Morphometric and Functional Correlation of Human Neuronal Somata: Pyramidal Motor, Special Sensory and General Sensory Systems

Abstract

Although there are huge numbers of nerve cells in the human central and peripheral nervous systems, morphometric comparison of neuronal somata related to their functions is rather rare, except for our own studies [1][2][3] where we used an ideal preparation method that yields the lowest recorded shrinkage ratio and the narrowest shrinkage range 4) . Classic explanations regarding the size and morphology of neurons have been made by Ramon y Cajal (1899) in his textbook 5) . He concluded as follows: "Physiologic characteristics do not appear to be related to size either. Although, in general, motoneurons are huge, some are very small; and sensory cells in dorsal root ganglia, as well as many retinal ganglion cells, are also large." His explanations have been accepted all over the world. However, since there were no modern morphometric techniques in his time, and his research was performed mainly with the silver impregnation method which may cause a wide range of strong tissue shrinkage, any comparison, in the strict sense of the word of neuronal sizes, under the microscope, in different parts of the nervous system or in different individuals using this method may not yield totally accurate results.With the help of a new preparation method and modern morphometry, we have conducted a comparative study of representative human neuronal somata for the reconsideration of those results from the morphological and functional points of view. MethodsOver the past twenty years, we have prepared many tissue sections of the human brain, spinal cord and spinal ganglia using the modified Klüver-Barrera (K-B) staining method after secondary chromic acid fixation followed by nitrocellulose embedding 4) . For the study of various nuclei such as the oculomotor, trochlear, inferior collicular, motor trigeminal, principal sensory trigeminal, abducens, facial, vestibular, ambiguus, hypoglossal, cochlear, medial superior olivary, solitary tract, trigeminal spinal tract, von Monakow, Goll, Burdach, we selected several sections of the cerebral cortex containing the precentral and postcentral gyri and of the diencephalon containing the posterior ventromedialis and ventrolateralis (VPM and VPL) thalamic nuclei from a 60-year-old male, as well as serial sections of the brainstem and cerebellum from a 63-year-old female. For the selection of the anterior horn cells and posterior horn proprius cells, the spinal cord of another 60-year-old male was cut into the cervical, thoracic, lumbar and sacral segments. Transverse sections in each segment were prepared. Serial Okajimas Folia Anat. Jpn., 85(4): 115-117, February, 2009 Summary: Using an ideal tissue preparation method, we found a definite correlation between various human neuronal somata from the view point of accurate morphometry and functional evaluations. We believe this study may be of value, or even indispensable in the correct understanding of neurological symptomatology and phenomenology.