Depression is a common mood disorder that is characterized by impairment of mood regulation, and ... more Depression is a common mood disorder that is characterized by impairment of mood regulation, and loss of interest in enjoyable activities. According to the previous studies, it has been reported that this disorder is related with elevated rates of cardiovascular morbidity and mortality. Threfore, as an important indicator for diagnosis and classifiation of cardiac dysfunctions, heart rate variability (HRV) has been widely used in depression. Differ from the previous studies in this fild, wavelet packet transform (WPT) is used for determination of effctive very low frequency (VLF), low frequency (LF), and high frequency (HF) bands in HRV signals of depressed patients in this study. Twenty patients who met the DSM-IV criteria for major depressive disorder and age, gender-matched twenty healthy controls were participated for this study. HRV data of these participants were fist were recorded using the Brainamp ExG data acquisition system and then decomposed into sub-bands including VLF, LF, HF using WPT with 9 level Daubechies (db4) family and variations of energy in these bands were analyzed in MATLAB. Th HRV measures as each sub-band average energy and sympathovagal balance (LF/HF ratio) were compared statistically between patients and controls. Th results of this study indicates that especially the mean energy values of sub-frequency ranges in VLF band for each participant are higher than that the values of other bands as LF and HF. In addition, the mean energy values of the regions in LF band of control subjects are signifiantly lower than the same measure of patients. In contrast, in comparison with control subjects, patients with major depression exhibited low HF band energy. Finally, results indicate that sympathovagal balance that reflcts the equilibrium between sympathetic and parasympathetic activity of the autonomic nervous system in patients was higher than that of control subjects indicating autonomic dysfunction throughout the entire experiment. It can be conclude that low cardiovagal activity in patients with major depression may contribute to the higher cardiac dysregulations of these patients.
Objectives: Complexity measures have been enormously used in schizophrenia patients to estimate b... more Objectives: Complexity measures have been enormously used in schizophrenia patients to estimate brain dynamics. However, the conflicting results in terms of both increased and reduced complexity values have been reported in these studies depending on the patients' clinical status or symptom severity or medication and age status. The objective of this study is to investigate the nonlinear brain dynamics of chronic, medicated schizophrenia patients and healthy control subjects using Katz's fractal dimension (FD). Moreover, in order to determine noise effect on complexity of EEG data, a noise elimination method based on wavelet and singular spectrum analysis (SSA) were assessed. Methods: Twenty-two schizophrenia patients and twenty-two age-and gender-matched control subjects underwent a resting state EEG examination with 120 s. The discrete wavelet transform (DWT) was applied for EEG decomposition. Using a SSA approach, noise was removed and EEG reconstructed by inverse wavelet transform. The brain complexity of participants was investigated and compared using Katz'sFD obtained from original and preprocessed EEG data. Results: Lower complexity values were found in schizophrenia patients. However, this difference was only statistically significant for each channel in preprocessed, noiseless EEG data. The most significant complexity differences between patients and controls were obtained in left frontal and parietal regions of the brain. Conclusion: Our findings demonstrate that the utilizing of complexity measures with preprocessing approaches on EEG data to analyze schizophrenics' brain dynamics might be a useful and discriminative tool for diagnostic purposes. Therefore, we expect that nonlinear analysis will give us more valuable results for understanding of schizophrenics' brain.
Background: Although patients with major depressive disorder (MDD) have dysfunctions in cognitive... more Background: Although patients with major depressive disorder (MDD) have dysfunctions in cognitive behaviors and the regulation of emotions, the underlying brain dynamics of the pathophysiology are unclear. Therefore, nonlinear techniques can be used to understand the dynamic behavior of the EEG signals of MDD patients. Methods: To investigate and clarify the dynamics of MDD patients' brains during different emotional states, EEG recordings were analyzed using nonlinear techniques. The purpose of the present study was to assess whether there are different EEG complexities that discriminate between MDD patients and healthy controls during emotional processing. Therefore, nonlinear parameters, such as Katz fractal dimension (KFD), Higuchi fractal dimension (HFD), Shannon entropy (ShEn), Lempel-Ziv complexity (LZC) and Kolmogorov complexity (KC), were computed from the EEG signals of two groups under different experimental states: noise (negative emotional content) and music (positive emotional content) periods. Results: First, higher complexity values were generated by MDD patients relative to controls. Significant differences were obtained in the frontal and parietal scalp locations using KFD (p o 0.001), HFD (p o 0.05), and LZC (p ¼ 0.05). Second, lower complexities were observed only in the controls when they were subjected to music compared to the resting baseline state in the frontal (p o 0.05) and parietal (p ¼ 0.005) regions. In contrast, the LZC and KFD values of patients increased in the music period compared to the resting state in the frontal region (p o 0.05). Third, the patients' brains had higher complexities when they were exposed to noise stimulus than did the controls' brains. Moreover, MDD patients' negative emotional bias was demonstrated by their higher brain complexities during the noise period than the music stimulus. Additionally, we found that the KFD, HFD and LZC values were more sensitive in discriminating between patients and controls than the ShEn and KC measures, according to the results of ANOVA and ROC calculations. Conclusion: It can be concluded that the nonlinear analysis may be a useful and discriminative tool in investigating the neuro-dynamic properties of the brain in patients with MDD during emotional stimulation.
