Because one this website tends to assume that modulation of visual cortical activity is the basis of the perceptual benefits of attention (though it may not be), the possibility of identifying a single functional class of neurons as driving that modulation is certainly an exciting one. Determining which classes of FEF neurons project to visual cortex will require further experiments, ones employing either newly developed cell-type-specific perturbation techniques (e.g., optogenetics) or more traditional electrophysiological approaches (e.g., Sommer and Wurtz, 2001). But, given the present results, coupled with other
recent studies, one can begin to see how the components of this particular neural circuit might fit together and how we might determine the role spike-field synchrony actually plays. If, for example, only visuomovement neurons project to V4, it would seem less likely that synchrony, as opposed to firing rate, plays an important role, particularly because firing rate increases are observed in both visual and visuomovement neurons during covert attention (Thompson et al., 2005 and Gregoriou et al., SAR405838 concentration 2012). Returning to the question of whether the neural circuitry of covert attention should be lumped with or split from the neural circuits controlling gaze, it is apparent from the results of Gregoriou
et al. that although FEF neurons collectively contribute to both functions, there is an apparent division of labor at the single-neuron level. Thus, although it might first be appropriate to lump the two functions together at the level of whole brain structures as “networks” (e.g., FEF, SC, and LIP), it is also reasonable to split those functions at the level of underlying neuronal contributions. For the latter, one might argue that we should expect the two functions to be split
at the level of single neurons, given that we already know that at some level in gaze control circuitry (e.g., oculomotor nucleus) neurons can only be involved in the gaze command (Awh et al., 2006). The major question then may not be whether overt and covert attention share the same underlying neural circuitry—they do, though not completely—but rather at what stage the circuitry diverges. At which point, is neuronal activity independent of one or the other function? Although the Gregoriou et al. results demonstrate differences in the profile of modulation between FEF neurons, it is nonetheless important to note that all types were modulated by covert attention in some way. For example, movement neurons were suppressed by covert attention, similar to a previous study (Thompson et al., 2005); thus, their activity is not independent of the behavior, just anticorrelated with it. Perhaps it might be wise to consider that, at least within the FEF, all neurons participate in the control of covert and overt attention, but in separable ways.