  Anti-seizure medications (ASMs) are the primary treatment for epilepsy, yet
medication tapering effects have not been investigated in a dose, region, and
time-dependent manner, despite their potential impact on research and clinical
practice.
  We examined over 3000 hours of intracranial EEG recordings in 32 subjects
during long-term monitoring, of which 22 underwent concurrent ASM tapering. We
estimated ASM plasma levels based on known pharmaco-kinetics of all the major
ASM types.
  We found an overall decrease in the power of delta band activity around the
period of maximum medication withdrawal in most (80%) subjects, independent of
their epilepsy type or medication combination. The degree of withdrawal
correlated positively with the magnitude of delta power decrease. This
dose-dependent effect was strongly seen across all recorded cortical regions
during daytime; but not in sub-cortical regions, or during night time. We found
no evidence of differential effect in seizure onset, spiking, or pathological
brain regions.
  The finding of decreased delta band power during ASM tapering agrees with
previous literature. Our observed dose-dependent effect indicates that
monitoring ASM levels in cortical regions may be feasible for applications such
as medication reminder systems, or closed-loop ASM delivery systems. ASMs are
also used in other neurological and psychiatric conditions, making our findings
relevant to a general neuroscience and neurology audience.
