By K. Baldar. Chaminade University of Honolulu, Hawaii.
The amygdalal and septal divisions are phylogenetically older than the thalamo- cingulate division buy kamagra super 160 mg with visa. The amygdalar division contributes to self-preservation (feeding generic kamagra super 160mg with amex, attack kamagra super 160 mg cheap, defense) purchase 160mg kamagra super amex. The septal division is concerned with sexual behav- ior and procreation. The thalamocingulate division contributes to sexual and family-related behaviors, including nurturance, autonomic arousal, and proba- bly some cognitive processes such as attention. Later, I describe progress in functional brain imag- ing research on pain that further elucidates the relationship of limbic activity to pain. The Autonomic Nervous System and Emotion The autonomic nervous system (ANS) plays an important role in regulating the constancy of the internal environment, and it does so in a feedback- regulated manner under the direction of the hypothalamus, the solitary nu- cleus, the amygdala, and other central nervous system structures (LeDoux, 1986, 1996). In general, it regulates activities that are not normally under voluntary control. Stimulation of the hypothalamus elicits highly integrated patterns of response that involve the limbic system and other structures (Morgane, 1981). Many researchers hold that the ANS comprises three divisions, the sym- pathetic, the parasympathetic, and the enteric (Burnstock & Hoyle, 1992; Dodd & Role, 1991). Broadly, the sympathetic nervous system makes possible the arousal needed for fight and flight reactions, whereas the parasympathetic system governs basal heart rate, metabolism, and respiration. The enteric nervous system innervates the viscera via a complex network of interconnected plexuses. The sympathetic and parasympathetic systems are largely mutual physi- ological antagonists—if one system inhibits a function, the other typically augments it. There are, however, important exceptions to this rule that demonstrate complementary or integratory relationships. The mechanism most heavily involved in the affective response to tissue trauma is the sym- pathetic nervous system. During emergency or injury to the body, the hypothalamus uses the sym- pathetic nervous system to increase cardiac output, respiration rate, and blood glucose. It also regulates body temperature, causes piloerection, al- ters muscle tone, provides compensatory responses to hemorrhage, and di- lates pupils. These responses are part of a coordinated, well-orchestrated response pattern called the defense response (Cannon, 1929; Sokolov, 1963, 1990). It resembles the better known orienting response in some respects, but it can only occur following a strong stimulus that is noxious or frankly painful. It sets the stage for escape or confrontation, thus serving to protect the organism from danger. In a conscious cat, both electrical stimulation of the hypothalamus and infusion of norepinephrine into the hypothalamus elicit a rage reaction with hissing, snarling, and attack posture with claw ex- posure, and a pattern of sympathetic nervous system arousal accompanies this (Barrett, Shaikh, Edinger, & Siegel, 1987; Hess, 1936; Hilton, 1966). PAIN PERCEPTION AND EXPERIENCE 67 lating epinephrine produced by the adrenal medulla during activation of the hypothalamo-pituitary-adrenocortical axis accentuates the defense re- sponse, fear responses, and aversive emotional arousal in general. Because the defense response and related changes are involuntary in na- ture, we generally perceive them as something that the environment does to us. We generally describe such physiological changes, not as the bodily responses that they are, but rather as feelings. We might describe a threat- ening and physiologically arousing event by saying that “It scared me” or that “It made me really mad. Emotions are who we are in a given circumstance rather than choices we make, and we commonly interpret events and circumstances in terms of the emotions that they elicit. ANS arousal, therefore, plays a major role in the complex psychological experience of injury and is a part of that experience. Early views of the ANS followed the lead of Cannon (1929) and held that emergency responses and all forms of intense aversive arousal are undiffer- entiated, diffuse patterns of sympathetic activation. Although this is broadly true, research has shown that definable patterns characterize emotional arousal, and that these are related to the emotion involved, the motor activ- ity required, and perhaps the context (LeDoux, 1986, 1996). An investigator attempting to understand how humans experience emotions must remember that the brain not only recognizes patterns of arousal; it also creates them. One of the primary mechanisms in the creation of emotion is feedback- dependent sympathetic efferent activation. The afferent mechanisms signal changes in the viscera and other organs, whereas efferent activity conveys commands to those organs.