The vulnerability–stress model is a hypothesis for symptom development in schizophrenia patients ... more The vulnerability–stress model is a hypothesis for symptom development in schizophrenia patients who are generally characterized by cardiac autonomic dysfunction. Therefore, measures of heart rate variability (HRV) have been widely used in schizophrenics for assessing altered cardiac autonomic regulations.The goal of this study was to analyze HRV of schizophrenia patients and healthy control subjects with exposure to auditory stimuli. More specifically, this study examines whether schizophrenia patients may exhibit distinctive time and frequency domain parameters of HRV from control subjects during at rest and auditory stimulation periods. Photoplethysmographic signals were used in the analysis of HRV. Nineteen schizophrenic patients and twenty healthy control subjects were examined during rest periods, while exposed to periods of white noise (WN) and relaxing music. Results indicate that HRV in patients was lower than that of control subjects indicating autonomic dysfunction throughout the entire experiment. In comparison with control subjects, patients with schizophrenia exhibited lower high-frequency power and a higher low-frequency to high-frequency ratio. Moreover, while WN stimulus decreased parasympathetic activity in healthy subjects, no significant changes in heart rate and frequency-domain HRV parameters were observed between the auditory stimulation and rest periods in schizophrenia patients. We can conclude that HRV can be used as a sensitive index of emotion-related sympathetic activity in schizophrenia patients.
Heart rate variability (HRV) is an important and useful index to assess the responses of the auto... more Heart rate variability (HRV) is an important and useful index to assess the responses of the autonomic nervous system (ANS). HRV analysis is performed using electrocardiography (ECG) or photoplethysmography (PPG) signals which are typically subject to noise and trends. Therefore, the elimination of these undesired conditions is very important to achieve reliable ANS activation results. The purpose of this study was to analyze and compare the effects of preprocessing on the spectral analysis of HRV signals obtained from PPG waveform. Preprocessing consists oftwo stages: filtering and detrending. The performance oflinear Butterworth filter is compared with nonlinear weighted Myriad filter. After filtering, two different approaches, one based on least squares fitting and another on smoothness priors, were used to remove trends from the HRV signal. The results of two filtering and detrending methods were compared for spectral analysis accomplished using periodogram, Welch's periodogram and Burg's method. The performance of these methods is presented graphically and the importance of preprocessing clarified by comparing the results. Although both filters have almost the same performance in the results, the smoothness prior detrending approach was found more successful in removing trends that usually appear in the low frequency bands of PPG signals. In conclusion, the results showed that trends in PPG signals are altered during spectral analysis and must be removed prior to HRV analysis.
Background: Schizophrenic patients are known to have difficulty processing emotions and to exhibi... more Background: Schizophrenic patients are known to have difficulty processing emotions and to exhibit impairment in stimuli discrimination. However, there is limited knowledge regarding their physiological responsivity to auditory stimuli. Objectives: The purpose of this study was to compare the respiratory effects of two types of auditory stimuli with emotional content, classical Turkish music (CTM) and white noise (WN), on schizophrenia patients and healthy control subjects. Methods: Forty-six individuals participated in the experiment, and respiratory signals derived from a strain-gauge were recorded. Two important respiratory patterns, respiration rate and depth, were analyzed. Results: The results indicated that the patients presented a significantly higher respi ration rate than control subjects during the initial baseline and WN exposure periods. Although CTM evoked an increase in respiration rates and a decrease in respiration depths in the control group, no significant differences were found during the stimulation periods in the patient group. The respiration rate was lower in the post-stimulation period than during the initial baseline period, and no respiration depth differences were found for the WN, music or post-stimulation periods in the schizophrenia group. Patients exhibited a greater respiration depth than the control subjects over all periods; however, a significant difference between the patient and control groups was obtained in the second resting condition and CTM exposure period. Furthermore, to analyze the effect of symptom severity on respiratory patterns, patients were divided into two classes according to their Positive and Negative Syndrome Scale score. Conclusions: Further studies are needed to correlate respiratory differences with emotionally evocative stimuli and to refine our understanding of the dynamics of these types of stimuli in relation to clinical state and medication effects.
