Within FEF, we selleck chemicals found attentional effects on synchrony in different frequency ranges for visual and movement neurons. An increase in gamma spike-field coherence with attention
for visual neurons parallels our own previous findings in the FEF using multiunit activity (Gregoriou et al., 2009a) as well as similar effects measured in visual area V4 with attention (Bichot et al., 2005, Fries et al., 2001 and Fries et al., 2008). It was also accompanied by an increase in gamma power of the LFP. Gamma frequency synchronization has been suggested to reflect local computations which mediate the enhancement of sensory representations (Buschman and Miller, 2007 and Kopell et al., 2000). Such an enhancement of sensory representations would be in agreement with the role of visual neurons in the covert attention task. The enhancement in gamma synchrony for visual neurons was contrasted by an increase in synchrony in lower frequencies, including the beta band for FEF movement neurons and a small but significant increase in LFP beta power within the FEF. A different pattern of beta band modulation was found in the memory-guided saccade task. A desynchronization in beta frequencies within the FEF was measured specifically Neratinib for neurons with saccade-related movement activity and a decrease in LFP beta power was found during the delay period. The increase in beta (and lower gamma) synchrony
and beta power with attention and the decrease in the memory-guided saccade task suggest that the contribution
of FEF neurons with movement activity is different in the two tasks and thus confirm that the two processes are subserved by different mechanisms. Given that the exact frequency range at which beta coherence modulation was found was somewhat different in the two tasks (saccade task, 17–23 Hz; covert attention task, 15–35 Hz), we cannot rule out the possibility that other factors besides saccade inhibition contribute to the increase in coherence in the covert attention task for movement cells. However, the fact that LFP beta power (15–25 Hz) was also differentially affected Megestrol Acetate in the two tasks indicates that beta band modulation reflects the distinct motor requirements of the two tasks. One could argue that preparing a saccade to a visible stimulus (in a covert attention task) could differ fundamentally from preparing a saccade to a remembered location (as in the memory-guided saccade task). If this is the case then the differential beta band modulation in the two tasks could reflect processes not related to the current state of the oculomotor network. However, the existing literature on the role of beta oscillations and synchrony in motor processes supports our suggestion. An increase in beta frequency oscillations has been associated with an inactive state of the motor system while a decrease of beta power has been reported to reflect motor preparation and motor execution in skeletomotor tasks (Baker et al., 1997, Gilbertson et al.