Frontal Lobe

FRONTAL LOBE, lobus frontalis cerebri, the anterior division of the brain, particularly developed in organisms standing highest on the zoological scale, and in particular in man. - Morphology. The frontal lobes appear as a paired formation, symmetrically arranged and having not infrequently a whole series of individual peculiarities in the details of the development of sulci and gyri (see Brain). In connection with functional peculiarities and symptomatology, it is necessary to distinguish the right and left frontal lobes, the three main gyri on their lateral surface, the posterior (precentral), middle, and anterior (pole of the frontal lobe) parts of these gyri, the medial surface of the frontal lobe, and its base with the adjacent olfactory tracts.--Blood supply to the frontal lobe occurs mainly through the system of the anterior cerebral artery. The frontal lobes contain association [specifically superior longitudinal fasciculus (arcuate), medial longitudinal fasciculus (subcallosal, fronto-occipital), uncinate fasciculus, fronto-occipital fasciculus, fronto-central fasciculus], commissural, and projection fiber systems; of the latter, special mention should be made of the fronto-tuberal, fronto-pallidal, fronto-pontine (Monakow), and fronto-cerebellar systems. Embryologically (myelogenetically) it has been established (Flechsig) that the development of the frontal lobes is later compared to other parts of the brain (Flechsig's terminal areas), which served as the basis for Flechsig's identification of the anterior frontal association center. The development of the frontal lobes of the brain stands in some relation to the development of the adrenal glands; this is emphasized by the fact that when the latter are underdeveloped, the frontal lobes are found to be underdeveloped.- Comparative anatomical data show that in lower apes and carnivores the frontal lobes are still very weakly expressed and even in higher apes their development is relatively small, whereas in man they occupy from 30% to 40% of the cerebral mantle. However, rich development of the frontal lobes is characteristic not only of primates, but also of ruminants (Monakow). The horse, cow, goat have frontal lobes that in volume occupy slightly less than 30% of the total brain volume and terminate bluntly rather than acutely as in lower apes and carnivores. The development of sulci and gyri in ruminants is very well expressed.. It is possible that the rich development of the frontal lobes in ruminants is related to the weak development of the motor zone of the limbs in them and the enormous importance that the musculature of the head and neck has for them.- Histology of the frontal lobe reduces to cyto- and myeloarchitectonic data (see Architecture of the cerebral cortex). The cortex of the frontal lobe is generally well developed, but not very rich in cells. The most characteristic feature must be considered the good development and regular arrangement of pyramidal cells in the 3rd and 5th layers of the cortex; this is not noted in other areas of the cortex (Economo); Betz giant pyramidal cells are not visible in the frontal parts of the cortex proper (distinction from the central gyri); the 6th layer of the cortex is also well expressed: elongated cells are well developed, regularly arranged and oriented in the direction of radial fibers; the 2nd and 4th layers are developed much more weakly, cells are small and triangular, in places absent. Toward the pole of the frontal lobe, the thickness of the cortex becomes smaller due to the reduction of pyramidal and elongated cells, while at the same time both granular layers appear better expressed. The number of deviations and individual peculiarities in the cytoarchitectonics of the frontal lobe is very great. In very recent times, investigations by Pfeifer have raised the question of the angioarchitectonics of the brain, i.e., in particular regarding the features of blood supply in the histological relation of the cerebral cortex and the frontal lobe. Experimental-physiological study of the frontal lobe began long ago, and there are quite a few works on this topic in various languages. Some researchers proved a definite connection of the frontal lobe with manifestations of mental life, others denied this connection. The difference in the conclusions of experimenters depends not only on the difference in the choice of animals and imperfections of methodology, but also on certain general premises directing the researcher's thought. Especially interesting in relation to the frontal lobe are experiments on animal training (Franz expressed the opinion that centers for learning should be sought in the frontal lobe) and experiments set up by the method of conditioned and associative reflexes in the laboratories of Pavlov and Bekhterev.