Although patients with major depressive disorder (MDD) have dysfunctions in cognitive behaviors a... more Although patients with major depressive disorder (MDD) have dysfunctions in cognitive behaviors and the regulation of emotions, the underlying brain dynamics of the pathophysiology are unclear. Therefore, nonlinear techniques can be used to understand the dynamic behavior of the EEG signals of MDD patients. To investigate and clarify the dynamics of MDD patients׳ brains during different emotional states, EEG recordings were analyzed using nonlinear techniques. The purpose of the present study was to assess whether there are different EEG complexities that discriminate between MDD patients and healthy controls during emotional processing. Therefore, nonlinear parameters, such as Katz fractal dimension (KFD), Higuchi fractal dimension (HFD), Shannon entropy (ShEn), Lempel-Ziv complexity (LZC) and Kolmogorov complexity (KC), were computed from the EEG signals of two groups under different experimental states: noise (negative emotional content) and music (positive emotional content) per...
Proceedings of the 10th IEEE International Conference on Information Technology and Applications in Biomedicine, 2010
The purpose of this study was to compare the autonomic signals in response to Classical Turkish M... more The purpose of this study was to compare the autonomic signals in response to Classical Turkish Music (CTM) of schizophrenia patients and healthy controls. Respiration and blood volume pulse signals were recorded in the rest and auditory stimulation periods from fifty participants. Respiration rate, heart rate and beat-to-beat interval values were extracted as features. Results indicated that patients had higher
Journal of clinical monitoring and computing, 2015
The vulnerability-stress model is a hypothesis for symptom development in schizophrenia patients ... more The vulnerability-stress model is a hypothesis for symptom development in schizophrenia patients who are generally characterized by cardiac autonomic dysfunction. Therefore, measures of heart rate variability (HRV) have been widely used in schizophrenics for assessing altered cardiac autonomic regulations. The goal of this study was to analyze HRV of schizophrenia patients and healthy control subjects with exposure to auditory stimuli. More specifically, this study examines whether schizophrenia patients may exhibit distinctive time and frequency domain parameters of HRV from control subjects during at rest and auditory stimulation periods. Photoplethysmographic signals were used in the analysis of HRV. Nineteen schizophrenic patients and twenty healthy control subjects were examined during rest periods, while exposed to periods of white noise (WN) and relaxing music. Results indicate that HRV in patients was lower than that of control subjects indicating autonomic dysfunction throu...
2010 15th National Biomedical Engineering Meeting, 2010
Here, respiratory signals were recorded from schizophrenia patients and healthy controls. The pur... more Here, respiratory signals were recorded from schizophrenia patients and healthy controls. The purpose of this study is to compare the respiratory effects as respiration rate and depth of different auditory stimuli in these two groups. Signals derived from a strain gauge attached to the chest were recorded for 8 min. which includes silence, Classical Turkish Music (CTM) and acoustic white
Depression is a common mood disorder that is characterized by impairment of mood regulation, and ... more Depression is a common mood disorder that is characterized by impairment of mood regulation, and loss of interest in enjoyable activities. According to the previous studies, it has been reported that this disorder is related with elevated rates of cardiovascular morbidity and mortality. Threfore, as an important indicator for diagnosis and classifiation of cardiac dysfunctions, heart rate variability (HRV) has been widely used in depression. Differ from the previous studies in this fild, wavelet packet transform (WPT) is used for determination of effctive very low frequency (VLF), low frequency (LF), and high frequency (HF) bands in HRV signals of depressed patients in this study. Twenty patients who met the DSM-IV criteria for major depressive disorder and age, gender-matched twenty healthy controls were participated for this study. HRV data of these participants were fist were recorded using the Brainamp ExG data acquisition system and then decomposed into sub-bands including VLF, LF, HF using WPT with 9 level Daubechies (db4) family and variations of energy in these bands were analyzed in MATLAB. Th HRV measures as each sub-band average energy and sympathovagal balance (LF/HF ratio) were compared statistically between patients and controls. Th results of this study indicates that especially the mean energy values of sub-frequency ranges in VLF band for each participant are higher than that the values of other bands as LF and HF. In addition, the mean energy values of the regions in LF band of control subjects are signifiantly lower than the same measure of patients. In contrast, in comparison with control subjects, patients with major depression exhibited low HF band energy. Finally, results indicate that sympathovagal balance that reflcts the equilibrium between sympathetic and parasympathetic activity of the autonomic nervous system in patients was higher than that of control subjects indicating autonomic dysfunction throughout the entire experiment. It can be conclude that low cardiovagal activity in patients with major depression may contribute to the higher cardiac dysregulations of these patients.
