Malcolm B. Carpenter

The organization of pallidosubthalamic fibers in the monkey.

A study was made to determine the topographical organization of pallido-subthalamic fibers in the rhesus monkey. Streotaxic lesions were produced in: (1) the lateral pallidal segment (12 lesions in 10 animals), (2) the medial pallidal segment (6 lesions in 6 animals), and (3) both pallidal segments (4 lesions in 4 animals). Degeneration resulting from these lesions was studied in transverse, horizontal and sagittal sections stained by the Nauta and Gygax technic14. The following conclusions were drawn from this study: 1 Pallidosubthalamic fibers arising in the lateral pallidal segment are topographically organized so that: (a) rostral and central regions of this segment project fibers to the rostral two-thirds of the subthalamic nucleus, and (b) rostral parts of this segment project fibers to the medial half of the subthalamic nucleus and central parts of this segment project fibers to the lateral half of the nucleus. 2 Dorsal and ventral regions of the rostral and central parts of the lateral pallidal segment are organized topographically so that: (a) fibers from dorsal regions of the rostral part terminate in lateral areas of the medial half of the subthalamic nucleus, while ventral regions project to more medial parts of this half of the nucleus, and (b) dorsal and ventral regions of the central part of this pallidal segment project to corresponding dorsal and ventral regions of the subthalamic nucleus. 3 Caudal parts of the lateral pallidal segment project fibers to dorsolateral regions of the caudal part of the subthalamic nucleus. 4 Observations in the present study suggest that pallidosubthalamic fibers terminating in medial and caudal parts of the subthalamic nucleus probably are derived from the medial pallidal segment. The hypothesis is presented that pallidosubthalamic fibers are topographically organized so that: (a) the most medial and lateral regions of the lateral pallidal segment project fibers respectively to medial and lateral parts of the subthalamic nucleus, and (b) the medial segment of the globus pallidus projects a small number of fibers to the subthalamic nucleus which terminate in regions caudal and medial to those that receive fibers from the lateral pallidal segment.

EFFECTS OF LESIONS IN THE SUBSTANTIA NIGRA UPON SUBTHALAMIC DYSKINESIA IN THE MONKEY.

THE SUBSTANTIA NIGRA, considered as one of the most important brainstem nuclei concerned with nonpyramidal motor function, has been the subject of relatively few physiological studies. Although repeated neuropathological studiesl-7 indicate that the substantia nigra is affected with a high degree of consistency in paralysis agitans, these observations have not elucidated the functional significance of this large mesencephalic nucleus. Certain clinicopathological studiesj+IO suggest that lesions or pathological processes invdving the substantia nigra may be associated with a particular form of the parkinsonian syndrome characterized by rigidity and akinesia. Experimental studies11 based upon relatively discrete stereotaxic lesions of the substantia nigra in the monkey indicate that lesions destroying up to 40% of this nucleus do not produce significant alterations of muscle tone or tremor or any detectable form of dyskinesia. These observations are similar to those of Carey and DeJong,12 except that the latter authors noted a mild hypotonicity. According to Denny-Brown,’3 attempts to produce lesions in the substantia nigra in the monkey resulted in acute bulbar and respiratory difficulties. This author has postulated that the substantia nigra may be particularly concerned with mechanisms of bulbar coordination. In experimental studies in the cat, Folkerts and SpiegeP4 reported that destruction of either the substantia nigra or red nucleus increased the excitability of regions of the pontine tegmentum from which tremor could be elicited by electric stimulation. These authors hypothesized that destruction of the substantia nigra results in a release of inhibitory influences acting upon neurons of the reticular formation, and postulated that such a mechanism might be involved in parkinsonian tremor. In spite of the fact that the functional significance of the substantia nigra remains an enigma, lesions produced in this structure have been reported to ameliorate various forms of human dyskinesia. Spiegel and Wycisl5 reported a case in which a patient with ballism was “relieved by a mesencephalic lesion that extended from the midbrain tegmentum into the medial part of the substantia nigra. The position of this lesion was confirmed at autopsy. Using ultrasonic techniques, Meyersl6 reported that lesions in the “nigral region” abolished contralateral tremor and simultaneously reduced muscle tone in parkinsonian patients. Randl7 has reported that lesions in the substantia nigra may alleviate dystonia symptoms remaining after lesions have been made in the globus pallidus and thalamus. The location and extent of these nigral lesions have not been confirmed. The purpose of the current study was to determine the physiological effects of nigral lesions upon subthalamic dyskinesia in the monkey. Subthalamic dyskinesia is basically a

