Article Figures & Data
Figures
- Figure 1.
The VE environment in which participants learned individual images associated with different HDs, and an example subject-specific RSC region-of-interest (ROI). a, The environment comprised four separate enclosed galleries connected by a handrail; (b) participants were required to monitor their orientation relative to global landmarks (eg, a cityscape) located at cardinal HDs; landmarks were visible only when outside of the galleries; (c) each gallery contained four paintings from a particular category of stimuli (eg, animals), and individual paintings occupied positions concordant with directions to the global landmarks; (d) individual images cueing specific HDs were presented during a subsequently scanned one-back task. Participants were required to judge whether the HD associated with the current image was the “same” or “different” to the preceding image; (e) Freesurfer was used to identify the RSC bilaterally in each participant (left RSC, red; right RSC, blue), (f) and these ROIs warped to standard space and used to extract average percentage signal change values for the different repetition conditions.
- Figure 2.
Behavioral performance (mean accuracy and RT ± SEM) on the one-back task, separated according to orientation and repetition. a, The fMRI sample (n = 9) showed very accurate performance on this task, with mean accuracy and RT matched across different orientations; (b) the excellent behavioral performance was replicated in a larger sample (n = 24), where these participants showed a small benefit in RT for stimuli cueing the 270° orientation.
- Figure 3.
Group average percentage signal change values (mean ± SEM) extracted from anatomical ROIs. a, In bilateral RSC, significant repetition suppression was associated with repeat HD relative to non-repeat HD trials. The percentage signal adaptation between these two conditions for each participant is also provided; positive values demonstrate that repetition of HD led to a reduction of the BOLD signal; (b) the same adaptation effect was evident also in bilateral thalamus; (c) in RSC attenuation did not continue over multiple repetitions of stimuli cueing the same HD; (d) and this plateau was apparent also in the thalamus. To test more directly for evidence of a plateau in the BOLD response after the first repetition of HD, the difference in activity between non-repeat HD and one-back repeat HD was compared with the difference in activity between one-back repeat HD and two-back repeat HD conditions. In both (e) RSC, and (f) the thalamus, significantly greater adaptation was found after the first repeat of HD compared with when HD was repeated over multiple trials. Individual-subject data are displayed here, with dashed lines connecting each subject's data points (*p < 0.05).
- Figure 4.
Whole-brain contrast image (non-repeat HD > repeat HD) with corresponding plots of mean percentage signal change values ± SEM extracted from the peak voxel in each cluster. Supporting the ROI analyses, significant repetition suppression was evident in the whole-brain contrast image in a number of regions including: (a) left RSC, (b) left thalamus, (c) right thalamus, and (d) precuneus. TFCE results are displayed on the MNI template brain, using a threshold of p < 0.01, FWE-corrected.
- Figure 5.
Significant repetition suppression effect in bilateral thalamus overlaid with the Morel (2007) thalamic atlas. According to this atlas, the peak coordinate of left thalamus cluster (−10, −16, 8; displayed center in the top row of the figure, accompanied by adjacent sagittal slices) was located in the ventral division of the ventral lateral posterior nucleus [VLpv; the second row of the figure comprises enlarged views of the left thalamus with color-coded overlay of the Morel (2007) atlas]. This cluster extended to the dorsal division of the ventral lateral posterior nucleus (VLpd), the central lateral nucleus (CL), the lateral dorsal nucleus (LD), lateral posterior nucleus (LP), the parvocellular division of the mediodorsal nucleus (MDpc), and the posterior division of the ventral posterior lateral nucleus (VPLp). The right thalamus cluster (12, −12, 18; third row center, again displayed center alongside two adjacent sagittal slices) spanned the same thalamic subregions. The peak, however, was located on the border of the dorsal division of the ventral lateral posterior nucleus (4th row of figure). Results are displayed on the MNI template brain, with TFCE statistical map thresholded, p < 0.01 FWE-corrected.
- Figure 6.
Consistency of repetition suppression in the RSC and thalamus in individual participants. a, Significant clusters of activity in the RSC were evident in seven of the nine participants. Clusters are significant at the whole-brain level (Z > 2.3, p < 0.05), overlaid (cyan) with the individual participant's RSC anatomical ROI. b, Peak voxel in the thalamus associated with the repetition suppression contrast at the single-subject level. Eight participants showed repetition suppression when HD was repeated over consecutive trials. This effect was significant in six participants using a small volume correction comprising the participant-specific bilateral thalamus mask (Z > 2.3, p < 0.05, corrected for multiple comparisons); this effect did not survive correction for multiple comparisons in participants (P)2 and P8 (images for these participants displayed at p = 0.01, uncorrected).
Tables
- Table 1.
MNI coordinates of peak voxels and local maxima in the whole-brain repetition suppression analysis (non-repeat HD > repeat HD; p < 0.01, FWE-corrected)
Region Voxels 1-p value t MNI coordinates x y z Left retrosplenial cortex 1444 0.998 7.37 −8 −48 4 5.49 16 −56 10 4.84 −12 −60 2 4.60 −14 −70 22 4.59 −8 −58 2 4.58 −6 −62 4 4.52 −8 −54 0 0.996 5.38 10 −46 −2 5.17 28 −56 4 4.61 16 −56 6 4.52 12 −54 4 4.40 16 −62 8 Left thalamus 871 0.998 7.13 −10 −16 8 5.18 −10 −8 16 5.09 −18 10 −8 4.94 −8 −18 4 4.90 −2 −20 10 0.996 4.30 0 −24 10 4.22 −12 −2 12 0.990 3.68 −10 −14 −4 Right thalamus 158 0.996 5.66 12 −12 18 5.33 14 −14 16 0.994 5.35 12 −16 8 Right precuneus 301 0.994 5.42 4 −60 52 4.84 4 −60 48 4.70 6 −64 50 0.992 4.34 −2 −78 46 4.32 −6 −80 44 4.32 16 −62 52 4.26 2 −68 46 4.24 10 −58 46 0.990 3.96 −2 −80 42 Right caudate 228 0.996 5.70 18 18 6 5.66 18 16 4 0.994 4.87 18 16 −4 4.82 20 12 −2 0.992 5.24 22 4 −10 0.990 4.29 18 26 −4 Brain stem 87 0.992 5.35 −4 −22 −10 4.55 0 −26 −14 0.990 3.92 −2 −24 −18 3.76 2 −32 −16 Superior temporal gyrus (posterior division) 42 0.994 6.56 46 −36 4 Inferior frontal gyrus 15 0.990 6.64 −54 10 −2 6.57 −56 8 −2 6.25 −58 4 0
