Cerebral localization of higher functions: anatomic structures before the identification of their memory function

The nature of memory and the search for its localization have been a subject of interest since Antiquity. After millennia of hypothetical concepts the core memory-related structures finally began to be identified through modern scientifically-based methods at the diencephalic, hippocampal, and neocortical levels. However, there was a clear temporal delay between the finding of these anatomic structures ignoring their function, and their identification related to memory function. Thus, the core structures begun to be identified with a pure anatomical view in the late Middle Ages on, while the memory function related to them was discovered much later, in the late Modern Period

Hippocrates and the anatomy of the nervous system

Hippocrates was one of the greatest physicians ever, and merited unquestionably, the title of ‘Father of Medicine’. He, together with other authors, formed an assemble of texts known as ‘Hippocratic Collection’ (or ‘Hippocratic Corpus’). There, the ample and brilliant medical experience remained documented, and left as a legacy. Even after almost two and a half millennia, these medical writings continue to be admired, and regarded as a lasting fount of inspiration. However, regarding anatomy, including that of the nervous system, and related structures, the texts are poor. About the nervous system, he mentioned the brain and its two hemispheres, the spinal cord, and the sensory organs. The related structures are also cited, comprising the meninges, the cerebrospinal fluid, and the blood vessels, as well as the skull, and the vertebral column. The functions of the brain were partly explained, and he ascribed to the brain the main ruling function of the body, a mark of encephalocentric position. Thus, counterposed to his ample medical accomplishments was his poor anatomical contribution. However, it must be recognized that the incipient contribution on anatomy that was legated, represented an important starting point for upcoming scholars and further studies on the subject

Alois Alzheimer and vascular brain disease: Arteriosclerotic atrophy of the brain.

Alois Alzheimer is best known for his description of neurofibrillary changes in brain neurons of a demented patient, identifying a novel disease, soon named after him by Kraepelin. However, the range of his studies was broad, including vascular brain diseases, published between 1894 and 1902. Alzheimer described the clinical picture of Arteriosclerotic atrophy of the brain, differentiating it from other similar disorders. He stated that autopsy allowed pathological distinction between arteriosclerosis and syphilis, thereby achieving some of his objectives of segregating disorders and separating them from syphilis. His studies contributed greatly to establishing the key information on vascular brain diseases, predating the present state of knowledge on the issue, while providing early descriptions of what would be later regarded as the dimensional presentation of the now called "Vascular cognitive impairment", constituted by a spectrum that includes a stage of "Vascular cognitive impairment not dementia" and another of "Vascular dementia"

DESCARTES and the brain

René Descartes (1596-1650), was a French mathematician, physicist, and philosopher, author of numerous texts, among which was the ‘Treatise on Man’ (L’Homme). There, he described the brain, after consulting authoritative anatomic texts, watching the work of butchers, and personally dissecting animals, and human material. His text, finished in 1633, and revised in 1640, was not published for religious reasons. A Latin translation was published posthumously (1662), and a French one two years later (1664)1,2. The brain, according to his hypothetical description, comprises a solid part constituted by “a tissue composed in a certain particular way” [nervous tissue]. He identified there two regions, a deep or internal one in direct contact with the cavities [ventricles] (EE), formed of a meshwork of filaments or ‘small tubules’ (AA), from which originate many delicate filaments, many occupy an external region, with intervals or ‘pores’ between them (BB), others course to the surface (CC), and longer ones converge caudally to form a stalk-like structure (D). In the middle of the brain is placed the gland H [pineal gland] (place of the ‘rational soul’). The whole structure is enveloped by a double membrane [meninges]3 (Figure). The ‘animal spirits’ (esprits animaux) are filtered by the pineal gland, and fill the cavities, being directed by the gland to the proper tubules, and pores, and from there by means of the stalk, to the rest of the body, constituting the basic mechanism underpinning the presumptive functions of this brain3.Thus, Descartes proposed, for the first time, a minute structure for this solid matter of the brain, although hypothetical, and based on it, a presumptive function