Objectives: Complexity measures have been enormously used in schizophrenia patients to estimate b... more Objectives: Complexity measures have been enormously used in schizophrenia patients to estimate brain dynamics. However, the conflicting results in terms of both increased and reduced complexity values have been reported in these studies depending on the patients' clinical status or symptom severity or medication and age status. The objective of this study is to investigate the nonlinear brain dynamics of chronic, medicated schizophrenia patients and healthy control subjects using Katz's fractal dimension (FD). Moreover, in order to determine noise effect on complexity of EEG data, a noise elimination method based on wavelet and singular spectrum analysis (SSA) were assessed. Methods: Twenty-two schizophrenia patients and twenty-two age-and gender-matched control subjects underwent a resting state EEG examination with 120 s. The discrete wavelet transform (DWT) was applied for EEG decomposition. Using a SSA approach, noise was removed and EEG reconstructed by inverse wavelet transform. The brain complexity of participants was investigated and compared using Katz'sFD obtained from original and preprocessed EEG data. Results: Lower complexity values were found in schizophrenia patients. However, this difference was only statistically significant for each channel in preprocessed, noiseless EEG data. The most significant complexity differences between patients and controls were obtained in left frontal and parietal regions of the brain. Conclusion: Our findings demonstrate that the utilizing of complexity measures with preprocessing approaches on EEG data to analyze schizophrenics' brain dynamics might be a useful and discriminative tool for diagnostic purposes. Therefore, we expect that nonlinear analysis will give us more valuable results for understanding of schizophrenics' brain.
Background: Although patients with major depressive disorder (MDD) have dysfunctions in cognitive... more Background: Although patients with major depressive disorder (MDD) have dysfunctions in cognitive behaviors and the regulation of emotions, the underlying brain dynamics of the pathophysiology are unclear. Therefore, nonlinear techniques can be used to understand the dynamic behavior of the EEG signals of MDD patients. Methods: To investigate and clarify the dynamics of MDD patients' brains during different emotional states, EEG recordings were analyzed using nonlinear techniques. The purpose of the present study was to assess whether there are different EEG complexities that discriminate between MDD patients and healthy controls during emotional processing. Therefore, nonlinear parameters, such as Katz fractal dimension (KFD), Higuchi fractal dimension (HFD), Shannon entropy (ShEn), Lempel-Ziv complexity (LZC) and Kolmogorov complexity (KC), were computed from the EEG signals of two groups under different experimental states: noise (negative emotional content) and music (positive emotional content) periods. Results: First, higher complexity values were generated by MDD patients relative to controls. Significant differences were obtained in the frontal and parietal scalp locations using KFD (p o 0.001), HFD (p o 0.05), and LZC (p ¼ 0.05). Second, lower complexities were observed only in the controls when they were subjected to music compared to the resting baseline state in the frontal (p o 0.05) and parietal (p ¼ 0.005) regions. In contrast, the LZC and KFD values of patients increased in the music period compared to the resting state in the frontal region (p o 0.05). Third, the patients' brains had higher complexities when they were exposed to noise stimulus than did the controls' brains. Moreover, MDD patients' negative emotional bias was demonstrated by their higher brain complexities during the noise period than the music stimulus. Additionally, we found that the KFD, HFD and LZC values were more sensitive in discriminating between patients and controls than the ShEn and KC measures, according to the results of ANOVA and ROC calculations. Conclusion: It can be concluded that the nonlinear analysis may be a useful and discriminative tool in investigating the neuro-dynamic properties of the brain in patients with MDD during emotional stimulation.
The vulnerability–stress model is a hypothesis for symptom development in schizophrenia patients ... more The vulnerability–stress model is a hypothesis for symptom development in schizophrenia patients who are generally characterized by cardiac autonomic dysfunction. Therefore, measures of heart rate variability (HRV) have been widely used in schizophrenics for assessing altered cardiac autonomic regulations.The goal of this study was to analyze HRV of schizophrenia patients and healthy control subjects with exposure to auditory stimuli. More specifically, this study examines whether schizophrenia patients may exhibit distinctive time and frequency domain parameters of HRV from control subjects during at rest and auditory stimulation periods. Photoplethysmographic signals were used in the analysis of HRV. Nineteen schizophrenic patients and twenty healthy control subjects were examined during rest periods, while exposed to periods of white noise (WN) and relaxing music. Results indicate that HRV in patients was lower than that of control subjects indicating autonomic dysfunction throughout the entire experiment. In comparison with control subjects, patients with schizophrenia exhibited lower high-frequency power and a higher low-frequency to high-frequency ratio. Moreover, while WN stimulus decreased parasympathetic activity in healthy subjects, no significant changes in heart rate and frequency-domain HRV parameters were observed between the auditory stimulation and rest periods in schizophrenia patients. We can conclude that HRV can be used as a sensitive index of emotion-related sympathetic activity in schizophrenia patients.
