Towards mechanisms of impaired consciousness: the role of fast EEG transients in epileptic brain
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1
Institute of Higher Nervous Activity and Neurophysiology, Russia
Spontaneous spike-wave discharges (SWD) are present in the cortical electroencephalogram (EEG) in several strains of rats such as WAG/Rij and GAERS. These rat strains are considered as a valid model of absence epilepsy. Absence epilepsy is characterized by loss/decrease of consciousness accompanied by the occurrence of SWD in EEG. It is known that (i) SWD are produced within cortico-thalamo-cortical network; (ii) SWD preferably occur during passive wakefulness, drowsiness, light non-REM sleep; (iii) physical or mental activity reduces the probability of occurrence of SWD and (iv) sensory processing is altered during SWD. Elaboration of mechanisms that govern loss of consciousness during absence epilepsy (SWD) is helpful in understanding neurophysiological aspects of normal consciousness. The present study is performed in WAG/Rij rats which all develop absence seizures. The purpose of the research is to investigate neuronal network mechanisms that underlay process of epileptogenesis in the neocortex thus contributing to loss of consciousness. EEG coherence study [1] demonstrates complex changes of intracortical, thalamo-cortical and intrathalamic associations in the thalamo-cortical network at the onset of absence seizures. Of great importance is strengthening of associations between somatosensory cortex and functionally related areas in the neocortex and the thalamus. Investigation of local field potential during SWD [2] indicates that the fast cortical components (e.g. EEG ripples and double spiking occurring in the frontal and parietal cortex) are the integrative part of SWD. A combination of the abovementioned facts suggests that (i) the newly observed pro-epileptic fast transients are localized in the somatosensory and frontal cortical areas and (ii) these two cortical areas display the most broad-band increase of coherence (5-60 Hz, including gamma frequencies) at the onset of absence seizures. Therefore, it seems likely that fast EEG transients are produced by the local cortical network (e.g., somatosensory and frontal areas). Altogether lead us to the following assumptions:- fast transients in EEG are implicated in the initiation of seizure activity, - fast transients in EEG may prerequisite epileptic lost of consciousness; - fast transients in EEG represent impaired functioning of local cortical networks (but scarcely involve the thalamus) and result to intracortical information processing. This study is supported by ‘the Russian Foundation for Humanitarian Research’ (grant 08-06-00174а)
References
1. Sitnikova E, van Luijtelaar G. Cortical and thalamic coherence during spike-wave seizures in WAG/Rij rats. Epilepsy Res., 2006, 71: 159-180.
2. Sitnikova E, van Luijtelaar G. Electroencephalographic characterization of Spike-Wave Discharges in cortex and thalamus in WAG/Rij rats. Epilepsia, 2007, 48 (12), 2296–2311
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Oral Presentation
Topic:
Animal Models of Cognition
Citation:
Sitnikova
E
(2008). Towards mechanisms of impaired consciousness: the role of fast EEG transients in epileptic brain.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.058
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Received:
28 Nov 2008;
Published Online:
28 Nov 2008.
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Correspondence:
Evgenia Sitnikova, Institute of Higher Nervous Activity and Neurophysiology, Moscow, Russia, jenia-s@mail.ru