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09-03-13, 01:17 AM
The primary-process emotional-affective networks of mammalian brains

Brain research supports the existence of at least seven primary-process (basic) emotional systems - SEEKING, RAGE, FEAR, LUST, CARE, GRIEF (formerly PANIC), and PLAY - concentrated in ancient subcortical regions of all mammalian brains.

In sum, affective neuroscientific analysis of basic emotions is based on several highly replicable facts: (i) Coherent emotional-instinctual behaviors can be aroused by electrically stimulating very specific subcortical regions of the brain; (ii) Wherever one evokes emotional action patterns with ESB, there are accompanying affective experiences. Again, the gold standard for this assertion is the fact that the brain stimulations can serve as “rewards” when positive-emotions are aroused - eg, SEEKING, LUST, CARE, and aspects of PLAY. When negative emotions are aroused - RAGE, FEAR, GRIEF - animals escape the stimulation; (iii) The above behavioral and affective changes are rarely, if ever, evoked from higher prefrontal neocortical regions, suggesting that higher brain areas may not have the appropriate circuitry to generate affective experiences, although the neocortex can clearly regulate (eg, inhibit) emotional arousals and, no doubt, prompt emotional feelings by dwelling on life problems.

The emotional primes are summarized in several monographs, with another appearing soon.24 Thumbnail descriptions are provided below, with one key reference for each.

The SEEKING/desire system

This extensive network confluent with the medial forebrain bundle (MFB) is traditionally called the “brain reward system.” In fact, this is a general-purpose appetitive motivational system that is essential for animals to acquire all resource needs for survival, and it probably helps most other emotional systems to operate effectively. It is a major source of life “energy”, sometimes called “libido.” In pure form, it provokes intense and enthusiastic exploration and appetitive anticipatory excitement/learning. When fully aroused, SEEKING25 fills the mind with interest and motivates organisms to effortlessly search for the things they need, crave, and desire. In humans, this system generates and sustains curiosity from the mundane to our highest intellectual pursuits. This system becomes underactive during addictive drug withdrawal, chronic stress, and sickness, and with accompanying feelings of depression. Overactivity of this system can promote excessive and impulsive behaviors, along with psychotic delusions and manic thoughts. All antipsychotics reduce arousability of this “reality-creating” mechanism of the brain. The term “reality-creating” is used to highlight the fact that this system appears to generate causal convictions about the nature of the world from the perception of correlated events (for a full discussion see Chapter 8 of Affective Neuroscience 3).

Neuroanatomically, SEEKING circuitry corresponds to the extensive medial forebrain bundle and major dopamine-driven, self-stimulation “reward” circuitry coursing from ventral midbrain to nucleus accumbens and medial frontal cortex, where it can promote frontal cortical functions related to planning and foresight. Rather than being a “pleasure or reinforcement system,” SEEKING coaxes animals to acquire resources needed for survival. It promotes learning by mediating anticipatory eagerness, partly by coding predictive relationships between events. It promotes a sense of engaged purpose in both humans and animals, and is diminished in depression and the dysphoria of withdrawal from addictive drugs. This is further highlighted by the simple fact that bilateral lesions of the system produce profound amotivational states in animals (all appetitive behaviors are diminished) and the elevated threshold for self-stimulation reward probably reflects the dysphoria state.

The RAGE/anger system

When SEEKING is thwarted, RAGE26 is aroused. Anger is provoked by curtailing animals' freedom of action. RAGE is a reliably provoked ESB of a neural network extending from the medial amygdala and hypothalamus to the dorsal PAG. RAGE lies close to and interacts with trans-diencephalic FEAR systems, highlighting the implicit source of classic “fight-flight” terminology. It invigorates aggressive behaviors when animals are irritated or restrained, and also helps animals defend themselves by arousing FEAR in their opponents. Human anger may get much of its psychic energy from the arousal of this brain system; ESB of the above brain regions can evoke sudden, intense anger attacks, with no external provocation. Key chemistries which arouse this system are the neuropeptide Substance P and glutamate, while endogenous opioids and y-aminobutyric acid (GABA) inhibit the system. A prediction is that glutamate and Substance P receptor antagonists (eg, aprepitant) may help control human anger. Additional medicines to control RAGE could presumably be developed through further detailed understanding of RAGE circuitry.

The FEAR/anxiety system

The evolved FEAR27 circuit helps to unconditionally protect animals from pain and destruction. FEAR-ESB leads animals to flee, whereas much weaker stimulation elicits a freezing response. Humans stimulated in these same brain regions report being engulfed by an intense free-floating anxiety that appears to have no environmental cause. Key chemistries that regulate this system are Neuropeptide Y and corticotrophin releasing factor (CRF); anti-anxiety agents such as the benzodiazepines inhibit this system by facilitating GABA transmission.

