Cortical Brain Functions ­ The Brodmann Legacy in the 21st Century

In 1909, Korbinian Brodmann described 52 functional brain areas, 43 of them found in the human brain. More than a century later, his devoted functional map was incremented by Glasser et al in 2016, using functional nuclear magnetic resonance imaging techniques to propose the existence of 180 functional areas in each hemisphere, based on their cortical thickness, degree of myelination (cortical myelin content), neuronal interconnection, topographic organization, multitask answers, and assessment in their resting state. This opens a huge possibility, through functional neuroanatomy, to understand a little more about normal brain function and its functional impairment in the presence of a disease.

Chronic low back pain and sick-leave: a functional magnetic resonance study

Abstract Background Chronic low back pain (CLBP) represents a problem in the occupational environment, often associated with disability, sick-leave demands, loss of productivity, anxiety, depression and high socioeconomic cost. The emergence of functional neuroimaging allowed new insights into brain structure and physiology in normality and chronic pain. While occupational related aspects are recognized as important risk factors for chronicity there have not been thus far evaluated by fMRI experiments. The overall objective of this study is to compare the neuronal correlates between groups of individuals CLBP with or without sick-leave demands. Methods A total of 74 individuals were divided into three groups: chronic low back pain with sick-leave demands [CLBP_L]; chronic low back pain without sick-leave demands [CLBP_NL]; individuals without pain or sick-leave demands [Control]. Functional magnetic resonance imaging was used to assess brain function during moderate acute pain stimulation task (thumb controlled pressure). Results After acute painful stimulation, a higher brain response was found in the anterior cingulate and superior and medium frontal gyrus was observed in CLBP_NL vs. CLBP_L ( p < 0,001) and increased brain response in the frontal pole and paracingulate region in control vs. CLBP_L ( p < 0.001) during acute pain stimulation. Conclusion The modulation of acute pain participates in the mechanism propagating chronic pain perception. The lower activation in the superior frontal gyrus observed in the CLBP_L group compared to CLBP_NL, reinforces the idea of an already existing activation in this area.(AU)

Individual-Level Lesion-Network Mapping to Visualize the Effects of a Stroke Lesion on the Brain Network: Connectograms in Stroke Syndromes

Structural and functional neuroimaging studies in generalized anxiety disorder: a systematic review

Objectives: Brain imaging studies carried out in patients suffering from generalized anxiety disorder (GAD) have contributed to better characterize the pathophysiological mechanisms underlying this disorder. The present study reviews the available functional and structural brain imaging evidence on GAD, and suggests further strategies for investigations in this field. Methods: A systematic literature review was performed in PubMed, PsycINFO, and Google Scholar, aiming to identify original research evaluating GAD patients with the use of structural and functional magnetic resonance imaging as well as diffusion tensor imaging. Results: The available studies have shown impairments in ventrolateral and dorsolateral prefrontal cortex, anterior cingulate, posterior parietal regions, and amygdala in both pediatric and adult GAD patients, mostly in the right hemisphere. However, the literature is often tentative, given that most studies have employed small samples and included patients with comorbidities or in current use of various medications. Finally, different methodological aspects, such as the type of imaging equipment used, also complicate the generalizability of the findings. Conclusions: Longitudinal neuroimaging studies with larger samples of both juvenile and adult GAD patients, as well as at risk individuals and unaffected relatives, should be carried out in order to shed light on the specific biological signature of GAD.

Análise do desempenho funcional de lactentes com síndrome congênita do zika: estudo longitudinal / Análisis del desempeño funcional de los lactantes con síndrome congénito del zika: estudio longitudinal / Analysis of the functional performance of infants with congenital zika syndrome: a longitudinal study

