The correlation between the two variables was statistically significant (r = 0.14, p < 0.01), indicating that the stronger the visual response relative to the motor response, the stronger the coupling with V4 during attention. It should be noted, that in contrast to the results in the covert attention task, no prominent

synchrony was found in the memory-guided saccade task between any type of FEF neuron and V4 LFPs, and there was no spatial effect on coherence, suggesting that the processes involved in the two tasks are markedly different. We next examined the effects of attention on spike-field Quizartinib ic50 coherence within FEF. First taking all cells together, we found that single unit spike-field coherence in the gamma frequency range was significantly enhanced with attention (Figure 6A; coherence averaged PCI-32765 ic50 between 35 and 60 Hz; paired t test p < 0.001), consistent with

our previous multiunit results (Gregoriou et al., 2009a). At the population level gamma band coherence increased by 12%. However, this enhancement of gamma synchrony with attention in FEF was specific to just the visual cells. Pure visual neurons showed a significant, 13% enhancement with attention in the gamma range (Figure 6B; 35–60 Hz, paired t test, p < 0.01), whereas visuomovement and movement neurons did not display significant modulation of synchrony in the gamma band with attention (Figures 6C and 6D; paired t test, visuomovement cells: p = 0.14, 9% increase; movement cells: p = 0.21, 9% increase with attention). Moreover, when the attentional effect on gamma synchrony was compared across the three neuronal classes a significant main effect of cell type was found (Kruskal-Wallis, p < 0.01) with visual to visuomovement and movement

FEF neurons comparisons revealing a significant difference (Tukey-Kramer, p < 0.05 for both comparisons) and no difference between visuomovement and movement neurons (p = 0.61). Interestingly, TCL however, movement cells did show a significant, 28%, increase in coherence with attention inside their movements fields at lower frequencies, spanning beta and lower gamma frequencies (15–35 Hz, paired t test, p < 0.001). For a distribution of attentional effects on frequencies from 35–60 Hz and 15–35 Hz see Figure S4. Although the increase in synchrony between 15 and 35 Hz could be attention-related, we also considered whether it might be caused by the inhibition of saccades into the movement field in the attention task, given that the task required that the animal attended to the stimulus in the field but suppressed any saccade to it. To distinguish whether the increase in synchrony between 15 and 35 Hz was due to attention to the movement field or inhibition of saccades into the movement field in the attention task, we examined coherence within FEF in the delayed saccade task.