Now you'll feel it, now you won't: EEG rhythms predict the effectiveness of perceptual masking.
Do ongoing brain states determine conscious perception of an upcoming stimulus? Using the high temporal resolution of EEG, we investigated the relationship between prestimulus neuronal oscillations and the perceptibility of two competing somatosensory stimuli embedded in a backward masking paradigm. We identified two prestimulus EEG signatures predictive for a suprathreshold yet weak target stimulus to become perceptually resistant against masking by a stronger distractor stimulus: (i) over left frontal cortex a desynchronization of the regional beta rhythm (approximately 20 Hz) 500 msec prior to a perceived target, and (ii) a subsequent additional attenuation of both mu (approximately 10 Hz) and beta "idling" rhythms over those pericentral sensorimotor cortices which are going to process the upcoming target stimulus. Furthermore, across subjects the probability for target perception strongly correlates with the individual absolute level of pre-target amplitudes in these frequency bands and locations. These signatures significantly differed from the EEG characteristics preceding detected and undetected single stimuli. We suggest that the early activation of left frontal areas involved in top-down attentional control is critical for preventing backward masking and leads the preparation of primary sensory cortices: The ensuing prestimulus suppression of sensory idling rhythms warrants an intensified poststimulus processing, and thus, effectively promotes conscious perception of suprathreshold target stimuli embedded into an ecologically relevant condition featuring competing environmental stimuli.
Schubert
Ruth
R
Neurophysics Group, Department of Neurology and Clinical Neurophysiology, Charité-University Medicine Berlin, Berlin, Germany. ruth.schubert@charite.de
Haufe
Stefan
S
Blankenburg
Felix
F
Villringer
Arno
A
Curio
Gabriel
G
D000328:Adult; D001703:Biophysics; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography; D004585:Electrooculography / Q000379:methods; D005260:Female; D005385:Fingers / Q000294:innervation; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D008297:Male; D010470:Perceptual Masking / Q000502:physiology*; D011237:Predictive Value of Tests; D011597:Psychomotor Performance / Q000502:physiology; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology*; D013223:Statistics as Topic; D013997:Time Factors; D055815:Young Adult