RESUMO O objetivo do estudo foi avaliar longitudinalmente o desempenho funcional de lactentes acometidos pela síndrome congênita do zika (SCZ). Realizou-se um estudo com lactentes provenientes do Laboratório de Estudos em Pediatria da Universidade Federal de Pernambuco e da Aliança de Mães e Famílias Raras, com idade entre 6 e 24 meses, de ambos os sexos. O Inventário de Avaliação Pediátrica de Incapacidade (PEDI) foi aplicado para análise do desempenho funcional em duas avaliações, com no mínimo seis meses de intervalo. A análise dos dados foi realizada pelo teste de Wilcoxon. Na amostra de 16 lactentes, observou-se que entre as avaliações houve mudança na classificação de normal para atraso nos domínios de autocuidado e função social, com diminuição significativa dos escores normativos (p=0,001 e p<0,001, respectivamente); na mobilidade, os lactentes inicialmente classificados com atraso também apresentaram redução dos escores normativos (p=0,001), mantendo-se na classificação. Apesar do aumento significativo nos escores brutos do autocuidado (p=0,024) e mobilidade (p=0,001), os lactentes continuaram classificados em atraso. Na assistência do cuidador, 100% dos lactentes se encontraram em atraso nos três domínios do PEDI, recebendo assistência máxima ou total. As principais modificações ambientais encontradas foram as centradas na criança. Em suma, os lactentes com SCZ deste estudo apresentaram atrasos significativos no desempenho funcional, com uma evolução lenta no intervalo de tempo avaliado.

RESUMEN El objetivo del estudio fue evaluar longitudinalmente el desempeño funcional de lactantes con síndrome congénito del zika (SCZ). Se realizó un estudio con lactantes de entre 6 y 24 meses, de ambos los sexos, identificados por el Laboratorio de Estudios en Pediatría de la Universidad Federal de Pernambuco y por la Aliança de Mães e Famílias Raras (Alianza de Madres y Familias Raras). Se aplicó el Inventario de Evaluación Pediátrica de Discapacidad (PEDI) para análisis del desempeño funcional en dos evaluaciones, con al menos seis meses de intervalo. El análisis de los datos fue realizado por la prueba de Wilcoxon. En la muestra de 16 lactantes se observó cambio en los campos de autocuidado y función social, de "normal" para "retraso", con disminución significativa de los puntajes normativos (p=0,001 y p<0,001, respectivamente). En la movilidad, los lactantes inicialmente clasificados con retraso también presentaron reducción de los puntajes normativos (p=0,001), manteniéndose en la clasificación. A pesar del aumento significativo en los puntajes netos del autocuidado (p=0,024) y movilidad (p=0,001), los lactantes continuaron clasificados en retraso. En la asistencia del cuidador, un 100% de los lactantes se encontraban en retraso en los tres dominios del PEDI, recibiendo asistencia máxima o total. Las principales modificaciones ambientales encontradas fueron las centradas en el niño. En resumen, los lactantes con SCZ presentaron retrasos significativos en el desempeño funcional, con una evolución lenta en el intervalo de tiempo evaluado.

ABSTRACT This study aimed to longitudinally evaluate the functional performance of infants affected by Congenital Zika Syndrome (CZS). A study was carried out with infants from the Laboratório de Estudos em Pediatria of the Universidade Federal de Pernambuco and the Aliança de Mães e Famílias Raras, aged between 6 and 24 months, of both genders. The Pediatric Evaluation of Disability Inventory (PEDI) was applied to analyze functional performance in two evaluations, with a minimum of six months interval between them. Data analysis was performed using the Wilcoxon test. In the sample of 16 infants, we observed a change in the classification from normal to delay in the domains of self-care and social function, with a significant decrease in normative scores (p=0.001 and p<0.001, respectively); in the mobility, individuals initially classified with delay also presented reduction of normative scores (p=0.001), remaining in the same classification. Despite the significant increase in gross self-care scores (p=0.024) and mobility (p=0.001), infants remained classified as delayed. Caregiver care was analyzed in these evaluation, in which 100% of infants were delayed in all three domains of the PEDI, receiving maximum or full care. The main environmental modifications were those focused on the child. We concluded that infants with CZS presented significant delays in functional performance, with a slow evolution in the evaluated range.

