Sefik Evren Erdener

Sefik Evren Erdener
Hacettepe University · Institute of Neurological Sciences and Psychiatry

MD PhD

About

62
Publications
10,989
Reads
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1,147
Citations
Citations since 2016
44 Research Items
928 Citations
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2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
Education
November 2009 - November 2014
Hacettepe University
Field of study
  • Neurology
September 2007 - September 2012
Hacettepe University
Field of study
  • Neuroscience
October 2003 - June 2009
Hacettepe University
Field of study
  • Medicine

Publications

Publications (62)
Article
Extracellular vesicles (EVs) are nanoparticles (30 to 1000 nm in diameter) surrounded by a lipid-bilayer which carry bioactive molecules between local and distal cells and participate in intercellular communication. Because of their small size and heterogenous nature they are challenging to characterize. Here, we discuss commonly used techniques th...
Article
Background: A requirement for nanoparticle (NP) research is visualization of particles within cells and tissues. Limitations of electron microscopy and low yields of NP fluorescent tagging warrant the identification of alternative imaging techniques. Method: Confocal reflectance microscopy (CRM) in combination with fluorescence imaging was assessed...
Article
Significance: Whether or not capillary pericytes contribute to blood flow regulation in the brain and retina has long been debated. This was partly caused by failure of detecting the contractile protein α -smooth muscle actin ( α -SMA) in capillary pericytes. Aim: The aim of this review is to summarize recent developments in detecting α -SMA and co...
Preprint
Full-text available
Functional neuroimaging, which measures hemodynamic responses to brain activity, has great potential for monitoring stroke patients. However, the neurophysiological interpretations of these hemodynamic signals remain a challenge as the stroke is likely to alter both neural activity and neurovascular coupling. To address this challenge, we simultane...
Article
Speech perception used to be seen as a solely an auditory phenomenon until the discovery of the “McGurk Effect” and in recent decades it has come to be understood as a multimodal, specifically, an auditory-visual process. Behavioural studies have shown that the magnitude of auditory-visual integration shows differences across ages and languages. A...
Article
Full-text available
Background Pain is generally concomitant with an inflammatory reaction at the site where the nociceptive fibers are activated. Rodent studies suggest that a sterile meningeal inflammatory signaling cascade may play a role in migraine headache as well. Experimental studies also suggest that a parenchymal inflammatory signaling cascade may report the...
Article
Full-text available
Laser speckle contrast imaging (LSCI) is a real-time full-field non-invasive technique, which is broadly applied to visualize blood flow in biomedical applications. In its foundation is the link between the speckle contrast and dynamics of light scattering particles-erythrocytes. The mathematical form describing this relationship, which is critical...
Article
Full-text available
Chronic cranial windows allow for longitudinal brain imaging experiments in awake, behaving mice. Different imaging technologies have their unique advantages and combining multiple imaging modalities offers measurements of a wide spectrum of neuronal, glial, vascular, and metabolic parameters needed for comprehensive investigation of physiological...
Conference Paper
Intrinsic and fluorescent calcium imaging was used to assess the evolution of hemodynamics and neural activity during stroke recovery. Recovery was assessed through cortical remapping of impaired limb, neurovascular coupling, and limb-use asymmetry.
Article
Full-text available
Ischemic stroke leads to a reduction or complete loss of blood supply causing injury to brain tissue, which ultimately leads to behavioral impairment. Optical techniques are widely used to study the structural and functional changes that result as a consequence of ischemic stroke both in the acute and chronic phases of stroke recovery. It is curren...
Article
Full-text available
We introduce dynamic light scattering imaging (DLSI) to enable the wide-field measurement of the speckle temporal intensity autocorrelation function. DLSI uses the full temporal sampling of speckle fluctuations and a comprehensive model to identify the dynamic scattering regime and obtain a quantitative image of the scatterer dynamics. It reveals e...
Article
Full-text available
A high‐speed, contrast‐free, quantitative ultrasound velocimetry (vUS) for blood flow velocity imaging throughout the rodent brain is developed based on the normalized first‐order temporal autocorrelation function of the ultrasound field signal. vUS is able to quantify blood flow velocity in both transverse and axial directions, and is validated wi...
Article
Utilization of functional ultrasound (fUS) in cerebral vascular imaging is gaining popularity among neuroscientists. In this article, we describe a chronic surgical preparation method that allows longitudinal studies and therefore is applicable to a wide range of studies, especially on aging, stroke, and neurodegenerative diseases. This method can...
Article
Full-text available
Although cortical spreading depolarizations (CSD) were originally assumed to be homogeneously and concentrically propagating waves, evidence obtained first in gyrencephalic brains and later in lissencephalic brains suggested a rather non-uniform propagation, shaped heterogeneously by factors like cortical region differences, vascular anatomy, wave...
Article
Although it has been documented that central nervous system pericytes are able to contract in response to physiological, pharmacological or pathological stimuli, the underlying mechanism of pericyte contractility is incompletely understood especially in downstream pericytes that express low amounts of alpha-smooth muscle actin (α-SMA). To study whe...
