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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Elektroencefalografiövervakning för bedömning av anestesidjup vid generell anestesiEn litteraturstudie

Pettersson, Nina, Grunér, Lynn January 2014 (has links)
Abstrakt Bakgrund: Varseblivning vid generell anestesi är något som för många patienter skapar oro och kan ge psykiska trauman postoperativt. I anestesisjuksköterskans arbete ingår det att övervaka anestesidjupet hos den sövda patienten och det finns många tekniska hjälpmedel som stöd. Syfte: Studiens syfte var att ta reda på om EEG-baserad övervakning är ett tillförlitligt hjälpmedel för anestesisjuksköterskan vid övervakning av anestesidjupet i generell anestesi. Följande frågeställningar har använts: Hur tillförlitlig är EEG-baserad övervakning för att bedöma anestesidjupet? Finns det skillnader mellan de olika EEG-baserade hjälpmedlen när det gäller tillförlitlighet att bedöma anestesidjupet? Finns det behov för EEG-baserad övervakning av anestesidjupet? Metod: Litteraturstudie. Artikelsökning gjordes i PubMed och 31 artiklar inkluderades och granskades enligt SBU’s mall för relevans bedömning. Sex stycken artiklar exkluderades och de resterande 25 artiklar genomgick kvalitetsgranskning med SBU:s kvalitetsgranskningsmall. (SBU, 2011). Vid analys formulerades sex rubriker. Resultat: I flera av studierna gjordes jämförelser mellan olika läkemedel och EEG-monitorer vilket gjorde det svårt att generalisera, men det som framsteg var bland annat att EEG-övervakning möjliggjorde för att mängden läkemedel som administreras till patienten kunde minskas, samt bidra till ett snabbare uppvaknade och extubering. Vid specifika grupper som löper stor risk att drabbas av varseblivning kunde EEG-övervakning vara till nytta vid bedömning av anestesidjupet. De flesta studier genomförde postoperativa intervjuerna, dock skiljde sig antal intervjuer samt tidpunkt för genomförande. Slutsats: EEG-övervakning kan minska mängden läkemedel som patienten får under anestesin. Det framkom skillnader mellan monitorer och vad de egentligen påvisar.
42

The Effects Of The Allocation Of Attention Congruent With Lateralized Cognitive Tasks On EEG Coherence Measurements

Hill, Cynthia DeLeon 05 1900 (has links)
The single task condition of the Urbanczyk and Kennelly (1991) study was conducted while recording a continuous electroencephalographic (EEG) record. Attention was allocated by instructed lateral head orienting and eye gaze either congruently or incongruently with lateralized cognitive tasks. Thirty university subjects retained a digit span or a spatial location span for a 20 second retention interval. EEG data were extracted from the 20 second retention intervals and interhemispheric coherence was calculated for homologous sites in the temporal, parietal and occipital regions of the brain. There was a main effect for group, with congruent orienting producing greater coherence values than incongruent orienting. This effect of attention on alpha coherence values was found in the low alpha (8-10 Hz) frequency band. This provides evidence that the lower alpha frequency band is reflective of manipulations of attention. The higher coherence measures for the congruent orienting group indicates that homologous regions of the two hemispheres are more coupled into a single system when lateralized attention activates the same hemisphere performing the cognitive task. In the higher alpha frequency band (11-13 Hz) group, sex, site and task interacted. This provides evidence that the higher alpha band is more affected by cognitive processing of the specific task undertaken. An interhemispheric brain system, affected by the lateral orientation of attention, may underlie psychometric intelligence's general “g” ability (Spearman, 1927.)
43

Méthodes d’analyse et intérêt de l’étude en EEG-IRMf des variations du signal BOLD dans le temps et dans l’espace au cours des anomalies épileptiformes / EEG-fMRI study of temporal and spatial BOLD signal changes during epileptiform abnormalities

