The upper levels of the nervous system often operate not by sending signals directly to the periphery of the body but instead by sending signals to the control centers of the spinal cord, simply commanding the cord centers to perform their functions.
The Limbic Cortex (Latin for border) also referred to as the Limbic System was coined by Broca in 1879. It is composed of the brain structures that lie in the border region between the Hypothalamus and its related structures, on the one hand, and the Cerebral Cortex. It is used to designate a heterogeneous set of structures in the Brainstem, Diencephalon, Striatum, Basal Forebrain, and Neocortex. Major structures of this system include the Hippocampus (sea horse), Amygdala, Septum (partition), Mammillary bodies, Olfactory bulbs, Fornix, and Cingulate (girdle) gyrus.
" The young man who has now wept is a savate, and the old man who will not laugh is a fool."
Each component of the Limbic Systen seems to have some involvement in the modulation of mood and effect. The Amygdala and related cortical-Limbic areas are associated not so much with the generation of emotion itself (as this is most probably coordinated chiefly by the Hypothatamus), but rather with directing emotions to their proper object and perhaps to the proper mental content.
Papez (1937),
suggested that emotions were the product of activity within the Limbic Cortex; arguing that the Emotional Brain consisted of a circuit in which information flowed from the Mammilary bodies in the Hypothalamus to the anterior Thalamic nucleus to the Cingulate cortex to the Hippocampus and back to the Mammilary bodies. Input could enter this circuit from other structures to be elaborated as emotional.
Hence, the term Limbic System now means this entire basal system of the brain that mainly controls a person's emotional behavior and drives; falling under the dominion of the Primary Process Thinking by the Id. 
In general, the intricate Limbic circuitry can be divided into the Amygdaloid and Hippocampal spheres of influence. The Hippocampus and its connections seem to be more closely associated with memory functions, whereas The Amygdala and its pathways are more closely related to the affective (or emotional) components of the human experience.
(See
Figure B )
The Limbic System (a term derived from the Latin word Limbus, meaning border), is polarized toward our internal environment and its requirements. Only the Limbic regions of the brain have substantial monosynaptic interconnections with the Hypothalmus. It is the Limbic Cortex and the Association Cortex which provide the Neural Networks that mediate between those inner urges of an individual and the contingencies of his extrapersonal environment.
Each component of the Limbic Cortex seems to have some involvement in the modulation of mood and affect. This correlation is particularly strong in the case of the Amygdala and the Temporopolar, Insular, Orbito-Frontal, and anterior Cingular regions with which it is interconnected. The Limbic components of the Temporal lobe (Amygdala, Hippocampus, para-Hippocampal Gyrus, Temporal pole) and related para-Limbic areas in the Insula, the Orbito-Frontal cortex, and the Cingulate Gyrus, have a low seizure threshold and frequently become the source of epileptic activity.
The Limbic Cortex participates in the regulation of autonomic tone. The Amygdala and Hypothalmus have a powerful influence on autonomic function, reflecting the direct connections they have with autonomic nuclei within the Brainstem. Electrical stimulation in the cortical components of the Limbic System (for example, anterior Insula, caudal orbito-Frontal cortex, Temporal pole, Cingulate Gyrus) results in marked and consistent autonomic responses. Insular stimulation tends to produce gastrointestinal responses, whereas stimulation of the other cortical components leads to cardiovascular and respiratory changes; inducing inhibitition of gastric peristalsis, respiratory arrest, and marked blood pressure changes (as much as 100 mm Hg). 
The Hippocampus
is a modified type of cortex (composed of only three neuronal layers) within the Temporal lobe which folds inward to form the ventral surface of the inferior horn of the Lateral Ventricle. It has many connections with most portions of the Neocortex as well as with basic structures of the Limbic System. Almost any type of sensory event causes instantaneous activation of different parts of the Hippocampus, and the Hippocampus in turn distributes many out going signals to the Hypothalamus and to other parts of the Limbic System.
The Hippocampal formation is composed of two distinct structures, known as Ammon's Horn (often referred to as the Hippocampus) and the Dentate gyrus. Ammon's horn can be divided into substructures, known as CA1, CA2, and CA3, on the basis of their cytoarchitecture and connectivity. Stimulation of different areas of the Hippocampus can cause almost any one of different behaviorial patterns, such as rage, passivity, excess sex drive, and so on.
Cells in the Caudate known as Tonically Active Neurons (TANs) tend to be found between Striosomes and Matrisomes. Striosomes are areas where information from an emotion-processing part of the brain, the Amygdala, reaches the Caudate; Matrisomes are clusters of axon terminals where information from the thinking, reasoning cerebral cortex reaches the Caudate. By virtue of their position, TANs can integrate emotion and thought. They fire in a characteristic pattern when the brain senses something with positive or negative emotional meaning. Cognitive-behavioral therapy (i.e. hypnotherapy) may change how TANs respond to Obsesive Compulsive Disorder (OCD) triggers.
