Mode of Action of Psychosurgery

Collectively, the brain’s limbic system is composed of the hippocampus,
amygdala, hippocampal and cingulate gyri, limen insulae, and posterior orbital
regions of cerebral frontal lobes. This system, its components linked by
nerve pathways, controls emotional expression, seizure activity, and memory
storage and recall. Moreover, cerebral lobe limbic system connections
from the dorsal convexity of a frontal lobe comprise two pathways running
to the cingulate gyrus and hippocampus and the hypothalamus and midbrain.
The frontal lobe orbital surface also projects to the septal area of the
hypothalamus. The limbic brain architecture therefore yields two neurotransport
circuits in a frontolimbic-hypothalamic-midbrain axis. These are a
medial frontal, cingulate, hippocampus circuit (MFCHC) and an orbital
frontal, temporal, amygdala circuit (OFTAC), which control hypothalamic
autonomic and endocrine action. The MFCHC and OFTAC connect in the
septa, preoptic area, midbrain, and hypothalamus.
The original Egas Moniz lobotomy divided the frontolimbic structures,
and its bad effects were due to the disabling impairment of frontal lobe
function. Psychosurgery on the anterior cingulate gyrus and on the thalamofrontal
bundle (bimedial leucotomy) divided different parts of the same
main circuit. Orbital undercutting severs red nerve tracts running from the
posterior orbital cortex to the limbic system. Although psychosurgery is currently
an uncommon procedure, when it is performed, the methods used
are lower medial quadrant leucotomy, making lesions just before the fourth
ventricle; stereotactic-subcaudate-tractotomy, making lesions with rear halves
in the subcaudate area; removal of the anterior two inches of the cingulate
gyrus; and stereotactic limbic leucotomy, lesioning the lower medial frontal
lobe quadrant. These operations cause varied endocrine and autonomic
disconnections and are thus chosen to suit the mental condition being
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