En el particular contexto filosófico de la Alemania de entreguerras, el joven H. Marcuse llevó a cabo una original recepción en clave marxista de la fenomenología existencial y de la Lebensphilosophie (I). En sus primeros artículos, «Contribuciones a una fenomenología del materialismo histórico» (1928) y «Sobre filosofía concreta» (1929), esa recepción se orientó al proyecto de elaboración de una fenomenología dialéctica y, vinculado con ello, al intento de fundamentar la acción radical en el concepto ontológico de historicidad (Geschichtlichkeit) sin descuidar (...) su componente material (II, III, IV). Asimismo, en la situación de caída (Verfallen) del Dasein, Marcuse va a otorgar una misión primordial a la filosofía concreta (V). (shrink)

Writing about loneliness has been a struggle in the midst of the pandemic. Characterized by loneliness, isolation, anxiety, and fear, the COVID-19 pandemic is an exceptionally challenging time. At various points while navigating this loneliness project amid a particularly lonely time, we lamented the seeming futility of it all. A main goal of developing a Feminist Loneliness Studies in this introduction is to understand the ways that systems of oppression – white supremacy, settler colonialism, anti-queer bias, misogyny, neoliberal capitalism, and (...) so on – create our lonely world. To date, there remains no comprehensive feminist analysis of the structural conditions that both produce and intensify experiences of loneliness. We aim to remedy this gap. That is, we seek to address what a Feminist Loneliness Studies can contribute to understanding the complexities of this complicated emotion. For example, what is the unique loneliness of the feminist killjoy who calls out, or calls in, existing forms of queerphobia, racism, and sexism? What does it mean to be a politicized person and how does that result in both alienation and isolation? What might the relationship be between white supremacy and loneliness? How is loneliness both individual and systemic, and what is the relationship between the two? What distinctive forms of loneliness are created by ableism, sanism, neoliberalism, capitalism, globalization, and the gig economy? Ought loneliness be avoided at all costs? What are the ethics of loneliness? In our introduction to this special issue, we unpack and theorize the potential perils and generative possibilities offered up by this profound emotion. Establishing a Feminist Loneliness Studies provides us with the space we need to begin addressing and comprehending loneliness. (shrink)

Con la obra de los jóvenes hegelianos (Junghegelianer) concluye el período clásico de la filosofía alemana. Bruno Bauer (1809-1882) fue uno de sus máximos exponentes, considerado en muchos aspectos como mentor del movimiento. En el primer apartado del presente artículo, se contextualiza la figura de Bauer en el trasfondo de las disputas generadas en el seno de la escuela hegeliana. A continuación, se analizan con mayor detenimiento dos nociones centrales en su pensamiento, especialmente durante el período comprendido entre 1829 y (...) 1848: su dialéctica de la autoconciencia infinita (unendlichen Selbstbewußtsein) y la forma adoptada por su crítica pura. (shrink)

Loneliness is intimately related to the ongoing epidemics of systemic forms of oppression, including white supremacy, capitalism, heteropatriarchy and settler colonialism. The epidemic of loneliness has only intensified and grown during the isolation engendered by the COVID-19 pandemic. In this article, we aim to think about how children's picturebooks wrestle with explaining loneliness and its antidotes and how these picturebooks are themselves manifestations of ongoing conversations related to Emotional Justice. We conclude by reviewing a number of children's books in order (...) to think about how the picturebook might itself be an artifact that helps to fight feelings of loneliness as well as teaching children and adults alike about the importance of connection. (shrink)

David Lewis is associated with the controversial thesis that some properties are more eligible than others to be the referents of our predicates solely in virtue of those properties’ being more natural; independently, that is, of anything to do with our patterns of usage of the relevant predicates. On such a view, the natural properties act as ‘reference magnets’. In this paper I explore (though I do not endorse) a related thesis in epistemology: that some propositions are ‘justification magnets’. According (...) to the doctrine of justification magnetism, we have better justification for some propositions than for others solely in virtue of certain features of those propositions; independently, that is, of anything to do with evidential support or cognitive accomplishment. In the course of discussing an objection to justification magnetism I describe (though I do not endorse) a novel approach to epistemology akin to interpretationism in the theory of reference. (shrink)

