Abstract
Louis Pierre Gratiolet (1815-1865) was one of the first modern anatomists to pay attention to cerebral convolutions. Born in Sainte-Foy-la-Grande (Gironde), he moved to Paris in 1834 to study medicine, as well as comparative anatomy under Henri de Blainville (1777-1850). In 1842, he accepted de Blainville’s offer to become his assistant at the Museum d’histoire naturelle and progressively abandoned medicine for comparative anatomy. He undertook a detailed study of brains of human and nonhuman primates and soon realized that the organizational pattern of cerebral convolutions was so predictable that it could serve as a criterion to classify primate groups. He noted that only the deepest sulci exist in lower primate forms, while the complexity of cortical folding increases markedly in great apes and humans. Gratiolet provided the first cogent description of the lobular organization of primate cerebral hemispheres. He saw the insula as a central lobe around which revolved the frontal, parietal, temporal (temporo-sphenoidal) and occipital lobes. He correctly identified most gyri and sulci on all brain surfaces, introduced the term “plis de passage” for some interconnecting gyri, and provided the first description of the optic radiations. In the early 1860s, Gratiolet fought a highly publicized battle against Paul Broca (1824-1880) on the relationship between brain and intelligence. Gratiolet agreed that the brain was most likely the seat of intelligence, but he considered human cognition far too subtle to have any direct relationship with brain size. He argued that a detailed study of the human brain architecture would be more profitable than Broca’s vain speculations on the relationship between brain weight and intelligence, which he considered a monolithic entity. Despite remarkable scientific achievements and a unique teaching capacity, Gratiolet was unable to secure any academic position until three years before his sudden death in Paris at age 49.
Highlights
The cerebral cortex is a relatively recent phylogenetic acquisition that reaches its highest level of complexity in human and nonhuman primates
The human cerebral cortex has a total area of approximately 2200 cm2 and a volume of about 500,000 mm3; it harbors around 20 - 30 billion neurons that are engaged in roughly 3 × 1014 morphologically differentiated inter-neuronal contacts [1]
The cerebral cortex forms the most voluminous portion of the human brain, but only one third of it is readily visible, the remaining part being hidden in the depths of sulci [1]
Summary
The cerebral cortex is a relatively recent phylogenetic acquisition that reaches its highest level of complexity in human and nonhuman primates. The human cerebral cortex has a total area of approximately 2200 cm and a volume of about 500,000 mm; it harbors around 20 - 30 billion neurons that are engaged in roughly 3 × 1014 morphologically differentiated inter-neuronal contacts [1]. This astonishing figure corresponds to the number of milliseconds that have elapsed in the last 10,000 years, that is, since the beginning of the Neolithic period [2]. This assay is devoted to the Louis Pierre Gratiolet, who was one of the first anatomists to systematically exploit the comparative approach as a tool to map the cortical surface in primates
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