Functional Comparison

We studied if our parcels were related to brain function. To do so we calculated their overlap with thresholded maps representing responses to functional stimuli [2]. These maps are also available for each subject in the HCP. Figure 4-right shows the functional comparison for two single subject parcellations. Figure 6 shows a projection from our groupwise parcels over averaged tFMRI activations. Each color encodes the response to a different stimulus thresholded with a z-score > 5. The comparison for the average-subject case was done against the average functional responses in the Unrelated100 population from the HCP. Table 2 shows the highest dice coefficient achieved by one of our regions for each task. Here it is important to remark than, in general, each stimulus will generate a functional response in both motor and sensory cortex. Our hypothesis is that this happens because, for example, while a subject is moving the hand he’s also feeling it. Therefore, an overlapping of 0.5 suggests that at least one of our parcels in the motor or sensory cortex is having a good overlapping with the functional response, as confirmed visually. Table 2 shows high dice coefficients for each subject, but shows even higher coefficients for the average subject. We hypothesize that averaging tractograms in the Euclidean space is removing the across-subject variability.

Relation between our pure extrinsic parcellation and the anatomical atlas of Desikan [5]

Fig. 5 Relation between our pure extrinsic parcellation and the anatomical atlas of Desikan [5]. Some regions from Desikan projected over a parcellation with less than 150 parcels. Motor and Sensitive cortex appears to be found

Table 1 Area proportion contained for parcels inside Desikan projections

Area proportion contained (see Fig. 4-left)

1

2

3

4

5

6

7

8

Variability

Single subj.

0.4

0.6

0.8

0.8

0.8

0.7

0.2

0.6

±0.1,jnin : 0.01. max : 0.16

Average subj.

0.0

0.3

0.9

0.8

0.8

0.3

0.2

0.6

N/A

 
Source
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