26 keep in mind that the conscious experience of the visual stimuli was always very weak and thus diYcult to rate (as is evident from the low visibility rating at baseline). On the other hand, if we take the dips in visibility rating of 120 and 140 ms seriously, then indeed one might speak of a ‘blind- sight’-like dissociation, since conscious experience was aVected while behavioral processing was not. But this eVect size was quite small, so we caution not to stretch interpreta- tions qualitatively where they are supported only slightly quantitatively. TMS-masking eVects in a sensitive paradigm Our data suggest that, instead of one, there may be at least two dips within the classical-masking time window sur- rounding 100 ms. We have already emphasized that our experiment was exploratory in nature, and future research should aim to replicate this Wnding. But the eVects are fasci- nating in our view. Methodologically, it is promising that our Wrst deliberate attempt to implement a ‘sensitive masking paradigm’ as outlined in the Introduction immediately yields a diVerent pattern of Wndings from that revealed conventionally. Indeed, we are not aware of previous studies having reported two temporally neighboring masking eVects. As outlined in the Introduction, previous TMS-masking studies have reported one dip around 100 ms (starting with Amas- sian et al. (1989), see Kammer (2007a) for an overview), and sometimes much earlier dips or much later dips (Corth- out et al. 1999, 2003; Heinen et al. 2005; Silvanto et al. 2005; Laycock et al. 2007; Camprodon et al. 2010; Koiv- isto et al. 2010). These secondary dips were, however, always separated from the classical dip by 60–100 ms, whereas we here separated two masking dips only 20 ms apart. Thus, if we for the moment assume that our masking eVects do reXect a disruption of early visual cortex pro- cesses, the two dips here might reXect a fundamentally diVerent brain process from the alternative dips presented in previous work. The reason previous studies have not identiWed two dips in such close proximity might be (1) too high TMS intensities, (2) not enough spatial resolution of the used TMS coil (in studies using the round coil), (3) too salient or complex stimuli, or (4) too large gaps between measured SOAs. As hypothesized in the Introduction, we propose that either/all of these paradigmatic factors might serve to eVectively decrease temporal resolution; ‘smearing out’ the masking eVect over time windows in the masking curve. (Incidentally, we can report that, when asking two participants with multiple dips to return for a high-intensity measurement, we found again only one broad masking dip in the classical masking time window). Theoretically, we might consider at least two explana- tions for neighboring dips. BrieXy, it might be that there is 123 Exp Brain Res (2011) 209:19–27 not one feedforward sweep and one feedback sweep, but rather multiple recurrent processes (e.g., Lamme and Roelfsema 2000). Communications between regions could repeatedly go back and forth (see, e.g., de Graaf et al. 2009) between hierarchical levels, or within—in the form of horizontal recurrent projections. Foxe and Simpson (2002) argued, conceptually and supported by data, that already at the earliest stages of occipital processing, after visual stimulation, recurrent inXuences may aVect ongoing processing. This makes sense ecologically; based on task demands or mere situational context, not all visual input is equally relevant. Indeed, the same authors reported recur- rent inXuences present in the earliest visual evoked poten- tials (Foxe and Simpson 2002). In our view, the very concept of distributed processing suggests that brain regions must interact intensively and repeatedly, if not continuously, to lead to our complex and yet rapid con- scious visual experiences. Thus, multiple recurrent loops may explain multiple, chronometrically neighboring, TMS-masking dips within the broad classical time win- dow. Alternatively, the two dips might correspond to arrival in early visual cortex of M-pathways and P-path- ways. Magnocellular (M) pathways are faster than parvo- cellular (P) pathways (Bullier 2001), and have been hypothesized to arrive at diVerent times, hence possibly allowing TMS to disturb them at diVerent times (see also Paulus et al. 1999). There is no way to distinguish between these options based on our current data. Conclusion Future studies might consider further exploring sensitive TMS-masking paradigms to illuminate these issues. Con- servatively, we will here conclude that our objective and subjective measures of awareness did not correspond well in a situation of sensitive TMS masking. TMS elicited an interesting pattern for objective performance, which was not mirrored by the subjective masking curve. In the data set here presented, we observed at least two dips of TMS- induced performance decrease, separated by only 20 ms, with no masking in-between. Our new Wnding of multiple dips within the classical-masking window might be attrib- uted to our sensitive TMS-masking paradigm. We con- clude that this pattern of preliminary Wndings is interesting on both group and individual level and both theoretically and methodologically stimulating for future research. Acknowledgments We would like to thank two anonymous review- ers for excellent suggestions that have certainly improved this report. We also acknowledge the Dutch Organization for ScientiWc Research (NWO) for supporting T.A.G. (personal grant number: 021-002-087) and A.T.S. (personal grant number: 452-06-003).