, 2010). Second, the activation-dependent

gamma phase shifts might play important roles in competition and/or spike-time dependent plasticity (Vinck et al., 2010a) Third, the vertical-position-dependent gamma phase might generate temporal input sequences that are optimal to activate postsynaptic neurons (Branco et al., 2010). For MUA-LFP gamma-band synchronization, we confirmed previous studies showing attentional enhancements in gamma-band LFP power and MUA-LFP coherence Entinostat mw in awake monkey V4 (Fries et al., 2001b and Gregoriou et al., 2009). The importance of this confirmation derives from the methodological advance in that we demonstrate such enhancements for MUA-LFP gamma PPC, which is free of any bias due to spike count or spike rate. An open Cabozantinib question addressed here is to what degree the effect of spatial attention on gamma locking is expressed in isolated single units and depends on electrophysiological cell class. Mitchell et al. (2007) showed that both putative interneurons and pyramidal cells have proportionally similar increases in firing rates with selective attention, a finding

confirmed here. However, we found that SUA-LFP gamma-band PPC is reduced with attention across the population of BS cells and unaffected for NS cells when firing rate differences are not considered. We showed that the discrepancy between the attentional effect on SUA and MUA gamma locking can be explained by an interaction between the attentional effects on SUA firing rate and locking strength: Enhanced locking of strongly firing neurons might explain the discrepancy between MUA and SUA results given that a MUA’s composition can change concordantly. We confirmed this by demonstrating that large attentional increases in gamma locking were seen for the most strongly firing SUs. When we performed a median split on SUA firing rate, the attentional effect on gamma-locking Dipeptidyl peptidase was negative for the weakly firing cells but positive for the strongly firing cells. It is conceivable that these particularly strongly firing/activated cells constitute

a specific cell subclass. These findings suggest that attention sharpens the composition of the synchronized assembly such that the most activated neurons are most synchronized and therefore exert the highest impact onto postsynaptic target neurons. Assuming that mainly the synchronized neurons effectively influence target neurons, a sharpening of the synchronized assembly potentially has an additional effect related to normalization mechanisms in the neuronal target group. Normalization mechanisms effectively lead to a situation in which different input neurons mutually reduce their respective gain. Therefore, eliminating less activated neurons from the synchronized assembly, and thereby from the postsynaptically effective assembly, might further enhance the relative gain of the more activated neurons.