Parte B. Formación y Crecimiento Profesional

Analysis of functional connectivity was performed using Granger Causality Mapping (Roebroeck, et al., 2005) as in Study 2. Two separate analyses were performed using the following seed regions: 1) left aIPSv hand/tool and, 2) left LOTC hand/tool. If aIPSv and left LOTC hand/tool areas are functionally connected with each other via their common functional role in hand/tool processing then one would expect the left relative to the right aIPSv hand/tool area to be significantly more connected to the left LOTC. In addition, I expect to replicate results reported in Study 2 by showing significantly stronger connectivity between left LOTC (relative to nearby EBA body region) and left aIPSv hand/tool regions.

In a first analysis the left and right aIPS hand/tool regions were defined using the contrast of hands and tools versus bodies, non-graspable objects and scrambled images. Mean cluster size (mm3) and Talairach coordinates (x,y,z) of each ROI were: the left aIPSv (589 mm3; x y z = -41, - 37, 39) and the right aIPSv (464 mm3; x y z = 37, -36, 42). Figure 4.7 (left panel) shows left aIPSv and right aIPSv hand/tool seed regions in three representative participants. The functional connectivity of these left and right aIPSv hand/tool regions was computed for each participant individually, resulting in 16 connectivity maps for each of the two regions (Figure 4.7, middle panel). The direct contrast of left and right aIPSv connectivity maps was performed using group- average paired-sample t-tests. As predicted results revealed significantly stronger connectivity between the left aIPSv and the left LOTC (x y z = -45, -61, -12; p<.05, corrected for multiple comparisons). See figure 4.7 (right panel) for group-average functional maps and Table 4.2 for corresponding Talairach coordinates. Significant high functional connectivity was also found for the region surrounding the left aIPSv seed region (x y z = -40, -37, 37; p<.05, corrected for multiple comparisons). Instead, the right aIPSv did not show any significant stronger connectivity pattern (relative to the left aIPSv) with any other brain region.

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Figure 4.7. Functional connectivity analyses for left aIPSv and right aIPSv hand/tool seed regions. Left panel shows parietal seed reference regions (left aIPSv hand/tool and right aIPSv hand/tool) in three representative participants for the functional connectivity analysis. Middle panel shows corresponding individual-subject functional connectivity maps (at

p<.01 (FDR corrected), dark red colour coded). Right panel shows the results of a direct contrast between the

connectivity maps of the two seed regions. Warm colours indicate regions showing increased functional connectivity with the left aIPSv hand/tool region relative to the right aIPSv hand/tool region (p<.05, corrected for multiple comparisons). The opposite contrast (right aIPSv hand/tool > left aIPSv hand/tool) did not reveal selective functional connectivity with any brain region.

In a second analysis the left LOTC hand/tool and the left EBA body areas were used as seed regions and defined using the following contrasts: (1) hands and tools versus bodies, non- graspable objects and scrambled images for the left LOTC hand/tool region, and (2) bodies versus hands, non-graspable objects and scrambled images for the left EBA body region. Mean cluster size (mm3) and Talairach coordinates (x, y, z) of each ROI were: the left LOTC (691 mm3; x y z = - 47, -66, -4) and the left EBA (605 mm3; x y z = -47, -75, 1. Figure 4.8 (left panel) shows the left LOTC hand/tool region and the left EBA body region in three representative subjects. These whole-brain connectivity maps were directly contrasted with each other using group-average paired-sample t-tests, in order to test for regionally selective functional connectivity that was

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consistent across participants. Replicating findings reported in Study 2, results revealed significantly stronger connectivity between the left LOTC hand/tool and left parietal areas (x y z= - 37, -55, 53, p<.05, corrected for multiple comparisons). See Figure 4.8 (right panel) for group- average functional maps and Table 4.2 for corresponding Tailarach coordinates. A significant high correlation was also found for the region surrounding the left LOTC hand/tool seed region (x y z = - 47, -62, -9; p<.05, corrected for multiple comparisons). In contrast, the nearby EBA body region did not show any significant stronger connectivity pattern (relative to the left LOTC hand/tool region) with any other brain region.

Figure 4.8. Functional connectivity analyses for left LOTC hand/tool and left EBA body seed regions. Left panel shows occipitotemporal seed reference regions (left LOTC hand/tool and left EBA body) in three representative subjects for the functional connectivity analysis. Middle panel shows corresponding individual-subject functional connectivity maps (at p<.01 (FDR corrected), dark red colour coded). Right panel shows the results of a direct contrast between the connectivity maps of the two seed regions. Warm colours indicate regions showing increased functional connectivity with the left LOTC hand/tool region relative to the left EBA body region (p<.05, corrected for multiple comparisons). The opposite contrast (left EBA body > left LOTC hand/tool) did not reveal selective functional connectivity with any brain region.

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These functional connectivity results converge and add onto findings reported in Study 2 showing that both left aIPSv and left LOTC hand/tool regions show mutual patterns of functional connectivity. More generally, analyses reported in Study 2 and the current Study 3 support the proposition of a unique functional link between the left lateralised occipitotemporal and parietal areas involved in processing hand and tool representations.

Table 4.2. Results of functional connectivity analyses in Study 3

Functional connectivity results x y z mm3

left aIPSv hand/tool seed region

left parietal 40 -37 37 5671

left LOTC -45 -61 -12 777

left LOTC hand/tool seed region

left parietal -37 -55 53 966

left LOTC -47 -62 -9 1342

Group-average Talairach coordinates and cluster size for all regions (p<.05, corrected) identified in the functional connectivity analysis are reported for left aIPSv and left LOTC main seed regions. To investigate mutual functional connectivity between aIPSv and left LOTC hand/tool regions, functional connectivity maps from the left aIPSv hand/tool seed region were contrasted with connectivity maps from the right aIPSv hand/tool seed region, and functional connectivity maps from the left LOTC hand/tool seed region were contrasted with connectivity maps from the left EBA body-selective seed region. LOTC = lateral occipitotemporal cortex, aIPS = anterior intraparietal sulcus, v = ventral.