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. 2016 Jan 10;26(4):1747–1761. doi: 10.1093/cercor/bhv324

Figure 8.

Figure 8.

Normalized strength of cortical projections to the M1 hand area. (a) To compare the pattern of projections from each distant cortical area to M1, we normalized the proportion of labeled cells. For each injection site (RL: rostro-lateral; CL: caudo-lateral; RM: rostro-medial; CM: caudo-medial), the proportion of labeled cells found in a distant cortical area was divided by that of the area with the most labeled cells. For example, for RM injections, PMd had the highest proportion of labeled cells (normalized value = 1.0). The percentage of labeled cells found in SMA following RM injections was approximately 4 times lower than in PMd (normalized value = 0.26). The cartoon in the middle of the figure shows the color code for the different injection sites (RL = green; CL = orange; RM = red; CM = blue). For each distant cortical area (SMA, PMd, PMv, area 1, area 2, and area 5), a cross diagram shows the normalized strength of its projections to the 4 subregions of the M1 hand area. In each quadrant, the value of the normalized projections is provided and the size of the color square is proportional to the strength of the projections. (b) Cartoon summarizing the pattern of projections to the M1 hand representation from the different areas of the sensorimotor cortex investigated in the present study (SMA, PMd, PMv, area 1, area 2, and area 5). Connections of M1 reported in other studies but not studied here are not shown (e.g., area 3a, S2, etc.). Thick arrows represent “major” projections and thin arrows “moderate” projections, based on the relative strength of connections (a). PMd had the broadest pattern of projections, sending major projections to RM and moderate projections to both RL and CM. In contrast, PMv had a more focal pattern, sending only major projections to RL. SMA had moderate projections to CM. All 3 parietal areas studied were mainly connected with the caudal part of M1. Area 1 had moderate projections to both CM and CL. Area 2 had major projections to CL and moderate projections to CM, and area 5 had major projections to CM and moderate projections to CL.