Poster D41, Monday, March 26, 8:00-10:00 am, Exhibit Hall C
Alpha and theta enhancement during self-ordered number generation
Bobby Ruijgrok1, Olga Kepinska2; 1Leiden University, 2University of California San Fransisco
Verbal working memory (VWM) capacity can be tested by means of self-ordered number generation. We report electrophysiological results of a VMW experiment consisting of a control task and a self-ordered task, based on a positron emission tomography study (Petrides et al., 1993). The authors examined differences in regional cerebral blood flow during the tasks. The self-ordered condition (compared to the control condition) generated bilateral activation within the mid-dorsolateral frontal cortex. Our goal was to connect this finding to neural oscillations. We recruited 94 participants and recorded their EEG using 32 cap-mounted electrodes. In the first session, participants counted aloud numbers from 1 to 10 at the rate of approximately one digit per second (upon presentation of a question mark). In the second session, participants randomly counted aloud numbers from 1 to 10 while monitoring that every number was only mentioned once in each trial, again being prompted by a question mark. Epochs, time-locked to the question mark onset, were extracted. The frequency bands for our power spectrum analysis were defined as 4-8Hz (theta band) and 8-12Hz (alpha band). Compared to the control task we found an increase of theta power at frontal electrodes in the self-ordered condition. The analysis of alpha oscillations showed a power increase at frontal, temporal and occipital electrodes. With these results we have replicated the finding of enhanced bilateral activity within the mid-dorsolateral frontal cortex. We further show that this activity is mostly underpinned by oscillations corresponding to the theta-band; alpha enhancement was distributed more broadly.
Topic Area: EXECUTIVE PROCESSES: Working memory