- Reflexological studies by Demidov, Saturnov, and Afanasiev did not lead to unambiguous conclusions. After the removal of both frontal lobes in a dog, Demidov failed to form conditioned reflexes from the eye, nose, ear, skin; according to Saturnov, however, after the removal of both frontal lobes, conditioned reflexes continue to be formed. Works from Bekhterev's laboratory lead to the conclusion that the prefrontal lobes do not exert a direct influence on the formation and execution of most natural and artificial associative motor reactions. Earlier experiments of the Pavlov laboratory (Babkin, Tikhomirov) showed that for the most part it was impossible to form conditioned positive cutaneous-mechanical reflexes specifically from the trunk; reflexes to agents related to other analyzers were preserved; conditioned cutaneous-mechanical reflexes from the limbs were sometimes elaborated. In animals after removal of the frontal lobes of the brain, very sharp disorders of behavior are observed, a helpless state, inability to get out of situations, difficulty in spatial orientation, change of character, impulsiveness, lack of reaction to threat, to estrus, disorder of motor coordination, loss of acquired training skills, change in pupillary reaction, nutritional decline despite voracity. Pathology. Very interesting general conclusions were obtained by Bolton (1910), who worked for 14 years in the field of cytoarchitectonics and processed a large number of pathological cases. He came to the conclusion that the outer cellular layer of the prefrontal region is the substrate of voluntary association. Dividing the brain into pre-Rolandic and post-Rolandic parts, Bolton ascribes control and executive functions to the former, and receptive and processing functions to the latter. The pre-Rolandic (i.e., frontal) part is divided in turn into two: the posterior, or psychomotor region, and the anterior, or prefrontal; to the latter, to use the author's expression, belong the control, choice, and definite coordination of the results of associations occurring behind the Rolandic fissure, as well as the allowance or prohibition for one or another of these results to undergo psychomotor transformation. As pathological processes in the frontal lobe, hemorrhages, softening, thrombosis, traumatic injury, gunshot wound, inflammation, abscess (see separate plate, figures 3 and 4), tumor, parasites can be observed. In the pathogenesis of disorders arising in connection with a lesion of the frontal lobe, one must always reckon with whether a given symptom is present as a result of the loss of function of the frontal lobe or as a result of its irritation. In addition to local diseases of the frontal lobe, their predominant participation in other general diseases of the brain is also of significance for pathology: in progressive paralysis, in which the pathological process often affects first and most strongly the frontal lobes of the brain, in schizophrenia, in various forms of mental underdevelopment, acquired dementia (arteriosclerosis), Pick's and Ganser's diseases, where one can also distinguish special aspects of pathological manifestations due to damage to the frontal lobes of the brain. S. S. Korsakov, based on his studies of microcephaly, constructed his doctrine of the "guiding power of the mind," which he connected with the function of the frontal lobe. Bekhterev believed that the frontal lobes have a psycho-regulatory significance, due to which reason, will, active attention suffer upon their lesion, and a disruption and alteration of personality occur. The pathognostic method of studying the frontal lobe shows that the function of the latter is connected with psychomotor functions, reflex activity (reflexes of limbs, pupils, pelves, organs), behavior, speech, writing, expressive movements, manifestations of affects, functions of active attention, volitional acts in their actuality. In the study of the brains of prominent people (geniology), a particularly rich development of various gyri of the frontal lobes was noted by a number of researchers; this was observed in some mathematicians, musicians, scientists. A very difficult question is the solution of the problem of the difference between the left and right frontal lobes in the functional relation and the question of the organology of the frontal lobe in general. Aside from the more definite connection of the posterior division of the 3rd frontal gyrus with the motor function of speech, that of the same posterior division of the 2nd frontal gyrus with the motor function of writing, conjugate eye movements, and finally that of the same part of the 1st frontal gyrus with trunk movements, one can speak of the connection of higher and subtler physiological and psychological functions with more anterior divisions of the frontal lobe. More highly organized functions can be referred to the left frontal lobe than to the right; this is especially noticeable in relation to the function of speech. The relation of the frontal lobe to mental life is expressed predominantly in manifestations of activity in the sense of initiative, voluntariness, active attention, and behavior (Khoroshko).

