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Clinical Neuroscience

SEPTEMBER 30, 2020

Neuroscience highlights: Main cell types underlying memory and spatial navigation

KRABOTH Zoltán, KÁLMÁN Bernadette

Interest in the hippocampal formation and its role in navigation and memory arose in the second part of the 20th century, at least in part due to the curious case of Henry G. Molaison, who underwent brain surgery for intractable epilepsy. The temporal association observed between the removal of his entorhinal cortex along with a significant part of hippocampus and the developing severe memory deficit inspired scientists to focus on these regions. The subsequent discovery of the so-called place cells in the hippocampus launched the description of many other functional cell types and neuronal networks throughout the Papez-circuit that has a key role in memory processes and spatial information coding (speed, head direction, border, grid, object-vector etc). Each of these cell types has its own unique characteristics, and together they form the so-called “Brain GPS”. The aim of this short survey is to highlight for practicing neurologists the types of cells and neuronal networks that represent the anatomical substrates and physiological correlates of pathological entities affecting the limbic system, especially in the temporal lobe. For that purpose, we survey early discoveries along with the most relevant neuroscience observations from the recent literature. By this brief survey, we highlight main cell types in the hippocampal formation, and describe their roles in spatial navigation and memory processes. In recent decades, an array of new and functionally unique neuron types has been recognized in the hippocampal formation, but likely more remain to be discovered. For a better understanding of the heterogeneous presentations of neurological disorders affecting this anatomical region, insights into the constantly evolving neuroscience behind may be helpful. The public health consequences of diseases that affect memory and spatial navigation are high, and grow as the population ages, prompting scientist to focus on further exploring this brain region.

Clinical Neuroscience

NOVEMBER 20, 2015

[Hyperglycaemic hemiballismus: implications from connectivity analysis for cognitive impairments]

KINCSES Tamás Zsigmond, VADÁSZ Dávid, NÉMETH Dezsõ, JANACSEK Karolina, SZABÓ Nikoletta, DÉZSI Lívia, BABOS Magor, VÖRÖS Erika, VÉCSEI László

[Hyperglycaemia induced movement disorders, such as hemiballism are rare disorders. The syndrome is characterised by the triad of hemiballism, contralateral T1-hyperintense striatal lesion and non-ketotic hyperglycaemia. Here we report a patient with untreated diabetes presenting with acute onset of hemiballism. MRI revealed T1 hyperintensity of the head of the caudate nucleus and the anterior putamen. The patient also had acantocytosis. Based on the detailed examination of the neuroradiological results and earlier findings we will imply on the pathomechanism. Based on previous findings microhemorrhages, extensive mineralisation, gemistocytic astrocytosis might play role in the development of the imaging signs. The connectivity pattern of the striatal lesion showed extensive connections to the frontal cortex. In coexistence with that the most severe impairment was found on the phonemic verbal fluency task measuring frontal executive functions. ]

Clinical Neuroscience

JANUARY 30, 2016

Unanswered questions in the transcranial magnetic stimulation treatment of patients with depression

MORVAI Szabolcs, NAGY Attila, KOVÁCS Attila, MÓRÉ Csaba, BERECZ Roland, FRECSKA Ede

According to the WHO fact sheet depression is a common mental disorder affecting 350 million people of all ages worldwide. Transcranial Magnetic Stimulation (TMS) is a technique which allows the investigator to stimulate and study cortical functions in healthy subjects and patients suffering from various mental and neurological disorders. In the early 1990s, studies revealed that it is possible to evoke long term mood changes in healthy volunteers by rapid rate repetitive, TMS (rTMS) over the frontal cortex. Subsequent studies involving depressed patients found frontal cortical rTMS administered daily to be clinically effective. In the past two decades, numerous trials examined the therapeutic potential of rTMS application in the treatment of mood disorders with constantly evolving treatment protocols. The aim of this paper is to review the literature of the past two decades, focusing on trials addressing the efficacy and safety of rTMS in depressed patients. Our primary goal is to evaluate the results in order to direct future studies which may help investigators in the development of treatment protocols suitable in hospital settings. The time is not far when TMS devices will be used routinely by practitioners primarily for therapeutic purpose rather than clinical research. To our knowledge, a widely accepted “gold standard" that would offer the highest efficacy, with the best tolerability has not been established yet. In order to approach this goal, the most important factors to be addressed by further studies are: localization, frequency, intensity, concurrent medication, maintenance treatments, number of pulses, trains, unilateral, or bilateral mode of application.

