Vincent Di Marino

The Bed Nucleus of the Stria Terminalis

The BST, long forgotten, is studied in this chapter, as a real dependency of the amygdala. The rostral part that plays the most important physiological role is studied in detail, from both macroscopic and microscopic points of view. The inputs and outputs are then reviewed. The prominent role of this structure which is even involved in the sexual characterisation of individuals is then analysed.

Inputs and Outputs

The authors state in the first lines of the chapter they can only report literature data. The inputs are studied first (afferent fibres to the amygdala come from the olfactory tract, midbrain, forebrain and brainstem). The outputs are discussed in reference to connection pathways seen in the previous chapter. Also reviewed are the amygdalofugal fibres joining the structures studied in the inputs.

Relations of the Nuclear Amygdaloid Complex

This chapter is one of the more important topics of this work. The reason is the large number of connections of the amygdala which, although not occupying the geometric centre of the half-brain, is nonetheless the strategic epicentre. The connections being examined in detail are both in the vicinity (connections with hippocampus) and in the relative remoteness (relations with the structures of the brainstem and of the diencephalon). The observed connections involve not only the grey matter but also the bundles of white matter, some of which have long been forgotten and that the authors now rehabilitate with extremely evocative dissections.

Vascularization of the Cerebral Amygdala

The vascularisation of the brain amygdala is reviewed from the few studies that have been devoted to it. This vascularisation apparently poor is actually rich enough but made of extremely fine vessels that only Indian ink injections can reveal.

Development of the Human Amygdaloid Complex

The study of the development of amygdaloid nuclear complex is discussed here. The authors show: 1. The successive appearance of nuclei that gather into a composite body 2. The essential role played by the medial ventricular eminence 3. The movements of the amygdaloid complex which, rejected by the lenticular nucleus in full development, has no alternative but to stand in contact with the hippocampus. The head of the latter will also be blocked against the amygdala wall.

Connection Pathways of the Cerebral Amygdala

The connections of the cerebral amygdala with the essential brain structures are studied in this chapter: The dorsal pathway represented by the stria terminalis is described as the path of the longest transmission. The ventral pathway wrongly qualified amygdalofugal is studied in turn with its traditional thalamic and hypothalamic components. Its third component, the diagonal band, is completely revisited by the authors, who present some previously unknown aspects. The anterior commissure is also annexed to this chapter, since it makes the contact the between the right and left amygdalae.

Morphology of the Human Amygdala

The chapter about morphology successively deals with macroscopic and global microscopic aspects of the human amygdala insisting especially on the changes in volume, the number of nuclei constituting the amygdaloid complex, their nomenclature and their characteristics and the specific microscopic aspect of each nucleus.

From Prefrontal Lobectomies to Amygdalectomies

The authors end the book by this short but very interesting historic chapter, which demonstrates the serious consequences of the even small cerebral tissue resections.

Definition and Generalities

The amygdaloid body or amygdaloid nuclear complex is an aggregate of several grey matter nuclei, of diencephalic origin, located in the anterior and medial parts of each of the two temporal lobes, connected not only to the entire limbic system but also to the sensory cortical areas, which receive and process the emotional inputs by triggering, via the thalamus, hypothalamus and brainstem, a series of reactions referred to as emotional expressions, dynamic, neuroendocrine, vegetative and hormonal, of variable intensity according to each individual and to the significance and violence of the triggering emotional factor. This amygdaloid body is controlled by the frontal brain. However, this control can bypassed at a specific moment, in cases of extreme urgency, especially when the survival of an individual is involved.

The Concept of “Extended Amygdala”

It is through the concept of Extended Amygdala that authors link the BST to amygdala. This extended amygdala connects the two formations that explains their interdependent coordination and functioning. The authors are able to show this extended amygdala in shape of an S, on beautiful tracking images.