Limbic System

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Limbic System

The Neurophysiology of Emotions

The brain is the organ of the mind. Anatomists have described the brain in terms of the evolutionary path we are on. We have old-age, middle-age and new-age parts, each with different properties. The old modules have remained much the same over the millennia. New structures grow out of and over the older brain modules, linked together with the brain equivalents of wiring harnesses and interface modules. Some of the interfaces between old and new modules seem to be incomplete and unstable, leaving a lot to be desired about human behavior.

The idea of the limbic system originated with attempts to explain how emotions are generated.

You can begin with 4 interconnected modules: the hypothalamus, the anterior thalamic nucleus, the cingulate gyrus and the hippocampus (the Papez circuit).

McLean added the orbitofrontal and medialfrontal cortices (prefrontal area), the parahippocampal gyrus and subcortical modules such as the amygdala, the medial thalamic nucleus, the septal area, basal nuclei and a few brainstem formations.

The limbic system generates feeding, fighting, fleeing and sexual behaviors. At the same time, the limbic system generates feelings, emotions and participates in the regulation of body functions.

https://www.visiblebody.com/blog/anatomy-physiology-limbic-system

Paul McLean suggested that the human brain could be viewed as three systems of different ages - an old reptilian brain, a middle (early mammalian) brain, topped off with a new, advanced brain, the neocortex.

The neocortex allows us to learn, adapt and create new modes of behavior. The neocortex has the computer equivalent of random access memory (RAM), allowing the input of new information

This new information is used to interpret and adjust the operation of read-only memory (ROM) which is built into old and middle brain modules and cannot be modified.

New babies are not born with the new brain programs.

Old programs are built into us and need not be learned. Old programs include some of the most negative qualities – predatory and territorial aggression, anger, and jealousy, for example. Some of our most positive qualities are also innate such as the tendencies to mate, bond and form social units with altruistic features.

The limbic system involves old brain modules that keep us alive and involved in worldly interactions. These innate programs link us to the world with appetites and drives. Appetites are states of need, giving rise to drives which energize our behavior and send us searching for gratification out there in the competitive, not-always-forgiving world. Hunger for food, food searches, and eating gratification are priorities for living creatures. After you are fed you can attend to the other needs.

The organs of in the chest and abdomen (viscera) interact with the brain through the autonomic nervous system that has three major divisions:

1. An old vagal system that fosters digestion and that responds to threats by cardiac output reduction and immobilization.

2. A spinal sympathetic nervous system that inhibits vagal influence on digestion and increases the metabolic rate to mobilize for "fight or flight."

3. A myelinated vagal system that regulates cardiac output and breathing in response to inner and outer signals.

Visceral regulation is a component of emotional processing and is affected by social experience. Dysfunction in visceral regulation systems can be both causes and effects of emotions. Anger for example, involves increased breathing, heart rate and blood pressure.

The vagus nerve is the tenth cranial nerve, integrated with the activities of other cranial nerves involved in social engagement: hearing, facial ｅxpression via facial musculature and eye movements; the coordination of breathing with sound production via laryngeal, pharyngeal and head-moving muscles.

Old programs nested in the limbic system include the most essential routines of animals: establishment and fighting in defense of territory, foraging, hunting, homing, hoarding, formation of social groups, greeting, grooming, courtship, mating, flocking, and establishment of social hierarchy by ritualistic display. Nested in these old modules are programs inherited from reptiles that continue to dominate the human experience.

Three reptilian behaviors are worth special mention:




1. Perseveration is the tendency for a fixed behavior to repeat or persist, even when the path is blocked or the real benefit of a behavior disappears. Eating behaviors, for example, are highly automated and resist change; "...reptiles are slaves to routine, precedent, and ritual..."

2. Frustration and anger are responses whenever seeking behaviors are blocked, or threats are perceived. The least degree of drive-blocked discomfort is frustration; "...there is hardly anything more surely to upset than the alteration of long-established routines."

3. Displacement occurs when there is no further supply of the gratification for the appetite or drive. Seeking behaviors shift laterally to find an alternative.




Three reptilian behaviors are worth special mention:

The limbic system contributes the for-me-ness of experiences and generates cathexes. McLean stated: "The primitive limbic system has the capacity to generate the strong feelings of conviction that we attached to our beliefs, regardless of whether they are true or false..."