Article
Full-text available
Ever since the introduction of thrombolysis and the subsequent expansion of endovascular treatments for acute ischemic stroke, it remains to be identified why the actual outcomes are less favorable despite recanalization. Here, by high spatio-temporal resolution imaging of capillary circulation in mice, we introduce the pathological phenomenon of d...
Article
Full-text available
Animal models of stroke are used extensively to study the mechanisms involved in the acute and chronic phases of recovery following stroke. A translatable animal model that closely mimics the mechanisms of a human stroke is essential in understanding recovery processes as well as developing therapies that improve functional outcomes. We describe a...
Conference Paper
By obtaining structural and functional information such as changes in tissue properties, cerebral blood flow, and hemodynamics through optical imaging, we aim to better interpret human MRI data and guide therapeutic interventions following stroke.
Article
Objective: A considerable fraction of ischemic stroke cases remain cryptogenic and there is increasing data suggesting the role of missed paroxysmal atrial fibrillations (pAF) in at least a number of these cases. Since electrophysiological identification of pAFs can be challenging, there has been an accumulation of proposed predictors and biomarke...
Preprint
Full-text available
Traumatic brain injury (TBI) is a major source of cognitive deficits affecting millions annually. The bulk of human injuries are mild, causing little or no macroscopic damage to neural tissue, yet can still lead to long-term neuropathology manifesting months or years later. Although the cellular stressors that ultimately lead to chronic pathology a...
Preprint
Full-text available
Ever since the introduction of thrombolysis and the subsequent expansion of endovascular treatments for acute ischemic stroke, it remains to be identified why the actual outcomes are less favorable despite recanalization. Here, by high spatio-temporal resolution imaging of capillary circulation in mice, we introduce the pathological phenomenon of d...
Article
Full-text available
The cerebral microcirculation holds a critical position to match the high metabolic demand by neuronal activity. Functionally, microcirculation is virtually inseparable from other nervous system cells under both physiological and pathological conditions. For successful bench-to-bedside translation of neuroprotection research, the role of microcircu...
Conference Paper
In this study, we tested two bipolar groups, manic-episode and depressive episode patients and heathy controls over a series of McGurk effect stimuli as well as auditory and visual-only (lip-read) speech stimuli. We hypothesized that the bipolar group's auditory-visual speech integration should be weaker than the control group. We also predicted th...
Preprint
Full-text available
We present a high-speed, contrast free, quantitative ultrasound velocimetry (vUS) for blood flow velocity imaging of the whole coronal section of rodent brain, complementing the high-speed, non-quantitative functional ultrasound imaging (fUS) and the low-speed, quantitative velocimetry by ultrasound localization microscopy (vULM). We developed the...
Preprint
Full-text available
Utilizing a high-speed camera and recording back-scattered laser light at more than 20,000 frames per second, we introduce the first wide-field dynamic laser speckle imaging (DLSI) in which we are able to quantify the laser speckle intensity temporal auto-correlation function g 2 (τ) for every pixel individually to obtain a quantitative image of th...
Article
Full-text available
Optical coherence tomography angiography (OCTA) has been widely used for en face visualization of the microvasculature, but is challenged for real three-dimensional (3-D) topologic imaging due to the "tail" artifacts that appear below large vessels. Further, OCTA is generally incapable of differentiating descending arterioles from ascending venules...
Article
Full-text available
The use of laser speckle contrast imaging (LSCI) has expanded rapidly for characterizing the motion of scattering particles. Speckle contrast is related to the dynamics of the scattering particles via a temporal autocorrelation function, but the quality of various elements of the imaging system can adversely affect the quality of the signal recorde...
Article
Full-text available
Systemic flow variations caused by the cardiac cycle can play a role or be an important marker in both normal and pathological conditions. The shape, magnitude and propagation speed of the flow pulse reflect mechanical properties of the vasculature and are known to vary significantly with vascular diseases. Most conventional techniques are not capa...
Article
Background and purpose: Reperfusion is the most significant determinant of good outcome after ischemic stroke. However, complete reperfusion often cannot be achieved, despite satisfactory recanalization. We hypothesized that microvascular protection was essential for achieving effective reperfusion and, hence, neuroprotection. To test this hypothe...
Article
Optical coherence tomography (OCT) allows label-free imaging of red blood cell (RBC) flux within capillaries with high spatio-temporal resolution. In this study, we utilized time-series OCT-angiography to demonstrate interruptions in capillary RBC flux in mouse brain in vivo. We noticed ∼7.5% of ∼200 capillaries had at least one stall in awake mice...
Article
We present a phase-resolved optical coherence tomography (OCT) method to extend Doppler OCT for the accurate measurement of the red blood cell (RBC) velocity in cerebral capillaries. OCT data were acquired with an M-mode scanning strategy (repeated A-scans) to account for the single-file passage of RBCs in a capillary, which were then high-pass fil...
Article
Full-text available
We evaluated the reversible electrophysiologic abnormalities of two cases of hypokalemia paralysis (HypoPP) because of its similar findings in acute motor axonal neuropathy (AMAN). Nerve conduction studies (NCS), repetitive nerve stimulation, and exercise tests were performed in both patients. Adding a 15 minute-exercise test to routine NCS may hel...
