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1.
J Orthop ; 54: 158-162, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-38586599

RESUMEN

Background: The health benefits of physical activity are well recognised. This study assessed whether golfers were more physically active after lower limb arthroplasty when compared to those that did not play golf (primary outcome). In addition pre and postoperative changes in health-associated quality of life (HAQoL) and joint specific outcomes between golfers and none golfers were assessed (secondary outcomes). Methods: There were 304 patients [THA (n = 155) or TKA (n = 149)] prospectively registered during a 4-month period undergoing lower limb arthroplasty. The mean age was 70.0 (range 37-92, standard deviation 10.2) years and included 188 (61%) females and 120 (39%) males. They completed pre and postoperative questionnaires assessing recreational activity, physical activity, HAQoL (EuroQol [EQ]), joint specific health (Oxford scores), and satisfaction. Results: Golfers (n = 33, 10.9%) were more likely to achieve longer than 3 hours of moderate activity during a week (48.5% vs 38.0%, odds ratio (OR) 3.4, p = 0.045) and achieved their recommended activity level (96.8% vs 77.7%, OR 8.6, p = 0.015) compared to non-golfers following arthroplasty. Postoperative EQ5D (p = 0.034) and EQVAS (p = 0.019) were significantly greater in golfers. The joint specific Oxford hip score was greater in golfers compared to non-golfers (mean difference 5.6, p = 0.022), however no difference was observed in the Oxford knee score following TKA (p = 0.495). Conclusion: Golfers were more likely to achieve their weekly recommended level of physical activity and had a greater HAQoL relative to those that did not play golf following lower limb arthroplasty. More specifically after THA golfers also had a greater postoperative joint specific outcome, but no such advantage was observed in those following TKA. Evidence Level: Level II, diagnostic study.

2.
PLoS One ; 19(3): e0299870, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38478487

RESUMEN

Bias and discrimination in appointment processes such as hiring decisions (and analogous selection procedures for performance evaluations, promotions, scholarships, and awards), are quantified statistically via the binomial distribution. These statistical measures are described and an easily used webapp for calculating them is provided. The measures considered include the likelihood that a given number of appointments arose from a fair process and the likelihood that an existing process would give rise to a fair outcome if it were repeated. These methods are illustrated by applying them to sex (including gender) discrimination and racial discrimination in senior appointments in the Australian university sector; both conscious and unconscious biases are included. Significant sex discrimination is found to have existed in the appointments of university chief executives (Vice Chancellors) who were in office in 2018, but with a moderate chance that current processes will yield fair outcomes in the future. However, there is no evidence of strong sex discrimination in the country's eight main research universities for senior appointments (i.e., Faculty Deans and members of their governing Boards or Senates) for those in office as of 2021. However, at the same dates, extreme racial discrimination was implicit in the selection procedures for both Vice Chancellors and senior appointments in all these universities. The University of Sydney's senior appointments were found to have had the most racially biased outcomes among the country's eight main research universities. Significantly, there is negligible statistical likelihood of achieving racially unbiased outcomes in the future in any of the contexts considered, unless the selection procedures are significantly modified.


Asunto(s)
Docentes , Racismo , Humanos , Australia , Citas y Horarios , Universidades
3.
J Clin Periodontol ; 51(1): 33-42, 2024 01.
Artículo en Inglés | MEDLINE | ID: mdl-37735867

RESUMEN

AIM: To develop and validate a new health-related quality of life measure to capture a wide range of gum-related impacts. MATERIALS AND METHODS: The measure was developed using a multi-stage approach and a theoretical model. Development involved semi-structured interviews, pilot testing, cross-sectional analysis among a general population (n = 152) to assess psychometric properties and test-retest reliability among a subsample (n = 27). RESULTS: Psychometric analysis supports the validity and reliability of the measure's impact scale. The measure has excellent internal reliability (nearly all item-total correlations above .4; Cronbach's alpha between .84 and .91 for subscales), with test-retest reliability also performing well (Intra-class correlation coefficient [ICC] of .91-.97 for subscales). Good content validity (indicated by large standard deviations for item and total scores) and construct validity (correlations of .54-.73 with global gum health rating for subscales, all p < .05) were also observed. Qualitative and quantitative data indicate that people with gum health-related symptoms experience different degrees of discomfort and impacts caused by their condition. CONCLUSIONS: The gum health experience questionnaire holds substantial promise as a measure of gum-related quality of life in people across the gum health-disease continuum. Further face validity, refining and reducing the number of items and longitudinal studies to test evaluative properties are required before the measure can be used with confidence.