Neurobiological understanding of suicide

Suicide is a complex phenomenon resulting from interactions between individual vulnerabilities and socio-environmental factors. The current review primarily focuses on research into the serotonin system, hypothalamic-pituitary-adrenal axis, neurotrophic factors, lipid metabolism, and functional neuroimaging studies. It has been found that dysfunctions in the serotonin system, hypothalamic-pituitary-adrenal axis abnormalities, and low brain-derived neurotrophic factor and cholesterol levels may be linked to suicide. Additionally, recent neuroimaging studies have suggested that structural and functional abnormalities in brain areas related to cognitive and emotional regulation may be associated with suicide. More research incorporating advanced methodological approaches may shed further light on the neurobiological basis of suicide.

Regional Brain Activity During Rest and Gastric Water Load in Subtypes of Functional Dyspepsia: A Preliminary Brain Functional Magnetic Resonance Imaging Study

BACKGROUND/AIMS: Functional dyspepsia (FD) remains a great clinical challenge since the FD subtypes, defined by Rome III classification, still have heterogeneous pathogenesis. Previous studies have shown notable differences in visceral sensation processing in the CNS in FD compared to healthy subjects (HS). However, the role of CNS in the pathogenesis of each FD subtype has not been recognized. METHODS: Twenty-eight FD patients, including 10 epigastric pain syndrome (EPS), 9 postprandial distress syndrome (PDS), and 9 mixed-type, and 10 HS, were enrolled. All subjects underwent a proximal gastric perfusion water load test and the regional brain activities during resting state and water load test were investigated by functional magnetic resonance imaging. RESULTS: For regional brain activities during the resting state and water load test, each FD subtype was significantly different from HS (P < 0.05). Focusing on EPS and PDS, the regional brain activities of EPS were stronger than PDS in the left paracentral lobule, right inferior frontal gyrus pars opercularis, postcentral gyrus, precuneus, insula, parahippocampal gyrus, caudate nucleus, and bilateral cingulate cortices at the resting state (P < 0.05), and stronger than PDS in the left inferior temporal and fusiform gyri during the water load test (P < 0.05). CONCLUSIONS: Compared to HS, FD subtypes had different regional brain activities at rest and during water load test, whereby the differences displayed distinct manifestations for each subtype. Compared to PDS, EPS presented more significant differences from HS at rest, suggesting that the abnormality of central visceral pain processing could be one of the main pathogenesis mechanisms for EPS.

Current Knowledge and Clinical Application of Brain Imaging in Alzheimer's Disease / 신경정신의학

Alzheimer's disease (AD) is a debilitating syndrome with cognitive decline and impairment in daily activities. Although clinical assessment forms the basis for diagnosing AD, structural and functional brain imaging tools have been known to enhance accuracy of differential diagnosis and prognosis prediction by presenting structural and functional signatures for AD. Associated with the important role of brain imaging in diagnosing and treating AD, brain imaging has been recommended in the current diagnostic guidelines of AD. Visual rating scales, a cost-effective diagnostic tool, have been known to assess atrophy and functional changes in patients with cognitive impairment as accurate as quantitative assessment. In this regard, visual rating scales for brain imaging interpretation could be useful in clinical settings. In this review, we interpret structural and functional brain imaging results with standardized visual rating scales, and review recent findings concerning brain imaging tools for differential diagnosing and predicting prognosis of AD.

The state of consciousness in patients in the vegetative and minimally conscious states / O estado de consciência em pacientes em estado vegetativo e em estado de consciência minima

Brain-injured patients may, with the assistance of life support, continue to perform basic bodily functions, but yet be deficient in wakefulness, awareness, decision making or other overt manifestations of consciousness. Here, we review two neurological states observed in brain injured patients with different degrees of brain impairment, the vegetative state (VS)and the minimally conscious state (MCS), and we discuss how these states are diagnosed through assessing patient behavioral responses during clinical examination. We consider howfunctional neuroimaging has revealed preserved cognitive capacities in patients that were supposed to be in the VS and has introduced a new diagnosis, cognitive motor dissociation.We review the GW Theory proposal that consciousness arises from functional connectivity (FC) of widely separated brain regions. We discuss how such high FC underlies the DefaultMode Network (DMN), a group of neural circuits that are active when an individual is not involved with external tasks and engages in introspective thinking. Finally, we discuss thefinding that the level of FC of the DMN is diminished in brain injured patients and the proposal that the level of residual DMN FC in brain injured patients is an index of their consciousness

