322,830 research outputs found
Fractal dimension and clinical neurophysiology fusion to gain a deeper brain signal understanding: A systematic review
No full textFractal dimension (FD) analysis, a powerful tool that has significantly advanced our understanding of brain complexity, evolving from basic geometrical characterization to the nuanced analysis of neurophysiological signals. This review integrates the theoretical foundations of FD calculation with its practical applications in clinical neurophysiology, focusing on the Higuchi method. This method, widely recognized for its effectiveness in analyzing clinical time series datasets, is a crucial aspect of our research. Emphasizing the importance of fractal properties in interpreting brain function, we explore how FD analysis reveals the brain's physiological and pathological states. The review systematically examines FD analysis's role across various neurological conditions, drawing on a meta-analysis of existing literature, including studies on Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, and schizophrenia. Additionally, we discuss its implications in aging and developmental research, particularly in elderly and young populations. By establishing FD analysis, particularly the Higuchi method, as an indispensable tool for evaluating brain dynamics, we highlight its potential for providing new insights and identifying biomarkers for these conditions. This exploration also underscores the ongoing challenges in synthesizing a unified model of brain function and the need for continued development of computational models that emulate the biological brain
An analysis of fMRI signal during voluntary breath hold and carbon dioxide challenge: physiological correction and modeling issues
No full textFunctional MRI data has to deal with physiological phenomena related to respiratory and cardiac functions. Correction techniques can minimize their effects with the risk of discarding relevant information. This is particularly significant when the focus is the study of emotions or ANS-CNS link. Here, we describe a study on the central control of breathing during voluntary breath hold (VBH) and CO2 challenge paradigms. Twenty 3mm thick oblique slices comprising brainstem, putamen, thalamus and cortical areas above corpus callosum were acquired. In VBH study, we compared linear and nonlinear models considering the time course of end-tidal CO2 (PETCO2) (1). Specifically, we used a polynomial static nonlinearity (2) applied to the individual PETCO2 time series within a multiple regression framework. Adjusted R squared (R2-adj) measures were compared at single subject level using different delays (till 12s) and polynomial orders, from 1, i.e. linear, up to 5. Data were analyzed both after applying and without applying retrospective cardiac and respiratory correction (RETROICOR) (3). The R2-adj results show an improvement using the fifth order nonlinearity: this finding is not spatially homogenous and is modified by RETROICOR. The R2-adj was higher without RETROICOR correction with respect to the corrected data, irrespectively of the model. These results indicate a complex relationship between the signal changes related to heartbeat and respiration and the model of PETCO2. The multiple regression analysis show that both the linear and nonlinear models highlight activations in the thalamus, putamen and anterior cingulate with a reduction of significant clusters after RETROICOR. Nonetheless, the nonlinear model applied to corrected data highlight significant clusters in the cingulate cortex, thalamus and pons, indicating a more complex relation of the brain activation with the PETCO2 than that captured by RETROICOR correction.
