anesthesia effects (e.g., a suppression of normal ambient excitability and variability) may contribute to the findings of Xing et al, even though anesthesia per-se is a common factor in many of the experiments considered above. Similarly the very small dimensions of electrical contact area of the electrodes could be a reason for the difference between the findings of Xing et al., and those of other studies [however, see (Nelson and Pouget, 2010)], though similar contact dimensions were used in other studies [e.g., (Kreiman et al., 2006)] that clearly show spread of LFPs over much greater distances than Xing et al. A final possibility we consider is the areal size of the activated substrate. When the activated area is small, the LFP attenuates more rapidly with distance (Nunez and Srinivasan, 2006), and thus, activation of a very small area with very small, isolated visual stimuli could conceivably produce LFP that spread over very small distances. If this were the case, however, it would argue strongly against the generality of the Xing et al. findings for understanding the neuronal substrates of “typical LFP,” which are recorded in circumstances involving easily audible (or visible) stimuli and awake behaving subjects where such precision of
