Propuestas de criterios para una justicia transicional

Regions of Interest (ROI) were defined on a group-level using data that underwent the above preprocessing and first-level pipeline. To ensure independence between the ROI analysis and definition, I chose ROIs using the replay data, as it was not used for the main analysis. At a group- level, I examined all replay scans taken prior to TMS irrespective of TMS test site. We looked at regions activated during replay presses (p < 0.05 family-wise-error (FWE) corrected). ROIs were defined by selecting the peak voxel of each activated region in the left and right hemisphere separately and drawing a sphere around the peak voxel (r = 12 mm) including only significant voxels. Based on prior literature, I defined the following ROIs:

Inferior frontal gyrus (IFG). We primarily wanted to examine regions that in previous

literature have shown activity modulation in bistable perception compared to a replay condition. Based on a meta-analysis of the past fMRI literature on bistability, Brascamp et al. (2018) concluded that inferior frontal cortex is consistently activated during bistability (analysis including contrasts from Lumer et al., 1998; Lumer & Rees, 1999; Kleinschmidt et al.,1998; Sterzer & Kleinschmidt, 2007; Zaretskaya et al., 2010; Knapen et al., 2011; Megumi et al., 2015; Frässle et al., 2014;

Brascamp et al. 2015). Our IFG regions were at MNI coordinates x = -44, y = 0, z = 6 cluster size (CS) 880 voxels (IFG-l) as well as x = 50, y = 14, z = 0, CS 846 voxels (IFG-r) (figure 3, rows 1 & 2).

Early visual cortex (V1). Early visual areas have been shown to display modulated

activity based on stimulus interpretation (Fang et al., 2008; Grassi et al., 2017). Also, TMS to V1 has been shown to modulate bistable dominance durations (Pearson et al., 2007). We therefore included left and right V1 as ROIs. Our occipital regions lay at MNI coordinates x = -26, y = -88, z = -10 CS 621 voxels (V1-l) as well as x = 28, y = -86, z = -8, CS 764 voxels (V1-r) (figure 3, rows 3 & 4).

Figure 3 — ROIs localised using replay button presses

Group whole-brain result showing activity during replay button presses for all fMRI recordings prior to TMS irrespective of TMS site (p < 0.05 FWE corrected). Crosshairs indicate peak voxels of the selected ROIs. Around the peak, a sphere was drawn (r = 12 mm) including only significant voxels, shown for each ROI in burgundy.

Thalamus. The role of the thalamus and in particular the LGN in the resolution of has

been demonstrated and its activity used to decode the content of bistable awareness (Haynes et al., 2005; Wunderlich et al. 2005). Also, cortical inputs to thalamus may be generally required to resolve bistability (Sillito et al., 2006). We therefore reasoned that TMS-induced modulation of bistability

16 14 12 10 8 6 4 2 0 IFG-l IFG-r V1-l V1-r Thal-l Thal-r M1-l

may at least in part involve thalamic nuclei and included them as ROI. Our thalamic regions lay at MNI coordinates x = -14, y = -18, z = 4, CS 900 voxels (Thal-l) as well as x = 12, y = -12, z = 4, CS 736 voxels (Thal-r) (figure 3, rows 5 & 6).

Left primary motor cortex (M1-l). Neuroimaging studies investigating the neural

signature of bistability have consistently found the involvement of left precentral gyrus or central sulcus (Lumer et al., 1998; Sterzer et al., 2002; Zaretskaya et al., 2010; 2013; Knapen et al., 2011, Roy et al., 2017). This is not surprising, since participants are normally asked to make button presses using the contralateral hand. However, the left motor cortex also dominantly shows activation in bistability compared to replay, even as the largest and most significant cluster in the present data (see Zaretskaya et al., 2010). While M1-l activity is usually shrug off as cognitively irrelevant for the resolution of perceptual ambiguity, I decided to investigate it for a conceptual reason: it is possible that previous TMS studies on bistability did not affect so much cognitive processes underlying awareness or attention, as much as participants ability to motor-express their percepts with button presses. If this were the case, then I would expect TMS modulation of left precentral activity. Our M1-l region lay at MNI coordinates x = -50, y = 28, z = 56, CS 505 voxels (figure 3, row 7).

Figure 4 — IPS functional localisation

Group whole-brain result showing the contrast “SFM block > replay block” for all fMRI recordings prior to TMS irrespective of TMS site. Crosshairs denote the peak voxel of the anterior intraparietal sulcus at MNI x = 30, y = -44, z = 56, threshold p < 0.005 (uncorrected). Euclidian distance to a previously reported IPS region (Lumer et al., 1998) is 7.8 mm.

IPS. Since it was stimulated by TMS, I naturally wanted to examine the IPS as ROI. For the

fMRI analysis I chose a group-level contrast to localise the IPS. Specifically, I examined all pre TMS scans irrespective of TMS site. We looked at right posterior parietal regions activated during the “SFM block > replay block” contrast (p < 0.005 uncorrected, figure 4). We now selected the peak voxel in the approximate ROI in the right hemisphere and drew a sphere around the peak voxel (r = 12 mm) including only significant voxels. This was done in order to safeguard consistency with the previous literature. Moreover, I wanted the ROI to capture where I actually stimulated with cTBS, hence decided against using a group-level defined IPS ROI. The peak voxel lay at a euclidian distance of 7.8 mm (Lumer et al., 1998), 6.6 mm (Zaretskaya et al., 2010) and 6.9 mm (Zaretskaya et al., 2013) from the peak IPS voxel reported by previous literature. To extract the ROI in the left

4.5 4 3.5 3 2.5 2 1.5 1 0.5 0

hemisphere, I flipped the right mask along the x axis. Our IPS regions lay at MNI coordinates x = ±30, y = -44, z = 56.

SPL & V5/MT. One prominent study investigating the causal interactions of right

posterior brain regions found a network of three sites causally interacting during bistable perception of a SFM rotating sphere using dynamic causal modelling (Megumi et al., 2015), namely the IPS-r (10 mm sphere around the peak coordinates of Lumer et al., 1998); SPL-r (10 mm sphere around the peak coordinates of Kanai et al. 2010) and V5/MT-r (10 mm sphere around the peak coordinates of Dumoulin et al., 2000 and Mars et al., 2011). This model could successfully predict rivalry dominance durations based on the coupling strength between these three ROIs. We therefore chose to include SPL and V5/MT in this study as well. We used the method of Megumi et al. (2015) to localise them and used their flipped image to extract the ROIs also in the left hemisphere. Our SPL regions lay at MNI coordinates x = ±38, y = -64, z = 32, while I extracted V5/MT from x = ±44, y = -67, z = 0.