Standard lore holds that magnetic forces are incapable of doing mechanical work. More precisely, the claim is that whenever it appears that a magnetic force is doing work, the work is actually being done by another force, with the magnetic force serving only as an indirect mediator. However, the most familiar instances of magnetic forces acting in everyday life, such as when bar magnets lift other bar magnets, appear to present manifest evidence of magnetic forces doing work. These sorts of (...) counterexamples are often dismissed as arising from quantum effects that lie outside the classical regime. In this paper, we show that quantum theory is not needed to account for these phenomena, and that classical electromagnetism admits a model of elementary magnetic dipoles on which magnetic forces can indeed do work. In order to develop this model, we revisit the foundational principles of the classical theory of electromagnetism, showcase the importance of constraints from relativity, examine the structure of the multipole expansion, and study the connection between the Lorentz force law and conservation of energy and momentum. (shrink)

We can understand viewed scenes and extract task-relevant information within a few hundred milliseconds. This process is generally supported by three cortical regions that show selectivity for scene images: parahippocampal place area (PPA), medial place area (MPA) and occipital place area (OPA). Prior studies have focused on the visual information each region is responsive to, usually within the context of recognition or navigation. Here, we move beyond these tasks to investigate gaze allocation during scene viewing. Eye movements rely on a (...) scene’s visual representation to direct saccades, and thus foveal vision. In particular, we focus on the contribution of OPA, which is i) located in occipito-parietal cortex, likely feeding information into parts of the dorsal pathway critical for eye movements, and ii) contains strong retinotopic representations of the contralateral visual field. Participants viewed scene images for 1034 ms while their eye movements were recorded. On half of the trials, a 500 ms train of five transcranial magnetic stimulation (TMS) pulses was applied to the participant’s cortex, starting at scene onset. TMS was applied to the right hemisphere over either OPA or the occipital face area (OFA), which also exhibits a contralateral visual field bias but shows selectivity for face stimuli. Participants generally made an overall left-to-right, top-to-bottom pattern of eye movements across all conditions. When TMS was applied to OPA, there was an increased saccade latency for eye movements toward the contralateral relative to the ipsilateral visual field after the final TMS pulse (400ms). Additionally, TMS to the OPA biased fixation positions away from the contralateral side of the scene compared to the control condition, while the OFA group showed no such effect. There was no effect on horizontal saccade amplitudes. These combined results suggest that OPA might serve to represent local scene information that can then be utilized by visuomotor control networks to guide gaze allocation in natural scenes. (shrink)

Transcranial Magnetic Stimulation (TMS) is a non-invasive neurostimulatory and neuromodulatory technique increasingly used in clinical and research practices around the world. Historically, the ethical considerations guiding the therapeutic practice of TMS were largely concerned with aspects of subject safety in clinical trials. While safety remains of paramount importance, the recent US Food and Drug Administration approval of the Neuronetics NeuroStar TMS device for the treatment of specific medication-resistant depression has raised a number of additional ethical concerns, including marketing, off-label use (...) and technician certification. This article provides an overview of the history of TMS and highlights the ethical questions that are likely arise as the therapeutic use of TMS continues to expand. (shrink)

Magnetic observations were essential for polar navigation, and were carried out systematically on both sea and land-based expeditions to the Canadian Arctic throughout the nineteenth century. John Franklin took a particular interest in magnetic studies and encouraged the Admiralty to adopt Robert Were Fox's dip circle. The establishment of the Toronto magnetic observatory provided a base for John Henry Lefroy's survey of the North West Territories. The Royal Navy's programme of magnetic research, commenced in the aftermath of the Napoleonic Wars, (...) was maintained until the British Arctic Expedition of 1875–76, commanded by Nares. In all these expeditions, the nature and limits of the observations were determined by the available instruments. (shrink)

