PURPOSE: Infraslow activity (ISA) occurring during the interictal state in focal epilepsy is largely unstudied. In this exploratory analysis, the authors aimed to characterize features of interictal ISA in a cohort of patients studied by stereoelectroencephography. METHODS: The interictal stereoelectroencephography records for 15 consecutive adult patients were retrospectively analyzed, after application of both conventional (1.6-70 Hz) and infraslow (0.01-0.1 Hz) bandpass filters. Visual analysis was complemented by time-frequency analysis to quantify the change in ISA power over hours. Linear correlation coefficient (R) calculations were used to map interictal connectivity in the infraslow band. RESULTS: Interictal ISA background fluctuations were present throughout the interictal state in all patients, manifesting as recurrent and stereotyped oscillations. These oscillations had an apparent modulatory effect on conventional-band activities and spikes ("spike-crested oscillations"). In the infraslow band, the correlations between electrode contacts were shown to have a stable structure over time. CONCLUSIONS: Infraslow activity exists as a fundamental component of wideband cortical dynamics in focal epilepsy, with features suggestive of scale-free (1/f) dynamics: evidence of phase-amplitude coupling and functional connectivity in the infraslow band. Rather than viewed as a focal paroxysmal activity, interictal ISA may be better understood as a network process, although this requires further study.
PURPOSE: Infraslow activity (ISA) occurring during the interictal state in focal epilepsy is largely unstudied. In this exploratory analysis, the authors aimed to characterize features of interictal ISA in a cohort of patients studied by stereoelectroencephography. METHODS: The interictal stereoelectroencephography records for 15 consecutive adult patients were retrospectively analyzed, after application of both conventional (1.6-70 Hz) and infraslow (0.01-0.1 Hz) bandpass filters. Visual analysis was complemented by time-frequency analysis to quantify the change in ISA power over hours. Linear correlation coefficient (R) calculations were used to map interictal connectivity in the infraslow band. RESULTS: Interictal ISA background fluctuations were present throughout the interictal state in all patients, manifesting as recurrent and stereotyped oscillations. These oscillations had an apparent modulatory effect on conventional-band activities and spikes ("spike-crested oscillations"). In the infraslow band, the correlations between electrode contacts were shown to have a stable structure over time. CONCLUSIONS: Infraslow activity exists as a fundamental component of wideband cortical dynamics in focal epilepsy, with features suggestive of scale-free (1/f) dynamics: evidence of phase-amplitude coupling and functional connectivity in the infraslow band. Rather than viewed as a focal paroxysmal activity, interictal ISA may be better understood as a network process, although this requires further study.
Authors: Olesya Grinenko; Jian Li; John C Mosher; Irene Z Wang; Juan C Bulacio; Jorge Gonzalez-Martinez; Dileep Nair; Imad Najm; Richard M Leahy; Patrick Chauvel Journal: Brain Date: 2018-01-01 Impact factor: 13.501