In the same sense, Kurt Goldstein, Poppelreuter, Feichtinger, Lhermitte, and Pfeifer have expressed themselves in recent years. Clinical features. The symptomatology of the frontal lobe is composed of general cerebral and local symptoms. At the present time, the knowledge of clinical symptom complexes in lesions of the frontal lobe can be linked to a greater or lesser extent with our knowledge of the histological structure of the cortex of the same part of the brain. Economo and Koskinas have elaborated a generalized cytoarchitectonic map and a map of the localizations of known syndromes of the cerebral cortex, which help in orienting oneself in the symptomatology of the frontal lobes as well. For an understanding of the symptomatology of the frontal lobe, it is necessary to become acquainted with the content of the concepts: asymbolia, agnosia, apraxia, aphasia, agraphia, amusia, amimia, anosmia, ataxia (see). The clinical material accumulated in recent years generally confirms and serves to develop and deepen Bolton's general scheme described above. The symptomatology of the frontal lobe, or frontal lobe syndrome, is composed of a series of psychomotor disorders belonging to the general group of disorders and losses of action, in particular speech, mimicry, manipulation, writing, playing a musical instrument, singing, and behavior, which are impaired predominantly and characteristically in terms of their activity, effectiveness, and volitional manifestations. Therefore, we see here the picture of motor (apractic or kinetic) aphasia (posterior part of F₃), amimia, dysmimia, motor agraphia, and amusia (posterior part of F₂). This is expressed by the fact that the patient loses voluntary speech, experiences various difficulties in the voluntary act of speech, can copy from a book, write to dictation, but has difficulty with voluntary writing, loses the capacity for facial expressiveness, develops a forced smile, laughter inappropriate to the mood, a pathological propensity for humor and joking (moria, Witzelsucht), loses the ability to reproduce a melody or rhythm while having good recognition and understanding of the musical phrase, and so on. Behavior disorders are expressed by unmotivated, purposeless acts, impulsive actions, disobedience and insubordination in the sphere of the elementary ward regime (e.g., urinates in bed instead of into the urinal, urinates on the floor in the middle of the ward; goes to the toilet when it is strongly requested of him to lie down and not get up; at the same time, the patient perfectly understands the improprieties he is committing and apologizes for what he has done). To the described picture of the frontal lobe syndrome, on the one hand, are added disorders in the sphere of more elementary motor acts, such as standing, walking, associated movements of the eyes and head, chewing, swallowing, articulation; this gives the picture of frontal ataxia, cortical irritation in the form of an epileptic or epileptiform seizure with a characteristic onset (turning of the eyes, head, neck to one side, increased blinking, smacking of the lips, etc.); these symptoms are localized predominantly in the posterosuperior part of the frontal lobe (posterior parts of F₂ and F₁); on the other hand, disorders of even more highly and finely organized functions must be attributed to the picture of the frontal syndrome, such as active attention (weakening of the capacity for memorization, powers of observation, accuracy of perceptivity, stability and scope of attention) and the characteristics of the personality, predominantly in its activity and expressiveness. Mental disorders observed in other localizations of the pathological process (for example, tumors), insofar as they enter into the above-described picture of the frontal syndrome, must be understood as a manifestation of a lesion of the frontal lobe of the brain. The question of diagnosis and topical diagnosis follows from the knowledge of the symptomatology of the frontal lobe. It is necessary to take into account the location of the source of infection or trauma near the frontal lobe (examination of the nose, pharynx, and accessory cavities); it is very important to perform an examination of local tenderness of the cranial bones in the region of the forehead and temple (percussion, palpation), to pay attention to the state (edema) of the eyelids, eyes (exophthalmos), the difference in the fundus oculi picture (sometimes this difference is particularly prominent in frontal localization), and to perform an examination of the sense of smell. Frequently, in frontal localization of the pathological process, a difference in the manifestations of skin and tendon reflexes, independent of pyramidal tract lesions, as well as a difference in the pupils, becomes apparent. Sometimes the complex of morbid manifestations in lesions of the frontal lobe simulates cerebellar disease and vice versa; in such cases, diagnostic errors have occurred even among the most experienced persons. For such cases, the performance of encephalography in various head positions (Khoroshko) is especially valuable.--Regarding the therapy and surgery of diseases of the frontal lobes of the brain, see Brain, particular pathology of brain diseases. Of tremendous prophylactic importance are trauma and gunshot wounds in the forehead and temple region, inflammatory-infectious and especially purulent processes in the same area, the region of the nose and accessory nasal cavities; for some reason, frontal lobe abscesses frequently develop in bronchiectasis. Insofar as the connection of the frontal lobes of the brain with the processes of active attention, effective activity, initiative, volitional efforts, and so on has been elucidated at the present time, to that extent the necessity arises to consider that during mental, volitional, and moral fatigue and overwork, the frontal lobes of the brain wear out, and moreover to a definite and not small degree. In overwork neurosis (neurasthenia), a peculiar headache and a peculiar sensation in the forehead frequently appear, apparently as a projection or irradiation of the disturbance or exhaustion that has occurred in the frontal lobes of the brain. Overwork is followed by arteriosclerosis and a persistent decrease in working capacity, i.e., disability. Thus, the general neurosis of overwork acquires local features of a localized pathological process. Therefore, a special and enormously socially significant role is played by a correct labor regime and, in particular, prophylactic leaves sufficient in duration for the rest of the over-worked frontal lobes of the brain.