We address a long-standing debate over whether classical magnetic forces can do work, ultimately answering the question in the affirmative. In detail, we couple a classical particle with intrinsic spin and elementary dipole moments to the electromagnetic field, derive the appropriate generalization of the Lorentz force law, show that the particle's dipole moments must be collinear with its spin axis, and argue that the magnetic field does mechanical work on the particle's elementary magnetic dipole moment. As consistency checks, we calculate (...) the overall system's energy-momentum and angular momentum, and show that their local conservation equations lead to the same force law and therefore the same conclusions about magnetic forces and work. We also compute the system's Belinfante-Rosenfeld energy-momentum tensor. (shrink)

One of the most conspicuous features of contemporary modeling practices is the dissemination of mathematical and computational methods across disciplinary boundaries. We study this process through two applications of the Ising model: the Sherrington-Kirkpatrick model of spin glasses and the Hopfield model of associative memory. The Hopfield model successfully transferred some basic ideas and mathematical methods originally developed within the study of magnetic systems to the field of neuroscience. As an analytical resource we use Paul Humphreys's discussion of computational and (...) theoretical templates. We argue that model templates are crucial for the intra- and interdisciplinary theoretical transfer. A model template is an abstract conceptual idea associated with particular mathematical forms and computational methods. (shrink)

SINGLE MAGNETIC NORTHPOLES AND SOUTPOLESAND THEIR IMPORTANCE FOR SCIENCETen lectures delivered at the University of Viennaduring the summer semester of 1947byDr. Felix EhrenhaftU. S. Visiting Profe...

SINGLE MAGNETIC NORTHPOLES AND SOUTPOLESAND THEIR IMPORTANCE FOR SCIENCETen lectures delivered at the University of Viennaduring the summer semester of 1947byDr. Felix EhrenhaftU. S. Visiting Profe...

We study the magnetic monopoles in non-Abelian gauge theories. The exact static, spherically symmetric solutions of the magnetic monopoles in both Yang-Mills and unified gauge theories are obtained. The energyE of the static system is calculable and it is either zero or infinite. The existence of the magnetic monopole solution is a consequence of symmetry rather than dynamics. We propose a new definition of the electromagnetic field tensor, which relates the static solution of gauge fields and the magnetic monopole solution. (...) Experimental implications are discussed. (shrink)

Rapid technological advances have produced a variety of novel techniques that allow a comprehensive assessment of brain function to be combined with detailed information about brain structure and connectivity. Any assessment that is based on exhibited behavior after brain injury will be prone to error for a number of reasons. These questions are explored in the context of recent studies in both healthy populations and brain injured patients that have sought to investigate covert awareness through the use of functional neuroimaging. (...) Those circumstances in which functional magnetic resonance imaging data can be used to infer awareness in the absence of a behavioral response are contrasted with those circumstances in which it cannot. This distinction is fundamental for understanding and interpreting patterns of brain activity following acute brain injury and has implications for clinical care, diagnosis, prognosis, and medicolegal decision-making after serious brain injury. (shrink)

By decomposing the charge-current density, it is demonstrated that the “built-in” spin magnetic moment of a free relativistic electron iseħ/2mc, wherem is the Lorentz mass.

Mathematical tradition has it that transformations characterized by a negative Jacobian determinant are referred to as improper transformations. The symmetry of a physical object corresponding to such an improper transformation becomes an improper symmetry. Improper symmetries have been successfully used for the purpose of crystal symmetry. The extension of these purely spatial symmetries to the domain of spacetime has led to a prejudicial use of light-cone properties, thus affecting adversely an unbiased symmetry classification. We pinpoint these prejudicial procedures and trace (...) their historical origin, while presenting an alternative that restores an unbiased treatment of improper spacetime symmetries. The applications discussed relate to recent developments in the symmetry classification of magnetic crystals and to the extension of Neumann's principle to the time domain. (shrink)