Tyvaert, Louise 18 October 2010 (has links)
L’épilepsie est une pathologie neurologique caractérisée par une activité neuronale excessive et hypersynchrone soit localisée soit diffuse. L’activité neuronale est principalement évaluée par la mesure de l’activité électrique neuronale en électroencéphalographie (EEG). L’EEG dispose d’une excellente résolution temporelle, mais d’une résolution spatiale médiocre. L’enjeu actuel est de développer une technique non-invasive capable d’explorer et de localiser l’activité neuronale avec une bonne résolution temporo-spatiale afin d’améliorer la prise en charge de l’épilepsie. L’activité neuronale peut également être définie par des modifications hémodynamiques et métaboliques (couplage neurovasculaire). L’imagerie par résonance magnétique fonctionnelle (IRMf) mesure ces dernières au travers de l’étude du signal BOLD (Blood Oxygenation Level Dependent) et permet l’exploration de l’activité neuronale avec une bonne résolution spatiale. L’EEG-IRMf permet l’étude du signal BOLD spécifiquement lors des événements EEG. Si cette technique a démontré un certain intérêt dans la localisation des générateurs des anomalies épileptiformes intercritiques, il n’est pas rare d’observer des discordances entre les réponses observées et le foyer épileptique supposé. En effet, les résultats représentent l’activité globale cérébrale au cours de l’anomalie EEG. Dans une première partie, nous avons cherché à améliorer la spécificité des réponses BOLD observées lors des anomalies intercritiques. Pour cela nous avons exploré l’effet des fluctuations de l’état de vigilance au cours de l’enregistrement EEG-IRMf. Les variations des rythmes EEG physiologiques, reflets de la vigilance, sont responsables de fluctuations du signal BOLD significatives. L’intégration de ces données dans le modèle linéaire général diminue la variance du signal BOLD de la période contrôle. Ainsi, les réponses BOLD obtenues pour les anomalies épileptiformes devraient être améliorées et moins discordantes avec la localisation du foyer supposé. Dans une deuxième partie, nous avons souhaité étudier les crises épileptiques. L’application de la technique d’EEG-IRMf dans les crises permettrait d’obtenir des informations spatiales plus fiables que les anomalies intercritiques (meilleur rapport signal sur bruit) et cruciales dans la définition de la zone épileptogène. Sur une série de 8 patients atteints de malformation de développement cortical, nous avons démontré la faisabilité de l’enregistrement des crises épileptiques en EEG-IRMf mais également l’intérêt des informations obtenues sur les structures impliquées lors de la décharge critique. Cependant, l’analyse actuelle modélise la crise comme un événement stationnaire dans le temps et dans l’espace. Et de façon plus nette que lors de l’étude des anomalies intercritiques, les réponses BOLD obtenues pour les crises sont diffuses et reflètent l’activité globale cérébrale sans distinction claire entre la zone génératrice et la zone de propagation. Au cours d’un deuxième travail, nous avons intégré dans l’analyse statistique les informations temporelles fournies par la mesure du signal BOLD. La résolution temporelle de l’IRMf apporte un bon échantillonnage de la réponse hémodynamique et permet une analyse fiable des variations temporelles du signal BOLD. Nous avons analysé les réponses BOLD des crises de 10 patients avec leur décours temporel. Les zones impliquées dans le départ des crises ont pu être discriminées de celles impliquées secondairement dans la propagation. Dans une troisième partie, nous avons utilisé les données BOLD non plus dans un but localisateur de l’activité neuronale mais afin de définir le rôle des structures impliquées dans l’activité épileptique. / "Epilepsy is a neurological disorder defined by an excessive and hypersynchronous neuronal activity. This abnormal cerebral activity can be focal or diffuse. The neuronal activity is commonly determined by the neuronal electric activity explored in electroencephalography (EEG). The EEG is characterized by a high temporal resolution and a low spatial resolution. The development of a new technique that can explore and localize the neuronal activity with a good temporal and spatial resolution is real challenge in the epilepsy field. The neuronal activity may also be defined by hemodynamic and metabolic changes (neurovascular coupling). These changes can be explored by the functional magnetic resonance imaging (fMRI).The fMRI records the BOLD signal (Blood Oxygenation Level Dependent) changes and allows the study of neuronal activity with an excellent spatial resolution. The simultaneous EEG-fMRI recording provides information about BOLD changes specifically correlated in time with EEG events. It has been demonstrated that this technique could provide valuable results on the generators of epileptiform interictal events. However, EEG-fMRI studies showed also some discrepancies between the location of BOLD responses and the suspected epileptic focus. Indeed, BOLD responses reflect not only the generator’s activity but also the global cerebral activity occurring at the time of the epileptiform event. In the first part, we tried to improve the specificity of the BOLD responses observed during interictal epileptiform abnormalities. Therefore, we explored the BOLD effect of the alertness fluctuations during prolonged EEG-fMRI recording. Physiological rhythms variations reflecting the brain state changes are responsible for noteworthy BOLD changes. Physiological EEG rhythms may be integrated to the EEG-fMRI analysis in studies with fluctuation of alertness, to eliminate possible confounding factors. The accuracy of the BOLD results obtained for interictal epileptiform events would be improved. In a second part, we proposed to use the EEG-fMRI technique to study epileptic seizures. This new application would provide information with a better spatial definition than the interictal study (better signal to noise ratio) and crucial for the definition of the epileptogenic zone in presurgical exploration. On a population of eight patients with a malformation of cortical development, we demonstrated that the EEG-fMRI recording during seizures is feasible and that the results showed original and valuable information on cerebral structures involved in the ictal discharge. However, the actual method uses a “bloc design” model and then suggests that the seizure is a stationary event in time and in space. With this method, BOLD responses obtained during ictal event are diffuse and reflect the cerebral global activity without discrimination between the seizure onset zone and the structures secondary involved in the propagation. In a second work, we proposed a new method adding in the statistical analysis the temporal information provided by the BOLD signal measurement. The temporal resolution of fMRI and the temporal sampling used in fMRI protocol are sufficient to study with a good accuracy the temporal variations of the BOLD signal. We analyzed the dynamic time course of the BOLD signal in ten patients with seizures inside the MRI.
44