This observation was supported by an exploratory analysis of CO2 challenges data (block design administration of 3% and 7% concentration levels). Group level Independent Component Analysis (ICA) was performed. The spatial distributions of task-related ICs obtained from both challenges were highly correlated (r=0.7). A similar IC was found from a free breathing task. Interestingly, a nonlinear analysis of IC amplitudes obtained from corrected data, normalized to reflect percent signal change, revealed a super-linear relationship with the CO2 changes in the putamen, thalamus and pons. Overall these results indicate a complex relationship between PETCO2 and BOLD changes, and the need of further exploring the effect of correction techniques for the study of breath control with fMRI
99mTc-MIBI radio-guided minimally invasive parathyroidectomy: experience with patients with normal thyroids and nodular goiters
No full textThe surgical approach to primary hyperparathyroidism (HPT) is changing. In patients with a high probability to be affected by a solitary parathyroid adenoma (PA), a unilateral neck exploration (UNE) or a minimally invasive radio-guided surgery (MIRS) using the intraoperative gamma probe (IGP) technique have recently been proposed. We investigated the role of IGP in a group of 84 patients with primary HPT who were homogeneously evaluated before surgery by a single-day imaging protocol including 99mTcO4/MIBI subtraction scan and neck ultrasound (US) and then operated on by the same surgical team. Quick parathyroid hormone (QPTH) was intraoperatively measured in all cases to confirm successful parathyroidectomy. In 70 patients with scan/US evidence of a single enlarged parathyroid gland (EPG) and with a normal thyroid gland, MIRS was planned. In the other 14 patients, the IGP technique was utilized during a standard bilateral neck exploration (BNE) because of the presence of concomitant nodular goiter (11 cases) or multiglandular disease (MGD) (3 cases). The IGP technique consisted of the following: (1) in the operating room, a low 99mTc-MIBI dose (37 MBq) was injected intravenously during anesthesia induction; (2) subsequently, the patient's neck was scanned with the probe by the surgeon to localize the cutaneous projection of the EPG; (3) in patients who underwent MIRS, the EPG was detected intraoperatively with the probe and removed through a small, 2 to 2.5 cm skin incision; (4) radioactivity was measured on the EPG both in vivo and ex vivo, the thyroid, the background and the parathyroid bed after EPG removal. In patients with concomitant nodular goiter, the radioactivity was also measured on the thyroid nodules. Surgical and pathologic findings were consistent with a single PA in 78 patients, parathyroid carcinoma in 2, and MGD in 4. MIRS was successfully performed in 67 of the 70 patients (97.7%) in whom this approach was planned. It must be pointed out that the IGP technique was particularly useful in detecting the PAs located in ectopic site (5 in the upper mediastinum, 2 at the carotid bifurcation) and deep in the neck (6 in the paratracheal/paraesophageal space). Moreover, MIRS was also successfully performed in the seven patients who had undergone previous parathyroid or thyroid surgery. In the other 3 of 70 patients (4.3%), a conversion to BNE was required because a parathyroid carcinoma (2 cases) and a MGD (1 case) were diagnosed during surgical intervention. It is worth noting that in this latter patient affected by MGD, in contrast with the other patients from our series, QPTH remained elevated after the removal of the preoperatively visualized EPG suggesting the persistence of occult hyperfunctioning parathyroid tissue, and another contralateral EPG was found at BNE. Regarding the group of patients in whom a BNE was planned, the IGP helped the surgeon to localize a supernumerary EPG ectopic in the thymus in a patient with MGD, and to localize a PA ectopic to the right carotid bifurcation in a patient with nodular goiter. However, it has to be pointed out that it was difficult for the surgeon to differentiate intraoperatively with the probe the radioactivity of the EPG from that of thyroid nodule(s) in the other 10 patients with HPT with a concomitant nodular goiter, particularly in 6 patients in whom 99mTc-MIBI uptake was higher in thyroid nodule(s) than in EPG. On the basis of these data we can conclude that: (1) in patients with primary HPT with a high scan/US probability to be affected by a single PA and with a normal thyroid gland, IGP appears to be an useful technique with the aim of performing MIRS; (2) a 99mTc-MIBI dose as low as 37 MBq appears to be adequate to successfully perform MIRS; (3) the measurement of QPTH is strongly recommended in patients with HPT selected for MIRS to confirm complete removal of hyperfunctioning parathyroid tissue; (4) MIRS can be useful also in patients with HPT who previously received parathyroid/thyroid surgery with the aim of limiting surgical trauma at reoperation and minimizing the related risk of complications; (5) with the exception of PA located in ectopic sites, IGP does not seem to be a recommendable technique in patients with HPT concomitant nodular goiter
