonstrated in middle-aged adults compared to young adults.

Glial Derived TGF-β Instructs Axon Midline Stopping

A fundamental question that underlies the proper wiring and function of the nervous system is how axon extension stops during development. However, our mechanistic understanding of axon stopping is currently poor. The stereotypic development of the Drosophila mushroom body (MB) provides a unique system in which three types of anatomically distinct neurons (γ, α’/β’, and α/β) develop and interact to form a complex neuronal structure. All three neuronal types innervate the ipsi-lateral side and do not cross the midline. Here we find that Plum, an immunoglobulin (Ig) superfamily protein that we have previously shown to function as a TGF-β accessory receptor, is required within MB α/β neurons for their midline stopping. Overexpression of Plum within MB neurons is sufficient to induce retraction of α/β axons. As expected, rescue experiments revealed that Plum likely functions in α/β neurons and mediates midline stopping via the downstream effector RhoGEF2. Finally, we have identified glial-derived Myoglianin (Myo) as the major TGF-β ligand that instructs midline stopping of MB neurons. Taken together, our study strongly suggests that TGF-β signals originating from the midline facilitate midline stopping of α/β neuron in a Plum dependent manner.

Upper Bounds for the Total π-Electron Energy of Benzenoid Hydrocarbons and Their Relations

Upper bounds for the total π-electron energy of benzenoid hydrocarbons, depending on the number of carbon atoms and carbon-carbon bonds, are examined and several of their properties established.

Origin of Biomolecular Chirality. Analysis of Frank’s Model

Frank ’s model for biochemical L-D stereoselection is examined and approximate analytical solutions of its generalized form are deduced, extending earlier results of Frank and Tennakone.

Number of Kekulé Structures as a Function of the Number of Hexagons in Benzenoid Hydrocarbons

The possible values of the number of Kekulé structures ( K) of a benzenoid hydrocarbon with h hexagons are examined. For normal benzenoids the lowest possible value of K is h + 1. Based on this result the benzenoid systems which have K up to 24 are determined. A number of results concerning enumeration and classification of benzenoid systems is reported.

Topological Resonance Energy is Real

It is proved that the zeros of the matching polynomial of a graph are real. Hence, topological resonance energy is also a real quantity.

Number of Kekulé Structures of Five-Tier Strips

Benzenoid systems called regular t-tier strips are examined. 27 classes of benzenoids belonging to the regular 5-tier strips can be distinguished. Combinatorial formulas are developed for the number of Kekulé structures of all these classes.

A Graph-theoretical Analysis of the HOMO-LUMO Separation in Conjugated Hydrocarbons

Graph-theoretical rules concerning the HOMO-LUMO separation in conjugated hydrocarbons are given. It has been found that a closure of odd-membered rings will not essentially change the HOMO-LUMO energy gap (ΔΕ). However, ΔΕ will be shifted down or up depending whether a (4m + 1)-or (4m + 3)-ring is closed. A closure of an even-membered ring increase the value of ΔΕ in the case of (4m + 2)- and decrease ΔΕ value in the case of (4m)-cycles if delocalized rings are formed. The effect is opposite if quinonoid rings are generated.

A Novel ROP/RAC effector links cell polarity, root-meristem maintenance, and vesicle trafficking

ROP/RAC GTPases are master regulators of cell polarity in plants, implicated in the regulation of diverse signaling cascades including cytoskeleton organization, vesicle trafficking, and Ca(2+) gradients [1-8]. The involvement of ROPs in differentiation processes is yet unknown. Here we show the identification of a novel ROP/RAC effector, designated interactor of constitutive active ROPs 1 (ICR1), that interacts with GTP-bound ROPs. ICR1 knockdown or silencing leads to cell deformation and loss of root stem-cell population. Ectopic expression of ICR1 phenocopies activated ROPs, inducing cell deformation of leaf-epidermis-pavement and root-hair cells [3, 5, 6, 9]. ICR1 is comprised of coiled-coil domains and forms complexes with itself and the exocyst vesicle-tethering complex subunit SEC3 [10-13]. The ICR1-SEC3 complexes can interact with ROPs in vivo. Plants overexpressing a ROP- and SEC3-noninteracting ICR1 mutant have a wild-type phenotype. Taken together, our results show that ICR1 is a scaffold-mediating formation of protein complexes that are required for cell polarity, linking ROP/RAC GTPases with vesicle trafficking and differentiation.

