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Theta increases with workload and is associated with numerous processes including working memory, problem solving, encoding, or self monitoring. These processes, in turn, involve numerous structures of the brain. However, the relationship between regional brain activity and the occurrence of theta remains unclear. In the present study, simultaneous EEG-fMRI recordings were used to investigate the functional topography of theta. EEG-theta was enhanced by mental arithmetic-induced workload. For the EEG-constrained fMRI analysis, theta-reference time-series were extracted from the EEG, reflecting the strength of theta occurrence during the time course of the experiment. Theta occurrence was mainly associated with activation of the insular cortex, hippocampus, superior temporal areas, cingulate cortex, superior parietal, and frontal areas. Though observation of temporal and insular activation is in accord with the theory that theta specifically reflects encoding processes, the involvement of several other brain regions implies that surface-recorded theta represents comprehensive functional brain states rather than specific processes in the brain. The results provide further evidence for the concept that emergent theta band oscillations represent dynamic functional binding of widely distributed cortical assemblies, essential for cognitive processing. This binding process may form the source of surface-recorded EEG theta.
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This study investigated differences in brain activation during meditation between meditators and non-meditators. Fifteen Vipassana meditators (mean practice: 7.9 years, 2h daily) and fifteen non-meditators, matched for sex, age, education, and handedness, participated in a block-design fMRI study that included mindfulness of breathing and mental arithmetic conditions. For the meditation condition (contrasted to arithmetic), meditators showed stronger activations in the rostral anterior cingulate cortex and the dorsal medial prefrontal cortex bilaterally, compared to controls. Greater rostral anterior cingulate cortex activation in meditators may reflect stronger processing of distracting events. The increased activation in the medial prefrontal cortex may reflect that meditators are stronger engaged in emotional processing.
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- Englisch (2)
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- Mathematics
- Adult (2)
- Biological Clocks/physiology (1)
- Brain/anatomy & histology/blood supply/*physiology (1)
- *Brain Mapping (1)
- Brain Mapping/methods (1)
- Case-Control Studies (1)
- Cerebrovascular Circulation/*physiology (1)
- Cognition/*physiology (1)
- Electroencephalography/methods (1)
- Evoked Potentials/*physiology (1)
- Female (2)
- Frontal Lobe/blood supply/*physiology (1)
- Functional Laterality/physiology (2)
- Gyrus Cinguli/blood supply/*physiology (1)
- Humans (2)
- Image Processing, Computer-Assisted/methods (1)
- Magnetic Resonance Imaging/methods (2)
- Male (2)
- *Meditation (1)
- Mental Processes/*physiology (1)
- Nerve Net/anatomy & histology/physiology (1)
- Neural Pathways/anatomy & histology/*physiology (1)
- Neuropsychological Tests (1)
- Oxygen/blood (1)
- Problem Solving/physiology (1)
- *Theta Rhythm (1)
- Thinking/physiology (1)
- Time Factors (1)