Asunto(s)
Enfermedades de las Encías , Calidad de Vida , Humanos , Reproducibilidad de los Resultados , Psicometría , Estudios Transversales , Encuestas y Cuestionarios
4.
Int J Biometeorol ; 68(3): 427-434, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38147120

RESUMEN

The aim of this study was to determine effects of parity (primiparous vs. multiparous), seasonal heat stress at calving (summer vs. winter), and time postpartum on some parameters associated with colostrum quality in Holstein cows reared in the Sonoran Desert ecosystem. Forty-seven cows (11 primiparous and 36 multiparous) expected to calve during summer, and 46 cows during winter (14 primiparous and 32 multiparous) were randomly selected. Management and feeding before and after parturition were similar for cows in both seasons. After parturition, colostrum from all cows was evaluated for volume, weight, temperature, density, and content of fat, protein, solids non-fat (SNF), and immunoglobulins (IGG). Data were analyzed with a model that included effects of parity status, calving season, and time postpartum, as well as all interactions. Colostrum produced in summer was warmer (P < 0.01) by almost 6 °C than winter colostrum, while colostrum from multiparous was warmer (P = 0.02) by 1.2 °C than that produced by primiparous cows. Colostrum volume and weight were not impacted by parity, calving season or time postpartum. Density, protein, and SNF content in colostrum were higher (P < 0.01) in multiparous vs. primiparous cows, as well as at parturition (0 h postpartum) than at 12 h postpartum (P < 0.01). At calving (0 h), spring colostrum had higher fat content (P < 0.01) and lower (P < 0.01) IGG concentration than that collected in summer, and no difference (P > 0.05) between seasons was observed for these components at 12 h postpartum. Multiparous cows produced colostrum with higher (P < 0.01) IGG concentrations than primiparous cows. In conclusion, only 0-h colostrum and that from multiparous cows was categorized as "Excellent," meanwhile the colostrum produced under summer heat stress was characterized as "Good" with reduced fat content. While the lacteal secretion collected at 12 post-partum still classified as colostrum, substantially lower contents of IGG, protein, fat, and SNF decreased its classification to "Poor" from the classification of "Excellent" at 0 h postpartum.


Asunto(s)
Calostro , Lactancia , Embarazo , Femenino , Humanos , Bovinos , Animales , Estaciones del Año , Leche , Ecosistema , Periodo Posparto , Inmunoglobulina G
5.
Ann R Coll Surg Engl ; 105(8): 692-708, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37906978

RESUMEN

INTRODUCTION: Sustainability in healthcare is a rapidly developing area of research with recent formal recognition from institutions around the world. We completed an update of a systematic review published in 2020. The aims of this review were to determine the reported carbon footprints of surgical operations in hospitals worldwide, identify variations in reported carbon footprints and highlight carbon hotspots associated with surgery. METHODS: A systematic review was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. The MEDLINE®, Embase® and Cochrane Library databases were searched, and eligibility criteria applied. The study characteristics, scope of product inventory and results were extracted and synthesised. A quality assessment of each study was completed to inform the reliability of the research. RESULTS: 1,308 articles were identified and 7 met the inclusion criteria for the review. The carbon footprint ranged from 28.49kg to 505.1kg carbon dioxide equivalents (CO2e). Medical devices and consumables were the greatest contributor to emissions, with material production and manufacture representing the majority of this carbon hotspot. There were significant methodological limitations and a lack of consistency in carbon footprint calculations between studies. CONCLUSIONS: This systematic review identifies medical devices and consumables as the largest carbon hotspot where healthcare providers should target their sustainability initiatives. Nevertheless, the number of studies was limited and the quality of the evidence was weak. We recommend that researchers in healthcare sustainability develop international standards for conducting and reporting such studies. This would allow for comparison of individual studies and facilitate meta-analysis of cumulative evidence. A reliable evidence base is a prerequisite for identifying optimal interventions to ensure societal benefits.