A continued musical and personal dialogue with the waves of epilepsy

Miles, Alan Douglas January 2018 (has links)
In the early hours of the morning several years ago I awoke with paramedics leaning over me. In a state of confusion, my first conscious decision was to enter my music production studio while they attempted to lead me to the ambulance. Music was important to me even in a disorientated post-ictal state (an altered state of consciousness following a seizure). Two weeks later I awoke with paramedics standing over me again. I had started to experience multiple seizures. During the previous weeks, I also experienced numerous incidents of memory loss when delivering presentations at work, feelings of being returned to the room following an absence of consciousness and suffering from temporal disorientation. I also experienced multiple episodes of déjà vu, aromas that were difficult to identify, visual distortions and waves of euphoria like momentary intoxication of an unknown origin. These experiences began to increase in frequency until my first tonic-clinic seizure. Following medical tests, I was diagnosed with epilepsy. It was a confusing period with no history of epilepsy in my family and no physiological causes could be identified. I viewed epilepsy as an overwhelming authority, it takes control of your life and asserts its power upon you, forcibly changing your reality in an instant. When I saw the EEG readouts from my tests I noticed how similar they were to sound waves. As an electronic musician, this project is being used as an artistic and cathartic opportunity to creatively transform the power of epilepsy and reassert my personal identity upon it. Symbolically reclaiming personal control and creatively transforming the psychological perception of personal power that is lost through the experience of epilepsy. Transforming it from an internal destructive force into an external and creative activity in my life. Capturing the cultural and emotional experiences of epilepsy and transforming them into cinematic electronic soundscapes using research and musical experimentation with EEG epilepsy signals. It is an existential exploration, the results will be tangible, accessible and reasonable in the transformation of the EEG epilepsy recordings from the uncontrollable unconscious into the creative conscious. This project will apply transposition, mathematics, research and creative exploration to map epilepsy EEG events into computer synthesized soundscapes, transforming the passive nature of diagnoses and treatment into a proactive and creative process. This thesis shares an individual's research and experiences of epilepsy with a community that have an interest in transforming the passive sufferer into a creatively active and articulate patient. Professor Dan Lloyd (Thomas C. Brownell) Professor of Philosophy at Trinity College states that: “It is observed that fMRI (Brain) activity is more similar to music than it is to language ... ” Lloyd D. (2011). If, as Lloyd suggests, brain activity is more like music than language then what might epilepsy be saying or possibly singing during these events? What are the audible timbres of these events? Researchers such as Wu et al, Psyche et al, Chafe and Parvizi have previously interpreted EEG data of epilepsy EEG events to aid medical research, but it is not exploring the emotional timbre of epilepsy from a patient’s perspective. The previous research derived musical notes from EEG signals to trigger MIDI instruments and modulate non-epilepsy related audio sources for medical identification purposes. This project examines the possible timbres derived directly from the EEG data to explore and creatively describe the emotional and physical experience from a patient’s perspective. This thesis presents the personal experience of epilepsy, the development of electroencephalography (EEG), the sociocultural history of epilepsy. the sonification and musification of EEG data, plus the concepts involved in the design of timbre and sound effect. For this project, a bespoke granular synthesizer called ‘The Oblique-Granizer’ (programmed with Cycling74's MAXMSP) has been constructed that employs EEG signals, converted to digital audio, to synthesize timbres that explore the description of human experience and emotions related to epilepsy. This thesis includes research that has been carried out into mathematical algorithms to generate musical notes and melodic information in electronic music compositions using EEG epilepsy seizure activity. The aim is to take back personal control by creatively transforming the EEG data and my psychological perception of epilepsy into electronic soundscapes and sonic textures through exploration of sonification and musification techniques.
45