Magnetic resonance imaging (MRI) can provide a number of measurements relevant to sport-related concussion (SRC) symptoms; however, most studies to date have used a single MRI modality and whole-brain exploratory analyses in attempts to localize concussion injury. This has resulted in highly variable findings across studies due to wide ranging symptomology, severity and nature of injury within studies. A multimodal MRI, symptom-guided region-of-interest (ROI) approach is likely to yield more consistent results. The functions of the cerebellum and basal ganglia transcend (...) many common concussion symptoms, and thus these regions, plus the white matter tracts that connect or project from them, constitute plausible ROIs for MRI analysis. We performed diffusion tensor imaging (DTI), resting-state functional MRI, quantitative susceptibility mapping (QSM), and cerebral blood flow (CBF) imaging using arterial spin labeling (ASL), in youth aged 12-18 years following SRC, with a focus on the cerebellum, basal ganglia and white matter tracts. Compared to controls similar in age, sex and sport (N = 20), recent SRC youth (N = 29; MRI at 8 ± 3 days post injury) exhibited increased susceptibility in the cerebellum (p = 0.032), decreased functional connectivity between the caudate and each of the pallidum (p = 0.035) and thalamus (p = 0.021), and decreased diffusivity in the mid-posterior corpus callosum (p < 0.038); no changes were observed in recovered asymptomatic youth (N = 16; 41 ± 16 days post injury). For recent symptomatic-only SRC youth (N = 24), symptom severity was associated with increased susceptibility in the superior cerebellar peduncles (p = 0.011) and reduced activity in the cerebellum (p = 0.013). Fewer days between injury and MRI were associated with reduced cerebellar-parietal functional connectivity (p < 0.014), reduced activity of the pallidum (p = 0.002), increased CBF in the caudate (p = 0.005), and reduced diffusivity in the central corpus callosum (p < 0.05). Youth SRC is associated with acute cerebellar inflammation accompanied by reduced cerebellar activity and cerebellar-parietal connectivity, as well as structural changes of the middle regions of the corpus callosum accompanied by functional changes of the caudate, all of which resolve with recovery. Early MRI post-injury is important to establish objective MRI-based indicators for concussion diagnosis, recovery assessment and prediction of outcome. (shrink)

The relation is developed between rotation generators of the Lorentz group and the magnetic fields of free-space electromagnetism. Using these classical relations, it is shown that in the quantum field theory there exists a longitudinal photomagneton, a quantized magnetic flux density operator which is directly proportional to the photon spin angular momentum. Commutation relations are given in the quantum field between the longitudinal photomagneton and the usual transverse magnetic components of quantized electromagnetism. The longitudinal component is phase free, but the (...) transverse components are phase dependent. All three components can magnetize material in general, but only the transverse components contribute to Planck's law. The photon therefore has three, not two, relativistically invariant degrees of polarization, an axial, longitudinal, polarization, and the usual right and left circular transverse polarizations. Since the longitudinal polarization is axial, it is a phase- free magnetic field. (shrink)

An attempt is made to introduce the concept of magnetic moment and magnetic induction directly from observed mechanical interactions between magnets, without bringing in the idealized notion of isolated magnetic poles.

In order to study whether there exist a period of activity in the human early visual cortex that contributes exclusively to visual awareness, we applied transcranial magnetic stimulation over the early visual cortex and measured subjective visual awareness during visual forced-choice symbol or orientation discrimination tasks. TMS produced one dip in awareness 60–120 ms after stimulus onset, while forced-choice orientation discrimination was suppressed between 60 and 90 ms and symbol discrimination between 60 and 120 ms. Thus, a time window specific (...) to visual awareness was found only in the orientation condition at 120 ms. The results imply that both conscious and unconscious perception depend on activity in early visual areas. On the basis of previous estimates of neural processing speed, we suggest that the late part of the activity period most likely involve local extrastriate–striate interactions which provide the contents for visual awareness but are not themselves sufficient for awareness to arise. (shrink)

