Fig 1.
Callithrix penicillata (CP1) encephalon.
(A) Superior view: 1. Frontal lobe 2. Occipital lobe 3. Parietal lobe 4. Temporal lobe 5. Sagittal/longitudinal fissure 6. Lateral sulcus (B) Lateral view: 7. Superior temporal sulcus (C) Medial view: 8. Calcarine sulcus 9. Sulcus of the corpus callosum 10. Hippocampal sulcus; (D) Medial view: 40a. corpus callosum genu 40b. corpus callosum trunk 40c. corpus callosum splenium 41. Fornix 42. Thalamus 43. Epiphysis 44. Hypothalamus 46. Septum pellucidum 49. Superior colliculus 50. Inferior colliculus 53. Metathalamus 54. Mesencephalon 55. Pons 56. Cerebellum 57. Ventriculus quartus 58. Bulb.
Table 1.
Presence of the main sulci in the medial region of the brain of modern humans and other primates, in special those belonging to the genera Pan, Papio, Macaca, Galago, Ateles, Cebus, and Sapajus.
Fig 2.
Saimiri ustus (SU1) encephalon.
(A) Superior view: 5. Sagittal/longitudinal fissure 6. Lateral sulcus 7. Superior temporal sulcus 12. Central sulcus 13. Lunatus sulcus. (B) Lateral view: 1. Frontal lobe 2. Occipital lobe 6. Lateral sulcus 7. Superior temporal sulcus 12. Central sulcus 13. Lunatus sulcus 28. Parietal rostral gyrus 29. Parietal caudal gyrus 30. Superior temporal gyrus 31. Inferior temporal gyrus. (C) Medial view: 9. Sulcus of the corpus callosum 14. Cingulate sulcus 15. Subparietal sulcus 19. Parieto-occipital sulcus 32. Medial frontal gyrus 33a. Cingulate gyrus isthmus 34. Precuneus 39. Cuneus. (D) Medial view: 8. Calcarine sulcus 8a. Superior ramus 8b. Inferior ramus 10. Hippocampal sulcus 17. Collateral sulcus 35. Occipital gyrus 36. Fusiform gyrus 37. Lingual gyrus 38. Para hippocampal gyrus 59. Uncus. E. Medial view: 40a. Corpus callosum genu 40b. Corpus callosum trunk 40c. Corpus callosum splenium 40d. Corpus callosum rostrum 41. Fornix 42. Thalamus 44. Hypothalamus 45. Medullary stria of thalamus 46. Septum pellucidum 48. Anterior commissure 49. Superior colliculus 50. Inferior colliculus 54. Mesencephalon 55. Pons 56. Cerebellum 58. Bulb 62. Mammillary body.
Fig 3.
Sapajus libidinosus (SP1) encephalon.
(A) Medial view: 9. Sulcus of the corpus callosum 14. Cingulate sulcus 18. Rostral sulcus 32. Medial frontal gyrus 33. Cingulate gyrus 33a. Cingulate gyrus isthmus. (B) Medial view: 8. Calcarine sulcus 8a. Superior ramus 8b. Inferior ramus 10. Hippocampal sulcus 11. Rhinal sulcus 15. Subparietal sulcus 16. Parieto-occipital sulcus 17. Collateral sulcus 20. Occipital-temporal sulcus 35. Occipital gyrus 59. Uncus 39. Cuneus. (C) Lateral view: 6. Lateral sulcus 7. Superior temporal sulcus 12. Central sulcus 13. Lunatus sulcus 21. Inferior occipital sulcus 22. Longitudinal superior sulcus 23. Longitudinal inferior sulcus 24. Vertical sulcus 26. Postcentral sulcus. (D) Medial view: 40a. Corpus callosum genu 40b. Corpus callosum trunk 40c. Corpus callosum splenium 42. Thalamus 44. Hypothalamus 49. Superior colliculus 50. Inferior colliculus 54. Mesencephalon 55. Pons 56. Cerebellum 57. Ventriculus quartus 58. Bulb 60. Optic chiasm 61. Oculomotor nerve.
Table 2.
Relative measurements of the sulci, gyri, encephalic trunk, and other structures as a function of brain length (length of the cerebral hemisphere from the frontal to the occipital pole for each species–RM (cm), or relative measure).
Table 3.
Absolute measurements (cm), of the distance between the main sulci and the occipital and frontal poles.
Table 4.
Straight and sinuous measurements of the main sulci in Callithrix penicillate.
Table 5.
Straight and sinuous measurements of the sulci on the medial aspect of the brain in Sapajus libidinosus.
Table 6.
Degree of sinuosity of the main sulci of primate species used in the present study.
Fig 4.
Brachyteles arachnoides (BA1) encephalon.
(A) Lateral view: 12. Central sulcus 25a. Superior precentral sulcus 25b. Inferior precentral sulcus 26. Postcentral sulcus 27. Inferior frontal sulcus. (B) Lateral view: 6. Lateral sulcus 7. Superior temporal sulcus 13. Lunatus sulcus 21. Inferior occipital sulcus. (C) Medial view: 8. Calcarine sulcus 8a. Superior ramus 8b. Inferior ramus 9. Sulcus of the corpus callosum 10. Hippocampal sulcus 11. Rhinal sulcus 14. Cingulate sulcus 18. Rostral sulcus 19. Superior part of cingulate gyrus. (D) Medial view: 16. Parieto-occipital sulcus 40a. Corpus callosum genu 40b. Corpus callosum trunk 40c. Corpus callosum splenium 40d. Corpus callosum rostrum 42. Thalamus 44. Hypothalamus 48. Anterior commissure 49. Superior colliculus 50. Inferior colliculus 54. Mesencephalon 55. Pons 56. Cerebellum 57. Ventriculus quartus 58. Bulb.
Table 7.
Degree of sinuosity and degree of inclination of the central sulcus shown as the calculated Encephalization Quotient (EQ) for Callithrix penicillata, Saimiri ustus, Sapajus libidinosus, and Brachyteles arachnoides compared with the data for humans according Testut and Latarjet [13].
Table 8.
Encephalon mass, height, length, width, and Encephalization Quotient (EQ) of primate species studied in the present study and previous studies.
Fig 5.
Polynomial regression of degree 3 shows a strong correlation between Encephalization Quotient (EQ) and brain mass (R2 = 0.98197).
A linear regression was also performed (R2 = 0.081803). From left to right, the points correspond to Callithrix (1), Macaca (2), Hylobates (3), Brachyteles (4), Saimiri (5), Sapajus (6), Pan (7), Gorilla (8) and Homo sapiens (9).
Fig 6.
Mean degree of sinuosity of Callithrix penicillata, Saimiri ustus, Sapajus libidinosus, and Brachyteles arachnoides.
The larger the value is, the smaller is the sinuosity.
Table 9.
General data of study specimens.
Fig 7.
Photograph of the left convex aspect of the Sapajus libidinosus brain indicating the distance from the superior and inferior extremities of the central sulcus to the frontal and occipital poles.
These measurements indicate the degree of inclination of the central sulcus.