Asunto(s)
Huella de Carbono , Hospitales , Humanos , Reproducibilidad de los Resultados
6.
J Neurosci Methods ; 398: 109958, 2023 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-37661056

RESUMEN

BACKGROUND: Characterization of normal arousal states has been achieved by fitting predictions of corticothalamic neural field theory (NFT) to electroencephalographic (EEG) spectra to yield relevant physiological parameters. NEW METHOD: A prior fitting method is extended to distinguish conscious and unconscious states in healthy and brain injured subjects by identifying additional parameters and clusters in parameter space. RESULTS: Fits of NFT predictions to EEG spectra are used to estimate neurophysiological parameters in healthy and brain injured subjects. Spectra are used from healthy subjects in wake and sleep and from patients with unresponsive wakefulness syndrome, in a minimally conscious state (MCS), and emerged from MCS. Subjects cluster into three groups in parameter space: conscious healthy (wake and REM), sleep, and brain injured. These are distinguished by the difference X-Y between corticocortical (X) and corticothalamic (Y) feedbacks, and by mean neural response rates α and ß to incoming spikes. X-Y tracks consciousness in healthy individuals, with smaller values in wake/REM than sleep, but cannot distinguish between brain injuries. Parameters α and ß differentiate deep sleep from wake/REM and brain injury. COMPARISON WITH EXISTING METHODS: Other methods typically rely on laborious clinical assessment, manual EEG scoring, or evaluation of measures like Φ from integrated information theory, for which no efficient method exists. In contrast, the present method can be automated on a personal computer. CONCLUSION: The method provides a means to quantify consciousness and arousal in healthy and brain injured subjects, but does not distinguish subtypes of brain injury.


Asunto(s)
Lesiones Encefálicas , Estado de Conciencia , Humanos , Estado de Conciencia/fisiología , Nivel de Alerta/fisiología , Encéfalo/fisiología , Vigilia/fisiología , Electroencefalografía/métodos
7.
Phys Rev E ; 107(6-1): 064401, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37464602

RESUMEN

The primary visual cortex (V1) is the first cortical area that processes visual information relayed from the thalamus. The topologies permitted in joint ocular dominance (OD), orientation preference (OP), and direction preference (DP) maps in V1 are considered, with the aim of finding a maximally symmetric periodic case that can serve as the basis for perturbations toward natural realizations. It is shown that mutual consistency of the maps selects just two possible such lattice structures, and that one of these is much closer to experiment than the other. This comprises a hexagonal lattice of alternating positive and negative OP singularities, with each unit cell or hypercolumn containing four such singularities, each of which radiates three DP discontinuities that follow OP contours and end at OP singularities of opposite sign. Other DP discontinuities emanate at 90 degrees to the midpoints of the ones that link OP singularities, and cross OP contours perpendicularly. These features explain experimentally observed relationships between DP discontinuities and OP contours, including sudden approximately 90-degree changes of direction in the former.

8.
PLoS One ; 18(4): e0282583, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37027371

RESUMEN

A model of the spatiotemporal evolution of urban areas is developed that simultaneously includes the effects on household utility of geography, population density, income distribution, and household preference for characteristics of dwellings and neighbors. The result is a utility function whose structure is similar to that of the energy of interacting spin systems in external fields. Spatiotemporal housing market evolution then results via transactions driven by increases in utility and changes in numbers of households and dwellings. It is shown that the model successfully predicts formation of monocentric and polycentric urban areas, stratification by wealth, segregation due to preferences for housing or neighbors, and the balance of supply and demand. These results go well beyond those of prior models that each dealt with subsets of these phenomena, and do so within a single, unified framework. Potential generalizations are discussed and further applications are suggested.


Asunto(s)
Vivienda , Características de la Residencia , Humanos , Población Urbana , Dinámica Poblacional , Composición Familiar , Economía
9.
Eur J Orthop Surg Traumatol ; 33(4): 1083-1089, 2023 May.
Artículo en Inglés | MEDLINE | ID: mdl-35362779

RESUMEN

BACKGROUND: Approximately 10% to 20% of patients with joint arthroplasties are golfers. The aim of this study was to assess if being a golfer is associated with functional outcomes, satisfaction or improvement in quality of life (QoL) compared to non-golfers following total knee arthroplasty. METHODS: All patients undergoing primary total knee arthroplasty (TKA) over a one-year period at a single institution were included with one-year postoperative outcomes. Patients were retrospectively followed up to assess if they had been golfers at the time of their surgery. Multivariate linear regression analysis was performed to assess the independent association of preoperative golfing status on postoperative function and health-related outcomes. RESULTS: The study cohort consisted of a total of 514 patients undergoing TKA. This included 223 (43.3%) male patients and 291 (56.7%) female patients, with an overall mean age of 70 (SD 9.5) years. The preoperative Oxford Knee Score (OKS) was significantly higher in golfers when adjusting for confounders (Diff 3.4 [95% CI 1 to 5.8], p = 0.006). There was no difference in postoperative outcomes between golfers and non-golfers. There was however a trend towards a higher Forgotten Joint Score (FJS) in the golfers (difference 9.3, 95% CI - 0.2 to 18.8, p = 0.056). Of the 48 patients who reported being golfers at the time of their surgery, 43 (89.6%) returned to golf and 88.4% of those were satisfied with their involvement in golf following surgery. CONCLUSIONS: Golfers had better preoperative and equal postoperative knee specific function compared to non-golfers. The majority of golfers returned to golf by one year and were satisfied with their involvement in the game. LEVEL OF EVIDENCE: III.