TANs respond dramatically to visual and auditory stimuli that are linked, through behavioual conditing, to a reward. TANs consceiveably play a central role in behavioral responses to hints (or cues) of an upcoming reward. Studies have demonstrated that TAN firing rates changed when a once-neutral cue became associated with a reward. Consider, for example, that a visual cue such as a flashing light means that a monkey will get a reward (juice) if that monkey performs a simple behavioral response (licking a spoon). When TANs detect a potential reward, they pause at first and then fire faster. But TANs do not respond to the light cue if that monkey has not learned to associate it with a reward. As the monkey's brain learns to recognize a reward, TANs fire in that characteristic pattern.
The Striatum and especially the Caudate, can be thought of as a neuronal mosaic of reason and emotion. It sits directly within the confluence of messages bearing cognative content (couttesy of the Matrisomes, where inputs arrive from the rational pre-fromtal cortes) and messages shot through with emonion (couttesy of the Striosomes, landing zones from inputs from the Limbic System). The juxtaposition of Striosomes and Matrisomes therefore seems highly conductive to interactions between emotion and thought. Together they provide the perfect mechanism of integrating the messages of the heart with whose of the mind.
Neurotransmitters
(those specialized chemical substances released by neurons), such as Acetylcholine (ACh) and Dopamine (DA), act upon the specialized proteins which are located on the post-synaptic membrane of the recipient neuron.
Receptors (as these specialized proteins are called), bind the neurotransmitter substances. Norepinephrine (NE), (another such neurotransmitter), triggers the beta-2 (ß-2) receptors of the sympathetic nervous system, as well as receptors envolved in Long-Term Memory. Epinephrine (Epi), acts as a catalyst, locking memories of exciting, shocking, or stimulating events in the brain. Serotonin (5-HT) is yet another neurotransmitter which is actively involved in many activities of the brain from its perception of pain to the prevention of depression and even the production of sleep.
Emotional states are associated with specific patterns of autonomic responses. Conceivably the influence of mental states upon autonomic activation in both normal and abnormal conditions is coordinated principally by the para-Limbic areas of the brain. There are three neurotransmitters in the brain which are believed to be important in emotional behavior:
Dopamine (DA), Norepinephrine (NE), and Serotonin (5-HT). Each of these substances are manufactored in a restricted region of the brainstem and sent via long axons to various places, especially to one in the forebrain.
Dopaminergic
projections to the forebrain are found within two basic systems: the Nigrostriatal system and the Mesocortical system. The Nigrostriatal system arises from cell bodies in the Substantia Nigra, whose axons project mostly to the Caudate nucleus and Putamen. The loss of these projections results in Parkinson's disease. The Mesocortical system, on the other hand, starts with cell bodies in the Tegmentum, in a region just above the Substantia Nigra known as the Ventral Tegmental Area of Tsai. Axons of these neurons project to the Limbic system, including certain regions of the Frontal lobe. It is an abnormality of these cells that is believed to occur in Schizophrenia.
(SeeFigure C )
Serotonin -
containing neurons are found in nine clusters of cells lying within the midline region of the Pons and upper Brainstem known as the Raphé Regions. These neurons project widely throughout the brain innervating all those structures, also receiving projections from Domamine and Norepinephrine neurons.
Norepinephrinergic
innervation of the brain arises from neurons at the level of the Pons in and around a nucleus known as the Locus Ceruleus. Fibers from this region form six major norepinephrinergic tracts projecting to the Hypothalamus, Thalamus, Limbic System, Neocortex, Cerebellum, and Spinal cord. Abnormalities in (NE) are suspect in some symptoms of depression.
Poly-Peptide
secreting neurons differ in biology from those neurons using amino acids and monoamines in ways other than the molecular structure of their transmitters. The amino-acid or monoamine transmitters are formed from dietary sources by one or two intracellular enzymatic steps; the end product of these enzymatic actions is the active transmitter molecule which is then stored in the nerve terminal until release. After release, the transmitter (or choline in the case of ACh) can be re-accumulated back into the nerve terminal by the energy-dependent active re-uptake property, thus conserving the requirement for de novo synthesis.
Peptide-secreting cells employ a much more formidable approach: Synthesis is directed by messengerRNA on ribosomes and thus this synthesis can only take place in the Perikaryon on dentrites of a neuron. Further, all peptides are synthesized as part of a much larger precursor molecule (or Prohormone) which has no biological activity and from which the active peptide is cleaved by special processing peptidases. The process for peptides thus starts with ribosomal synthesis of the prohormone, which is then packaged int vesicles in the smooth endoplasmic reticulum, and transported from the perikaryon to the nerve terminals for eventual release.
" Emotions are often considered the heart of therapeutic change. Changes in emotion will ideally be accompanied by corresponding changes in attitude, behavior, self-image, family structure, disipline and enjoyment."
Symptoms
are generally the subjective experience of a pathological condition, but occasianally , they may include objective signs of pathological conditions as well. Symptoms should be thought of as Unconscious Metaphors for the patient. Just as symptoms are the symbols or metaphors of experience, they too are the coping or defense mechanisms that may have made a great deal of sense to the patient in the proper context from which they arose.
For You.com®
Mÿth
a service of
Ther°al L . Bynum, M.D.
Here