Heart rate variability (HRV) is an important and useful index to assess the responses of the auto... more Heart rate variability (HRV) is an important and useful index to assess the responses of the autonomic nervous system (ANS). HRV analysis is performed using electrocardiography (ECG) or photoplethysmography (PPG) signals which are typically subject to noise and trends. Therefore, the elimination of these undesired conditions is very important to achieve reliable ANS activation results. The purpose of this study was to analyze and compare the effects of preprocessing on the spectral analysis of HRV signals obtained from PPG waveform. Preprocessing consists oftwo stages: filtering and detrending. The performance oflinear Butterworth filter is compared with nonlinear weighted Myriad filter. After filtering, two different approaches, one based on least squares fitting and another on smoothness priors, were used to remove trends from the HRV signal. The results of two filtering and detrending methods were compared for spectral analysis accomplished using periodogram, Welch's periodogram and Burg's method. The performance of these methods is presented graphically and the importance of preprocessing clarified by comparing the results. Although both filters have almost the same performance in the results, the smoothness prior detrending approach was found more successful in removing trends that usually appear in the low frequency bands of PPG signals. In conclusion, the results showed that trends in PPG signals are altered during spectral analysis and must be removed prior to HRV analysis.
Background: Schizophrenic patients are known to have difficulty processing emotions and to exhibi... more Background: Schizophrenic patients are known to have difficulty processing emotions and to exhibit impairment in stimuli discrimination. However, there is limited knowledge regarding their physiological responsivity to auditory stimuli. Objectives: The purpose of this study was to compare the respiratory effects of two types of auditory stimuli with emotional content, classical Turkish music (CTM) and white noise (WN), on schizophrenia patients and healthy control subjects. Methods: Forty-six individuals participated in the experiment, and respiratory signals derived from a strain-gauge were recorded. Two important respiratory patterns, respiration rate and depth, were analyzed. Results: The results indicated that the patients presented a significantly higher respi ration rate than control subjects during the initial baseline and WN exposure periods. Although CTM evoked an increase in respiration rates and a decrease in respiration depths in the control group, no significant differences were found during the stimulation periods in the patient group. The respiration rate was lower in the post-stimulation period than during the initial baseline period, and no respiration depth differences were found for the WN, music or post-stimulation periods in the schizophrenia group. Patients exhibited a greater respiration depth than the control subjects over all periods; however, a significant difference between the patient and control groups was obtained in the second resting condition and CTM exposure period. Furthermore, to analyze the effect of symptom severity on respiratory patterns, patients were divided into two classes according to their Positive and Negative Syndrome Scale score. Conclusions: Further studies are needed to correlate respiratory differences with emotionally evocative stimuli and to refine our understanding of the dynamics of these types of stimuli in relation to clinical state and medication effects.
Although patients with major depressive disorder (MDD) have dysfunctions in cognitive behaviors a... more Although patients with major depressive disorder (MDD) have dysfunctions in cognitive behaviors and the regulation of emotions, the underlying brain dynamics of the pathophysiology are unclear. Therefore, nonlinear techniques can be used to understand the dynamic behavior of the EEG signals of MDD patients. To investigate and clarify the dynamics of MDD patients׳ brains during different emotional states, EEG recordings were analyzed using nonlinear techniques. The purpose of the present study was to assess whether there are different EEG complexities that discriminate between MDD patients and healthy controls during emotional processing. Therefore, nonlinear parameters, such as Katz fractal dimension (KFD), Higuchi fractal dimension (HFD), Shannon entropy (ShEn), Lempel-Ziv complexity (LZC) and Kolmogorov complexity (KC), were computed from the EEG signals of two groups under different experimental states: noise (negative emotional content) and music (positive emotional content) per...