Clinical Neuroscience

MARCH 30, 2016

[The therapeutic use of transcranial magnetic stimulation in major depression]

NÉMETH Viola Luca, CSIFCSÁK Gábor, KINCSES Zsigmond Tamás, JANKA Zoltán, MUST Anita

[The antidepressive effect of repetitive transcranial magnetic stimulation (rTMS) has been investigated for almost 20 years now. Several studies have been published aiming to identify the exact and reliable parameters leading to the desired therapeutic effect. However, the related literature shows great variability. The current overview aims to provide a comprehensive overview of factors associated with the therapeutic effect of rTMS in major depression. High frequency stimulation of the left dorsolateral prefrontal cortex (DLPFC) for 3-6 weeks leads to mood improvement comparable to the effect of antidepressive medications in 35-40% of patients. Pharmacotherapy resistant patients treated with rTMS reach remission for 3 months on average. Low frequency stimulation of the right DLPFC appears to be similarly effective, though much less investigated so far. In addition to the exact delineation of the stimulation area, treatment outcome is also related to stimulation intensity as well as the number of sessions and impulses. Considering the safety and tolerability aspects of rTMS, it might be a significant therapeutic support for therapy resistant patients. Above this, patients diagnosed with major depression might benefit from the additional positive influence of rTMS improving the effect of antidepressive medication. Based on converging research evidence, the Food and Drug Administration (FDA) agency approved the use of rTMS as a treatment option for therapy resistant major depression in 2008. So far, in Hungary rTMS is primarily considered as a promising tool in research settings only. Hopefully, patients suffering from major depression will increasingly benefit from the positive therapeutic effect of this intervention.]

Clinical Neuroscience

MARCH 30, 2016

[Individual evaluation of loreta abnormalities in idiopathic generalized epilepsy]

CLEMENS Béla, PUSKÁS Szilvia, BESENYEI Mónika, KONKÁDOR István, HOLLÓDY Katalin, FOGARASI András, BENSE Katalin, EMRI Miklós, OPPOSITS Gábor, KOVÁCS Noémi Zsuzsanna, FEKETE István

[Background – Contemporary neuroimaging methods disclosed structural and functional cerebral abnormalities in idiopathic generalized epilepsies (IGEs). However, individual electrical (EEG) abnormalities have not been evaluated yet in IGE patients. IGE patients were investigated in the drug-free condition and after 3-6 month of antiepileptic treatment. To estimate the reproducibility of qEEG variables a retrospective recruited cohort of IGE patients was investigated. 19- channel resting state EEG activity was recorded. For each patient a total of 2 minutes EEG activity was analyzed by LORETA (Low Resolution Electromagnetic Tomography). Raw LORETA values were Z-transformed and projected to a MRI template. Z-values outside within the [+] 1. In drug-free condition, 41-50% of IGE patients showed abnormal LORETA values. 2. Abnormal LORETA findings showed great inter-individual variability. 3. Most abnormal LORETA-findings were symmetrical. 4. Most maximum Z-values were localized to frontal or temporal cortex. 5. Succesfull treatment was mostly coupled with disappearence of LORETA-abnormality, persistent seizures were accompanied by persistent LORETA abnormality. 1. LORETA abnormalities detected in the untreated condition reflect seizure-generating property of the cortex in IGE patients. 2. Maximum LORETA-Z abnormalities were topographically congruent with structural abnormalities reported by other research groups. 3. LORETA might help to investigate drug effects at the whole-brain level.]

Clinical Neuroscience

MARCH 30, 2019

EEG-based connectivity in patients with partial seizures with and without generalization

DÖMÖTÖR Johanna, CLEMENS Béla, EMRI Miklós, PUSKÁS Szilvia, FEKETE István

Objective - to investigate the neurophysiological basis of secondary generalization of partial epileptic seizures. Patients and methods - inter-ictal, resting-state EEG functional connectivity (EEGfC) was evaluated and compared: patients with exclusively simple partial seizures (sp group) were compared to patients with simple partial and secondary generalized seizures (spsg group); patients with exclusively complex partial seizures (cp group) were compared to patients with cp and secondary generalized seizures (cpsg group); the collapsed sp+cp group (spcp) was compared to those who had exclusively secondary generalized seizures (sg group). EEGfC was computed from 21-channel waking EEG. 3 minutes of waking EEG background activity was analyzed by the LORETA Source Correlation (LSC) software. Current source density time series were computed for 23 pre-defined cortical regions (ROI) in each hemisphere, for the 1-25 Hz very narrow bands (1 Hz bandwidth). Thereafter Pearson correlation coefficients were calculated between all pairs of ROI time series in the same hemisphere. Z-scored correlation coefficients were compared at the group level (t-tests and correction for multiple comparisons by local false discovery rate, FDR). Results - Statistically significant (corrected p<0.05) EEGfC differences emerged at specific frequencies (spsg > sg; cpsg > cp), and at many frequencies (sg > spcp). The findings indicated increased coupling between motor cortices and several non-motor areas in patients with partial and sg seizures as compared to patients with partial seizures and no sg seizures. Further findings suggested increased coupling between medial parietal-occipital areas (structural core of the cortex) and lateral hemispheric areas. Conclusion - increased inter-ictal EEGfC is associated with habitual occurrence of secondary generalized seizures.

