Abstract
Histology studies revealed that the macaque insular cortex was characterized by the gradual organizations containing agranular, dysgranular and granular insula. However, no consensus has been reached on the elaborate subdivisions of macaque insula. Until now, no neuroimaging study to our knowledge combining connectivity-based gradients and parcellation has been performed to investigate the topographic organization of the macaque insular cortex. In this study, we used high-resolution ex vivo diffusion-weighted imaging data to explore the macaque insular cortex’s global gradient organization and subdivisions. We found a rostrocaudal organization of the dominant gradient in the macaque insula using a diffusion map embedding. Meanwhile, extracting the 25% top and bottom components from the dominant and second gradient, which explained variance over 60% in total within ten gradients, the connectivity-based parcellation method was performed to subdivide each component into two subregions confirmed by the cross-validation analysis. Furthermore, permutations tests identified that two subregions from each component showed significant differences between their connectivity fingerprints. Finally, we found that the dominant and second gradients were significantly correlated with the T1w/T2w and cortical thickness maps in the macaque insula. Taken together, the global gradients combining the subdivisions examined the topographic organization of the macaque insular cortex based on the structural connectivity, which may contribute to a better understanding of the intricate insular cortex anatomy.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- 6VR
- area 6 of cortex, ventral part, rostral subdivision
- 8AV
- area 8 of cortex, anteroventral part
- 36R
- area 36, rostral part
- Acb
- accumbens nucleus
- AK
- auditory koniocortex
- Amyg
- amygdaloid nucleus
- Gu
- gustatory cortex
- INS
- insular cortex
- IPL
- Inferior parietal lobule
- MST
- medial superior temporal area
- PaA
- paraauditory area
- PaI
- parainsular cortex
- Pd
- pallidus
- PE
- parietal area PE
- Pir
- piriform cortex
- PPt
- posterior parietal area
- ProK
- prokoniocortex
- ProM
- promotor
- ReI
- retroinsular area
- ROI
- region of interest
- S2
- secondary somatosensory cortex
- Str
- striatum
- STS
- superior temporal sulcus
- Tha
- thalamus
- TP
- temporopolar area
- TPt
- temporoparietal cortex