Proceedings of the 10th IEEE International Conference on Information Technology and Applications in Biomedicine, 2010
The purpose of this study was to compare the autonomic signals in response to Classical Turkish M... more The purpose of this study was to compare the autonomic signals in response to Classical Turkish Music (CTM) of schizophrenia patients and healthy controls. Respiration and blood volume pulse signals were recorded in the rest and auditory stimulation periods from fifty participants. Respiration rate, heart rate and beat-to-beat interval values were extracted as features. Results indicated that patients had higher
Journal of clinical monitoring and computing, 2015
The vulnerability-stress model is a hypothesis for symptom development in schizophrenia patients ... more The vulnerability-stress model is a hypothesis for symptom development in schizophrenia patients who are generally characterized by cardiac autonomic dysfunction. Therefore, measures of heart rate variability (HRV) have been widely used in schizophrenics for assessing altered cardiac autonomic regulations. The goal of this study was to analyze HRV of schizophrenia patients and healthy control subjects with exposure to auditory stimuli. More specifically, this study examines whether schizophrenia patients may exhibit distinctive time and frequency domain parameters of HRV from control subjects during at rest and auditory stimulation periods. Photoplethysmographic signals were used in the analysis of HRV. Nineteen schizophrenic patients and twenty healthy control subjects were examined during rest periods, while exposed to periods of white noise (WN) and relaxing music. Results indicate that HRV in patients was lower than that of control subjects indicating autonomic dysfunction throu...
2010 15th National Biomedical Engineering Meeting, 2010
Here, respiratory signals were recorded from schizophrenia patients and healthy controls. The pur... more Here, respiratory signals were recorded from schizophrenia patients and healthy controls. The purpose of this study is to compare the respiratory effects as respiration rate and depth of different auditory stimuli in these two groups. Signals derived from a strain gauge attached to the chest were recorded for 8 min. which includes silence, Classical Turkish Music (CTM) and acoustic white
To investigate the heart rate variability, blood volume pulse signals were recorded from schizoph... more To investigate the heart rate variability, blood volume pulse signals were recorded from schizophrenia patients and healthy controls in this study. Totally 8-minutes recorded signals during silence, acoustic white noise, Classical Turkish Music and silence periods were investigated using the low frequency and high frequency power components of heart rate variability analysis. A reduced parasympathetic activity in schizophrenia patients during the whole procedure was found. We found increased sympathetic activity and sympathovagal balance during auditory stimuli in both groups.
Özetçe Son yıllarda, kaotik analiz olarak adlandırılan doğrusal olmayan analiz yöntemleri fizyolo... more Özetçe Son yıllarda, kaotik analiz olarak adlandırılan doğrusal olmayan analiz yöntemleri fizyolojik sinyallerin incelenmesinde yaygın olarak kullanılmaktadır. Bu çalışmada, şizofreni hastalarının beyin sinyallerinin kaotik dinamiklerini incelemek amacıyla şizofreni hastaları ve sağlıklı bireylerden kaydedilen elektroensefalogram (EEG) sinyalleri üzerinde en büyük Lyapunov üsteli ve ilinti boyutu hesaplanmıştır. EEG sinyalleri sol-sağ frontal ve parietal loblardan 2 dakika boyunca yüzey elektrotları aracılığı ile kaydedilmiştir. Şizofrenilerin en büyük Lyapunov üsteli değerleri kontrol grubuna göre daha düşük bulunurken, ilinti boyutları anlamlı bir farklılık göstermemiştir. Sonuçta, kullanılan kaotik analiz yöntemlerine göre sağlıklı bireylerle karşılaştırıldığında şizofrenilerin hastalığa bağlı beyin dinamiklerinin farkları ortaya konmuştur. Abstract Recently, nonlinear analysis techniques which are known as chaotic analysis have been widely used for investigating of physiological signals. In this study, largest Lyapunov exponents and correlation dimension which are obtained from brain signals of schizophrenia patients and healthy subjects were calculated. Electroencephalogram (EEG) signals were acquired by surface electrodes from left-right frontal and parietal lobes during 2 minutes. It was found that schizophrenia patients had lower largest Lyapunov exponent than control subjects. There was not a statistically significant difference between control subjects and schizophrenia patients in terms of correlation dimension. As a result of chaotic analysis methods, the difference in terms of brain dynamics between schizophrenia patients and healthy subjects has been discussed.
— It has been reported that schizophrenia patients have altered cardiac autonomic regulation and ... more — It has been reported that schizophrenia patients have altered cardiac autonomic regulation and changed heart rate variability. The goal of this study was to analyze whether schizophrenia patients may exhibit distinctive Heart rate variability time and frequency domain parameters for control subjects compared both at rest and during auditory stimulation periods. Photoplethysmographic signals of thirteen schizophrenic patients and thirteen healthy subjects were used in the analysis of heart rate variability. Results show that heart rate in patients was higher than that of control subjects indicating autonomic dysfunction throughout the entire experiment. In comparison with control subjects, patients with schizophrenia exhibited lower high frequency power and a greater low-frequency to high-frequency ratio. Moreover, while alerting stimulus decreased parasympathetic activity in healthy subjects, no significant changes in heart rate and frequency-domain HRV parameters were observed between the auditory stimulation and rest periods in schizophrenia patients.