EEG Untersuchung zum Zusammenhang zwischen Emotionsverarbeitung und Aufmerksamkeitsprozessen von stark und wenig angstsensitiven Personen / EEG examination about the connection of emotion and attention processing of people with high and low anxiety sensitivity

Kempkes, Lisa Marleen January 2013 (has links) (PDF)
Gegenstand der vorliegenden Arbeit ist die Untersuchung des Einflusses der Angstsensitivität auf die Emotionsverarbeitung und selektive Aufmerksamkeitsprozesse. Anhand des Angstsensitivitätsindex-3 (ASI-3) wurden die Probanden in stark und wenig angstsensitiv eingeteilt. Der Selbstbeurteilungsfragebogen ASI-3 erfasst in welchem Maß die betreffende Person auf typische angstauslösende Stimuli mit Symptomen reagiert (Kemper, et al., 2009). Bei 53 gesunden, freiwilligen Probanden wurde, während der Präsentation von Bildern mit positiven, negativen und neutralen Inhalt, ein EEG (Elektroenzephalogramm) abgeleitet. In Anlehnung an das Paradigma von Schupp und Kollegen (Schupp, et al., 2007) wurde jede Bildkategorie jeweils in einem Durchgang als Target- und gleichzeitig die beiden anderen Kategorien als Non-Target-Bedingung dargeboten. Außerdem wurde ein Durchgang mit der Anweisung „alle gleich beachten“ (PB-Bedingung) durchgeführt. Die Angstsensitivität beeinflusst den Verlauf des EPN (early posterior negative potential). Bei hoch angstsensitiven Probanden zeigt sich ein stärker negativer Verlauf der EPN-Amplitude als bei wenig Angstsensitiven. Diese Aussage gilt für die Darbietung von neutralen und positiven Bildern bei der PB-Bedingung. Bei Probanden mit hoher Angstsensitivität verläuft sowohl bei der Target-Bedingung als auch bei der Non-Target-Bedingung das EPN signifikant negativer, als bei denjenigen mit niedriger Angstsensitivität. Ebenfalls zeigte sich das EPN-Potential während der Target- und Non-Target-Bedingung bei positiven und neutralen Bildern für hoch angstsensitive Probanden signifikant negativer als bei wenig angstsensitiven Probanden. Im LPP (late positive potential) zeigte sich kein Einfluss der Angstsensitivität auf den Verlauf des Potentials. Keine geschlechtsspezifischen Unterschiede konnten im LPP und EPN festgestellt werden. / The subject of this study is an examination of the influence of anxiety sensitivity on the processing of emotions and selective attention processes. In the present study 53 healthy, voluntary participants have been categorized as highly and little anxiety sensitive according to the anxiety sensitivity index 3 (ASI-3) (Kemper, et al., 2009). The self-evaluation questionnaire ASI-3 determines to which degree the test person reacts with symptoms to typical anxiety-causing stimuli. Event-related brain potentials were measured while subjects viewed images with positive, negative and neutral content. Drawing on Schupp et al’s paradigm each category of images has been displayed at one stage as target condition and the 2 others simultaneously as non-target condition (Schupp, et al., 2007). Also, one stage has been conducted with the subjects being instructed to “regard all equally” (PB-condition). Anxiety sensitivity influences the EPN (early posterior negative potential) waveform. Highly anxiety sensitive subjects displayed an increased negativity of the EPN amplitude than little anxiety sensitive ones. This statement can be made both for neutral and positive images under the PB-condition. The amplitude of the EPN is significantly more negative in subjects with high anxiety sensitivity both in target-condition and non-target-condition when compared to subjects with lower anxiety sensitivity. Similarly, the EPN potential for highly anxiety sensitive subjects during target and non-target condition with positive and neutral images was found to be significantly more negative. In LPP (late positive potential) no influence of anxiety sensitivity on the course of potential could be established. No gender-specific differences have been identified in either LPP or EPN.
46