Pacientes com lesão cerebral, quando assistidos, podem continuar a desempenhar funções fisiológicas básicas, mesmo estando com a vigília, a atenção, a capacidade de decisão e outras funções de consciência prejudicadas. Revisamos aqui dois níveis de distúrbio de consciência o estado vegetativo (VS) e o nível de consciência mínima (MCS), e discutimos como são diagnosticados através das respostas comportamentais durante o exame clínico. Abordamos como a neuroimagem funcional revelou capacidades cognitivas preservadas em pacientes supostamente em estado vegetativo, introduzindo um novo diagnóstico: a dissociação cognitivo-motora. Revisamos a proposta da Global Workspace (GW) teoria de que a consciência surge a partir de um alto grau de conectividade funcional (FC) entre áreas cerebrais distantes. Discutimos como esta alta conectividade é a base do Default Mode Network (DMN), uma rede neural ativada quando o indivíduo não está envolvido com tarefas externas e se volta para atividade mental introspectiva. Finalmente, discutimos os achados de redução do nível de FC no DMN em pacientes com lesão cerebral e a proposta de que o mesmo poderia ser um índice do nível de consciência nesses pacientes.

Interictal abnormal fMRI activation of visual areas during a motor task cued by visual stimuli in migraine / Ativação interictal anormal de áreas visuais por ressonância magnética funcional durante uma tarefa visuo-motora em indivíduos com enxaqueca

ABSTRACT Objective To assess changes in blood-oxygen-level-dependent activity after light deprivation compared to regular light exposure in subjects with migraine in the interictal state and in controls. Methods Ten subjects with migraine and ten controls participated in two sessions of functional magnetic resonance imaging. In each session, they performed a finger-tapping task with the right hand, cued by visual stimuli. They were scanned before and after 30 minutes of light deprivation or light exposure. In subjects with migraine, functional magnetic resonance imaging was performed interictally. Analysis of variance was made with the factors time (before or after), session (light deprivation or exposure), and group (migraine or control). Results There were significant “group” effects in a cluster in the bilateral cuneus encompassing the superior border of the calcarine sulcus and extrastriate cortex. There were no significant effects of “time”, “session”, or interactions between these factors. Conclusion The main result of this study is consistent with aberrant interictal processing of visual information in migraine. Light deprivation did not modulate functional magnetic resonance imaging activity in subjects with or without migraine.

RESUMO Objetivo Avaliar mudanças na atividade cerebral por meio de ressonância magnética funcional após privação luminosa comparada à exposição à luz, em indivíduos com enxaqueca no estado interictal e em controles. Métodos Dez indivíduos com enxaqueca e dez controles participaram de duas sessões de ressonância magnética funcional. Em cada sessão, realizaram uma tarefa motora com a mão direita guiada por estímulos visuais. Foram colhidas imagens antes e após 30 minutos de privação luminosa ou exposição à luz. Em indivíduos com enxaqueca, a ressonância funcional foi realizada no período interictal. Foi feita a análise de variância com fatores tempo (antes ou depois), sessão (privação ou exposição à luz) e grupo (enxaqueca ou controle). Resultados Houve efeitos significativos de “grupo” em uma área no cúneo bilateral, incluindo a borda superior do sulco calcarino e o córtex extraestriado. Não houve efeitos significativos de “tempo”, “sessão” ou interações entre estes fatores. Conclusão O principal resultado deste estudo sugere um processamento interictal anormal das informações visuais em indivíduos com enxaqueca. A privação luminosa não modulou a atividade na ressonância magnética funcional em indivíduos com ou sem enxaqueca.

