PubMed · 6708879
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
B Lake. 1984-04-14. Cardiac exercise testing.. https://doi.org/10.5694/j.1326-5377.1984.tb108198.x
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Inverse solution techniques based on electroencephalograph (EEG) measurements have become a powerful means of gaining knowledge about the functioning of the brain. A model of the head and a potential computation method are necessary to describe the EEG problem mathematically. The generation of realistically shaped three-compartment models of the head is discussed. The isolated problem approach for the boundary element method is applied to develop a fast and accurate numerical solution of the EEG forward problem. Accuracy studies with this approach show that dipole positions can be reconstructed within a distance of 3 mm from the original positions. Inverse simulations indicate that the incorporation of the individual head shape may significantly influence the reconstructed dipole position but not its magnitude and orientation, in comparison with the commonly used three-sphere model. However, the presence of noise in the simulated potential data affects the solutions based on realistically shaped models more than those of the simple three-sphere model. The increased sensitivity of the former models to noise in the data remains a serious drawback for their practical application to EEG source localisations.
Explore the source record for details and available documents.
Thirty years ago Zeeman conjectured that the dynamics of the EEG might be modeled by the "equation of motion" of a Duffing oscillator, a pendulum with a nonlinear, cubic, restoring force. In this study the idea is extended to the evoked potential (EP). A transient sensory EP reflects activity from several neuronal groups, pools of neurons that fire in synchrony, with voltage-time curves that overlap appreciably. When the dynamics of each neuronal group is modeled by a Duffing oscillator, multi-electrode transient VEPs are well predicted. Predictions based on Duffing oscillator dynamics are substantially better than those based on the assumption that each neuronal group follows a simpler exponentially damped sinusoid or a function that simulates a post-synaptic potential. The component voltage-time curves are reasonably consistent over 7 subjects, suggesting sequential activation of neuronal groups with delays of several tens of milliseconds between them. The scalp topographies of the components suggest their origins in the occipital cortex.