Einfluss des COMT-Polymorphismus auf das Sensorische Gating bei erwachsenen ADHS-Patienten und gesunden Kontrollen / Impact of COMT-Val158Met-polymorphism on sensory gating in adult ADHD-patients and healthy controls

Daubitz, Torsten January 2014 (has links) (PDF)
Wesentlicher Inhalt der vorliegenden Dissertation war die EEG-Ableitung und EKP-Messung zur Untersuchung des sensorischen Gatings anhand des P50-Paarstimulus-Paradigmas bei einer Gruppe von ADHS-Patienten (n=23) sowie einer vergleichbaren Gruppe gesunder Erwachsener (n=25). Die Ableitung des EEGs erfolgte nach dem allgemein anerkannten internationalen 10/20-System, die Auswertung mit der Software Brain-Vision-Analyzer®. Bislang beschränkten sich viele Studien zur ADHS allein auf Untersuchungen im Kindesalter, da es sich bei der Aufmerksamkeits-Defizit-Hyperaktivitätsstörung (ADHS) um eine der häufigsten psychiatrischen Störungen des Kindes- und Jugendalters überhaupt handelt. Da diese bei Betroffenen meist aber bis in das Erwachsenenalter fortbesteht, lag der Schwerpunkt dieser Arbeit speziell auf der Untersuchung erwachsener ADHS-Patienten. In der ADHS-Gruppe konnte ein beeinträchtigtes Sensorisches Gating mit höheren Gatingquotienten im Vergleich zur gesunden Kontrollgruppe gezeigt werden. Des Weiteren galt es, mögliche Einflüsse des COMT-Val/Met-Polymorphismus auf die P50 herauszuarbeiten. Hypothetisch sollten Probanden mit dem katalytisch aktiveren Val/Val-Allel und dem dadurch resultierenden relativen Dopaminmangel ein schlechteres Sensorisches Gating aufweisen, als Probanden mit den Allelausprägungen Val/Met oder Met/Met. In der Patientengruppe fanden sich diesbezüglich keine signifikanten Unterscheidungen. Hingegen wiesen Träger des Val-Allels in der gesunden Normgruppe eine Beeinträchtigung des Gatings mit dem Nachweis der größten Gatingquotienten auf. Weitere signifikante Unterschiede zwischen den Allelen Val/Met und Met/Met wurden nicht gezeigt. Auch die bildschematische Darstellung der EEG-Datensätze mittels LORETA kam zu dem Ergebnis einer verstärkten frontalen Hirnaktivierung zum Zeitpunkt des Teststimulus (tS) im superioren frontalen Cortex in der gesunden Kontrollgruppe und gilt als Ausdruck normal funktionierender (inhibitorischer) Gating-Regelkreise. Diese verstärkte Aktivierung des frontalen Cortex fand sich bei ADHS-Patienten nicht und stützt somit die Hypothese eines Gating-Defizits bei ADHS-Patienten bedingt durch ein präfrontales Defizit. Ein positiver Einfluss von Nikotin auf die P50 konnte nicht gezeigt werden, wobei aufgrund der kleinen Studiengröße keine abschließende Beurteilung möglich scheint. Ob die Messung der P50 nach Beobachtung eines einschränkten Gatings bei ADHS-Patienten künftig als Endophänotyp der adulten ADHS-Erkrankung herangezogen werden kann, bleibt weiteren Untersuchungen vorbehalten. Basierend auf den vorliegenden Ergebnissen scheinen weitere Studien an größeren Kollektiven sinnvoll. Neben dem COMT-Polymorphismus ist ggf. die Untersuchung von Polymorphismen weiterer Dopamin relevanter Enzyme und deren Einfluss auf das sensorische Gating zu diskutieren. / OBJECTIVE: Sensory Gating deficits are a common and well described endophenotype in schizophrenia patients. Abnormalities of prefrontal cortical function are discussed in line with deficits in attentional control associated with genetic risk. Multiple susceptibility genes which may impact on molecular mechanisms of prefrontal function have been examined, such like COMT-Val158Met-polymorphism in the catechol-O-methyltransferase (COMT) gene, which accounts for a 4-fold variation in enzyme activity and dopamine catabolism. Homozygous Val-allel-carriers seem to have the lowest dopamine levels. METHOD: Main issue of this study was to examine the electrophysiological phenomenon of sensory gating in a group of adult ADHD-patients (n = 23) and a similar group of normal healthy controls (n = 25) with a combined 21-channel-EEG-ERP-recording and the measure of the P50-double-click-paradigm. A second part of the study was to reveal the impact of COMT-Val158Met-polymorphism on sensory gating with hypothetical highest gating-quotients in homozygous val-allel-carriers with the (relative) lowest dopamine levels. RESULTS: In ADHD-patients a deficit in P50-sensory gating with higher gating-quotients was described. Healthy controls showed a normal P50-suppression confirming normal capacity of inhibitory prefrontal networks, underlined in the LORETA-analysis as well. In ADHD-patients no impact of COMT-polymorphism on sensory gating was seen though in healthy controls. Homozygous healthy Val-allel-carriers showed the highest gating quotients compared to Val/Met- or Met/Met-allel-carriers. Nicotine had no effects on sensory gating in this study. CONCLUSIONS: Sensory Gating deficits in ADHD-patients have to be taken into account as a possible endophenotype in the attention-deficit-hyperactive-disorder. If there is a strong impact of COMT-Val158Met-polymorphism on sensory gating even in ADHD affected persons, has to be evaluated in future studies. More research in major groups is needed to proof these findings.
47

