Fig 4. Cortical t-maps showing regions of significant standardized cortical theta activity according to task period/sub-period.

Occipital-theta activity is observed throughout all sub-periods in the memory item presentation (MIP) period in the slow task (A), while prominent only in the beginning sub-period in the fast task (B). Frontal-theta is significantly active during the holding period in both tasks. The occipital and frontal regions were selected as target regions due to their significantly positive standardized cortical theta activities in both tasks during the MIP and holding periods, respectively (C).