The LUST/sexual systems

Sexual LUST,28 mediated by specific brain circuits and chemistries, distinct for males and females, is aroused by male and female sex hormones, which control many brain chemistries including two “social neuropeptides” - oxytocin transmission is promoted by estrogen in females and vasopressin transmission by testosterone in males. These brain chemistries help create gender-specific sexual tendencies. Oxytocin promotes sexual readiness in females, as well as trust and confidence, and vasopressin promotes assertiveness, and perhaps jealous behaviors, in males. Distinct male and female sexual tendencies are promoted by these steroid hormones early in life, with sexual activation by gonadal hormones at puberty. Because brain and bodily sex characteristics are independently organized, it is possible for animals that are externally male to have female-typical sexual urges and, others with female external characteristics to have maletypical sexual urges. The dopamine-driven SEEKING system participates in the search for sexual rewards just as for all other types of rewards, including those relevant for the other social-emotional systems described below.

The CARE/maternal nurturance system

Brain evolution has provided safeguards to assure that parents (usually the mother) take care of offspring. Some of the chemistries of sexuality, for instance oxytocin, have been evolutionarily redeployed to mediate maternal care - nurturance and social bonding - suggesting there is an intimate evolutionary relationship between female sexual rewards and maternal motivations.29 The shifting hormonal tides at the end of pregnancy (declining progesterone, and increasing estrogen, prolactin, and oxytocin) invigorate maternal urges days before the young are born. This collection of hormonal and associated neurochemical changes also help assure strong maternal bonds with offspring.

The GRIEF/separation distress system

system was initially called the PANIC system, but few understood the intent of that primary-process terminology, so we shifted to the more comprehensible tertiary-process term of GRIEF30 (highlighting once more terminological problems in emotion research: what are the differences between the tertiary-level emotions of bereavement, grief, and mourning, for instance?). In any event, young socially dependent animals have powerful emotional systems to solicit nurturance. They exhibit intense crying when lost, alerting caretakers to attend to their offspring. ESB mapping of this separation-distress system has highlighted circuitry running from dorsal PAG to anterior cingulate, and it is aroused by glutamate and CRF and inhibited by endogenous opioids, oxytocin, and prolactin - the major social-attachment, socialbonding chemistries of the mammalian brain. These neurochemicals are foundational for the secure attachments that are so essential for future mental health and happiness. It is still worth considering that panic attacks may reflect sudden endogenous spontaneous loss of feelings of security (acute separation-distress) rather than sudden FEAR. We predict that these circuits are tonically aroused during human grief and sadness, feelings that accompany low brain opioid activity.

The PLAY/rough-and-tumble, physical socialengagement system

Young animals have strong urges for physical play - running, chasing, pouncing, and wrestling. These “aggressive” - assertive actions are consistently accompanied by positive affect - an intense social joy - signaled in rats by making abundant high frequency (~50 kHz) chirping sounds, resembling laughter. One key function of social play is to learn social rules and refine social interactions. Subcortically concentrated PLAY31 urges may promote the epigenetic construction of higher social brain functions, including empathy. Further studies of this system may lead to the discovery of positive affect promoting neurochemistries that may be useful in treating depression.32

These seven emotional networks provide psychiatric research with various endophenotypes important for advancing psychiatric understanding of affective order and disorder. For preclinical modeling, these emotional systems provide a variety of affectively important BrainMind networks to guide not only psychiatrically relevant research, but as already highlighted, the development of more specifically acting psychiatric medicines. To highlight one concrete possibility, there will follow a brief focus on how such systems may help us understand the genesis and better treatment of depression.

09-03-13, 01:23 AM
Three "brains" in one-

The brain may be viewed as a hierarchy of three "separate" brains: a lower vegetative/reflexive brain, a higher adaptive/skilled brain, and an intermediate brain concerned with emotions and instincts.

The vegetative brain corresponds roughly to the brain stem and is concerned with controlling vital bodily functions (respiration, digestion, circulation) as well as with integrating brain reflexes.

The adaptive and skilled brain corresponds to the cerebral cortex (the neocortex).

It has sensory, motor functions, and association/integrative areas that serve in complex perception and execution of skilled sensory and motor functions (e.g., hand movements, speech) as well as higher mental functions (e.g.,learning, thoughts, introspection, planning).

Limbic system's role in emotions and instinctive behaviors-

Limbic system (LS) structures are concerned with central (neural) control over the expression of emotions, instinctive behaviors, drives, motivation and feelings.

In lower vertebrates, the LS is called the rhinencephalon (smell brain) because of its intimate connection to the central olfactory structures.

In these animals, many instinctive behaviors are guided by the sense of smell.

The cerebral cortex and LS have access to brain stem motor areas, permitting them to carry out their respective adaptive and instinctive controls over behavior.

Kapit/Macey/Meisami, "The Physiology Coloring Book", (Nervous System), "Emotions, Instinct & The Limbic Brain", P108