Rhawn Joseph, Limbic System II, Hypothalmus
Pathological laughter has frequently been reported to occur with hypophyseal and midline tumors involving the hypothalamus, aneurysm in this vicinity, hemorrhage, astrocytoma or pappiloma of the 3rd ventricle (resulting in hypothalamic compression), as well as surgical manipulation of this nucleus (Davison & Kelman, 1939; Dott, 1938; Foerster & Gabel, 1933; Martin, 1950; Money & Hosta, 1967; Ironside, 1956; List, Dowman, & Bagheiv, 1958).
For example, Martin (1950, p.455) describes a man who while "attending his mother's funeral was seized at the graveside with an attack of uncontrollable laughter which embarrassed and distressed him considerably." Although this particular attack dissipated, it was soon accompanied by several further fits of laughter and he died soon thereafter. Post-mortem a large ruptured aneurysm was found, compressing the mammillary bodies and hypothalamus.
In a similar case (Anderson, 1936; Cited by Martin, 1950), a patient literally died laughing following the eruption of the posterior communicating artery which resulted in compression (via hemorrhage) of the hypothalamus. "She was shaken by laughter and could not stop: short expirations followed each other in spasms, without the patient being able to make an adequate inspiration of air, she became cyanosed and nothing could stop the spasm of laughter which eventually became noiseless and little more than a grimace. After 24 hours of profound coma she died."
Because laughter in these instances has not been accompanied by corresponding feeling states, this pseudo-emotional condition has been referred to as "sham mirth" (Martin, 1950). However, in some cases, abnormal stimulation in this region (such as due to compression effects from neoplasm) has triggered corresponding emotions and behaviors -- presumably due to activation of other limbic nuclei.
For example, laughter has been noted to occur with hilarious or obscene speech--usually as a prelude to stupor or death--in cases where tumor has infiltrated the hypothlamus (Ironside, 1956). In several instances it has been reported by one group of neurosurgeons (Foerster & Gagel, 1933) that while swabbing the blood from the floor of the 3rd ventricle, patients "became lively, talkative, joking, and whistling each time the infundibular region of the hypothalamus was manipulated." In one case, the patient became excited and began to sing.
Stimulation of the lateral hypothalamus can induce extremes in emotionality, including intense attacks of rage accompanied by biting and attack upon any moving object (Flynn et al. 1971; Gunne & Lewander, 1966; Wasman & Flynn, 1962). If this nucleus is destroyed, aggressive and attack behavior is abolished (Karli & Vergness, 1969). Hence, the lateral hypothalamus is responsible for rage and aggressive behavior.
As noted, the lateral maintains an oppositional relationship with the medial hypothalamus. Hence, stimulation of the medial region counters the lateral area such that rage reactions are reduced or eliminated (Ingram, 1952; Wheately, 1944), whereas if the medial is destroyed there results lateral hypothalamic release and the triggering of extreme savagery.
In man, inflammation, neoplasm, and compression of the hypothalamus have also been noted to give rise to rage attacks (Pilleri & Poeck, 1965), and surgical manipulations or tumors within the hypothalamus have been observed to elicit manic and rage-like outbursts (Alpers, 1940). These appear to be release phenomenon, however. That is, rage, attack, aggressive, and related behaviors associated with the hypothalamus appears to be under the inhibitory influence of higher order limbic nuclei such as the amygdala and septum (Siegel & Skog, 1970). When the controlling pathways between these areas are damaged (i.e. disconnection) sometimes these behaviors are elicited.
For example, Pilleri and Poeck (1965) described a man with severe damage throughout the cerebrum including the amygdala, hippocampus, cingulated, but with complete sparing of the hypothalamis who continually reacted with howling, growling, and baring of teeth in response to noise, a slight touch, or if approached. Hence, the hypothalamus being released responds reflexively in an aggressive-like non-specific manner to any stimulus. Lesions of the frontal-hypothalamic pathways have been noted to result in severe rage reactions as well (Fulton & Ingraham, 1929; Kennard, 1945).
Nevertheless, like "sham mirth", rage reactions elicited in response to direct electrical activation of the hypothalamus immediately and completely dissipate when the stimulation is removed. As such, these outbursts have been referred to as "sham rage".