Spectral and coupling characteristics of somatosensory cortex and centromedian thalamus differentiate between pre- and inter-ictal 5–9 Hz oscillations in a genetic rat model of absence epilepsy
Year: 2024
Type: article
Abstract: Spike-wave-discharges (SWD) are the electrophysiological hallmark of absence epilepsy. SWD are generated in the thalamo-cortical network and a seizure onset zone was identified in the somatosensory cortex (S1). We have shown before that inhibition of the centromedian thalamic nucleus (CM) in GAERS rats resulted in a selective suppression of the spike component while rhythmic cortical 5–9 Hz oscillations remained present. Such oscillations are often seen to precede SWD activity in this well-validated genetic rat model of absence epilepsy, but are also seen in seizure-free periods. The present study characterizes the profile of 5–9 Hz oscillations in thalamo-cortical circuits during pre- and inter-ictal states. Here we recorded local-field-potentials in S1, CM and the secondary motor cortex of GAERS. Time-frequency analysis was used to assess spectral power and non-linear-association analysis was used to determine coupling strength and directionality between brain areas. Phase-specific electrical stimulation was used to compare cortical excitability and to assess the risk for epileptic afterdischarges. Coupling strength and spectral power were higher for the inter-ictal compared to the pre-ictal 5–9 Hz oscillations. However, coupling strength during pre-ictal oscillations was higher than during passive wakefulness. Double pulse stimulation during 5–9 Hz oscillations was more likely to induce epileptic afterdischarges compared to stimulation during passive wakefulness. While no overall differences in cortical excitability were revealed, phase-specific differences in excitability were noticed during the oscillation. Our findings indicate that intermediate coupling between S1 and CM favors SWD generation, thereby adding to the previous notion that 5–9 Hz oscillations represent high-risk periods for seizure generation. In general, pre-ictal oscillations display a unique electrophysiological profile in GAERS that might pave the way for qualification as biomarker for SWD generation and seizure prediction. • Inter-ictal 5–9 Hz oscillations are high-risk periods for seizure generation. • Pre- and inter-ictal 5–9 Hz oscillations differ in their spectral composition. • Coupling strength between S1 & CM differs for pre- and inter-ictal 5–9 Hz oscillations. • Cortical excitability is the same for pre- and inter-ictal 5–9 Hz oscillations. • Cortical excitability varies across up and down states of the oscillations.
Source: Neurobiology of Disease
Institutions: University of Münster, National University of Singapore
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,430
Funder: Deutsche Forschungsgemeinschaft
Awards: G3321633341, G787056584
OpenAlex ID: W4405761182