Binary coding of Kekulé structures of catacondensed benzenoid hydrocarbons

An algorithm is described by means of which the Kekulé structures of a catacondensed benzenoid molecule (with h hexagons) are transformed into binary codes (of length h). By this, computer-aided manipulations with, and memory-storage of Kekulé structures are much facilitated. Any Kekulé structure can easily be recovered from its binary code.

Modeling boiling points of cycloalkanes by means of iterated line graph sequences

A class of models for predicting boiling points of cycloalkanes is put forward, based on iterated line graphs L(i), i = 1, 2,., of the molecular graph G = L(0). Let m(i) be the number of edges of L(i), i = 0, 1, 2,. The models analyzed are of the form a(0)m(i)()(0) + a(1)m(i)(1) + a(2)m(i)(2) +. + a(k)m(ik) + b. Our optimal QSPR formulas contain m(0), m(1), m(2), m(3), and/or m(4) but never m(5) and m(6). Their precision is as good as or better than the approximations recently reported by Rücker and Rücker (J. Chem. Inf. Comput. Sci. 1999, 39, 788-802).

Quest for molecular graphs with maximal energy: a computer experiment

If lambda(1), lambda(2),..., lambda(n) are the eigenvalues of a graph G, then the energy of G is defined as E(G) = the absolute value of lambda(1) + the absolute value of lambda(2) +.... + the absolute value of lambda(n). If G is a molecular graph, representing a conjugated hydrocarbon, then E(G) is closely related to the respective total pi-electron energy. It is not known which molecular graph with n vertices has maximal energy. With the exception of m = n - 1 and m = n, it is not known which molecular graph with n vertices and m edges has maximal energy. To come closer to the solution of this problem, and continuing an earlier study (J. Chem. Inf. Comput. Sci. 1999, 39, 984-996, ref 7), we performed a Monte Carlo-type construction of molecular (n,m)-graphs, recording those with the largest (not necessarily maximal possible) energy. The results of our search indicate that for even n the maximal-energy molecular graphs might be those possessing as many as possible six-membered cycles; for odd n such graphs seem to prefer both six- and five-membered cycles.

On walks in molecular graphs

Walks in molecular graphs and their counts for a long time have found applications in theoretical chemistry. These are based on the fact that the (i, j)-entry of the kth power of the adjacency matrix is equal to the number of walks starting at vertex i, ending at vertex j, and having length k. In recent papers (refs 13, 18, 19) the numbers of all walks of length k, called molecular walk counts, mwc(k), and their sum from k = 1 to k = n - 1, called total walk count, twc, were proposed as quantities suitable for QSPR studies and capable of measuring the complexity of organic molecules. We now establish a few general properties of mwc's and twc among which are the linear dependence between the mwc's and linear correlations between the mwc's and twc, the spectral decomposition of mwc's, and various connections between the walk counts and the eigenvalues and eigenvectors of the molecular graph. We also characterize the graphs possessing minimal and maximal walk counts.

Relation between distance-based topological indices

The pi-index of the line graph of the molecular graph of an alkane is shown to be related to the pi, Harary, and reciprocal Wiener indices of that alkane. Thus a mathematical relation between several distance-based topological indices is obtained.

An algorithm for the calculation of the hyper-Wiener index of benzenoid hydrocarbons

An algorithm for the calculation of the hyper-Wiener index (WW) of benzenoid hydrocarbons (both cata- and pericondensed) is described, based on the consideration of pairs of elementary cuts of the corresponding benzenoid graph B. A pair of elementary cuts partitions the vertices of B into four classes. WW is expressed as a sum of terms of the form n11n22 + n12n21, each associated with a pair of elementary cuts; nrs, r, s = 1, 2 are the numbers of vertices in the respective four classes. The algorithm proposed enables a relatively easy calculation of WW, finding expressions for WW of homologous series of benzenoid hydrocarbons, and envisaging the relations between WW and molecular structure.

