ABSTRACT
Affect is a term used in psychology for a feeling or an emotion.1
Emotions, such as fear, evolved in humans as reactive, short-term physiological (such an increased heart rate) and behavioural (‘flight’ or ‘fight’) specializations under the control of the brain, which assisted the survival of our ancestors in hostile environments. The human brain comprises three regions: the psychologically primitive hindbrain (sometimes referred to as the ‘reptilian brain’), the midbrain, and psychologically complex forebrain2 (the labels ‘hind’, ‘mid’ and ‘fore’ refer to the positions of these regions in the developing embryo). The forebrain, which overlies the midbrain and the hindbrain, consists of the cerebral cortex, the limbic system, the thalamus and the hypothalamus. One of the key components of the limbic system is the amygdala (its name is
from the Latin amygdala meaning ‘almond’), a structure specialized for processing emotional stimuli (electrical stimulation of it usually produces the emotion of fear). The cerebral cortex itself has two symmetrical hemispheres (the ‘left’ and ‘right’ brains) connected by a dense ‘information superhighway’ consisting of over 200 million axons (nerve fibres) – the corpus callosum (which we met in the last chapter in relation to the bisected brain). The forebrain develops comparatively late in the embryo and was also the latest part of the central nervous system to develop in the evolution of Homo sapiens.
