Event-related alpha synchronization/desynchronization in a memory-search task in adolescent survivors of childhood cancer

Objectives: Event-related desynchronization (ERD) and synchronization (ERS) of the 8–10 and 10–12 Hz frequency bands of the background EEG were studied in 19 adolescent survivors of childhood cancer (11 leukemias, 8 solid tumors) and in 10 healthy control subjects performing an auditory memory task. Methods: The stimuli were auditory Finnish words presented as a Sternberg-type memory-scanning paradigm. Each trial started with the presentation of a 4 word set for memorization whereafter a probe word was presented to be identified by the subject as belonging or not belonging to the memorized set. Results: Encoding of the memory set elicited ERS and retrieval ERD at both frequency bands. However, in the survivors of leukemia, ERS was turned to ERD during encoding at the lower alpha frequency band. ERD was lasting longer at the lower frequency band than at the higher frequency band, in each study group. At both frequency bands, the maximum of ERD was achieved later in the cancer survivors than in the control group. Conclusion: The previously reported type of ERD/ERS during an auditory memory task was reproducible also in the survivors of childhood cancer, at different alpha frequency bands. However, the temporal deviance in ERD/ERS magnitudes, in the cancer survivors, was interpreted to indicate that both survivor groups had prolonged information processing time and/or they used ineffective cognitive strategies. This finding was more pronounced in the group of leukemia survivors, at the lower alpha frequency band, suggesting that the main problem of this patient group might be in the field of attention.