EEG ACTIVATION PATTERNS DURING THE PERFORMANCE OF TASKS INVOLVING DIFFERENT COMPONENTS OF MENTAL CALCULATION

In this study we demonstrate the existence of different patterns of EE G activation during the performance of 4 different tasks involving dif ferent components of mental calculation in normal subjects. The EEG wa s recorded in all monopolar leads of the 10/20 system using linked ear lobes as reference. Absolute and relative power were calculated in th e delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz) and beta (12.5-19 Hz) bands. The tasks were presented randomly and the EEG seg ments preceding presentation of the stimulus were considered as the re st corresponding to the task requested by the stimulus. Tasks were of 4 different types, involving number comprehension, recognition of math ematical symbols, the calculation process and the spatial component. A NOVAs between the rest periods showed no differences in any band. Neit her did ANOVAs between tasks. However, other variables (task minus res t), which were calculated as the differences in power between task and rest respectively, showed significant differences between tasks in th e delta and beta bands in the frontal lobes. In addition, new variable s were calculated as the difference between tasks, since many factors were common across several tasks. These variables correspond to the EE G change due to a specific component of mental calculation. Significan t differences were obtained in delta and theta bands in right posterio r areas and in the beta band in frontal areas. We concluded that the E EG differences observed during different components of mental calculat ion suggest the participation of different networks.