Theta oscillations in primate prefrontal and anterior cingulate 1 cortices in forewarned reaction time tasks

35 Previously, we introduced a monkey model for human frontal midline 36 theta oscillations, as a possible neural correlate of attention. It was based on 37 homologous theta oscillations found in the monkey's prefrontal and anterior 38 cingulate cortices (areas 9 and 32) in a self-initiated hand-movement task. 39 However, it has not been confirmed whether theta activity in the monkey 40 model consistently appears in other situations demanding attention. Here, 41 we examined the detailed properties of theta oscillations in four variations of 42 forewarned reaction time tasks with warning (S1) and imperative (S2) 43 stimuli. We characterized the theta oscillations generated exclusively in 44 areas 9 and 32, as follows: 1) in the S1-S2 interval where movement 45 preparation and reward expectation were presumably involved, the theta 46 power was higher than in the pre-S1 period; 2) in the no-go trials of go/no-go 47 tasks instructed by S1, the theta power in the S1-S2 interval was lower than 48 in the pre-S1 period in an asymmetrical reward condition, while it was 49 moderately higher in a symmetrical condition; 3) the theta power after 50 reward delivery was higher than in the unrewarded trials; 4) the theta power 51 in the pre-S1 period was higher than in the resting condition; 5) when the 52