CHAPTER L\I1I 



Amygdala 



p. GLOOR 



Department of Neurology and Neurosurgery, McGill University and the 

 Montreal Neurological Institute, Alontreal, Canada 



CHAPTER CONTENTS 



Anatomical Introduction 



Anatomical and Physiological Studies of Amygdaloid Con- 

 nections 

 Afferent Connections 



Olfactory connections and olfactory functions of amygdala 

 Other afferent sensory connections of amygdala 

 Nonsensory afferent connections to amygdala 

 Efferent Connections 

 Anatomical studies 



Subcortical connections 

 Cortical connections 

 Electrophysiological studies of efferent amygdaloid con- 

 nections 

 Commissural Connections 

 Electrical Activity of Amygdala 

 Stimulation Studies 

 Excitability 



Electrocorticographic Responses 



Effects upon Spontaneous or Evoked Somatomotor Ac- 

 tivities 

 Motor Responses 

 Vegetative Responses 

 Endocrine Responses 



Integrated Behavioral Responses and Psychic Phenomena 

 Feeding behavior 

 Attention, fear and rage 

 Rewarding experiences 

 Sexual behavior 



Modifications of level of awareness, confusion and inter- 

 ference with memory recording mechanisms 

 Topographical Representation of Function in Amygdala 

 Mediation of Amygdaloid Stimulation Responses 

 Dynamic Aspects 

 Lesion Experiments 

 Pathophysiology 

 Epilepsy 

 Hallucinations 

 Functional Significance of Amygdala 



ANATOMICAL INTRODUCTION 



THE AMYGDALA (synonyms for which are the amvg- 

 daloid nucleus and the amygdaloid complex) is a 



subcortical formation of the rhinencephalon or limi)ic 

 system. It is included within this system on the grounds 

 of its phylogenetic history and its fiber connections. 

 In mammals it represents a mass of gray matter lying 

 in the depth of the temporal lobe ventral to the 

 lentiform nucleus with which it is partly continuous. 

 In the human brain (255) it is part of the uncus of 

 the hippocampal gyrus and lies anterior to the 

 rostral end of the pes hippocampi from which it is 

 separated by the thin ventricular cleft forming the tip 

 of the temporal horn of the lateral ventricle. Although 

 essentially a suijcortical structure, the amvgdala 

 emerges to the cortical surface with its medial part, 

 thus participating in the formation of the cortex of 

 the uncus in man or of the anterior piriform lobe in 

 lower mammalian forms. 



The amygdala is subdivided into several subnuclei 

 which can be identified in all mammalian brains' 

 (fig. i). These are usually grouped into two nuclear 

 complexes (122): a) the basolateral complex with the 

 lateral, the accessory basal and the basal nuclei (the 

 latter being further subdivided into a large-celled 

 lateral and a small-celled medial portion) and /;) the 

 corticomedial complex with the central, medial and 

 cortical nuclei, the nucleus of the lateral olfactory 

 tract and the corticoamygdaloid transition area. 

 Both basolateral and corticomedial complexes merge 

 anteriorly into the anterior amygdaloid area (62, 109) 

 and more posteriorly are separated by the small- 

 celled intercalated masses (109). The designation of 



' They have been described in detail for many mammalian 

 forms: marsupials 126, 131, 162, igi), Insectivora (47, 235, 

 246), Chiroptera (122, 131, 235), rodents (32, 109, 131, 242, 

 243, 246, 256), Edentata (233, 235), Carnivora (62, 130, 184, 

 247), Ungulata (69), Proboscoidea (235), Cetacea (i, 30, 156), 

 primates (49, 131, 132, 157, 184, 247) and man (31, 46, 118, 

 132, 164, 177, 235). 



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