Asunto(s)
Artroplastia de Reemplazo de Rodilla , Osteoartritis de la Rodilla , Humanos , Masculino , Femenino , Anciano , Artroplastia de Reemplazo de Rodilla/efectos adversos , Calidad de Vida , Estudios Retrospectivos , Articulación de la Rodilla/cirugía , Rodilla/cirugía , Osteoartritis de la Rodilla/cirugía , Resultado del Tratamiento
11.
J Foot Ankle Surg ; 62(1): 162-167, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-35868982

RESUMEN

The learning curve to reach technical proficiency for third-generation percutaneous or minimally invasive chevron and Akin osteotomies (PECA/MICA) is recognized to be steep however it is poorly defined in the literature. This study is a retrospective review of the first 58 consecutive PECA cases of a single surgeon. The primary outcome was the number of cases required to reach technical proficiency as defined by the operation time. Secondary outcomes included radiation exposure, radiographic deformity correction, and complication rates. Between November 2017 and March 2019, 61 consecutive PECA cases were performed with outcome data available for 58 of these (95%). Technical proficiency was reached after 38 cases. Operation time and radiation exposure significantly decreased after this transition point (p < .05). There was no difference in complication rate or radiographic deformity correction regardless of position along the learning curve (p > .05). In conclusion, the mean number of cases required to reach technical proficiency in third-generation PECA is 38 cases. The complication rate does not correlate to the number of cases performed, therefore surgeons interested in learning minimally invasive surgery can be reassured that there is unlikely to be an additional risk of harm to a patient during the learning curve.


Asunto(s)
Juanete , Hallux Valgus , Humanos , Hallux Valgus/diagnóstico por imagen , Hallux Valgus/cirugía , Curva de Aprendizaje , Osteotomía , Estudios Retrospectivos , Procedimientos Quirúrgicos Mínimamente Invasivos , Resultado del Tratamiento
12.
Community Dent Health ; 39(4): 218, 2022 Nov 30.
Artículo en Inglés | MEDLINE | ID: mdl-36449009

RESUMEN

Readers will have noticed the ways we have been modernising Community Dental Health this year. In March we dispensed with hard copies of the journal, publishing it only online. This change was in line with our subscribers' reading behaviours and minimised our environmental impact by reducing the carbon footprints of printing, of using paper and of postage. Subscribers can now also access papers as soon as they are accepted, ahead of publication. Our newly commissioned reviews digest key topics in dental public health to help busy readers keep up with emerging knowledge. In addition, our move to prioritise systematic reviews, by accelerating peer review and fast-tracking publication ensures subscribers' confidence that they are reading the most up to date evidence in our discipline.

13.
Neuroimage ; 263: 119622, 2022 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-36096279

RESUMEN

Modeling a natural system such as the brain aims to deepen understanding and to help to explain and link multiple phenomena into a coherent picture. In any specific case, this requires a clear view of the aims of each modeling project, followed by coordinated selection of the model's style and components; theoretical, numerical, and statistical analysis methods; distillation and presentation of results; and resulting well supported conclusions. The ten rules presented here apply to modeling of the brain and other systems and are designed to assist in carrying out integrated modeling with valid and well-supported outcomes that effectively achieve the modeling aims; referees can also use them when assessing the validity of modeling in submitted manuscripts.

14.
Sci Rep ; 12(1): 13740, 2022 08 12.
Artículo en Inglés | MEDLINE | ID: mdl-35961995

RESUMEN

Accumulation of waste in cortical tissue and glymphatic waste clearance via extracellular voids partly drives the sleep-wake cycle and modeling has reproduced much of its dynamics. Here, new modeling incorporates higher void volume and clearance in sleep, multiple waste compounds, and clearance obstruction by waste. This model reproduces normal sleep-wake cycles, sleep deprivation effects, and performance decreases under chronic sleep restriction (CSR). Once fitted to calibration data, it successfully predicts dynamics in further experiments on sleep deprivation, intermittent CSR, and recovery after restricted sleep. The results imply a central role for waste products with lifetimes similar to tau protein. Strong tau buildup is predicted if pathologically enhanced production or impaired clearance occur, with runaway buildup above a critical threshold. Predicted tau accumulation has timescales consistent with the development of Alzheimer's disease. The model unifies a wide sweep of phenomena, clarifying the role of glymphatic clearance and targets for interventions against waste buildup.