This paper introduces and reproduces a document from Feyerabend’s Nachlass including: (i) Feyerabend’s 1967 tentative translation into English of an original German typescript reporting the lecture notes of an academic course on magnetic monopoles delivered by physicist Felix Ehrenhaft (1879-1952) at the University of Vienna in the 1947 summer semester; and (ii) Feyerabend’s memoir focusing on Ehrenhaft in postwar Vienna.In addition to making available to a larger audience Ehrenhaft’s lectures on a highly controversial topic, the publication of Feyerabend’s typescript offers (...) the opportunity to reconsider, delve deeper into and cast a brighter light on a rather neglected aspect in the growing literature on Feyerabend’s thought: the significance of Ehrenhaft for the development of Feyerabend’s intellectual biography. (shrink)

Neuropsychological patients exhibiting category-selective visual agnosias provide unique insights into the cognitive functions of the human brain. Transcranial magnetic stimulation, in contrast, can be used to draw causal inferences, as one of the effects of the cortical disruption induced by magnetic stimulation is to act as a “virtual lesion” lasting from tens of milliseconds up to approximately one hour, depending on the type of stimulation. This specificity offers a unique advantage in psychological testing as TMS can be used to test (...) where and when cognitive computations are performed. This article briefly describes TMS, considers the small but growing number of studies that use TMS to disrupt face processing. It discusses how TMS can be used in the future to understand better how faces are cortically represented in the human brain. (shrink)

The quantization of the magnetic flux in superconducting rings is studied in the frame of a topological model of electromagnetism that gives a topological formulation of electric charge quantization. It turns out that the model also embodies a topological mechanism for the quantization of the magnetic flux with the same relation between the fundamental units of magnetic charge and flux as there is between the Dirac monopole and the fluxoid.

The crystallization behaviour of Fe 70.8 Nb 3.7 Cu 1 Al 2.7 Mn 0.7 Si 13.5 B 7.6 alloy prepared in the form of amorphous ribbons by melt-spinning technique was studied using differential scanning calorimetry and the temperature variation in resistivity. An X-ray diffaction and transmission electron microscopy study showed the formation of f -Fe and/or Fe 3 nanoparticles after the first stage of crystallization. The activation energy for this nanophase formation was 68 kcal mol m 1 . The brittleness (...) of the alloy increased with the formation of nanoparticles after heat treatment. Superior soft magnetic properties were achieved when the material was heat treated at 790 K for 15 min. The particle size at the optimum heat treatment condition for superior soft magnetic properties was found to be 6.0 - 0.5 nm which was less compared than for the Fe-Nb-Cu-Si-B system. The observed coercivity value at the optimum heat treatment condition was found to be 0.32 A m m 1 . The presence of Al in the alloy reduced the particle size and the magnetic anisotropy energy of the system, which resulted in superior soft magnetic properties of the heat-treated materials. (shrink)

Electrical resistivity and ac-calorimetric measurements reveal a complex magnetic phase diagram for single crystals of the ferromagnetic Kondo-lattice compound CeAgSb2 at high pressures up to 80 kbar. The ferromagnetic order at TC = 9.6 K at ambient pressure is completely suppressed at a critical pressure PC = 35 kbar. Another magnetic transition, possibly antiferromagnetic, found above 27 kbar, attains a maximum value TN 6 K at 44 kbar and then appears to be completely suppressed by 50 kbar. Thermodynamic and transport (...) measurements in the ferromagnetic state indicate an energy gap Δ 30 K in the spin-wave excitation spectrum at ambient pressure which decreases to Δ 10 K at P = 30 kbar. No superconductivity is observed at ambient pressure above T 0.1 K, under applied pressure in the ferromagnetic state (P = 28.5 kbar), nor in the antiferromagnetic state (P = 33 − 46 kbar) above 0.3 K. © 2003 The American Physical Society. (shrink)

Recent critiques of methodological naturalism (MN) claim that it fails by conflicting with Christian belief and being insufficiently humble. We defend MN by tracing the real history of the debate, contending that the story as it is usually told is mythic. We show how MN works in practice, including among real scientists. The debate is a red herring. It only appears problematic because of confusion among its opponents about how scientists respond to experimental anomalies. We conclude by introducing our preferred (...) approach, Science‐Engaged Theology. (shrink)

