Influence of ocular filtering in EEG data on the assessment of drug‐induced effects on the brain

Abstract

Ocular artifacts in EEG signals affect the interpretation of clinical study results. The aim of this study was to assess the influence of automatic ocular filtering procedures in the conclusions drawn from a pharmaco-EEG trial. Regression analysis, gold standard, and blind source separation (BSS), Second Order Blind Identification algorithm, ocular filtering procedures were compared using time, frequency, topographic and tomographic brain mapping approaches and pharmacokinetic-pharmacodynamic (PK-PD) relationships. Data consisted of EEGs obtained from 20 volunteers who received single oral doses of haloperidol 3 mg, risperidone 1 mg, olanzapine 5 mg and placebo in a randomized cross-over double-blind design. Although the BSS-based technique preserved brain activity more than regression analysis in anterior leads, in general, topographic significance probability maps globally showed similar results with both methods for most spectral variables. However, different results were obtained when using whole multi-channel information for studying drug effects in the brain: (i) higher correlations between PK and PD time courses showing that BSS allowed estimation of spectral variables more accurately related to drug effects and (ii) larger and more symmetric drug related tomographic LORETA maps showing that BSS led to results that were more neurophysiopharmacologically sound. Definitely, the BSS-based procedure is an effective and efficient preprocessing method to remove ocular artifacts from EEG data. The selection of the ocular filtering procedure could determine different results whose impact depends on the evaluating tool applied to analyze the pharmaco-EEG data.

Electroencephalogram-based pharmacodynamic measures: a review

“…A recent study by Romero et al [129] examined the effects of ocular filtering on the EEG effects of risperidone, olanzapine, and haloperidol in healthy volunteers. The effects included EEG spectral power increases (in alpha and combined delta-theta powers after risperidone administration as well as relative and absolute delta powers after olanzapine administration) and decreases (in the combined delta-theta centroid after haloperidol administration as well as combined delta-theta centroid and absolute alpha power after olanzapine administration) that were both augmented by application of the BSS-based ocular artifact removal method.…”

Quantitative Resting State Electroencephalography in Patients with Schizophrenia Spectrum Disorders Treated with Strict Monotherapy Using Atypical Antipsychotics

“…Antipsychotic drugs have produced relatively consistent effects on quantitative EEG findings in previous reports [8], but these findings are mainly based on administering antipsychotics to healthy subjects [5,[9][10][11] or patients with chronic schizophrenia [7]. In normal healthy subjects, the use of sedative, low-potency neuroleptics (such as chlorpromazine) is characterized by increases in delta and theta power and decreases in alpha and beta power [7].…”

Estado del Arte en Neurotecnologías para la Asistencia y la Rehabilitación en España: Tecnologías Fundamentales

“…El grupo BIOART ha desarrollado métodos automáticos de filtrado de los artefactos oculares, cardíacos o musculares que contaminan las señales EEG basados en la técnica de separación ciega de fuentes. Dichos algoritmos han sido validados tanto en señales simuladas como reales (Romero et al, 2009a), así como el efecto de esta etapa de preprocesado en los estudios de fármaco-EEG (Romero et al, 2009b). El estudio de la conectividad a partir de señales EEG ha permitido conocer, de manera no invasiva, los cambios inducidos en las relaciones entre regiones cerebrales por fármacos psicoactivos.…”