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MEG investigations of cortico-hippocampal information processing
Claudia TescheBrain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, 02015 HUT, Espoo, Finland
The main advantage of MEG and EEG over other functional imaging technologies is in the non-invasive detection of temporal characteristics of neuronal population activity. The majority of recent MEG studies have concentrated on the analysis of signals generated in relatively compact regions of fissural cortex. Investigation of deeper structures, such as thalamus, hippocampus, and cerebellum, have only become practical with the advent of whole-scalp MEG arrays. The methodology of the detection of activity in deep brain areas is illustrated through the identification of short-latency MEG responses to intermittent somatosensory stimulation. The timing of initial thalamic [1] and cerebellar [2] evoked population responses demonstrates parallel activation of the thalamo-cortical and spinocerebellar pathways. Early (20 - 30 ms) activation of both contralateral somatosensory SI and also of SII, which is often viewed as association cortex, demonstrates immediate processing of intermittent somatosensory input [3]. Hippocampal ~100 ms and ~300 ms responses followed activation of SI and SII cortices. The initiation of both hippocampal and cerebellar responses observed prior to anticipated but omitted stimuli suggest engagement of both structures in the processing of temporal features of somatosensory input.
Supported by NIH NINDS grant NS34533.
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