This paper discusses historical-critical thought to address the problems of restoration and preservation of tape music, proposing viable solutions to the matter of digitizing the historically valuable data that exists on and is represented by magnetic tapes. A detailed program of research and restoration and some software for helping in creation of critical editions of the musical works are proposed. We also present some of the issues and controversies that must be considered and approaches we have applied in the preservation (...) of tape music, highlighting how these interpretations can impact later performances of these tape documents. Fundamentally, we argue that the act of tape music restoration has a parallel with the interpretation of the “Urtext score” in the performance of music from the Common Practice Era. (shrink)

Autism is a group of complex neurodevelopmental disorders characterized by impaired social interaction and restricted/repetitive behavior. We performed a large-scale retrospective analysis of 1,996 clinical neurological structural magnetic resonance imaging (MRI) examinations of 781 autistic and 988 control subjects (aged 0 to 32 years), and extracted regionally distributed cortical thickness measurements, including average measurements as well as standard deviations which supports the assessment of intra-regional cortical thickness variability. The youngest autistic participants (< 2.5 years) were diagnosed after imaging and were (...) identified retrospectively. The largest effect sizes and the most common findings not previously published in the scientific literature involve abnormal intra-regional variability in cortical thickness affecting many (but not all) regions of the autistic brain, suggesting irregular gray matter development in autism that can be detected with MRI. Atypical developmental patterns have been detected as early as 0 years old in individuals who would later be diagnosed with autism. (shrink)

Single-pulse and repetitive transcranial magnetic stimulation are used in clinical practice for diagnostic and therapeutic purposes. However, rTMS-based therapies that lead to a significant and sustained reduction in neuropsychiatric symptoms remain scarce. While it is generally accepted that the stimulation frequency plays a crucial role in producing the therapeutic effects of rTMS, less attention has been dedicated to determining the role of the electric field strength. Conventional threshold-based intensity selection approaches, such as the resting motor threshold, produce variable stimulation intensities (...) and electric fields across participants and cortical regions. Insufficient standardization of electric field strength may contribute to the variability of rTMS effects and thus therapeutic success. Computational approaches that can prospectively optimize the electric field and standardize it across patients and cortical targets may overcome some of these limitations. Here, we discuss these approaches and propose that electric field standardization will be instrumental for translational science frameworks aimed at deciphering the subcellular, cellular, and network mechanisms of rTMS. Advances in understanding these mechanisms will be important for optimizing rTMS-based therapies in psychiatry. (shrink)

BackgroundHigh frequency repetitive transcranial magnetic stimulation of the left dorsolateral prefrontal cortex has shown significant efficiency in the treatment of resistant depression. However in healthy subjects, the effects of rTMS remain unclear.ObjectiveOur aim was to determine the impact of 10 sessions of rTMS applied to the DLPFC on mood and emotion recognition in healthy subjects.DesignIn a randomised double-blind study, 20 subjects received 10 daily sessions of active or sham rTMS. The TMS coil was positioned on the left DLPFC through neuronavigation. (...) Several dimensions of mood and emotion processing were assessed at baseline and after rTMS with clinical scales, visual analogue scales, and the Ekman 60 faces test.ResultsThe 10 rTMS sessions targeting the DLPFC were well tolerated. No significant difference was found between the active group and the control group for clinical scales and the Ekman 60 faces test. Compared to the control group, the active rTM... (shrink)

While an accurate assessment of risk is always important, it is especially so in pediatric research. Recognizing the pivotal nature of the minimal-risk standard, we set out to determine under what circumstances pediatric magnetic resonance imaging research does or does not meet this standard. We found that while the physical and psychological risks that attend the MRI procedure do not exceed minimal risk, the sedation and contrast enhancement that are sometimes associated with MRI research do, as both exceed the level (...) of risk encountered by typical, healthy children in their everyday experiences. (shrink)

