The connections of the amygdala and of the anterior temporal cortex in the human brain

Abstract

In recent years the functions of the temporal lobe have been of prime interest to experimental and clinical workers in the field of neurology. Much of this interest has been stimulated by the intriguing problems raised by the clinical symptomatology of temporal lobe epilepsy and by the many observations made in the course of surgical treatment of this form of epilepsy by anterior and mesial temporal lobe excisions inchding the amygdala. Electroencephalographic observations, the responses induced by electrical stimulation of temporal lobe structures during operation and the results of careful pre-and postoperative psychological testing of the patients undergoing these neurosurgical operations have considerably advanced our knowledge of the functional significance of the temporal lobe in man. Thus the physiology of this area has become increasingly a human physiology and, as such, it obviously should rest upon a firm first-hand knowledge of the human anatomy of this region. However, a great deal of our knowledge of the hv.man anatomy of this area rests upon inferences drawn by analogy from studies carried out in subhuman mammalian species.Therefore, it seemed to us timely to restudy the anatomy of this region i n the human brain itself, especially since with the rapid development of stereotaxic neurosurgery a precise knowledge of the specifically human anatomy of this and other a r e x of the brain will assume more and more practical importance.In this presentation of our investigations we shall restrict ourselves to the connections of the amygdala and of the neighboring temporal cortex. The posterior border of the area to be considered here is not shxply defined, but runs roughly along the vein of Labbk. It does not include Heschl's gyrus and its connections nor does it include Ammon's formation. We excluded from our study the callosal connections of the temporal lobe, corticostriatal connections and the primary olfactory connections of the amygdala and of the periamygdaloid cortex. MATE:RIALS AND METHODSThe method applied to this study was that of fiber dissection in the previously frozen brain as developed by one of us (Klingler, '35). In addition a wax model of the basal ganglia and of the neighboring cortex constructed by on of us (Klingler. '41) on the basis of Weigert-stained serial sections through the human brain proved to bc very helpful. Limited use has been made of myelin stained coronal sections of the human brain. Only normal material was used. Technique o f fixing, freezing and dissecting the brainFor fiber dissection studies of the human brain it is important that all parts, including the deepest structures are well fixed. Fixation in the customary 10% iormalin is inadequate, for it fixes rapidly and well the external parts close to the surface, but penetration of the formalin into the deeper parts is slow and insufficient and thus results i n their inadequate fixation. In brains so fixed fiber dissection studies cannot be carried out in a satisfactory way. It is, therefore, necessary to fix the bra...

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