Binswanger and the carotid sinus

The ‘carotid sinus’ is an arterial dilatation placed usually at the beginning of the internal carotid artery. The medial wall of this dilatation appears modified, with a reduction of the media, and an increase of the adventitia, besides containing nervous terminations, forming thus a sensorial structure. This dilatation was possibly first observed by John Bell (1808), and clearly described and named by Cruveilhier (1834). However, many authors credited the initial finding to Burns (1811), followed by a number of researchers, as Luschka (1862), Manson (1866), Meyer (1876), Schäfer (1878), most with a view related to aneurysm formation, but some seeing the formation as a normal trait. Finally, Binswanger (1879) reaffirmed that the dilatation meant a normal feature of the region, based on his own observations, and on the opinion of some forerunners. Besides, he was the first to classify this dilatation regarding the variability of its localization. The thinning of this region was initially identified by Meyer (1876) and detailed by Binswanger (1879), at bare eye visual inspection and on microscopic examination, observing there an important reduction of the width of the tunica media. Despite Meyer’s effort, and mostly Binswanger’s, the microscopic findings are incipient, what can be explained by the limitations of the histological techniques at the time. However, there is no doubt that Binswanger and his forerunners provided important information for the upcoming research, comprising the structure, innervation, and function of this formation

Alzheimer and vascular brain diseases: Focal and diffuse subforms.

Alois Alzheimer is best known for his description of the pre-senile neurodegenerative disease named after him. However, his previous interest in vascular brain diseases, underlying cognitive and behavioral changes, was very strong. Besides describing the Arteriosclerotic atrophy of the brain and the arteriosclerotic subtype of Senile dementia which he viewed as main forms of vascular brain diseases, he also identified and described a series of conditions he considered subforms. These may be divided, as suggested by the authors of the present paper, into 3 groups: gliosis and sclerosis, subcortical atrophies, and apoplectic. The subforms of the three groups present characteristic neuropathological features and clinical, cognitive and behavioral manifestations. These provide the basis, together with part of the main forms, for the contemporary condition known as Vascular Cognitive Impairment

Aristoteles and the anatomy of the nervous system

Aristoteles was probably the first anatomist in the modern sense of this term. He wrote on human anatomy relying on the external aspects, and the lacking data on internal structures were generalized through the study of lower animals. The different body regions were described according to a precise topography, and his contribution to the development of anatomy was extensive, as he correctly described many organs and introduced new terms to indicate anatomical structures. Regarding the nervous system, he identified the brain and the two hemispheres, the cerebellum, and the spinal cord. The brain coverings, the meninges, were identified, a tougher external, and a delicate internal, and the related blood vessels. He described the bony casing, the skull and part of its bones and sutures, as well as the vertebral column formed by distinct holed vertebrae. The sensory organs were also defined, but he overlooked the presence of nerves, confusing such structures with vessels, tendons, ducts, among other similar structures. Additionally, he explained the functions of the brain, to which he attributed an important role, despite his cardiocentric standpoint. More than twenty and three centuries have elapsed since Aristoteles began his biological investigation, and his work was and continues to be admired, despite the inaccuracies that were pointed out by later authors. Evidently, knowledge on anatomy of the nervous system before Aristoteles was very scant, thus, it must be recognized that the pioneer anatomical studies he performed may be seen as fundamental, leaving a solid ground for future research on anatomy

Discovery of Apraxia

Skilled movements certainly exist since the dawn of the humans, embedded in the actions of daily living, and also represented by tools and weapons making and use, as well as by artistic activities as drawing and engraving. A very long period of time elapsed until such actions were recognized as special, and the designation ‘praxis’ was attributed to such ability of produce refined movements. Another long time passed, and only recently disturbances of such actions caused by brain lesions were identified, leading to the concept of ‘apraxia’. Studies on this subject progressed quickly, and in a few decades reached the state resembling to what is seen nowadays