Are late positive potentials to emotional pictures affected by spatial cues?

Sand, Anders January 2009 (has links)
<p>Perceived distance between motivationally significant stimuli andobserver has been shown to affect arousal. To study effects ofperceived motion and distance on affective picture processing, eventrelatedpotentials were recorded in two experiments as neutral andunpleasant pictures were presented with different cues to induceperceptions of changes in spatial distance. The cues were either thetarget picture or independent circles that increased or decreased insize, or the target picture presented in a static small or large size. Inboth experiments, late positive potentials at centroparietal electrodeswere more pronounced, and self-reports more negative, forunpleasant compared to neutral stimuli. The results of theexperiments do not, however, provide evidence that inducedperceptions of motion or distance affect late positive potentials.</p>
48

Are late positive potentials to emotional pictures affected by spatial cues?

Sand, Anders January 2009 (has links)
Perceived distance between motivationally significant stimuli andobserver has been shown to affect arousal. To study effects ofperceived motion and distance on affective picture processing, eventrelatedpotentials were recorded in two experiments as neutral andunpleasant pictures were presented with different cues to induceperceptions of changes in spatial distance. The cues were either thetarget picture or independent circles that increased or decreased insize, or the target picture presented in a static small or large size. Inboth experiments, late positive potentials at centroparietal electrodeswere more pronounced, and self-reports more negative, forunpleasant compared to neutral stimuli. The results of theexperiments do not, however, provide evidence that inducedperceptions of motion or distance affect late positive potentials.
49

Inhibition of Gamma Oscillations in Healthy Subjects and Patients with Schizophrenia