Altered Functional Connectivity of the Default Mode Network in Low-Empathy Subjects

Empathy is the ability to identify with or make a vicariously experience of another person's feelings or thoughts based on memory and/or self-referential mental simulation. The default mode network in particular is related to self-referential empathy. In order to elucidate the possible neural mechanisms underlying empathy, we investigated the functional connectivity of the default mode network in subjects from a general population. Resting state functional magnetic resonance imaging data were acquired from 19 low-empathy subjects and 18 medium-empathy subjects. An independent component analysis was used to identify the default mode network, and differences in functional connectivity strength were compared between the two groups. The low-empathy group showed lower functional connectivity of the medial prefrontal cortex and anterior cingulate cortex (Brodmann areas 9 and 32) within the default mode network, compared to the medium-empathy group. The results of the present study suggest that empathy is related to functional connectivity of the medial prefrontal cortex/anterior cingulate cortex within the default mode network. Functional decreases in connectivity among low-empathy subjects may reflect an impairment of self-referential mental simulation.

How to Perform and Interpret Functional Magnetic Resonance Imaging Studies in Functional Gastrointestinal Disorders

Functional neuroimaging studies have revealed the importance of the role of cognitive and psychological factors and the dysregulation of the brain-gut axis in functional gastrointestinal disorder patients. Although only a small number of neuroimaging studies have been conducted in functional gastrointestinal disorder patients, and despite the fact that the neuroimaging technique requires a high level of knowledge, the technique still has a great deal of potential. The application of functional magnetic resonance imaging (fMRI) technique in functional gastrointestinal disorders should provide novel methods of diagnosing and treating patients. In this review, basic knowledge and technical/practical issues of fMRI will be introduced to clinicians.

Manifestaciones neuroftalmológicas en enfermedades neuroendocrinas / Neurophthalmological findings in neuroendocrine diseases

La neuroftalmología es considerada una especialidad frontera por su vínculo con otras múltiples especialidades médicas, clínicas y quirúrgicas. Los tumores de hipófisis son de tal importancia desde el punto de vista neuroftalmológico que son tratados separadamente en casi todos los textos de la especialidad. El objetivo de la presente revisión es aproximarnos, sobre la base de los conocimientos actuales, a los hallazgos neuroftalmológicos de algunas enfermedades neuroendocrinas, haciendo hincapié en dos temas fundamentales: los adenomas hipofisarios y el síndrome de neoplasias endocrinas múltiples, y demostrar además el importante papel del neuroftalmólogo en estas dos entidades. Quedan aquí evidenciadas las variadas manifestaciones neuroftalmológicas de estas entidades neuroendocrinas, el importante cometido del oftalmólogo en el diagnóstico y el ulterior seguimiento de los pacientes con adenomas hipofisarios, así como lo decisiva que puede resultar su actuación en la identificación de los hallazgos asociados al síndrome de neoplasias endocrinas múltiples tipo 2 B(AU)

Neurophthalmology is considerate frontier speciality because of their relationships with many other medical and surgical specialities. Pituitary tumors are so important from neuro-ophthalmological point of view that they appear as special chapter in text books. Our objective in the present review is to refer the neurophthalmological finfings in two main entities: pituitary adenomas and multiple endocrine neoplasia syndromes and to establish the important role of neuro-ophthalmologist in those neuroendocrine conditions. It was proved the diversity of neurophthalmological findings in neuroendocrine entities, the important role of ophthalmologist in diagnosis and pursuance of patients with pituitary adenomas and its peremptory role in screening finding associated to 2 B type multiple endocrine neoplasia syndrome(AU)

Language and reading development in the brain today: neuromarkers and the case for prediction / Desenvolvimento da linguagem e da leitura no cérebro atualmente: neuromarcadores e o caso de predição