The goal of this study was to analyze whether schizophrenia patients may exhibit distinctive sub-... more The goal of this study was to analyze whether schizophrenia patients may exhibit distinctive sub-band EEG features from control subjects compared both at rest and during auditory stimulation periods. EEG signals of thirty schizophrenic patients and age-gender matched healthy subjects were recorded from F3 left frontal region and analyzed using wavelet decomposition and Welch power spectral density (PSD) methods. Results show that PSD of all EEG sub-bands in patients was higher than that of control subjects during all periods of the experiment. Moreover, auditory stimuli evoked a significant decrease of Welch PSD of beta activity of EEG data in both groups. However, no significant change was found between stimulation periods in schizophrenia group. This methodology can be used to analyze EEG signals of schizophrenia patients to reach discriminative features between patients and controls.
In this study, blood volume pulse and galvanic skin response (GSR) of patients with ST elevation ... more In this study, blood volume pulse and galvanic skin response (GSR) of patients with ST elevation myocardial infarction before angiography and before discharged periods from hospital were acquired and investigated. The purpose of this study was to investigate discriminating features for markers of acute cardiac pain. The recordings were lasted in 5 minutes. We found that Welch PSD and mean GSR values were different in MI patients during this two measurement periods. Further studies are needed to increase our understanding of the causes of these differences in relation to clinical state.
Özetçe Bu çalışmada, majör depresif bozukluk (MDB) hastalarından ve sağlıklı kişilerden kan hacmi... more Özetçe Bu çalışmada, majör depresif bozukluk (MDB) hastalarından ve sağlıklı kişilerden kan hacmi sinyali, kalp hızı değişkenini incelemek ve majör depresyon rahatsızlığı ile kardiyak otonomik aktivite arasındaki bağlantıyı gözlemlemek amacıyla toplanmıştır. Kayıtlar ikişer dakikalık beş bölümden oluşmak üzere toplam on dakika sürmüştür. Kaydedilen sinyallerden kalp hızı değişkenine ait güç, maksimum genlik ve frekans öznitelikleri çıkartılarak iki grup arasındaki farklılıklar incelenmiştir. Maksimum genlik bileşeni MDB hastalarında sağlıklı gruba göre yüksek çıkmıştır. Her iki grup arasında anlamlı fark bulunmuş ve MDB ile kardiyak otonomik aktivite arasında bir bağlantı olduğu görülmüştür. Abstract In this study blood volume pulse signals were recorded from major depressive disorder patients to investigate heart rate variability to prove the relationship between major depressive disorder and autonomic cardiac activity. The recording consisted of five period with two minutes duration and total recording was ten minute. The difference between two groups was investigated with power, maximum amplitude and frequency components of heart rate variability. Maximum amplitude component in MDD patients was higher than healthy group. Significant difference was observed between the MDB and control group and the relationship between MDD and cardiac autonomic activity was proved.
Özetçe Bu çalışmada, şiddetli göğüs ağrısı ile hastaneye başvurup EKG analizi sonucu ST elevasyon... more Özetçe Bu çalışmada, şiddetli göğüs ağrısı ile hastaneye başvurup EKG analizi sonucu ST elevasyonlu kalp krizi tanısı alan ve hemen anjiyoya alınan hastalardan fotopletismograf aracılığı ile kan hacmi sinyalleri 5 dakika boyunca kaydedilmiştir. Ayrıca hastalardan taburcu edilmeden önce de kan hacmi sinyalleri aynı süre kaydedilerek kalp hızı değişkenliği frekans ekseninde incelenmiştir. Welch güç spektral analizi sonucu alçak frekans (AF), yüksek frekans (YF) güç bileşenleri ve AF/YF oranı ile bulunan sempatovagal denge özniteliklerindeki değişim iki farklı kayıt zamanı arasında karşılaştırılmıştır. Anjiyo öncesi kalp hızı değişkenliğinin AF güç bileşeni ve AF/YF oranı parametrelerinin hasta krizi atlattıktan sonra taburcu öncesi değerlerine göre oldukça yüksek olduğu gözlenmiştir. Kriz sırasındaki artmış sempatik aktivasyonun istatistiki olarak anlamlı olduğu bulunmuştur. Abstract In this study, blood volume pulse signals via photoplethysmography have been acquired from patients, who have serious chest pain, with ST segment elevation myocardial infarction according to the ECG before angiography and before patients discharged from the hospital periods during 5 minutes duration. The data were analyzed using Welch spectrum analysis to find heart rate variability parameters in frequency domain. The low frequency (LF), high frequency (HF) power components and LF/HF sympathovagal balance have been compared between these two periods. LF power component and LF/HF rate of heart rate variability have been found higher before angiography procedure in patients. It has been found that increased sympathetic activity during infarction is statistically important.