Functional Neuroanatomy of Man

This large and extensive text represents the part of the 35th British edition of Grays Anatomy that concerns the central nervous system (CNS), the peripheral nervous system, and the organs of special sense. Extractions of these sections from the parent volume, largely for economic reasons, have resulted in certain unusual features: (1) a pagination that begins on p 746 and ends on p 1170; (2) the absence of a coordinated bibliography; and (3) the presence of cross references as they appear in the parent volume. Only the lack of a coordinated bibliography in an encyclopedic text of this nature presents any problem, and this is offset by an appended list of publications and footnote citations. In almost every sense, this is probably the most complete modern neuroanatomical text, covering virtually every aspect of the subject in an orderly, systematic fashion. Its organization, use of headings and subtitles, and particularly the

Studies on the Diencephalon

This monograph represents the papers and discussion of the fourth biennial research symposium held at the Lankenau Hospital, Philadelphia, in November 1964. Twenty-three participants, many from abroad, contributed papers in the fields of anatomy, biochemistry, psysiology, and pharmacology. Each participant is widely recognized as an outstanding investigator and an authority. Papers dealing with the ultrastructure of neural tissue concern neuroglia, the unit membrane structure, and neuronal junctions-both synaptic and electrotonic. Observations of glial processes in the central nervous system indicate that they are distributed in a manner so as to isolate receptive surfaces of neurons from nonspecific afferent influences, a hypothesis suggested by Cajal. Data concerning the unit membrane concept are reviewed in the light of new evidence. In one chapter there is a comprehensive review of electron microscopy of neural junctions involved in central nervous system transmission. The section dealing with electrotonic junction is especially interesting and is based largely upon observations in electric fish. The final chapter on ultrastructure deals with synaptic vesicles as structural and biochemical units of the central nervous system. The biochemical part of this symposium contains chapters dealing with the chemical forces controlling permeability of excitable membranes, energy metabolism of the nerve cell, biosynthesis of phospholipids and sphingolipids, and storage and metabolism of neurotransmitters. David Nachmansohn’s account of chemical forces controlling permeability changes in excitable membranes reflects a lifetime of investigative work on this problem. One chapter in this section suggests that neuronal circuits are macrocybernetic units in which connections between conducting elements are made by synapses which are selforganizing microcybernetic units. Papers in the physiology and pharmacology sections of the symposium concern the thermodynamics of nerve and the electric organ, the mechanism of neuromuscular block by quaternary ammonium compounds, the pharmacology of synaptic transmission in the central nervous system, and the nerve impulse. It is apparent that wide differences of opinion still exist concerning neurohumoral transmission at synapses and neuroeffector junctions. This reviewer found the comments of Richard Richter concerning the new biology and the clinic particularly concise. The clinician apparently places his hopes for solutions of particular problems mainly in the development of biochemistry. The techniques of macromolecular neurochemistry appear to offer new approaches to these problems subtle enough to discern metabolic disturbances that have eluded other avenues of investigation. The reflections of Sir John Eccles on the strategy of neurophysiological research constitute a frank and revealing discussion of the joys and pitfalls of an investigative career. It should be read by all contemplating such a career. The collected papers of this symposium on the new biology of neural tissue should have wide appeal and offer all readers interested in the nervous system an opportunity to review the recent advances in special areas of basic inquiry. The organizers of this symposium should be congratulated for bringing together such a distinguished group of scientists.

Elements of Neurophysiology

According to the author, this textbook was written to fulfill a need for a simple yet comprehensive introduction to neurophysiology for medical and graduate students. The need for such a text has long been recognized but few have accepted this challenge. In a brief introductory chapter the author provides historical background, considers the basic structure of the neuron, and broadly explains the aims and instruments of neurophysiology. Roughly twothirds of the text is devoted to the fundamentals of neurophysiology; material is presented in a graded fashion, with clear definitions of new terms as they are introduced. Early chapters concern the action potential, excitability, and membrane potential. More complete analysis of the physiological mechanisms underlying the membrane and action potentials follows which considers the Nernst equation, the Donnan theory of the membrane potential, and the sodium pump. One chapter devoted to the conduction of the action potential analyzes continuous conduction, structure of myelinated nerves, saltatory conduction, and properties of the nodes of Ranvier. It is interesting to see the way the author has interwoven anatomical, physiological, and biochemical data, as in those chapters dealing with metabolism related to conduction, nerve growth and maintenance, and neuromuscular transmission. Receptors, including those of the special sense, are succinctly discussed but not in greater detail than in standard physiology texts. An important part of the text is devoted to the properties of reflexes, reflex transmission, and the integration of reflexes. The remaining chapters of the text are concerned with higher levels of the central nervous system and their more complex functions. These chapters incorporate a great deal of the recent literature on the electrophysiology of the cerebral cortex, the reticular formation, and the mechanisms related to sleep and sensory perception. Worthy of special note is inclusion of recent advances in the understanding of the activities of single cells in the visual cortex and similar superb studies of somesthetic sensory mechanisms and their representation in the thalamus and cerebral cortex. The author, in this reviewer’s opinion, accomplished a tremendous undertaking. He has assembled a voluminous literature and presented the facts as we know them in an orderly, systematic, and understandable manner. Throughout the book he has provided numerous well-chosen illustrations and line drawings that reinforce and extend the text. Each chapter has an ample list of references, and references in the text give both the author’s name and the year of the pertinent publication. This appears to be a textbook that will fulfill the requirements of most students and will enlighten the minds of all who seek to understand the complexities of the nervous system. It deserves a prominent place in every neurological library. MALCOLM n. CARPENTER, M.D.