Presumed ocular myasthenia and micropsia. A case report

A 68-year-old woman presented with diplopia. Fluctuations of dysfunction of lateral rectus muscles in both eyes were detected on consecutive examinations. The diagnosis of ocular myasthenia was proposed. After the initiation of therapy, the patient complained of disturbing micropsia. The micropsia and diplopia were relieved by occlusion of one eye or by a base-out prism over one of the patient's eyeglass lenses. Mechanisms of micropsia are discussed.

Optic nerve compression by carotid arteries in low-tension glaucoma

Low-tension glaucoma (LTG) is manifested by glaucomatous optic nerve damage and visual field loss despite normal intraocular pressure (IOP). We describe 62 patients with classical signs of LTG. Computed tomography (CT) was performed in all patients. In 56 of the patients (90.3%), pathology of the intracavernous carotid arteries adjacent to the intracranial opening of the optic canal could be demonstrated. In 28 patients (45.2%) a clear asymmetry of the optic nerve cupping was found and could be correlated with the severity of the carotid artery pathology. A control group of 24 age-matched patients included five (20.8%) with intracavernous carotid artery calcification and only one (4.2%) with intracavernous ectasia. We suggest that calcification, dilatation and ectasia of the carotid artery into the optic canal may play an important role in the pathogenesis of many cases of LTG. The close proximity of the carotid artery to the optic nerve at this location may result in compressive neuropathy with subsequent glaucomatous damage of the optic nerve head.

Suggested mechanism for acute transient myopia after sulfonamide treatment

This report describes the occurrence of acute transient myopia in a patient treated with sulfonamide. We followed this patient by performing A-scan ultrasonographic ocular measurements documenting the anterior chamber depth, lens thickness, and axial length during the acute and convalescent periods. The outstanding feature in this case was the documented ultrasonographically significant reduction of the anterior chamber depth combined with lens thickening. This could be caused by a forward displacement of the lens as a result of allergic ciliary body edema and rotation. These changes could explain the mechanism of drug-induced transient myopia.

Orbital pseudotumor presenting as acute glaucoma with choroidal and retinal detachment

A 68-year-old woman presented with acute visual loss, elevated intraocular pressure (IOP), and a flat anterior chamber combined with retinal and choroidal detachment. The diagnosis of orbital pseudotumor was based on the patient's poor response to conventional therapy and on computerized tomography and ultrasound findings. After treatment with oral corticosteroids, the inflammatory process, elevated IOP, and choroidal and retinal detachment resolved.

Malignant prolactinoma

Malignant prolactinoma is a rare entity and only a few cases have been published. The diagnostic criteria and the clinical course remain unclear. We present a case of malignant prolactinoma in a woman with a 30-year duration of the disease. In the terminal stage of the disease the prolactinoma metastasized to the left eye, the prolactin level reaching 196000 mU/l. Bromocriptine in high doses was not effective. The response to pergolide was good in the first two years of treatment; thereafter an escape effect was observed. The patient died in a comatose state. A review of previously published cases follows.

Lumbar spine dimensions in paraparetic patients: a 10 year follow up study

Lumbar spinal AP radiographs of 13 C3-T11 paraparetic patients taken at about a 10 year interval were compared. The height (H) and maximum width (W) of the interapophysolaminar spaces (IALS), the width of the vertebral bodies at their waist (V) and the relationship between them showed minimal change over the follow up period. The difference between the late and early mean IALS height values increased caudally but was statistically significant only below L5. Subjective evaluation of the consecutive x-ray films revealed few new degenerative abnormalities. It is concluded that the normal aging process, which includes horizontal spreading of the lumbar vertebral bodies and narrowing of the lumbar spinal canal, is not accelerated by paraparesis and may even be retarded by relative immobilization.