Özetçe Bu çalışmada, ST segment elevasyonlu enfarktüs tanısı alan hastalardan koroner girişim önc... more Özetçe Bu çalışmada, ST segment elevasyonlu enfarktüs tanısı alan hastalardan koroner girişim öncesi ve kriz sonrası hasta taburcu edilmeden önce olmak üzere iki farklı zaman diliminde 5 dakika boyunca EEG sinyalleri kaydedilmiştir. Kalp krizi sırası ve sonrasında beyin sinyallerindeki kaotik dinamikleri incelemek amacıyla sol parietal ve sol temporal bölgelerden kaydedilen sinyallerin en büyük Lyapunov üsteli hesaplanarak değerlerdeki farklılık karşılaştırılmıştır. Sonuçta, hastalarda enfarktüs sırasında parietal bölgede bulunan azalmış Lyapunov üstelinin o bölgede azalmış kaotik davranışı yansıttığı bulunmuştur. Abstract In this study, EEG signals have been recorded from patients with ST segment elevation myocardial infarction before angiography and before patients discharged from the hospital periods during 5 minutes duration. In order to investigate chaotic dynamics in the brain signals of left parietal and left temporal regions of patients during and after infarction, the differences between values of maximum Lyapunov exponent have been compared. As a result of this study, it has been found that decreased Lyapunov exponent in parietal region of brains' of patients during infraction reflects decreased chaotic behavior in this region.
Elevated rates of cardiac morbidity have been frequently reported in major depressive disorder (M... more Elevated rates of cardiac morbidity have been frequently reported in major depressive disorder (MDD) patients as a result of the relationship between autonomic dysfunctions and varied cardiovascular activity. Heart rate variability (HRV) analysis is an important and non-invasive way for assessing the variances in autonomic nervous system activity of MDD patients. In spectral domain, HRV analysis is usually done by either Fourier transformation (FT) or discrete wavelet transformation (DWT) to divide the data into lowfrequency (LF) and high-frequency (HF) bands. However, while FT is not a proper method for non-stationary HRV data, DWT does not exactly produce required frequency ranges of each LF and HF bands. The purpose of the present study is to investigate the spectral HRV measures obtained by wavelet packet transform (WPT) with absolutely excellent approximation to predefined frequency ranges of bands. Eighteen healthy controls and age-and gender-match eighteen patients with MDD were participated in this study. Sympathovagal balance (LF/HF ratio) that reflects the variation of sympathetic and parasympathetic activities was compared between two groups. Individuals with depression had a significantly higher LF/HF ratio. Our findings suggest that dysfunctions in coordination between sympathetic and parasympathetic nervous system activity in MDD patients can be evaluated by WPT based HRV analysis with high resolution decomposition for required LF and HF bands.
Major depressive disorder (MDD) is a psychiatric mood disorder characterized by cognitive and fun... more Major depressive disorder (MDD) is a psychiatric mood disorder characterized by cognitive and functional impairments in attention, concentration, learning and memory. In order to investigate and understand its underlying neural activities and pathophysiology, EEG methodologies can be used. In this study, we estimated the nonlinearity features of EEG in MDD patients to assess the dynamical properties underlying the frontal and parietal brain activity. EEG data were obtained from 16 patients and 15 matched healthy controls. A wavelet-chaos methodology was used for data analysis. First, EEGs of subjects were decomposed into 5 EEG sub-bands by discrete wavelet transform. Then, both the Katz's and Higuchi's fractal dimensions (KFD and HFD) were calculated as complexity measures for full-band and sub-bands EEGs. Last, two-way analyses of variances were used to test EEG complexity differences on each fractality measures. As a result, a significantly increased complexity was found in both parietal and frontal regions of MDD patients. This significantly increased complexity was observed not only in full-band activity but also in beta and gamma sub-bands of EEG. The findings of the present study indicate the possibility of using the wavelet-chaos methodology to discriminate the EEGs of MDD patients from healthy controls.
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Papers by PhD Saime Akdemir Akar