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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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Now showing 1 - 4 of 4
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    Baseline prepulse inhibition dependency of orexin A and REM sleep deprivation
    (Springer, 2024) Öz, Pınar; Kamali, Osman; Gör, Ceren; Uzbay, İsmail Tayfun; Saka, Hacer Begüm; Graduate School of Health Sciences
    RationalePrepulse inhibition (PPI) impairment reflects sensorimotor gating problems, i.e. in schizophrenia. This study aims to enlighten the role of orexinergic regulation on PPI in a psychosis-like model.ObjectivesIn order to understand the impact of orexinergic innervation on PPI and how it is modulated by age and baseline PPI (bPPI), chronic orexin A (OXA) injections was carried on non-sleep-deprived and sleep-deprived rats that are grouped by their bPPI.MethodsbPPI measurements were carried on male Wistar rats on P45 or P90 followed by grouping into low-PPI and high-PPI rats. The rats were injected with OXA twice per day for four consecutive days starting on P49 or P94, while the control groups received saline injections. 72 h REMSD was carried on via modified multiple platform technique on P94 and either OXA or saline was injected during REMSD. PPI tests were carried out 30 min. after the last injection.ResultsOur previous study with acute OXA injection after REMSD without bPPI grouping revealed that low OXA doses might improve REMSD-induced PPI impairment. Our current results present three important conclusions: (1) The effect of OXA on PPI is bPPI-dependent and age-dependent. (2) The effect of REMSD is bPPI-dependent. (3) The effect of OXA on PPI after REMSD also depends on bPPI.ConclusionOrexinergic regulation of PPI response with and without REMSD can be predicted by bPPI levels. Our findings provide potential insights into the regulation of sensorimotor gating by sleep/wakefulness systems and present potential therapeutic targets for the disorders, where PPI is disturbed.
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    Reorganization of brain connectivity across the spectrum of clinical cognitive decline
    (SPRINGER-VERLAG ITALIA SRL, 2024) Dal, Demet Yüksel; Yıldırım, Zerrin; Gurvit, Hakan; Acar, Burak; Department of Physics; Kabakçıoğlu, Alkan; Department of Physics;  ; College of Sciences;  
    Clinical cognitive decline, leading to Alzheimer's Disease Dementia (ADD), has long been interpreted as a disconnection syndrome, hindering the information flow capacity of the brain, hence leading to the well-known symptoms of ADD. The structural and functional brain connectome analyses play a central role in studies of brain from this perspective. However, most current research implicitly assumes that the changes accompanying the progression of cognitive decline are monotonous in time, whether measured across the entire brain or in fixed cortical regions. We investigate the structural and functional connectivity-wise reorganization of the brain without such assumptions across the entire spectrum. We utilize nodal assortativity as a local topological measure of connectivity and follow a data-centric approach to identify and verify relevant local regions, as well as to understand the nature of underlying reorganization. The analysis of our preliminary experimental data points to statistically significant, hyper and hypo-assortativity regions that depend on the disease's stage, and differ for structural and functional connectomes. Our results suggest a new perspective into the dynamic, potentially a mix of degenerative and compensatory, topological alterations that occur in the brain as cognitive decline progresses.
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    Cathodal tDCS stimulation of left anterior temporal lobe eliminates cross-category color discrimination response time advantage
    (Elsevier, 2020) N/A; Department of Psychology; Department of Psychology; Akbıyık, Seda; Göksun, Tilbe; Balcı, Fuat; Master Student; Faculty Member; Faculty Member; Department of Psychology; N/A; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; N/A; 47278; 51269
    The linguistic category-advantage in color perception refers to better discrimination performance for stimuli that belong to different categories (e.g., green vs. blue) than equidistant stimuli from the same category (e.g., blue). Despite the robust nature of category-advantage in color perception, the related cognitive and neural mechanisms are not fully understood. Some views attribute this effect to early alteration of visual processing of color while others attribute it to post-perceptual conceptual processing. The current study investigated the causal role of the left anterior temporal lobe (ATL), as a post-perceptual semantic hub, in categorical color perception. We modulated the activity of the left ATL via cathodal tDCS or sham stimulation (within-subject) while participants were discriminating between successive presentations of color patches. Without stimulation, we found a category-advantage effect in both accuracy and response times. The inhibition of left ATL eliminated the category-advantage effect in terms of RTs but not accuracies. Our results point at the causal role of ATL in categorical color perception and provide indirect support for a post-perceptual processing account of this robust phenomenon.
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    Post-activation depression of primary afferents reevaluated in humans
    (Elsevier, 2020) N/A; N/A; N/A; N/A; N/A; N/A; N/A; Özyurt, Mustafa Görkem; Topkara, Betilay; Şenocak, Beatrice Selen; Budan, Abdullah Salih; Yüce, Murat Necdet; Türker, Kemal Sıtkı; PHD Student; PHD Student; Master Student; Undergraduate Student; Undergraduate Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; School of Medicine; School of Medicine; School of Medicine; N/A; N/A; N/A; N/A; N/A; N/A; 6741
    Amplitude variation of Hoffmann Reflex (H-reflex) was used as a tool to investigate many neuronal networks. However, H-reflex itself is a subject to intrinsic changes including post-activation depression (P-AD). We aimed to investigate P-AD and its implication on motor control in humans. Upon tibial nerve stimulation in 23 healthy participants, peak-to-peak amplitude change of H-reflex was investigated using surface electromyography (SEMG) of soleus muscle. Variety of stimulus intensities, interstimulus intervals (ISIs), voluntary contraction levels/types and force recording were used to investigate the nature of P-AD. We have shown that P-AD was significantly stronger in the shorter ISIs. The only exception was the ISI of 200 msecs which had a weaker P-AD than some of the longer ISIs. Sudden muscle relaxation, on the other hand, further increased the effectiveness of the ongoing P-AD. Moreover, P-AD displayed its full effect with the first stimulus when there was no muscle contraction and was efficient to reduce the muscle force output by about 30%. These findings provide insight about the variations and mechanism of P-AD and could lead to improvements in diagnostic tools in neurological diseases.