Abstract
In the last decades, several electrophysiological markers have been investigated to better understand how humans precede a signaled event. Among others, the pre-stimulus microstates’ topography, representing the whole brain activity, has been proposed as a promising index of the anticipatory period in several cognitive tasks. However, to date, a clear relationship between the metrics of the pre-stimulus microstates [i.e., the global explained variance (GEV) and the frequency of occurrence (FOO)] and well-known electroencephalography marker of the anticipation (i.e., the alpha power reduction) has not been investigated. Here, after extracting the microstates during the expectancy of the semantic memory task, we investigate the correlations between the microstate features and the anticipatory alpha (8–12 Hz) power reduction (i.e., the event-related de-synchronization of the alpha rhythms; ERD) that is widely interpreted as a functional correlate of brain activation. We report a positive correlation between the occurrence of the dominant, but not non-dominant, microstate and both the mean amplitude of high-alpha ERD and the magnitude of the alpha ERD peak so that the stronger the decrease (percentage) in the alpha power, the higher the FOO of the dominant microstate. Moreover, we find a positive correlation between the occurrence of the dominant microstate and the latency of the alpha ERD peak, suggesting that subjects with higher FOO present the stronger alpha ERD closely to the target. These correlations are not significant between the GEV and all anticipatory alpha ERD indices. Our results suggest that only the occurrence of the dominant, but not non-dominant, microstate should be considered as a useful electrophysiological correlate of the cortical activation.
Highlights
Electroencephalography (EEG) records the human brain electric activity with a high temporal and a reasonably good spatial resolution
Here, we extract the pre-stimulus microstates during the expectancy of a semantic memory task, and we investigate the correlations between the microstate features and the anticipatory alpha ERD indices describing both the whole anticipatory period and the dynamics of alpha band modulation
Dominant and non-dominant pre-stimulus microstates were extracted in the period that precedes the semantic memory task
Summary
Electroencephalography (EEG) records the human brain electric activity with a high temporal and a reasonably good spatial resolution. This is a popular neuroimaging modality for understanding how humans precede and prepare for a signaled event, providing several neural correlates in both time and frequency domains In this regard, the alpha (8–12 Hz) power reduction (event-related de-synchronization, ERD) is a typical marker of the neural mechanisms that contribute to the development of temporal expectations, and it is widely observed in the period. It is widely adopted to investigate the period that precedes an expected event, the alpha ERD measure, as other common EEG correlates of anticipation in the time domain (i.e., contingent negative variation, CNV), has some limitations, e.g., its regional specificity This measure requires evaluation of an epoch lasting one or more seconds. The whole brain is continuously in a different state (Kondakor et al, 1997)
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