The anterior cingulate cortex (ACC) is the cortical part of the limbic system. The cingulate gyrus lies above the corpus callosum and is reciprocally connected with the anterior nuclear group of the thalamus through the thalamic radiations and with the hypothalamus by way of the mammillothalamic tract. The cingulate cortex is also connected with the parahippocampal gyrus and septal area by way of the cingulum.

This central position gives the ACC control over cognitive and emotional processing. The ACC is part of a brain system that monitors performance to regulate behavior. For example the left anterior cingulate cortex (ACC) is coupled with left inferior frontal gyrus during letter-recognition decisions. The right ACC is coupled with right parietal areas during visuospatial decisions. The ACC can detect errors in action but also predicts the probability of error based on past experience. The ACC provides a competitive advantage by anticipating and avoiding errors.

Conflict monitoring by the ACC can determine the need for greater cognitive control and cause greater prefrontal cortex activity and appropriate adjustments in behavior.

Decision making involves prediction of the outcome of a given action. Obviously, the expectation of a pleasant outcome makes a behavior more likely. When outcomes are not pleasurable, regret is attached to the decision to act. Cricelli et al found that regret involved the orbitofrontal, and anterior cingulate cortex. They stated: ‘We measured brain activity using functional magnetic resonance imaging (fMRI) while subjects selected between two gambles; regret followed information about the favorable outcome of choices not made. Subjects became increasingly regret-aversive, a cumulative effect reflected in enhanced activity within the medial orbitofrontal cortex and amygdala. This pattern of activity reoccurred just before making a choice, suggesting that the same neural circuitry mediates direct experience of regret and its anticipation. “

The posterior cingulate cortex assesses the risk involved in obtaining rewards. Lee suggested: “Choosing to accept enough risk, but not too much, is an important survival skill, and depending on the circumstances, animals may either seek or avoid risk. Given the choice between a sure bet and a larger but uncertain reward, Macaques consistently take the riskier option, and posterior cingulate cortex neurons represent the risk of those choices.”

Drives to maintain brain concentrations of food (and drug) substances are organized in the old brain or limbic structures which do not ask consciousness for permission to operate. The old brain is characterized by a low-level consciousness and a high level of automaticity. Most insightful people will describe the split in their personalities as though automatic behaviors take over and consciousness simply monitors the events which follow.

The idea of "will-power" is difficult to substantiate since there does not seem to be a brain procedure with which we reach from high-level thinking down into machine level programming where automatic behaviors are produced. The characteristic of addictive behavior is the recurrent search for a food, beverage, or drug which supplies specific molecules. Drugs can be ingested, inhaled or injected. This substance search mode may be concealed by layers of social behavior that are more or less acceptable. The drinker, smoker and drug user develop repertoires of social behaviors and mannerisms which conceal and support their habit.

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  Emotions and Feelings

  • This book investigates the for-me-ness of experiences, using psychology, neuroscience and philosophy. Everyone has some idea what emotions and feelings are but their exact nature is elusive. We can begin by noting that emotions and feelings are not the same. Generally, humans are ignorant of internal processes and invent all manner of imaginary and irrelevant explanations to explain feelings. The term “emotion” is best used to point to animal and human behavior. There are a small number of primary emotions and variations that involve mixtures of emotional displays with other behaviors. Joy, anger, fear and pain are pure emotions. Other, more complex and derivative experiences act as interfaces to emotions. Love, jealousy and hate are not emotions. These are descriptions of complex interactions and evaluations that involve a range of feelings and interface to true emotions some of the time. For example, lovers experience a range of feelings and display different emotions at different times. Euphoria is the benefit of being in love. Sadness and anger are the cost of being in love. Jealousy, like love, is another complex of cognitions, feelings and emotions that exist to monitor and regulate close relationships. The absence of emotional display is highly valued in polite society. Humans have advanced toward civil and productive social environments that are emotionally neutral. Emotional neutrality is a requirement for acceptable behavior in school and work environments.

    Emotions and Feelings is available as an eBook download. The book is intended for a well-educated smart reader who is interested in Human Nature and the daily experience of humans in groups. The author is Stephen Gislason