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Öğe Analysis of the time-varying energy of brain responses to an oddball paradigm using short-term smoothed Wigner-Ville distribution(Elsevier Science Bv, 2005) Tagluk, ME; Çakmak, ED; Karakas, SCognitive brain responses to external stimuli, as measured by event related potentials (ERPs), have been analyzed from a variety of perspectives to investigate brain dynamics. Here, the brain responses of healthy subjects to auditory oddball paradigms, standard and deviant stimuli, recorded on an Fz electrode site were studied using a short-term version of the smoothed Wigner-Ville distribution (STSW) method. A smoothing kernel was designed to preserve the auto energy of the signal with maximum time and frequency resolutions. Analysis was conducted mainly on the time-frequency distributions (TFDs) of sweeps recorded during successive trials including the TFD of averaged single sweeps as the evoked time-frequency (ETF) brain response and the average of TFDs of single sweeps as the time-frequency (TF) brain response. Also the power entropy and the phase angles of the signal at frequency f and time t locked to the stimulus onset were studied across single trials as the TF power-locked and the TF phase-locked brain responses, respectively. TFDs represented in this way demonstrated the ERP spectro-temporal characteristics from multiple perspectives. The time-varying energy of the individual components manifested interesting TF structures in the form of amplitude modulated (AM) and frequency modulated (FM) energy bursts. The TF power-locked and phase-locked brain responses provoked ERP energies in a manner modulated by cognitive functions, an observation requiring further investigation. These results may lead to a better understanding of integrative brain dynamics. (c) 2004 Elsevier B.V. All rights reserved.Öğe Learning of serial digits leads to frontal activation in functional magnetic resonance imaging: Clinical implications(Elsevier Science Bv, 2004) Karakas, HM; Karakas, S[Abstract Not Available]Öğe Morphological and microscopical examination of the rat brachial plexus(Tubitak Scientific & Technological Research Council Turkey, 2001) Uzun, A; Cengiz, N; Kavakli, A; Karakas, SThe rat brachial plexus was studied morphologically and the average numbers of the fascicles were studied by light microscope. For this purpose, we used 30 Wistar albino adult rats (16 males, 14 females; 180-250 g). The rats were anaesthetized by urethane (0.6 ml/100 g body weight injected i.p.). The brachial plexus was prepared for the microdissection technique and was evaluated in terms of its formation. Sections of the origin level of roots (C-5, C-6, C-7, C-8 and Th-1) and the terminal branches (ulnar, median, radial (musculospiral), axillary (circumflex), and musculocutaneous nerves) were taken and the average numbers of fascicles were calculated. The results of our investigation show that the rat brachial plexus is formed by the inferior primary divisions of the last four cervical and the first thoracic of the spinal nerves (C-5, C-6, C-7, C-8 and Th-1). C-4 might join with C-5 but we did not observe a connection between the Th-2 and Th-1. The diameters of the roots and terminal branches of the brachial plexus were approximately 0.5-1.2 mm and 0.5-1.1 mm, respectively. The numbers of fascicles for the roots and terminal branches were calculated to be approximately 2-4 and 1-4, respectively.
