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PubMed2002

Linear spatial integration for single-trial detection in encephalography.

Conventional analysis of electroencephalography (EEG) and magnetoencephalography (MEG) often relies on averaging over multiple trials to extract statistically relevant differences between two or more experimental conditions. In this article we demonstrate single-trial detection by linearly integrating information over multiple spatially distributed sensors within a predefined time window. We report an average, single-trial discrimination performance of Az approximately 0.80 and faction correct between 0.70 and 0.80, across three distinct encephalographic data sets. We restrict our approach to linear integration, as it allows the computation of a spatial distribution of the discriminating component activity. In the present set of experiments the resulting component activity distributions are shown to correspond to the functional neuroanatomy consistent with the task (e.g., contralateral sensorymotor cortex and anterior cingulate). Our work demonstrates how a purely data-driven method for learning an optimal spatial weighting of encephalographic activity can be validated against the functional neuroanatomy.

Algorithms↗
PubMed1975

Air filling of the subarachnoid space over the cerebral convexities at repeat encephalography.

In order to check the constancy of convexity block, the airencephalograms (AEG) of seventeen patients who had undergone two separate examinations were reexamined. A satisfactory filling by air of the basal cisterns or Sylvian fissures was a prerequisite for including the AEG in this series. Consistent results related to air filling of the parietal region were obtained at the two examinations except in one patient with clinical signs of a pontine neoplasm. When the AEG was repeated in a very short time and with unchanged clinical conditions, the degree of air filling over the convexity was practically identical. But, with progressive neurological signs, the parietal air blocks showed a slight increase and also extended to the frontal region. It was concluded, firstly, that upper convexity block is a reproducible finding; secondly, that it is related to organic brain disease, the extent of the convexity block being correlated to the degree of clinical deterioration. As judged from other studies using isotope cisternography, the subarachnoid space is usually not complelely obstructed. It is suggested that the organically changed brain and leptomeninges create special physical conditions for the appearance of convexity air block in the AEG.

Adult↗