1400 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



Stimulation were mapped out in subcortical and corti- 

 cal structures (96). 



In confirmation of anatomical data it was found 

 that the subcortical projection areas of the basolateral 

 and the corticomedial sul)di\ision of the amygdala 

 overlap widely and that the efferent fibers, as judged 

 by latency measurements, end in the basal septal 

 region, the base of the head of the caudate nucleus, 

 the preoptic area, the anterior hypothalamus and in 

 the region of the ventromedial hypothalamic nucleus, 

 the latter receiving direct fibers probably from the 

 corticomedial complex only. The subcortical area, 

 from which responses to amygdaloid stimulation were 

 recorded, was however much larger than this 

 'primary projection field' and extended back to 

 the mesencephalic tegmentum, including the re- 



mainder of the hypothalamus, the subthalamus, the 

 entopeduncular nucleus and a small, essentially 

 anteroventral part of the diffuse thalamic projection 

 system (see also p. 1401 ). The responses recorded in 

 this 'secondary projection field" are relayed from the 

 'primary' area over polysynaptic neuronal links, as 

 indicated by the rapid and progressive increase of 

 response latency as the recording electrode is moved 

 away from the 'primary projection field.' 



The two main subdivisions of the amygdala appear 

 to discharge into the subcortex over two distinctly 

 different fiber systems. Only the corticomedial com- 

 plex seems to give origin to stria terminalis fibers 

 since only in response to stimulation of this part of 

 the amygdala were short-latency responses recorded 

 in the stria terminalis. Responses from the basolateral 



FIG. 3. Diagram of the neuronal organization of the amygdaloid projection system as revealed 

 by electrophysiological studies. Ac, nucleus accumbens; Am. b-l., basolateral subdivision of amygdala; 

 Am.m., corticomedial subdivision of the amygdala; A.X, anterior thalamic nuclei; Cd., caudate 

 nucleus; CI, inferior coUiculus; Cm, centre median; C.S, superior coUiculus; GL, lateral geniculate 

 body; Gm, medial geniculate body; Ha, anterior hypothalamus; Hip., hippocampus; Hfi, posterior 

 hypothalamus; IL, intralaminar nuclei of thalamus; LP, nucleus lateralis posterior thalami; MD, 

 nucleus medialis dorsalis thalami; A/ft, mesencephalon; .Mm., mammillary body; .\Hirn, nucleus 

 ventromedialis hvpothalami, Pii/, pulvinar; R, nucleus reticularis thalami; Rel, reticular formation; 

 RPo, regio preoptica; Spl, septum; and I'a, nucleus ventralis anterior thalami. The dolled area repre- 

 sents the subcortical integrative areas regulating 'global' mechanisms and the limbic structures 

 projecting into it. [From Gloor (96).] 



