Spectral Pattern Analysis of Propofol Induced Spindle Oscillations in the Presence of Auditory Stimulations

This study’s primary objective is to analyze human EEG spindle oscillations during propofol-induced anesthesia and to address possible activation sources. Such an analysis also has a secondary role of investigating the short- term spectral patterns and their functional role

THE EFFECT OF THE ATTENTION TO EAR ADVANTAGE DURING DICHOTIC LISTENING TEST

Dikotik dinleme testi; işitsel sistemdeki fonetik işlemlemenin asimetrisi çalışmalarında kullanılan girişimsel olmayan, uygulaması kolay ve düşük maliyetli bir yöntemdir. Sessiz-sesli harflerden oluşan hecelerin (consonant-vowel/CV) aynı anda, iki farklı kulaktan dinletilmesiyle yapılan testte, katılımcılar duydukları hece için yanıtlarını verirler. Klasik dikotik dinleme testi sonucunda sağlıklı kişilerin %65-90'nında sağ kulak tercih edilir. Kulak tercihi mekanizmasını açıklamak için anatomik bağlantılara dayanan duyusal (aşağıdan yukarıya işlemleme/bottom up processing) ve kortikal kontrolün (yukarıdan aşağıya kontrol/top down control) rol aldığı dikkate bağlı iki ana model ileri sürülmüştür. Bazı patolojik durumlarda yapılan çeşitli dikotik dinleme testi araştırmalarında, bu testin sol hemisferdeki merkezlerin normal çalışıp çalışmadığının belirlenmesi, dikkat eksikliğinin tespiti, kallozal transfer fonksiyonunun tayininde kullanılabileceği önerilmektedir. Amaç: Konuşma heceleri uygulanan sağlıklı gönüllülerde işitsel sistemde baskın hemisferin tayin edilmesi ve dikkat yönergesinin bu asimetrik yapıya etkisinin araştırılmasıdır. Ayrıca dikotik dinleme testinin Türk toplumu için geçerliliğinin değerlendirilmesidir. Gereç ve yöntem: 20 sağlıklı gönüllüye (20 sağlak, 12 erkek) 36 adet CV dikotik hece, dikkat hiçbir kulağa yönlendirilmeden (non-forced/NF), dikkat sağ kulağa (forced right ear attention/FR) ve sol kulağa (forced left ear attention/FL) yönlendirilerek uygulandı. Kişilerin verdiği yanıtlar yeni geliştirilen elektronik bir sistemle değerlendirildi. İstatistiksel analizde yineleyen ölçümlerde ANOVA testi kullanıldı. Bulgular: NF durumda ortalama %53,95 sağ kulak tercihi (REA), FR durumda %61,23 REA ve FL durumda %37,72 REA bulundu. FL durumda ise sol kulak tercihi %47,19 olup, NF ve FR durumundan yüksekti. Sonuç: Sağlıklı bireylerde sol hemisfer üstünlüğü bulunmaktadır. Yukarıdan aşağıya kontrol mekanizmasıyla kulak tercihi değiştirilebilmektedir. Burada uygulanan dikotik dinleme testleri Kulak Burun Boğaz, Odyoloji, Nöroloji, Psikiyatri ve ilgili diğer bilim dallarının işbirliğiyle geliştirilerek işitme merkezi hasarı ve dikkat bozukluğu hastalıklarının tayininde ve ayrıca bu hastalıkların tedavilerinin izleminde kullanılabilir. The dichotic listening test is a non-invasive, low cost and easy to apply technique used in studying asymmetry of phonetic processing. In this test, participants are presented with two syllables, one in each ear, simultaneously and are asked to declare the syllab le they hear. Syllables are constructed as consonant-vowel (CV) pairs. In the classical dichotic listening test, 65-90% of healthy individuals declare the syllable presented in the right ear. In order to explain this right ear advantage (REA), anatomical and attention- related models are proposed. According to these models, REA can be associated with left hemisphere dominance; besides, attention drive top down control can modify REA. It is suggested that this test can be used to investigate attention deficits, functioning of different areas in left hemisphere and callosal transfer function in studies of pathological conditions. Objective: Establishing dominant hemisphere of healthy subjects in auditory system and investigation of effect of instructional attention on this asymmetry. Also, correlation of this new Turkish version of the dichotic test results with other nation's dichotic test results. Material and method: 36 CV syllable pairs were presented to 20 healthy subjects (all right-handed, 12 male) in three different conditions: no direction of the attention (nonforced, NF), directing attention to right ear (forced-right, FR), directing attention to left ear (forced-left, FL). Declarations of the heard syllable were recorded by a recently developed electronic system. In statistical analysis, repeated measures of ANOVA's was used. Results: REA was 53.95% (±17.20) in NF condition, 61.23% in FR condition, 37.72% in FL condition. In FL condition, the rate of left ear advantage was found to be %47.19, which was greater than in NF and FR conditions. Conclusion: In healthy subjects, left hemisphere dominance was found. REA can be modified by top down control mechanisms. Dichotic listening test can be used in determination of conditions related to auditory cortex malfunctions and attention deficit disorders as well as in follow-up of medical treatments of these types of disorders