One striking feature of the contemporary modeling practice is its interdisciplinarity: the same function forms and equations, and mathematical and computational methods are being transferred across disciplinary boundaries. Within philosophy of science this interdisciplinary dimension of modeling has been addressed by both analogy and template-based approaches that have proceeded separately from each other. We argue that a more fully-blown account of model transfer needs both perspectives. We examine analogical reasoning and template application through a detailed case study on the transfer (...) of the Ising model from physics into neuroscience. Our account combines the analogy and template-based approaches through the notion of a model template that highlights the conceptual side of model transfer. (shrink)

The mathematical model of physical problems interprets physical phenomena closely. This research work is focused on numerical solution of a nonlinear mathematical model of fractional Maxwell nanofluid with the finite difference element method. Addition of nanoparticles in base fluids such as water, sodium alginate, kerosene oil, and engine oil is observed, and velocity profile and heat transfer energy profile of solutions are investigated. The finite difference method involving the discretization of time and distance parameters is applied for numerical results by (...) using the Caputo time fractional operator. These results are plotted against different physical parameters under the effects of magnetic field. These results depicts that a slight decrease occurs for velocity for a high value of Reynolds number, while a small value of Re provides more dominant effects on velocity and temperature profile. It is observed that fractional parameters α and β show inverse behavior against u y, t and θ y, t. An increase in volumetric fraction of nanoparticles in base fluids decreases the temperature profile of fractional Maxwell nanofluids. Using mathematical software of MAPLE, codes are developed and executed to obtain these results. (shrink)

In this paper Mele and Robb defend their (1998) paper against a variety of objections and further their develop their defense of Frankfurt-style cases.

Magnetic resonance imaging is a noninvasive imaging tool that utilizes a strong magnetic field and radio frequency waves to visualize in great detail organs, soft tissue, and bone. Unlike conventional x-rays, there is no exposure to ionizing radiation and at most field strengths the procedure is considered safe for nearly every age group. Because it is non-invasive and possesses excellent spatial resolution, the use of MRI as a research tool has increased exponentially over the past decade. Uses have ranged from (...) add-ons to a clinical study to studies of brain development in typically developing children. In addition, a major effort has been made in recent years to use MRI to study brain function. Because the clinical utility of fMRI has not yet been realized, fMRI is still considered highly exploratory, and we cannot yet identify incidental findings of a functional nature. (shrink)

Recent magnetic resonance imaging and pathological studies have indicated that axonal loss is a major contributor to disease progression in multiple sclerosis. 1 H magnetic resonance spectroscopy, through measurement of N -acetyl aspartate, a neuronal marker, provides a unique tool to investigate this. Patients with primary progressive multiple sclerosis have few lesions on conventional MRI, suggesting that changes in normal appearing white matter, such as axonal loss, may be particularly relevant to disease progression in this group. To test this hypothesis (...) NAWM was studied with MRS, measuring the concentration of N -acetyl derived groups. Single-voxel MRS using a water-suppressed PRESS sequence was carried out in 24 patients with primary progressive multiple sclerosis and in 16 age-matched controls. Ratios of metabolite to creatine concentration were calculated in all subjects, and absolute concentrations were measured in 18 patients and all controls. NA/Cr was significantly lower in NAWM in patients than in controls, as was the absolute concentration of NA. There was no significant difference in the absolute concentration of creatine between the groups. This study supports the hypothesis that axonal loss occurs in NAWM in primary progressive multiple sclerosis and may well be a mechanism for disease progression in this group. (shrink)

Transcranial magnetic stimulation is a relatively non-invasive technique to interfere with the function of small cortical areas through currents induced by alternating magnetic fields emanating from a handheld coil placed directly above the targeted area. This technique has clear effects on a whole range of measures of brain function and has become an important research tool in neuropsychiatry. More recently, TMS has been studied in psychiatry mainly to assess its putative therapeutic effects in the treatment of refractory major depression. Most (...) studies indicate that both low-frequency TMS and higher frequency repetitive TMS may have some antidepressant properties. This is most interesting and opens a whole new avenue of low invasive techniques to stimulate the brain in major depression. However, definite therapeutic effects of clinical significance still remain to be demonstrated. (shrink)