When separated, it is clear that while increases in alpha synchrony were on color trials, they were primarily limited to the orientation rule ensemble (Figure 6, left column). Indeed, electrode pairs with increased alpha synchrony during the color rule were more likely to show increased beta synchrony for the orientation rule than color rule (55/117 and 24/90 pairs, respectively; p < 10−5, permutation test). Synchronized alpha activity may reflect inhibition of task-irrelevant processing (Ray and Cole, 1985; Klimesch et al., 1999; Pfurtscheller, 2001; Palva and Palva, 2007; Haegens et al., 2011b). Thus, alpha synchrony during color trials may reflect “deselection” of the dominant (but check details currently

irrelevant) orientation ensemble, allowing the weaker (but currently relevant) color ensemble to be boosted. Indeed, alpha increases in the orientation rule ensemble were associated with enhancement of individual color rule neurons.

Alpha power during the preparatory interval of color trials was positively correlated with the activity level of color rule-preferring, but not orientation rule-preferring, neurons during rule application to the test stimulus (Figure S4, correlation coefficient of 0.014, p = 0.0019 versus 0.003, p = selleck inhibitor 0.47, for color and orientation rule-preferring neurons, respectively, for 100 ms after stimulus onset; color > orientation, p = 0.047, see Supplemental Information for details). There was no direct evidence for suppression Rutecarpine of the orientation ensemble (e.g., a negative correlation between alpha power and the activity of orientation-preferring neurons on color trials). However, these neurons are already suppressed during the color

rule, so further suppression may be harder to detect. Synchrony at both alpha and beta was correlated with behavioral reaction time, further suggesting their functional role. There was significantly stronger rule-selective synchrony in both bands on trials with shorter reaction times (Figure 7; alpha: p = 3.43 × 10−10, beta: p = 2.71 × 10−3, Wilcoxon signed-rank test), even after controlling for the effects of preparatory time and rule on reaction time (see Table S1). This stronger synchrony with faster reaction times occurred prior to test stimulus for both alpha and beta (Figure 7; stronger selectivity in beta: −20 to 0 ms, alpha: −240 to 0 ms prior to stimulus onset, Wilcoxon signed-rank test, p < 0.05, Bonferroni correction), suggesting preparatory facilitation of test stimulus processing. Our results suggest distinct synchronous PFC ensembles support different rules. Rule-selective beta-band synchrony may help to dynamically link neurons in order to support task performance. Indeed, task-relevant (rule- and stimulus-selective) neurons were more synchronized to the corresponding ensemble for the current rule.