Nd:YAG laser trabeculopuncture in angle-recession glaucoma

Nd:YAG laser trabeculopuncture (YLT) was performed in 12 eyes of 12 patients with angle-recession glaucoma. Confluent, 1-clock-hour trabeculotomy was attempted in all eyes. The calculated average laser energy was 181 +/- 86 mJ. Where possible, the midtrabecular meshwork was treated, preferably at the superior half. After a mean follow up of 12.0 +/- 5.6 months, intraocular pressure (IOP) was controlled (less than or equal to 19 mm Hg) in five eyes (41.7%). YLT was associated with blood reflux during or after treatment in all successfully treated eyes. In eyes that failed, blood reflux could be detected in only two of seven eyes (28.6%). YLT failed to control IOP in all five eyes that had angle-recession for 360 degrees. Following YLT, IOP rose in two eyes (16.6%), minimal hyphema occurred in one eye, and temporary flare and cells developed in the anterior chamber in all eyes. Six eyes (50%) required glaucoma surgery (four had trabeculectomy and two had Molteno implant surgery). We recommend YLT only for selected cases of uncontrolled angle-recession glaucoma in which at least part of the trabecular meshwork by gonioscopy appears to maintain its anatomical structure, permitting penetration into Schlemm's canal.

The Range of the Wiener Index and Its Mean Isomer Degeneracy

Sharp lower and upper bounds for the Wiener index (W) of a connected (n, m)-graph are reported; n = number of vertices, m = number of edges. The mean isomer degeneracy of W is estimated and is shown to unboundedly increase with increasing n. Thus the isomer-discriminating power of W is confirmed to be very low in the case of large molecules.

Identification, prevention, and treatment of silicone oil pupillary block after an inferior iridectomy

We treated two patients in whom silicone oil pupillary block developed despite a patent inferior iridectomy. The clinical characteristics of this complication were a deep anterior chamber, specular reflexes from the iris surface, identification by biomicroscopy of aqueous trapped inferiorly in the vitreous cavity, and no convection currents in the anterior chamber. This complication may be prevented by early face-down positioning of the patient after the operation, and the avoidance of large, centrally located, inferior iridectomies. We recommend that the iridectomy be placed peripherally no larger than 2 mm and propose a new technique for breaking the silicone oil block, which was clearly successful in one of the patients.

Postoperative complications after Molteno implant surgery

We performed Molteno implant surgery in one eye each of 41 patients with uncontrolled glaucoma. Intraocular pressure was controlled (intraocular pressure less than or equal to 18 mm Hg) in 32 eyes (78%). The mean preoperative intraocular pressure was 40 +/- 13.2 mm Hg, whereas the mean postoperative intraocular pressure was 16 +/- 6.6 mm Hg. Patients were followed up for an average of 16 months after the operation. Visual acuity was unchanged in 23 eyes (56%), improved in nine eyes (22%), and poorer in nine eyes (22%). The major complications included shallow anterior chamber and hypotony in six eyes (14.6%), vitreous hemorrhage in two eyes (4.9%), retinal detachment in one eye (2.4%), and malignant glaucoma in two eyes (4.9%). Less grave complications included hyphema in four eyes (9.8%), peripheral choroidal effusion in 15 eyes (36.6%), obstruction of the tube in six eyes (14.6%), recession of the tube into the angle in two eyes (4.9%), erosion of the tube in one eye (2.4%), and Tenon's cyst formation in three eyes (7.3%).

Metastatic thyroid carcinoma masquerading as lacrimal gland tumor

A 56-year-old woman presented with orbital signs and symptoms suggestive of lacrimal gland tumor. An excised biopsy specimen was obtained and showed glandular tissue, which could be confused with lacrimal gland acini. Closer microscopic examination and immunohistochemical studies revealed a metastatic tumor of thyroid gland origin. Initially, there was no identifiable nodule in the thyroid, but 3 months later a thyroid nodule was found by ultrasound and radioisotope scan. The histopathologic appearance of the thyroid nodule was similar to that found in the orbit. This case demonstrates the usefulness of immunohistochemistry in establishing a diagnosis when the microscopic appearance is inconclusive.