Clinical Neuroscience

JULY 30, 2017

[Calcium ion is a common denominator in the pathophysiological processes of amyotrophic lateral sclerosis]

PATAI Roland, NÓGRÁDI Bernát, MESZLÉNYI Valéria, OBÁL Izabella, ENGELHARDT József István, SIKLÓS László

[Amyotrophic lateral sclerosis (ALS), the most frequent motor neuron disease is characterized by progressive muscle weakness caused by the degeneration of the motor neurons in the spinal cord and motor cortex. However, according to the recent observations, ALS is a rather complex syndrome which frequently involves symptoms of cognitive impairment. Therefore, ALS cases can be interpreted in a clinico-pathological spectrum spanning from the classical ALS involving only the motor system to the fronto-temporal dementia. The progression of the disease, however, manifested in the degeneration of the upper and lower motor neurons, is based on the same complex pathobiology. The main elements of the pathomechanism, such as oxidative stress, excitotoxicity, immune/inflammatory processes and mitochondrial dysfunction are well described already, which operate in orchestrated way and amplify the deleterious effect of each other. It is assumed that calcium ions act as a catalyst in this interaction, hence each of the individual mechanisms has strong, positive and reciprocal calcium dependence thus may combine the individual pathological processes into a unified escalating mechanism of neuronal destruction. This review provides an overview of the role of calcium in connecting and amplifying the major mechanisms which lead to degeneration of the motor neurons in ALS. ]

Clinical Neuroscience

JULY 30, 2015

[The role of β-amyloid and mitochondrial dysfunction in the pathogenesis of Alzheimer’s disease]

SZARKA András

[Alzheimer’s disease is the most common form of dementia in mid- and late life. The 7-10% of the population over 65 and the 50-60% of the population over 85 are affected by this disease. On the contrary of its prevalence the pathogenesis of the disease is not well defined and there is no effective neuroprotective therapeutic agent. Three predominant neuropathological features of the Alzheimer’s disease brain are intracellular neurofibrillary tangles consisting mainly of the hyperphosphorylated protein t; the extracellular amyloid deposits (neuritic plaques) consisting of amyloid b peptide; and the extensive neuronal cell loss in the hippocampus and in portions of the cerebral cortex. The possible reason of the extensive neuronal cell loss can be the mitochondrial dysfunction observed in Alzheimer’s disease. Beyond the unclarified pathogenesis the causality of these characteristic neuropathologic phenomena are still unknown. In this study we would like to deal with two actual hypotheses, with the amyloid cascade and with the mitochondrial cascade hypotheses. We try to give an overview of these two hypotheses and to depict their interrelationship.]

Clinical Neuroscience

MAY 30, 2015

Altered BOLD response within the core face-processing network in congenital prosopagnosia

NÉMETH Kornél, ZIMMER Márta, NAGY Krisztina, BANKÓ Éva, VIDNYÁNSZKY Zoltán, VAKLI Pál, KOVÁCS Gyula

Background and purpose - Congenital prosopagnosia is a life-long disorder of face perception. To study the neural backgrounds of congenital prosopagnosia we measured the blood oxygen level-dependent response of congenital prosopagnosic participants, using functional magnetic resonance imaging. Methods - We tested three persons of the family (father, daughter and son), having symptoms of congenital prosopagnosia, as well as healthy controls, using combined neuropsychological and functional magnetic resonance imaging methods. To reveal the neural correlates of the impairments, blood oxygen level-dependent responses within the occipito-temporal cortex were measured to faces and nonsense object images in a block-design experiment. Results - Neuropsychological tests demonstrated significant impairments of face perception/recognition in each subject. We found that the activity of the fusiform and occipital face areas as well as of the lateral occipital cortex was significantly reduced in congenital prosopagnosic participants when compared to controls. Analysis of the hemodynamic response function revealed a lower peak response, but also a significantly faster and stronger decay of the blood oxygen level-dependent response in the occipito-temporal areas in congenital prosopagnosic participants when compared to controls. Conclusion - Our results emphasize the dysfunction of the core face processing system, as well as the lateral occipital complex, in congenital prosopagnosia. Further, the functional impairment of these areas is signalled best by the altered hemodynamic response function, showing abnormally low initial peak and stronger and faster decay in the later parts of the blood oxygen level-dependent response.

Clinical Neuroscience

SEPTEMBER 30, 2014

[The relevance of traumatic life events in schizophrenia spectrum disorders]

KOCSIS-BOGÁR Krisztina, PERCZEL FORINTOS Dóra

[The central goal of this manuscript was to review literature about the interconnections of traumatic life events and symptoms of schizophrenia spectrum of the last 15 years. First of all, the stress-diathesis model and the traumagenic neurodevelopmental model are shortly presented. Psychological effects of traumas and specific psychotic symptoms in connection with traumatic events are discussed. The course of the disease in patients affected by previous traumas and possible mediating factors are also addressed. Studies of both clinical and community samples are cited. It was also our aim to review literature about the neurobiological and neurocognitive processes in people affected by schizophrenia and/or traumatic life events. The role of prefrontal and medial temporal regions are explored with a special emphasis on contextual memory and hippocampal functioning. Finally, the possible effects of exploring traumatic life events on the treatment of schizophrenia are discussed.]