Neuronal oscillations in the EEG under varying cognitive load: A comparative study between slow waves and faster oscillations

Abstract

the support of our participants, Suzannah Helps (Developmental Brain-Behaviour Laboratory, School of Psychology, University of Southampton, UK) for her contributions to the task design, and Daniel Durstewitz (Central Institute of Mental Health, Mannheim, Germany) for useful comments on the manuscript. We also thank all three anonymous reviewers for their constructive comments. AbstractObjective: This study has been specifically designed to investigate very low frequency neuronal oscillations (VLFO, <0.5 Hz) during resting states and during goal-directed tasks of graded difficulty levels, quantify the changes that the slow waves undergo in these conditions and compare them with those for higher frequency bands (namely delta, theta and alpha).Methods: To this end we developed a multistage signal processing methodology comprising blind source separation coupled with a neural network based feature extraction and classification method.Results: Changes in the amplitude and phase of brain sources estimates in the VLF band between rest and task were enhanced with increased task difficulty, but remained lower than those experienced in higher frequency bands. The slow wave variations were also significantly correlated with task performance measures, and hence with the level of task-directed attention.Conclusions: These findings suggest that besides their prominent sensitivity to external stimulation, VLFOs also contribute to the cortical ongoing background activity which may not be specifically related to task-specific attention and performance.Significance: Our work provides important insight into the association between VLF brain activity and conventional EEG frequency bands, and presents a novel framework for assessing neural activity during various mental conditions and psychiatric states. Highlights• We present a novel approach for exploring the functional relationship between very low frequency EEG oscillations (VLFO, <0.5 Hz) recorded at rest and those following the transition to goaldirected tasks of graded difficulty levels.• We show that slow waves (i) are attenuated but not extinguished following a rest to task transition, and (ii) are sensitive to variations in cognitive load; (iii) the rest-to-task changes in the slow wave band correlate with performance measures and (iv) the changes are lower than those in higher frequency bands, tentatively suggesting the VLFOs' contribution to the cortical ongoing background activity.• We present a new signal processing methodology for quantifying changes in band-limited EEG activity -this method, developed to gain insight into the neurophysiological role of the slow waves, could be explored with respect to altered functioning of brain oscillators in psychiatric and neurobehavioural disorders such as schizophrenia and ADHD. C. Demanuele et al., 20123

“Can waiting awaken the resting brain?” A comparison of waiting- and cognitive task-induced attenuation of very low frequency neural oscillations

“…The key aim of the present study is to address this issue by comparing the level of VLF oscillation attenuation occurring in the transition from rest to two types of waiting task to that seen in the transition from rest to a simple cognitive reaction time task. Direct current EEG (DC-EEG) was used to measure VLF oscillations as it has excellent temporal resolution and offers a more direct measure of neural activity than BOLD signals (Demanuele et al, 2013). The current study builds on previous research which has identified a robust resting state VLF EEG network with high spatial stabilitiy and temporal reliability (Helps et al, 2008).…”

Spontaneous activity in the waiting brain: A marker of impulsive choice in attention-deficit/hyperactivity disorder?

“…Our study supports the view that in terms of spontaneous brain activity, waiting, despite some characteristics in common with resting, is similar to other goal-directed activities such as performing information processing tasks. Prior debates about the functional status of EEG-VLFO as a measure of real neuronal activity, and the extent to which it is functionally similar to BOLD oscillations (Demanuele et al, 2013;Vanhatalo et al, 2005), notwithstanding, the localization of sources to midline structures in the current study raises new questions about the relationship between the EEG-VLFO network and the DMN. Indeed recent studies using simultaneous EEG-fMRI recordings have identified a direct association between spontaneous BOLD signals and EEG in both infra-slow (Hiltunen et al, 2014) and higher frequency domains (Laufs et al, 2003;Mantini et al, 2007).…”

Modeling multiple time scale firing rate adaptation in a neural network of local field potentials

“…Adding rate adaptation to this model is motivated by the physiological importance of slow oscillations of LFPs (Steriade et al 1993, Demanuele et al 2013) and data implicating a related role for rate adaptation. Slow oscillations (~0.1-1 Hz) are sometimes parsed into Up and Down states (Steriade 2006), where rate adaptation is thought to play a role in the transitions (Destexhe et al 2007).…”