title: Brain oscillatory 4-30 Hz responses during a visual n-back memory task with varying memory load.
abstract: Brain oscillatory responses of 4-30 Hz EEG frequencies elicited during the performance of a visual n-back task were examined in 36 adult volunteers. Event-related desynchronization (ERD) and event-related synchronization (ERS) responses were examined separately for targets and non-targets in four different memory load conditions (0-, 1-, 2- and 3-back). The presentation of all stimuli in all memory load conditions elicited long-lasting theta frequency (approximately 4-6 Hz) ERS responses which were of greater magnitude for the target stimuli as compared to the non-target stimuli. Alpha frequency range (approximately 8-12 Hz) ERD responses were observed in all memory load conditions for both targets and non-targets. The duration of these alpha ERD responses increased with increasing memory load and reaction time. In all memory load conditions, early appearing beta rhythm (approximately 14-30 Hz) ERD responses were elicited, and with increasing memory load, these beta ERD responses became longer in duration. Additionally, beta ERS responses were observed in the 0- and 1-back memory load conditions. The current results reveal a complex interplay between brain oscillations at different frequencies during a cognitive task performance.
authors.affiliation: Cognitive Science Unit, Department of Psychology, University of Helsinki, P.O. Box 9, 00014 Helsinki, Finland. mirka.pesonen@helsinki.fi
authors.forename: Mirka
authors.initials: M
authors.lastname: Pesonen
authors.forename: Heikki
authors.initials: H
authors.lastname: Hämäläinen
authors.forename: Christina M
authors.initials: CM
authors.lastname: Krause
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D001921:Brain / Q000502:physiology*; D003344:Cortical Synchronization; D004569:Electroencephalography; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time; D013826:Theta Rhythm; D014796:Visual Perception / Q000502:physiology*