Asunto(s)
Enfermedad de Alzheimer , Proteínas tau , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/metabolismo , Humanos , Sueño , Privación de Sueño/metabolismo , Proteínas tau/metabolismo
15.
Community Dent Health ; 39(1): 3, 2022 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-35235721

RESUMEN

Welcome to the first issue of Community Dental Health to be published online only. The journal has been marching ahead now for many years and has reached unprecedented levels of recognition in several aspects of quality. Our Impact Factor (a measure of how often our papers are cited) has risen to its highest ever level of 1.349. A record 383 manuscripts were submitted last year, and as we can only publish 11% of this number, peer review and natural selection combine so that only the very best papers reach the readers.


Asunto(s)
Políticas Editoriales , Factor de Impacto de la Revista , Humanos
16.
Neurochirurgie ; 68(3): 273-279, 2022 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-34998798

RESUMEN

OBJECTIVE: To define the prognostic factors for progression and to determine the impact of the histological grading (according to the World Health Organization) on the progression-free survival (PFS) of filum terminale ependymomas. METHODS: A retrospective chart review of 38 patients with ependymoma of the filum terminale was performed, focusing on demographic data, preoperative symptoms, tumor size, quality of resection, presence of a tumor capsule, and histological grade. RESULTS: Gross total resection (GTR) was achieved in 30 patients (78.9%). Histopathological analysis found 21 (55.3%) myxopapillary grade I ependymoma (MPE), 16 (42.1%) ependymoma grade II (EGII), and 1 (2.6%) ependymoma grade III. There was no significant difference between the mean±SD volume of MPE (5840.5±5244.2mm3) and the one of EGII (7220.3±6305.9mm3, p=0.5). The mean±SD follow-up was 54.1±38.4 months. At last follow-up, 30 (78.9%) patients were free of progression. In multivariate analysis, subtotal resection (p=0.015) and infiltrative tumor (p=0.03) were significantly associated with progression. The PFS was significantly higher in patients with encapsulated tumor than in patients with infiltrative tumor (log-rank p=0.01) and in patients who had a GTR in comparison with those who had an incomplete resection (log-rank p=0.05). There was no difference in PFS between patient with MPE and EGII (p=0.1). CONCLUSION: The progression of ependymoma of the filum terminale highly depends on the quality of resection, and whether the tumor is encapsulated. Except for anaplastic grade, histopathological type does not influence progression.


Asunto(s)
Cauda Equina , Ependimoma , Neoplasias de la Médula Espinal , Adulto , Cauda Equina/patología , Cauda Equina/cirugía , Ependimoma/diagnóstico , Ependimoma/patología , Ependimoma/cirugía , Humanos , Pronóstico , Supervivencia sin Progresión , Estudios Retrospectivos , Neoplasias de la Médula Espinal/cirugía , Resultado del Tratamiento
17.
Biol Cybern ; 116(1): 33-52, 2022 02.
Artículo en Inglés | MEDLINE | ID: mdl-34773503

RESUMEN

Physiologically based neural field theory (NFT) is extended to encompass cortical plasticity dynamics. An illustrative application is provided which treats the evolution of the connectivity of left- and right-eye visual stimuli to neuronal populations in the primary visual cortex (V1), and the initial, linear phase of formation of approximately one-dimensional (1D) ocular dominance columns (ODCs) that sets their transverse spatial scale. This links V1 activity, structure, and physiology within a single theory that already accounts for a range of other brain activity and connectivity phenomena, thereby enabling ODC formation and many other phenomena to be interrelated and cortical parameters to be constrained across multiple domains. The results accord with experimental ODC widths for realistic cortical parameters and are based directly on a unified description of the neuronal populations involved, their connection strengths, and the neuronal activity they support. Other key results include simple analytic approximations for ODC widths and the parameters of maximum growth rate, constraints on cortical excitatory and inhibitory gains, elucidation of the roles of specific poles of the V1 response function, and the fact that ODCs are not formed when input stimuli are fully correlated between eyes. This work provides a basis for further generalization of NFT to model other plasticity phenomena, thereby linking them to the range multiscale phenomena accounted for by NFT.


