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Morphological Analysis of the Inferior Frontal Sulcus in the Chimpanzee (Pan troglodytes) Brain

Poster No:

2114 

Submission Type:

Abstract Submission 

Authors:

Erika Nolan1,2, Claude Y. Lepage2, Auriane Journet1, William Hopkins3, Michael Petrides2,1

Institutions:

1McGill University, Montreal, Quebec, Canada, 2Montreal Neurological Institute, Montreal, Quebec, Canada, 3MD Anderson Cancer Center Texas, Houston, TX, USA

First Author:

Erika Nolan  
McGill University|Montreal Neurological Institute
Montreal, Quebec, Canada|Montreal, Quebec, Canada

Co-Author(s):

Claude Y. Lepage  
Montreal Neurological Institute
Montreal, Quebec, Canada
Auriane Journet  
McGill University
Montreal, Quebec, Canada
William Hopkins  
MD Anderson Cancer Center Texas
Houston, TX, USA
Michael Petrides  
Montreal Neurological Institute|McGill University
Montreal, Quebec, Canada|Montreal, Quebec, Canada

Introduction:

There has been considerable interest in the neuroanatomical similarities of the homologue of Broca's region in nonhuman primates to further understanding of the evolution of language. The inferior frontal sulcus (ifs) is a critical landmark below which lie language production areas in the human brain, and its homologue may be found in the chimpanzee brain (see Fig.11-3). Defining the morphology of the ifs may provide insight into the structural blueprints that permit the development of language in human brains.
Supporting Image: Figure1Schematics.png
 

Methods:

MRI scans of the brains of 50 chimpanzees (Pan troglodytes; 22 male and 28 female) from the National Chimpanzee Brain Resource (NCBR) were examined. The MRI scans were acquired using a 3T scanner (Siemens Trio, T1W images, 0.6-0.90 mm isotropic) at the Yerkes National Primate Research Center. The MRI scans were registered to an NCBR volumetric chimpanzee template4 using a 12-parameter registration. Cortical surfaces were reconstructed from the MRI scans using CIVET-Chimp (see reference #5 for similar methods used in CIVET-Macaque), which permitted 3D investigation of the sulcal contours and fundus. The ifs and adjacent sulci were identified in each hemisphere (100 hemispheres in total, 50 left and 50 right) on the basis of recent sulcal investigations6-7. The morphological patterns of the ifs were then categorized by type and according to the connections with surrounding sulci. Finally, the individual surfaces were registered to a common surface template obtained by averaging the surfaces of the subjects under study. The ifs was then labeled on the resampled surfaces using Freeview. The labels were averaged across subjects, such that the spatial probability map quantifies the likelihood of each surface vertex belonging to the ifs.

Results:

The ifs can be categorized into five types, each having a different frequency of occurrence. Type 1: the ifs connects posteriorly with the inferior precentral sulcus in 40% of hemispheres (46% of left; 34% of right). Type 2: the ifs connects anteriorly with the rectus sulcus, in addition to connecting posteriorly with the inferior precentral sulcus in 49% of hemispheres (46% of left; 52% of right). Type 3: the ifs connects anteriorly with the rectus sulcus only in 6% of hemispheres (4% of left; 8% of right). Type 4: the ifs is an independent sulcus with no connections to neighbouring sulci in 5% of hemispheres (4% of left; 6% of right). Type 5: the ifs additionally connects to other adjacent sulci (i.e., fronto-orbital sulcus and middle frontal sulcus) in 15% of hemispheres (16% of left; 14% of right). With regard to its relationship with surrounding sulci, the connection of the ifs with the inferior precentral sulcus was completely fused in 75% of hemispheres (90% of left; 60% of right), superficially fused in 14% of hemispheres (2% of left; 26% of right) and in 11% of hemispheres (8% of left; 14% of right) there was no connection. The connection of the ifs with the rectus sulcus was complete in 12% of hemispheres (12% of left; 12% of right), superficial in 43% of hemispheres (38% of left; 48% of right), and there was no connection in 45% of hemispheres (50% of left; 40% of right). Finally, there was a complete connection of the ifs with other adjacent sulci in 9% of hemispheres (10% of left; 8% of right) and a superficial connection in 6% of hemispheres (6% of left; 6% of right). See Fig. 2 for examples of the different patterns of the ifs in three hemispheres.
Supporting Image: Figure2ExamplesPatterns.png
 

Conclusions:

The present study demonstrates that, despite its considerable variability, the ifs can be clearly differentiated from adjacent sulci by means of 3D examination of the sulcal contours and fundus. The morphological descriptions presented here provide a means of identifying accurately the ifs in the chimpanzee (Pan troglodytes) and contributes to a better understanding of the structural organization of a region that, in the human brain, evolved to play a critical role in language production.

Neuroanatomy, Physiology, Metabolism and Neurotransmission:

Cortical Anatomy and Brain Mapping 1
Neuroanatomy Other 2

Keywords:

Cross-Species Homologues
Language
MRI
Other - Chimpanzee; Sulci ; Neuroanatomy; Morphology; Inferior Frontal Sulcus; Prefrontal Cortex

1|2Indicates the priority used for review

Provide references using author date format

1. Petrides, M. (2019). Atlas of the morphology of the human cerebral cortex on the average MNI brain. Academic Press.
2. Bailey, P., Bonin, G., & McCulloch, W.S. (1950). The isocortex of the chimpanzee. University of Illinois Press.
3. Eberstellar, O. (1890). Das Stirnhirn: ein Beitrag zur Anatomie der Obserflaeche des Grosshirns (Vol 3). Urban & Schwarzenberg.
4. Devenyi, G., Sherwood, C., Hopkins, W.D., Raznahan, A. & Chakravarty, M. (2020). Chimpanzee high-resolution minimum deformation average and application to aging and sex differences. Organization for Human Brain Mapping.
5. Lepage, C., Wagstyl, K., Jung, B., Seidlitz, J., Sponheim, C., Ungerleider, L., Wang, X., Evans, A.C. & Messinger, A. (2021). CIVET-Macaque: an automated pipeline for MRI-based cortical surface generation and cortical thickness in macaques. NeuroImage, 227, 117622.
6. Falk, D., Zollikofer, C.P.E., de Leon, M.P., Semendeferi, K., Warren, J.L.A., & Hopkins, W.D. (2018). Identification of in vivo sulci on the external surface of eight adult chimpanzee brains: Implications for interpreting early hominin endocasts. Brain, Behavior and Evolution, 91(1), 45-58.
7. Hopkins, W.D., Sprung-Much, T., Amiez, C., Procyk, E., Petrides, M., Schapiro, S.J., & Sherwood, C.C. (2022). A comprehensive analysis of variability in the sulci that define the inferior frontal gyrus in the chimpanzee (Pan troglodytes) brain. American Journal of Biological Anthrophology, 179(1), 31-47.