Article
Quantitative measurements of intravascular microscopic dynamics, such as absolute blood flow velocity, shear stress, and the diffusion coefficient of red blood cells (RBCs), are fundamental to understanding the blood flow behavior within the microcirculation, and for understanding why diffuse correlation spectroscopy (DCS) measurements of blood flo...
Article
Full-text available
Sensory neuronopathy is a well-established presentation in paraneoplastic neurological syndromes that is mostly associated with small cell lung cancer and anti-Hu antibodies. Motor neuronopathy, on the other hand, is an extremely rare observation in this syndrome. A 56-year-old man presented with asymmetric brachial diparesis and sensory ataxia. El...
Article
Full-text available
Multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy is characterized by asymmetric multifocal motor and sensory loss and conduction blocks in peripheral nerves. Peripheral demyelinating diseases may be accompanied by demyelination in central nervous system (CNS). In this report, a MADSAM patient with a solitary tumefactive demye...
Article
Full-text available
Reflex seizures can be triggered by a variety of stimuli. We present a case with drug-resistant complex partial seizures originating in right temporal lobe triggered extensively by visual, auditory, and mental exposure to multidigit numbers. The patient was investigated in video-EEG monitoring unit and seizures were triggered by numerical stimuli....
Article
Abstract Under pathological conditions such as brain trauma, subarachnoid hemorrhage and stroke, cortical spreading depression (CSD) or peri-infarct depolarizations contribute to brain damage in animal models of neurological disorders as well as in human neurological diseases. CSD causes transient megachannel opening on the neuronal membrane, which...
Article
Full-text available
In dacrystic seizures lacrimation has previously been reported as an ictal autonomic event accompanying emotional and somatic signs. However, it has not been observed as an isolated event in autonomic seizures. We report a patient experiencing complex partial seizures characterized by lacrimation as the initial and most prominent ictal event, with...
Article
Similarities between laboratory animals and humans in anatomy and physiology of the cephalic nociceptive pathways allowed scientists to create successful models that have significantly contributed to our understanding of headache. They have also been instrumental for development of novel anti-migraine drugs dissimilar to classical pain killers. On...
Article
A 64-year-old woman presented with a 6-month history of intermittent episodes of ataxia and dysarthria. She had been on metronidazole 1,500 mg daily for ulcerative colitis for 10 months. Cranial MRI 3 months before admission revealed hyperintensity in corpus callosum and bilateral dentate nuclei (figure 1, A-C). MRI on admission revealed cystic nec...
Article
The initial phase in the development of a migraine is still poorly understood. Here, we describe a previously unknown signaling pathway between stressed neurons and trigeminal afferents during cortical spreading depression (CSD), the putative cause of migraine aura and headache. CSD caused neuronal Pannexin1 (Panx1) megachannel opening and caspase-...
Article
Full-text available
Although controversial, paradoxical embolism via patent foramen ovale (PFO) may account for some of the migraine attacks in a subset of migraine with aura (MA) patients. Induction of MA attacks with air bubble injection during transcranial Doppler ultrasound in MA patients with PFO supports this view. It is likely that cerebral embolism in patients...
Article
To review the literature on early visual manifestations of subacute sclerosing panencephalitis (SSPE) with regard to two patients who had visual problems preceding the onset of neurological symptoms. One patient had cortical visual disturbances and the other had visual loss due to retinal pigment epithelial changes. SSPE is a chronic encephalitis c...
Article
Full-text available
We read with great interest the recent article by Cornelius et al1 on sleep disorders of patients with voltage-gated potassium channel (VGKC) complex autoimmunity. They underlined that sleep abnormalities in VGKC complex autoimmunity were mostly unknown. Dream-enactment behavior occurred in 3 patients (60%) with limbic encephalitis, but none of the...
Article
Full-text available
Intravital or multiphoton microscopy and laser-speckle imaging have become popular because they allow live monitoring of several processes during cerebral ischemia. Available rodent models have limitations for these experiments; e.g., filament occlusion of the proximal middle cerebral artery (MCA) is difficult to perform under a microscope, whereas...
Article
Ischemic cell death is a complex process and the initial distinction between apoptosis and necrosis appears to be an oversimplification. We previously reported that in ischemic neurons with disrupted plasmalemma, apoptotic mechanisms were also active. In the present study, we investigated cellular co-localization of another necrotic feature, lysoso...
Conference Paper
Objective: The aim of the descriptive study is to investigate the knowledge level and attitudes regarding CCHF of patients and relatives who applied to a health center in Ankara. Material and Methods: The data were collected with a survey in between 8th-15th September, 2008 from 117 volunteer patients and relatives 18 years of age and older in Keci...
Article
This study, performed in two phases, compared the smoking status of first- and last-year pharmacy students and identified underlying factors of smoking using both "quantitative" and "qualitative" research techniques. The quantitative phase was a cross-sectional study with 207 students (of these, 102 were first-year and 105 were last-year students)....

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