Asunto(s)
Predominio Ocular , Corteza Visual , Plasticidad Neuronal , Corteza Visual Primaria , Corteza Visual/fisiología
18.
J Exp Orthop ; 8(1): 113, 2021 Dec 04.
Artículo en Inglés | MEDLINE | ID: mdl-34862946

RESUMEN

PURPOSE: The Forgotten Joint Score (FJS-12) is a valid tool in the evaluation of patients undergoing hip arthroscopy, assessing the unique concept of joint awareness in the setting of a patient's hip pathology. The preoperative burden on patients' mental wellbeing of impaired joint function or symptoms is well established. The purpose of this study was to determine patients' awareness of their hip joint whilst awaiting hip arthroscopy for femoroacetabular impingement, to explore any association between joint awareness and mental health status, and to determine whether this relates to time spent waiting for arthroscopy preoperatively. METHODS: A prospective database of patients undergoing hip arthroscopy between January 2018 and November 2020 was analysed. All patients with a diagnosis of femoroacetabular impingement (FAI) undergoing arthroscopic treatment were included. Questionnaires included the FJS-12, twelve item international hip outcome tool (iHOT-12), EuroQol 5D-5L (EQ-5D-5L) and the Tegner activity score. Pearson's correlation coefficient was used to assess relationships between continuous variables. RESULTS: Preoperative functional outcomes were completed by 81 patients (97.5%) prior to undergoing hip arthroscopy. Median preoperative FJS-12 score was 16.67 (IQR 8.33 - 29.68). Forty-four patients reported any level of anxiety/depression preoperatively (54.3%). Preoperative FJS-12 showed a significant negative correlation with worsening mental health status (r = - 0.359, p <  0.001), and a significant positive correlation with EQ-5D-5L (r = 0.445, p <  0.001). The duration of symptoms or time on the waiting list did not correlate with increased joint awareness or worsened mental health. CONCLUSION: Joint awareness is high when awaiting hip arthroscopy for FAI. Increasing levels of joint awareness correlate with poorer mental health status and poorer quality of life measures, however these parameters do not seem to be associated with increased duration of symptoms prior to surgery or time on the waiting list for surgery.

19.
R Soc Open Sci ; 8(12): 211562, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34966557

RESUMEN

The propagator, or Green function, of a class of neural activity fields and of haemodynamic waves is evaluated exactly. The results enable a number of related integrals to be evaluated, along with series expansions of key results in terms of Bessel functions of the second kind. Connections to other related equations are also noted.

20.
Phys Rev E ; 104(3-1): 034411, 2021 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-34654199

RESUMEN

The problem of finding a compact natural representation of brain dynamics and connectivity is addressed using an expansion in terms of physical spatial eigenmodes and their frequency resonances. It is demonstrated that this discrete expansion via the system transfer function enables linear and nonlinear dynamics to be analyzed in compact form in terms of natural dynamic "atoms," each of which is a frequency resonance of an eigenmode. Because these modal resonances are determined by the system dynamics, not the investigator, they are privileged over widely used phenomenological patterns, and obviate the need for artificial discretizations and thresholding in coordinate space. It is shown that modal resonances participate as nodes of a discrete spectral network, are noninteracting in the linear regime, but are linked nonlinearly by wave-wave coalescence and decay processes. The modal resonance formulation is shown to be capable of speeding numerical calculations of strongly nonlinear interactions. Recent work in brain dynamics, especially based on neural field theory (NFT) approaches, allows eigenmodes and their resonances to be estimated from data without assuming a specific brain model. This means that dynamic equations can be inferred using system identification methods from control theory, rather than being assumed, and resonances can be interpreted as control-systems data filters. The results link brain activity and connectivity with control-systems functions such as prediction and attention via gain control and can also be linked to specific NFT predictions if desired, thereby providing a convenient bridge between physiologically based theories and experiment. Amplitudes of modes and resonances can also be tracked to provide a more direct and temporally localized representation of the dynamics than correlations and covariances, which are widely used in the field. By synthesizing many different lines of research, this work provides a way to link quantitative electrophysiological and imaging measurements, connectivity, brain dynamics, and function. This underlines the need to move between coordinate and spectral representations as required. Moreover, standard theoretical-physics approaches and mathematical methods can be used in place of ad hoc statistical measures such as those based on graph theory of artificially discretized and decimated networks, which are highly prone to selection effects and artifacts.

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