ABSTRACT
OBJECTIVE: The aim of this study was to determine the test-retest consistency of the event-related desynchronization/event-related synchronization (ERD/ERS) method during the performance of an auditory memory task. METHODS: The EEG was recorded while 12 subjects performed an auditory memory task on two separate occasions (mean test-retest interval 9 days). Differences in the ERD/ERS responses between the first and second registrations were examined in 4 EEG frequency bands of interest: 4-6, 6-8, 8-10 and 10-12 Hz. RESULTS: We observed significant differences in the ERD/ERS responses between the first and second registration in all studied frequency bands when examined as a function of time and experimental task. The test-retest reliability of the ERD/ERS values was highest in the theta frequency range (4-6 and 6-8 Hz), poorer in the 8-10 Hz and poorest in the 10-12 Hz alpha frequency range. CONCLUSIONS: The test-retest effect was seen in the ERD/ERS responses of all studied frequency bands during an auditory memory task.
Subject(s)
Brain/physiology , Evoked Potentials/physiology , Memory/physiology , Adult , Analysis of Variance , Auditory Perception/physiology , Electroencephalography , Electrooculography , Female , Finland , Humans , Language , Male , Memory, Short-Term/physiology , Reaction Time , Reproducibility of Results , VoiceABSTRACT
OBJECTIVES: To examine the effects of working memory load on the event-related desynchronization (ERD) and synchronization (ERS) of several narrow EEG frequency bands. METHODS: ERD/ERS responses of the 4-6, 6-8, 8-10 and 10-12 Hz EEG frequency bands were studied in 24 normal subjects performing a visual sequential letter task (so-called n-back task) in which memory load was varied from 0 to 2. RESULTS: In the 4-6 Hz theta frequency band, a long-lasting synchronization was observed in the anterior electrodes, especially after the presentation of targets. In the 6-8 and 8-10 Hz frequency bands, anterior ERS was elicited especially in the 2-back condition (highest memory load). In contrast to the responses of the 8-10 Hz frequency band, in the 10-12 Hz frequency band the 2-back experimental condition elicited the greatest ERD. CONCLUSIONS: In the highest memory load (2-back) experimental condition the attentional capacities were most probably exceeded, resulting in 6-8 and 8-10 Hz ERS. This might reflect an inhibition of such brain areas (frontal cortices) no longer involved in task completion when alternative strategies are needed and utilized. These more 'cognitive' strategies were then reflected as an increase in 10-12 Hz ERD. Additionally, our results support the assumption that the simultaneously recorded ERD/ERS responses of different narrow EEG frequency bands differ and reflect distinct aspects of information processing.
Subject(s)
Brain/physiology , Cortical Synchronization , Evoked Potentials/physiology , Memory/physiology , Adult , Electroencephalography , Female , Humans , MaleABSTRACT
The effects of electromagnetic fields (EMF) emitted by cellular phones on the ERD/ERS of the 4-6 Hz, 6-8 Hz, 8-10 Hz and 10-12 Hz EEG frequency bands were studied in 16 normal subjects performing an auditory memory task. All subjects performed the memory task both with and without exposure to a digital 902 MHz EMF in counterbalanced order. The exposure to EMF significantly increased EEG power in the 8-10 Hz frequency band only. Nonetheless, the presence of EMF altered the ERD/ERS responses in all studied frequency bands as a function of time and memory task (encoding vs retrieval). Our results suggest that the exposure to EMF does not alter the resting EEG per se but modifies the brain responses significantly during a memory task.
Subject(s)
Brain/physiopathology , Electromagnetic Fields/adverse effects , Memory Disorders/etiology , Memory Disorders/physiopathology , Memory/physiology , Telephone , Adult , Electroencephalography , Female , Humans , Male , Psychomotor Performance/physiologyABSTRACT
PURPOSE: To examine the effects of electromagnetic fields (EMF) emitted by cellular phones on the event-related desynchronization/synchronization (ERD/ERS) responses of the 4-6, 6-8, 8-10 and 10-12Hz EEG frequency bands during cognitive processing. MATERIALS AND METHODS: Twenty-four subjects performed a visual sequential letter task (n-back task) with three different working memory load conditions: zero, one and two items. All subjects performed the memory task both with and without exposure to a digital 902 MHz EMF in counterbalanced order. RESULTS: The presence of EMF altered the ERD/ERS responses in the 6-8 and 8-10 Hz frequency bands but only when examined as a function of memory load and depending also on whether the presented stimulus was a target or not. CONCLUSIONS: The results suggest that the exposure to EMF modulates the responses of EEG oscillatory activity approximately 8 Hz specifically during cognitive processes.