Short‐lived brain state after cued motor imagery in naive subjects

Abstract

Multi-channel electroencephalography recordings have shown that a visual cue, indicating right hand, left hand or foot motor imagery, can induce a short-lived brain state in the order of about 500 ms. In the present study, 10 able-bodied subjects without any motor imagery experience (naive subjects) were asked to imagine the indicated limb movement for some seconds. Common spatial filtering and linear single-trial classification was applied to discriminate between two conditions (two brain states: right hand vs. left hand, left hand vs. foot and right hand vs. foot). The corresponding classification accuracies (mean +/- SD) were 80.0 +/- 10.6%, 83.3 +/- 10.2% and 83.6 +/- 8.8%, respectively. Inspection of central mu and beta rhythms revealed a short-lasting somatotopically specific event-related desynchronization (ERD) in the upper mu and/or beta bands starting approximately 300 ms after the cue onset and lasting for less than 1 s.

Event-related desynchronization (ERD) in the alpha band during a hand mental rotation task

“…Several previous studies have reported that suppression of alpha-band activity reflects an increased excitability of neurons in the involved cortical regions [6,16]. This result suggests that this effect primarily indicates an increase of activity in the central-parietal regions and that the parietal cortex is involved in mental rotation.…”

“…But event-related synchronization (ERS) is related to inhibition of these networks [16]. Furthermore, alpha/beta desynchronization over sensorimotor regions has also been detected during imaging the performance of an action or even observing actions executed by someone else [15,16]. These characteristics led us to tentatively link the suppression of alpha/beta activity with the mental rotation of hands.…”

“…There is reliable evidence that pre-movement suppression over sensorimotor regions in the alpha-and beta-bands, known as event-related desynchronization (ERD), is thought to be associated with activated motor networks in the brain. But event-related synchronization (ERS) is related to inhibition of these networks [16]. Furthermore, alpha/beta desynchronization over sensorimotor regions has also been detected during imaging the performance of an action or even observing actions executed by someone else [15,16].…”

Bedside detection of awareness in the vegetative state: a cohort study

“…First, brain-state classifi cation with no previous training for the individual has produced low classifi cation accuracies in healthy participants (eg, about 75% for right-hand vs feet imagery 8 ), and the same would be true for any patient group. Second, diff erences in attention or capabilities of the working memory could have had a role in the variance of classifi cation accuracies within the patient group.…”

“…6 In some individuals, these ERDs might be accompanied by increases in power (event-related synchronisations [ERS]) over motor areas contralateral to, or surrounding, the ERD. 8,9 With classifi cation techniques, the form of motor imagery being done by a conscious individual can be accurately identifi ed on the basis of these EEG responses alone. 10 We investigated whether these general principles could be adapted to reliably detect covert conscious awareness in a convenience sample of patients who seemed to be entirely vegetative on the basis of repeated and thorough clinical assessment by specialist teams.…”