Farzan, Faranak 23 February 2011 (has links)
The pathophysiology of psychiatric disorders such as schizophrenia is not fully understood due, in part, to the shortcomings of available neurophysiological techniques. Previous studies have shown that patients with schizophrenia have deficits in dorsolateral prefrontal cortex (DLPFC). In this regard, two major deficits were observed: impairments in gamma-aminobutyric-acid (GABA) neurotransmission and cortical gamma (30-50Hz) oscillations. Previous in vitro and animal studies have linked the modulation of gamma oscillations with GABAB receptor mediated inhibition. Objectives: The first objective was to examine the effect of GABAB receptor mediated inhibition on cortical oscillations in the motor cortex and DLPFC in healthy subjects by using the novel technique of transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) and through the TMS paradigm long interval cortical inhibition (LICI), which has been associated with GABAB receptor mediated inhibition. Second, to evaluate the psychometric properties of this neurophysiological paradigm, the validity and reliability of EEG indices of LICI were examined. Finally, the effect of LICI on cortical oscillations was examined in the DLPFC and motor cortex of patients with schizophrenia compared to healthy subjects and patients with bipolar disorder. Hypothesis: It was predicted that EEG measures of LICI would show validity and reliability, and it was hypothesized that patients with schizophrenia would show deficits in inhibition of gamma oscillations in DLPFC compared to healthy subjects and patients with bipolar disorder. Results: The first experiment showed that in healthy subjects LICI inhibited gamma oscillations in the DLPFC but not in the motor cortex. The second experiment demonstrated the validity and reliability of EEG indices of LICI were confirmed in healthy subjects. Finally, patients with schizophrenia had a selective deficit in inhibition of gamma oscillations in the DLPFC which appeared to be independent of illness duration or antipsychotic medication, and it was not observed in bipolar disorder. Conclusions: TMS combined with EEG allows for measuring modulatory effect of LICI on cortical oscillations. Inhibition of gamma oscillations in the DLPFC may be an essential neurophysiological process that may be impaired in schizophrenia. Future studies should ascertain the potential of gamma inhibition deficit as a biological marker for this illness.
50

Inhibition of Gamma Oscillations in Healthy Subjects and Patients with Schizophrenia

Farzan, Faranak 23 February 2011 (has links)
The pathophysiology of psychiatric disorders such as schizophrenia is not fully understood due, in part, to the shortcomings of available neurophysiological techniques. Previous studies have shown that patients with schizophrenia have deficits in dorsolateral prefrontal cortex (DLPFC). In this regard, two major deficits were observed: impairments in gamma-aminobutyric-acid (GABA) neurotransmission and cortical gamma (30-50Hz) oscillations. Previous in vitro and animal studies have linked the modulation of gamma oscillations with GABAB receptor mediated inhibition. Objectives: The first objective was to examine the effect of GABAB receptor mediated inhibition on cortical oscillations in the motor cortex and DLPFC in healthy subjects by using the novel technique of transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) and through the TMS paradigm long interval cortical inhibition (LICI), which has been associated with GABAB receptor mediated inhibition. Second, to evaluate the psychometric properties of this neurophysiological paradigm, the validity and reliability of EEG indices of LICI were examined. Finally, the effect of LICI on cortical oscillations was examined in the DLPFC and motor cortex of patients with schizophrenia compared to healthy subjects and patients with bipolar disorder. Hypothesis: It was predicted that EEG measures of LICI would show validity and reliability, and it was hypothesized that patients with schizophrenia would show deficits in inhibition of gamma oscillations in DLPFC compared to healthy subjects and patients with bipolar disorder. Results: The first experiment showed that in healthy subjects LICI inhibited gamma oscillations in the DLPFC but not in the motor cortex. The second experiment demonstrated the validity and reliability of EEG indices of LICI were confirmed in healthy subjects. Finally, patients with schizophrenia had a selective deficit in inhibition of gamma oscillations in the DLPFC which appeared to be independent of illness duration or antipsychotic medication, and it was not observed in bipolar disorder. Conclusions: TMS combined with EEG allows for measuring modulatory effect of LICI on cortical oscillations. Inhibition of gamma oscillations in the DLPFC may be an essential neurophysiological process that may be impaired in schizophrenia. Future studies should ascertain the potential of gamma inhibition deficit as a biological marker for this illness.

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