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Although fMRI methods are well recognized as a powerful tool in neuroimaging, they still suffer from lack of repeatable quantitative measures of effect studied, especially in disease group studies, where pathologically changed brain morphologies or distortions caused by head movement arise. In such cases where typical statistical parametric mapping (SPM) approach based on general linear model (GLM) modeling fails, additional methods, giving complementary measures to standard statistical maps SPM may comprise an alternative approach. This subject covers two basic methodologies, which will be presented in this presentation: (1) A novel technique called Mean Regional Response (MRR) uses features derived from time-intensity curves in anatomically or functionally defi ned regions of interest (ROIs). Resulting features can be used for higher level analysis, like ANOVA or highlight differences between groups of subjects allowing inference about group separation; (2) Structural Equation Modeling (SEM) technique is focused on the extraction of connections between the active regions. Although SEM still do not allow arbitrary connection patterns, its use allows determination of time varying and bi-directional, asymmetric connections for groups of interest (patient vs. controls etc.). A methodological basics of BOLD modeling, which can be considered as a basis for most detection and classifi cation methods, will be presented and illustrated with author’s fMRI studies
The aim of the present paper is the assessment of the overall complexity of spontaneous and non-paroxysmal EEG signals obtained from three groups of human subjects, e.g., healthy, seizure and mania. Linear complexity measure suitable for multi-variate signals, along with nonlinear measures such as approximate entropy (ApEn) and Taken's estimator are considered. The degree of linear complexity is significantly reduced for the pathological groups compared with healthy group. The nonlinear measures of complexity are significantly decreased in the seizure group for most of the electrodes, whereas a distinct discrimination between the maniac and healthy groups based on these nonlinear measures is not evident.
The present work presents three experiments investigating cortical activities in the gamma band in humans. On the basis of theoretical models and animal experiments, synchronized oscillatory neuronal activity is discussed as the key mechanism by which the brain binds information processesed in different cortical areas to form a percept. Using an identical stimulation design - the same as used in animal studies - it was shown that induced gamma band responses in the EEG resemble the same features as those found in the intracortical recordings of animals. In addition, the present work demonstrates that these cortical activities are not higher harmonics of the alpha band and that they are senstive to the features of the stimulus. These results support the notion that gamma band activity is not just a by-product of neuronal activity and that alpha- and gamma band activies most certainly represent different cortical funtional states.
Analysis of inducible transcription factors (ITFs) expression is often applied to map drug-induced changes of neuronal activity in brain. Administration of cocaine and alcohol induces ITFs in a large number of brain structures. However, induction of ITFs in a brain region does not necessarily indicate a pharmacological effect of the drug in this brain region. Many of the brain regions could be activated by secondary effects. Perception of stimulus properties of the drug or locomotor effects of the drug are possible secondary effects. Anesthesia can block induction of ITFs by cocaine and alcohol suggesting that ITF expression in a majority of brain regions is more sensitive to secondary effects than to pharmacological effects of these drugs. In agreement with this hypothesis is our finding that the majority of brain regions responding with ITF expression to alcohol administration do not respond to voluntary alcohol self-administration in animals. Only a few brain regions show similar ITF induction after both administration and self-administration of this drug. Presumably these brain regions could be responding to pharmacological effects of alcohol. Given the low resolution of invasive techniques, ITF mapping experiments will continually contribute to our understanding of mechanisms of drug addiction and alcoholism.
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