ABSTRACT Objectives: The goal of this article is to provide an account of language development in the brain using the new information about brain function gleaned from cognitive neuroscience. By addressing the evidence obtained from non-invasive brain imaging in the light of prediction, this account goes beyond describing the association between language and specific brain areas to advocate the importance and possibility of predicting language outcomes using brain-imaging data. The goal is to address the current evidence about language development in the brain and the possibility of prediction of language outcomes. Sources: Recent studies will be discussed in the light of the evidence generated for predicting language outcomes and using new methods of analysis of brain data. Summary of the data: The present account of brain behavior will address: (1) the development of a hardwired brain circuit for spoken language; (2) the neural adaptation that follows reading instruction and fosters the “grafting” of visual processing areas of the brain onto the hardwired circuit of spoken language; and (3) the prediction of language development and the possibility of translational neuroscience. Conclusions: Brain imaging has allowed for the identification of neural indices (neuromarkers) that reflect typical and atypical language development; the possibility of predicting risk for language disorders has emerged. A mandate to develop a bridge between neuroscience and health and cognition-related outcomes may pave the way for translational neuroscience.

RESUMO Objetivos: Apresentar um relato sobre o desenvolvimento da linguagem no cérebro com as novas informações sobre função cerebral obtidas na neurociência cognitiva. Com o uso das evidências obtidas de imagens cerebrais não invasivas em face da predição, o relato vai além da descrição da associação entre linguagem e áreas específicas do cérebro e defende a importância e a possibilidade de predizer os resultados de linguagem por meio de dados de imagens cerebrais. E tratar das evidências atuais sobre desenvolvimento da linguagem no cérebro e abordar a possibilidade de predição de resultados de linguagem. Fontes: Estudos recentes serão discutidos em face das evidências geradas pela predição de resultados de linguagem e pelo uso de novos métodos de análise de dados cerebrais. Resumo dos dados: Este relato de comportamento cerebral abordará: (1) o desenvolvimento de um circuito cerebral de linguagem falada; (2) a adaptação neural que segue a instrução da leitura e incentiva a “inserção” de áreas de processamento visual do cérebro no circuito de linguagem falada; e (3) a predição do desenvolvimento da linguagem e a possibilidade de uma neurociência translacional. Conclusões: As imagens cerebrais permitiram a identificação de índices neurais (neuromarcadores) que refletem o desenvolvimento da linguagem típico e atípico; surge a possibilidade de prever o risco de disfunções de linguagem. A responsabilidade de desenvolver uma ligação entre neurociência e resultados relacionados a saúde e cognição pode abrir o caminho para a neurociência translacional.

Aspectos neurofuncionais do cerebelo: o fim de um dogma / Neurofunctional Aspects of Cerebellum: The End of a Dogma

Há séculos o cerebelo é considerado uma estrutura do sistema nervoso central responsável exclusivamente pela coordenação do movimento, fazendo diversas conexões com as áreas motoras e associativas do córtex cerebral. No entanto, nos últimos anos, avanços em neuroimagem funcional têm atribuído ao cerebelo funções cognitivo- afetivas, identificando-as anatômica e funcionalmente. Nesta revisão, os autores trazem as mais recentes informações sobre as funções cerebelares, considerando a síndrome cognitivo-afetiva correlacionada ao cerebelo e pondo fim a mais um dogma das neurociências.

For centuries the cerebellum is considered a structure of the central nervous system solely responsible for coordination of the movement, making several connections with themotor areas and associations areas of the cerebral cortex. However, in recent years, advances in functional neuroimaging has assigned the cerebellum cognitive-affective functions, identifying the anatomy and functionally pathways. In this review, the authors come with the latest information about the cerebellar functions, whereas the syndrome cerebellar cognitive-affective, it correlated, putting an end to more a dogma in neuroscience.

Causes, effects and connectivity changes in MS-related cognitive decline / Causas, efeitos e alterações de conectividade no declínio relacionado à esclerose múltipla

Cognitive decline is a frequent but undervalued aspect of multiple sclerosis (MS). Currently, it remains unclear what the strongest determinants of cognitive dysfunction are, with grey matter damage most directly related to cognitive impairment. Multi-parametric studies seem to indicate that individual factors of MS-pathology are highly interdependent causes of grey matter atrophy and permanent brain damage. They are associated with intermediate functional effects (e.g. in functional MRI) representing a balance between disconnection and (mal) adaptive connectivity changes. Therefore, a more comprehensive MRI approach is warranted, aiming to link structural changes with functional brain organization. To better understand the disconnection syndromes and cognitive decline in MS, this paper reviews the associations between MRI metrics and cognitive performance, by discussing the interactions between multiple facets of MS pathology as determinants of brain damage and how they affect network efficiency.