Although other processes governed predominantly by other neurotrans- mitters almost certainly play important roles in the complex experience of emotion during pain kamagra super 160mg, I emphasize the role of central noradrenergic process- ing and the medial forebrain bundle here purchase 160mg kamagra super overnight delivery. This limited perspective offers the advantage of simplicity order kamagra super 160 mg with visa, and the literature on the role of central norad- renergic pathways in anxiety generic kamagra super 160mg visa, panic, stress, and posttraumatic stress disor- der provides a strong basis (Bremner et al. This processing involves the medial forebrain bundle that subdivides into two central noradrenergic pathways: the dorsal and ventral noradrenergic bundles. Locus Ceruleus and the Dorsal Noradrenergic Bundle Substantial evidence supports the hypothesis that noradrenergic brain pathways are major mechanisms of anxiety and stress (Bremner et al. The majority of noradrenergic neurons originate in the locus ceru- leus (LC). This pontine nucleus resides bilaterally near the wall of the fourth ventricle. The locus has three major projections: ascending, de- scending, and cerebellar. The ascending projection, the dorsal noradre- nergic bundle (DNB), is the most extensive and important pathway for our purposes (Fillenz, 1990). Projecting from the LC throughout limbic brain and to all of neocortex, the DNB accounts for about 70% of all brain nor- epinephrine (Svensson, 1987). The LC gives rise to most central noradrener- gic fibers in spinal cord, hypothalamus, thalamus, hippocampus (Aston- Jones, Foote, & Segal, 1985), and, in addition, it projects to limbic cortex and 70 CHAPMAN FIG. Consequently, the LC exerts a powerful influence on higher level brain activity. The noradrenergic stress response hypothesis holds that any stimulus that threatens the biological, psychological, or psychosocial integrity of the indi- vidual increases the firing rate of the LC, and this in turn results in increased release and turnover of norepinephrine in the brain areas involved in noradrenergic innervation. Studies show that the LC reacts to signaling from sensory stimuli that potentially threaten the biological integrity of the indi- vidual or signal damage to that integrity (Elam, Svensson, & Thoren, 1986b; 3. The major sources of LC afferent input are the paragigantocellularis and prepositus hypoglossi nuclei in the medulla, but destruction of these nu- clei does not block LC response to somatosensory stimuli (Rasmussen & Aghajanian, 1989). Other sources of afferent input to the locus include the lat- eral hypothalamus, the amygdala, and the solitary nucleus. Whether nocicep- tion stimulates the LC directly or indirectly is still uncertain. Nociception inevitably and reliably increases activity in neurons of the LC, and LC excitation appears to be a consistent response to nociception (Korf, Bunney, & Aghajanian, 1974; Morilak, Fornal, & Jacobs, 1987; Stone, 1975; Svensson, 1987). Notably, this does not require cognitively mediated attentional control because it occurs in anesthetized animals. Foote, Bloom, and Aston-Jones (1983) reported that slow, tonic spontaneous activity at the locus in rats changed under anesthesia in response to noxious stimula- tion. Experimentally induced phasic LC activation produces alarm and ap- parent fear in primates (Redmond & Huang, 1979), and lesions of the LC eliminate normal heart-rate increases to threatening stimuli (Redmond, 1977). In a resting animal, LC neurons discharge in a slow, phasic manner (Rasmussen, Morilak, & Jacobs, 1986). The LC reacts consistently, but it does not respond exclusively, to noci- ception. LC firing rates increase following nonpainful but threatening events such as strong cardiovascular stimulation (Elam, Svensson, & Thoren, 1985; Morilak et al. Highly novel and sudden stimuli that could represent po- tential threat, such as loud clicks or light flashes, can also excite the LC in experimental animals (Rasmussen et al. Thus, the LC responds to bi- ologically threatening or potentially threatening events, of which tissue in- jury is a significant subset. Amaral and Sinnamon (1977) described the LC as a central analog of the sympathetic ganglia. Viewed in this way, it is an extension of the autonomic protective mechanism described earlier.