Studies on the Diencephalon.

This small monograph presents in English translation an anthology of selected writings of Ramon y Cajal on perhaps the most complex subdivision of the neuraxis, the diencephalon. The subject matter has been organized synthetically in a systematic and comprehensive manner using where possible the nomenclature of current English language textbooks. The monograph contains many illustrations from the original papers; but unlike some of the original illustrations, the legends are complete. There is a good table of contents, a well organized index, and bibliography citing references in their entirety, which was not always the custom of Cajal or early investigators. Each chapter gives in a footnote the original source of the translated material, thus making it possible for the reader to compare for himself the original with the translation. An interesting comparison is made of pioneer neuroanatomists and early cartographiers, some of whom represented explored and unexplored regions in equal detail.

Neurological Aspects of Auditory and Vestibular Disorders

This monograph presents the papers and discussion given at the eleventh annual scientific meeting of the Houston Neurological Society in March of 1963. The symposia organized by the society under the guidance of Dr. Fields represent a unique collection of monographs dealing with broad aspects of neurology and related areas. Each symposium brings together the views of leading authorities in the basic and clinical sciences and, in essence, represents a critical appraisal of the research efforts, the clinical advances, and the unsolved problems of both. These generalizations particularly apply to the latest volume based on papers by anatomists, physiologists, neurologists, and otologists. The first part of the monograph concerns neurological aspects of the auditory system in which recent advances in our understanding of this special sense are succinctly summarized. The initial chapter by G. L. Rasmussen provides a superb account of the dual innervation of the hair cells of the organ of Corti, a review of efferent cochlear fibers, and a summary of descending auditory pathways. The second and third chapters deal with the physiology of peripheral and central auditory mechanisms. Remaining short chapters concern conditioning to auditory signals and auditory tests for disorders of the central pathways. A case report of auditory deficits following section of the vestibular nerve is of interest mainly because of the critical discussion it provoked. A larger part of the book, devoted to the vestibular system, begins with a superb rCsumC by A. Brodal of the anatomic organization of vestibular connections. These data have been presented previously in many papers by the author and his distinguished colleagues. Studies of the ascending vestibular projections in relation to disturbances of conjugate horizontal eye movements offer correlations of anatomic and physiological observations which have clinical significance. Gernandt’s contribution to the symposium is a physiological analysis of somatic and visceral influences arising from vestibular stimulation. Although there is an extensive chapter on nystagmography, relatively little information concerning the neural mechanisms underlying nystagmus is presented. In view of the great importance of nystagmus in vestibular disorders, it is surprising that this important topic is neglected. Clinical papers deal with motion sickness and its implications in space flight, the differential diagnosis of vertigo, the effects of vascular disorders on the vestibular system, and the treatment of MBnihe’s disease. The study dealing with factors influencing blood flow in the vertebrobasilar system is of special interest, for it directs attention to a subject area that seems to have been neglected. Neurologists, otologists, and basic scientists interested in these fields will find the information in this monograph of great value. The editors and publishers should be commended for creating a source book with a wide appeal.

Man's Brain, A Study in Dissection.

This small paperback book is a dissection manual for students of medicine and dentistry that represents a part of Volume II of Mans Anatomy written by the same authors. The book has been reprinted without change of pagination and with the complete index of the larger work. There is no table of contents, but the material is conveniently divided into 17 chapters. The style of the book is descriptive with simple instructions for identifying the gross features of the brain, the meninges, the venous sinuses, and the arterial blood supply. It is illustrated by a series of excellent, somewhat diagrammatic, line drawings which are clearly and accurately labeled. A considerable part of the material is presented in outline fashion which usually delights students. Developmental aspects of the nervous system are considered in relation to regional areas resulting in some scattering of material. The diagrams and discussion of the development of