Brain function assessment in different conscious states

Background: The study of brain functioning is a major challenge in neuroscience fields as human brain has a dynamic and ever changing information processing. Case is worsened with conditions where brain undergoes major changes in so-called different conscious states. Even though the exact definition of consciousness is a hard one, there are certain conditions where the descriptions have reached a consensus. The sleep and the anesthesia are different conditions which are separable from each other and also from wakefulness. The aim of our group has been to tackle the issue of brain functioning with setting up similar research conditions for these three conscious states.Methods: In order to achieve this goal we have designed an auditory stimulation battery with changing conditions to be recorded during a 40 channel EEG polygraph (Nuamps) session. The stimuli (modified mismatch, auditory evoked etc.) have been administered both in the operation room and the sleep lab via Embedded Interactive Stimulus Unit which was developed in our lab. The overall study has provided some results for three domains of consciousness. In order to be able to monitor the changes we have incorporated Bispectral Index Monitoring to both sleep and anesthesia conditions.Results: The first stage results have provided a basic understanding in these altered states such that auditory stimuli have been successfully processed in both light and deep sleep stages. The anesthesia provides a sudden change in brain responsiveness; therefore a dosage dependent anesthetic administration has proved to be useful. The auditory processing was exemplified targeting N1 wave, with a thorough analysis from spectrogram to sLORETA. The frequency components were observed to be shifting throughout the stages. The propofol administration and the deeper sleep stages both resulted in the decreasing of N1 component. The sLORETA revealed similar activity at BA7 in sleep (BIS 70) and target propofol concentration of 1.2 μg/mL.Conclusions: The current study utilized similar stimulation and recording system and incorporated BIS dependent values to validate a common approach to sleep and anesthesia. Accordingly the brain has a complex behavior pattern, dynamically changing its responsiveness in accordance with stimulations and states. © 2010 Ozgoren et al; licensee BioMed Central Ltd

The Neuroelectric Activity of The Brain in Extracorporeal Circulation: Preliminary Results

Objective: The use of a cardiopulmonary machine during cardiac surgery causes a non-physiological circulation in the brain and the other body organs. This situation usually causes brain ischemia. Due to this or other factors, neurological disorders such as stroke and psychiatric disorders are encountered during the perioperative period. In this study, it was aimed to compare neuroelectrical activity measured during extracorporeal circulation in coronary bypass surgery with preoperative values of the patient

Neuroelectric responses of sportsmen and sedentaries under cognitive stress

Stress and anxiety are states which sportsmen are continuously exposed to. Our study aimed to evaluate neuroelectrical peripheral and central nervous system responses of sportsmen (SPR) and sedentary individuals (SED) during concentration grid test (CGT) employed under time pressure. Forty three SPR and 33 SED participated in the study. Neuroelectrical responses were simultaneously obtained during baseline and CGT. All responses were observed to increase under stress in both SED and SPR. The SPR's stress related peripheral responses were lower than SED's. When central values were evaluated a stress related increase according to baseline was observed in all frequency powers in all of the participants. Statistical comparison of increase rates revealed a significantly greater increase in beta in SED compared to SPR. Beta has been associated to alertness and cortical arousal. As SED exhibit greater beta increase under stress compared to SPR their state of cortical arousal and alertness may be interpreted to be higher than SPR. However the SPR's weak increase in beta and their lower peripheral responses taken together may imply that they are better in stress management. In fact according to their performance scores the SPR's higher level of performance under stress compared to SED shows that they are better at maintaining and focusing their attention under stress than SED

Dichotic listening revisited: Trial-by-trial ERP analyses reveal intra- and interhemispheric differences

The dichotic listening (DL) paradigm is often used to assess brain asymmetries at the behavioral level. The aim of this study was to evaluate the dynamic temporal and topographical characteristics of event related potentials (ERPs) obtained with diotic and dichotic consonant-vowel (CV) stimuli from the same subjects. We used a novel approach in which we concurrently analyzed on a trial-by-trial basis ERP parameters during trials that resulted in a right ear advantage (REA) or left ear advantage (LEA) or that were presented under diotic (homonymous) conditions. CV syllables were used as auditory stimuli (/ba/, /da/, /ga/, /ka/, /pa/, /ta/). The EEG measurements were performed with 64 channels by mainly focusing on the N1P2, N2P3 and late negativity (LN) components. Overall, behavioral data revealed a clear REA. The central area showed higher amplitudes than the other locations for N1P2 responses. Additionally, responses were faster for the diotic, compared to the dichotic conditions. The LN had shorter latencies in trials resulting in a REA, compared with those producing a LEA. This result makes it likely that the overall REA is a time-bound effect. which can be explained by the structural theory of Kimura. Furthermore, the results demonstrated a specific spatiotemporal shift from central to frontal areas between N1P2 and LN that was pronounced in dichotic trials. This shift points towards the involvement of frontal areas in resolving conflicting input. (C) 2008 Elsevier Ltd. All rights reserved

Distribution of Paw Preference in Female and Male Rats: Assessed by A Modified Version Food-Reaching Test

We re-studied the distribution of paw preference in male and female rats using a new food-reaching test. Paw preference was assessed using a modified new version of food reaching task in quadrupedal position. Of the total sample (N=165). Of 165 rats, 86 (52.12%) were right-handed, 72 (43.64%) were left-handed, and 7 (4.24%) were mixed-handed. Of the in male (N=74) 36(48.65%) were right-handed, 35 (47.30%) were left-handed, and 3 (4.05%) were mixed-handed. The right-minus left paw reaches fitted to gaussian data with two prominent peaks due to right and left preference. In female (N=91) 50(54.94%) were right-handed, 37(40.66%) were left-handed, and 4 (4.40%) were mixed-handed. The female right-preference showed a right-bais compared to males. The males left-preference were more than female left-preference. The distribution of right minus left paw reach was not U-shaped, it was J-shaped like in humans. The results indicate that the distribution of paw preference in rats is similar to that of other animals and to human handedness. It was concluded that there is a right-bias in paw rats, which is caused by the female right-preference under the influence of a biological factor. The right-pawed males were found to be least lateralized than the male left-preference, and female right-and left preference. The brain is in general more lateralized than the female brain