We further examined whether LFP power was tuned to the spatial target location. We found that a significant number of FEF (18/209; 8.61%, P<0.05, Binomial test) but not ACC (11/233; 4.72% NS; ACC versus FEF: P=0.099, Chi-square test) channels showed significant spatial tuning of power within the theta frequency band (3–9 Hz) during the delay period in the time window of 400–1,100 ms following target stimulus onset (Fig. 2a, one-way analysis of variance, P<0.05). In addition, a significant number of FEF (50/209; 23.92%, P<0.05, Binomial test) but not ACC channels (14/233; 6.08% NS; difference ACC versus FEF: P<0.001, Chi-square test) showed significant tuning in the beta band (12–30 Hz). Thus, we found spatial tuning of LFP power in theta and beta frequencies in FEF but not in ACC. The observed power modulation of the FEF LFPs is in line with previous FEF single-unit recording results, which suggest a high degree of spatial tuning in FEF neurons22.
