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Abstract:
Delirium is a highly prevalent syndrome, yet the underlying
mechanisms are not well understood. Criterions for diagnosis are
short-time disturbances of consciousness and cognition. Slowing of
brain electrical activity, especially enhancement of frontotemporal
slow wave activity after electroconvulsive therapy (ECT), which is
known to produce delirium, have been reported. We set out to relate
the neuropsychological features to the topographic frequency
distribution of brain electrical activity and estimated the
respective source by applying Low Resolution Brain Electromagnetic
Tomography (LORETA, see Ref. 1). So far, 12 patients with major
depression have been investigated before (t0), shortly after (t1),
and 24 hours (t2) after ECT with EEG and neuropsychological
testing. Changes of theta activity at Fz electrode position (t1-t2)
showed a correlation with changes in test performance of awareness
of the surrounding (r=0.59; p<0.05) and of retrieval from
episodic memory (r=0.71; p<0,05). Source analysis revealed a
slow-wave focus in anterior cingulate cortex (ACC) and
supplementary motor area (Brodmann's Area 6; t-test: p<0.05).
The results indicate a relation between the appearance of this
focus and the appearance of the core features of delirium which is
consistent with neuropsychological theories about attentional
functions of ACC. As a model, the Supervisory Attentional System
which has been located into the ACC may be functionally disturbed
in delirium.
1 Pascual-Marqui et al. 1994. Int J Psychophysiol 18: 49-65
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