Functional connectome of arousal and motor brainstem nuclei in living humans by 7 Tesla resting-state fMRI
No full textBrainstem nuclei play a pivotal role in many functions, such as arousal and motor control. Nevertheless, the connectivity of arousal and motor brainstem nuclei is understudied in living humans due to the limited sensitivity and spatial resolution of conventional imaging, and to the lack of atlases of these deep tiny regions of the brain. For a holistic comprehension of sleep, arousal and associated motor processes, we investigated in 20 healthy subjects the resting-state functional connectivity of 18 arousal and motor brainstem nuclei in living humans. To do so, we used high spatial-resolution 7 Tesla resting-state fMRI, as well as a recently developed in-vivo probabilistic atlas of these nuclei in stereotactic space. Further, we verified the translatability of our brainstem connectome approach to conventional (e.g. 3 Tesla) fMRI. Arousal brainstem nuclei displayed high interconnectivity, as well as connectivity to the thalamus, hypothalamus, basal forebrain and frontal cortex, in line with animal studies and as expected for arousal regions. Motor brainstem nuclei showed expected connectivity to the cerebellum, basal ganglia and motor cortex, as well as high interconnectivity. Comparison of 3 Tesla to 7 Tesla connectivity results indicated good translatability of our brainstem connectome approach to conventional fMRI, especially for cortical and subcortical (non-brainstem) targets and to a lesser extent for brainstem targets. The functional connectome of 18 arousal and motor brainstem nuclei with the rest of the brain might provide a better understanding of arousal, sleep and accompanying motor functions in living humans in health and disease
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Structural connectivity of autonomic, pain, limbic, and sensory brainstem nuclei in living humans based on 7 Tesla and 3 Tesla MRI
No full textautonomic, pain, limbic, and sensory processes are mainly governed by the central nervous system, with brainstem nuclei as relay centers for these crucial functions. yet, the structural connectivity of brainstem nuclei in living humans remains understudied. these tiny structures are difficult to locate using conventional in vivo MRI, and ex vivo brainstem nuclei atlases lack precise and automatic transformability to in vivo images. to fill this gap, we mapped our recently developed probabilistic brainstem nuclei atlas developed in living humans to high-spatial resolution (1.7 mm isotropic) and diffusion weighted imaging (DWI) at 7 tesla in 20 healthy participants. to demonstrate clinical translatability, we also acquired 3 Tesla DWI with conventional resolution (2.5 mm isotropic) in the same participants. results showed the structural connectome of 15 autonomic, pain, limbic, and sensory (including vestibular) brainstem nuclei/nuclei complex (superior/inferior colliculi, ventral tegmental area-parabrachial pigmented, microcellular tegmental–parabigeminal, lateral/medial parabrachial, vestibular, superior olivary, superior/inferior medullary reticular formation, viscerosensory motor, raphe magnus/pallidus/obscurus, parvicellular reticular nucleus-alpha part), derived from probabilistic tractography computation. through graph measure analysis, we identified network hubs and demonstrated high intercommunity communication in these nuclei. we found good (r =.5) translational capability of the 7 tesla connectome to clinical (i.e., 3 Tesla) datasets. furthermore, we validated the structural connectome by building diagrams of autonomic/pain/limbic connectivity, vestibular connectivity, and their interactions, and by inspecting the presence of specific links based on human and animal literature. these findings offer a baseline for studies of these brainstem nuclei and their functions in health and disease, including autonomic dysfunction, chronic pain, psychiatric, and vestibular disorders
Hessian-based neck tracing of dendritic spines: a preliminary study on confocal images
No full textAlterations in dendritic spines morphology and topology are known to be implied in several neurodegenerative diseases. However, visualizing and reconstructing the exact morphology of spine necks using conventional confocal imaging is still a challenge. In the light of this, we propose the extension of Hessian matrix eigenvalue analysis for the detection of tubular structures to the problem of 3D neck tracing. In this work we stress the relevance of the tracing procedure initialization, for the novel application of this standard approach to the specific scenario. Preliminary results on confocal microscopy images from ex-vivo human samples allowed to obtain almost 80% of necks keeping an average distance of less than one voxel from the reference segmentation and half of them fully overlapping with it. The preliminary results are promising, since they pave the way towards the development of this model-free solution to accurately trace spine neck
- …