Declínio cognitivo é uma situação frequente mas ainda pouco compreendida na esclerose múltipla (EM). Atualmente, não são totalmente conhecidos os principais determinantes da disfunção cognitiva na doença, tendo sido apontadas fortes associações entre danos à substância cinzenta e declínio cognitivo. Estudos multiparamétricos mostram que os diferentes fatores patológicos da EM participam como causas interdependentes de atrofia da substância cinzenta e dano cerebral permanente. Eles são associados a efeitos funcionais intermediários (detectados por RM funcional) representando um equilíbrio entre desconexão cerebral e alterações (mal) adaptativas. Portanto, uma abordagem de imagem mais abrangente é necessária, com o objetivo de encontrar associações entre alterações estruturais e a organização funcional cerebral. Para melhor compreender o declínio cognitivo na EM, esse artigo propões uma revisão dos principais métodos de imagem por RM e suas correlações com função cognitiva, discutindo as múltiplas faces patológicas da EM e seu impacto na eficiência das redes neurais.

Functional Neuroimaging in Neuro-Otology / 대한평형의학회지

Neuro-otologic symptoms such as dizziness, hearing loss, or tinnitus give rise to peripheral change-induced neuroplasticity or central pathology-induced structural or functional changes. In this regard, functional neuroimaging modalities such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), quantitative electroencephalography (qEEG), or functional near infrared spectroscopy have provided researchers with possibility to observe neuro-otologic disease-induced central functional changes. Among these methods, PET and fMRI are advantageous over qEEG or MEG with regard to spatial resolution, while qEEG and MEG are advantageous over PET or fMRI with regard to temporal resolution. Also, fMRI or MEG is not suitable for patients with implanted devices, whereas PET is not ideal for repetitive measures due to radiation hazard. In other words, as these modalities are complementary to one another, researchers should choose optimum imaging modality on a case by case basis. Hereinafter, representative functional neuroimaging modalities and their application to neuro-otologic research will be summarized.

Functional Imaging of Tinnitus / 한양의대학술지

Tinnitus is an auditory phantom characterized by the perception of sound without the presence of an external acoustical source. The peripheral auditory system is considered to contribute to the initiation of tinnitus but only explains the severity and distress level to a limited degree. The neuropsychological models of tinnitus have been developed to explain the pathophysiology of tinnitus as a malfunctioning feedforward/feedback signal in the central neural system including the auditory brainstem, limbic system, auditory cortices, and other anatomical features. Functional neuroimaging techniques have been introduced in recent decades and have provided non-invasive tools to assess the working human brain in vivo. Researchers have found these techniques valuable in examining the neural correlates of tinnitus and have been able to not only support the neuropsychological model but to expand it. Though neuroimaging studies on tinnitus only began in 1990s, they have been increasing exponentially in number. In this review, we investigate the current state of functional neuroimaging studies on tinnitus in humans. The characteristics of commonly used functional neuroimaging techniques including positron emission tomography (PET), functional magnetic resonance imaging (fMRI), electroencephalography (EEG) and magnetoencephalography (MEG) are also discussed. We briefly review recent studies on the tinnitus-brain relationship that have used those research tools.

Movement Disorders Following Cerebrovascular Lesions in Cerebellar Circuits

Cerebellar circuitry is important to controlling and modifying motor activity. It conducts the coordination and correction of errors in muscle contractions during active movements. Therefore, cerebrovascular lesions of the cerebellum or its pathways can cause diverse movement disorders, such as action tremor, Holmes' tremor, palatal tremor, asterixis, and dystonia. The pathophysiology of abnormal movements after stroke remains poorly understood. However, due to the current advances in functional neuroimaging, it has recently been described as changes in functional brain networks. This review describes the clinical features and pathophysiological mechanisms in different types of movement disorders following cerebrovascular lesions in the cerebellar circuits.