ABSTRACT
BACKGROUND: Electrical stimulation of the cortex using subdurally implanted electrodes can causally reveal structural connectivity by eliciting cortico-cortical evoked potentials (CCEPs). While many studies have demonstrated the potential value of CCEPs, the methods to evaluate them were often relatively subjective, did not consider potential artifacts, and did not lend themselves to systematic scientific investigations. NEW METHOD: We developed an automated and quantitative method called SIGNI (Stimulation-Induced Gamma-based Network Identification) to evaluate cortical population-level responses to electrical stimulation that minimizes the impact of electrical artifacts. We applied SIGNI to electrocorticographic (ECoG) data from eight human subjects who were implanted with a total of 978 subdural electrodes. Across the eight subjects, we delivered 92 trains of approximately 200 discrete electrical stimuli each (amplitude 4-15â¯mA) to a total of 64 electrode pairs. RESULTS: We verified SIGNI's efficacy by demonstrating a relationship between the magnitude of evoked cortical activity and stimulation amplitude, as well as between the latency of evoked cortical activity and the distance from the stimulated locations. CONCLUSIONS: SIGNI reveals the timing and amplitude of cortical responses to electrical stimulation as well as the structural connectivity supporting these responses. With these properties, it enables exploration of new and important questions about the neurophysiology of cortical communication and may also be useful for pre-surgical planning.
Subject(s)
Cerebral Cortex/physiology , Electric Stimulation/methods , Electrocorticography/methods , Signal Processing, Computer-Assisted , Adult , Artifacts , Electrocorticography/instrumentation , Electrodes, Implanted , Evoked Potentials , Female , Humans , Male , Middle AgedABSTRACT
The use of intrathecal analgesics is an important treatment consideration for many patients with chronic cancer pain. This review describes the various opioid and nonopioid analgesics that have been used in this setting, including morphine, hydromorphone, fentanyl, meperidine, methadone, sufentanil, local anesthetics, clonidine, ketamine, baclofen, midazolam, betamethasone, and octreotide. We discuss available evidence for their analgesic and adverse effects.
