Affective neuroscience of the emotional BrainMind: evolutionary perspectives and implications for understanding depression.

2010·1.1 MB·English

by  Panksepp, Jaak

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Affective neuroscience of the emotional
BrainMind: evolutionary perspectives and
implications for understanding depression
Jaak Panksepp, PhD
P
sychiatric disorders commonly reflect affective
imbalances within the brain. Accordingly, a key question
in psychiatric research is the neural nature of emotional
feelings. For instance, in depression research, one of the
most important unanswered questions is: Why does
depression feel so bad? What is the “psychological pain”
that leads people to lose their joy of living? Exactly the
same affective issues confront us when we study addic-
tions. Here we explore the possibility that chronic affec-
tive changes may arise from functional changes in basic
emotional systems of the brain. For example, diminished
arousability of specific positive affective systems along
with elevated activation of distinct negative affective net-
works may be the fundamental source of depressive affect.
Cross-species affective neuroscience studies confirm that primary-process emotional feelings are organized within prim-
itive subcortical regions of the brain that are anatomically, neurochemically, and functionally homologous in all mam-
mals that have been studied. Emotional feelings (affects) are intrinsic values that inform animals how they are faring in
the quest to survive. The various positive affects indicate that animals are returning to “comfort zones” that support sur-
vival, and negative affects reflect “discomfort zones” that indicate that animals are in situations that may impair survival.
They are ancestral tools for living—evolutionary memories of such importance that they were coded into the genome in
rough form (as primary brain processes), which are refined by basic learning mechanisms (secondary processes) as well as
by higher-order cognitions/thoughts (tertiary processes). To understand why depression feels horrible, we must fathom
the affective infrastructure of the mammalian brain. Advances in our understanding of the nature of primary-process
emotional affects can promote the development of better preclinical models of psychiatric disorders and thereby also
allow clinicians new and useful ways to understand the foundational aspects of their clients' problems. These networks
are of clear importance for understanding psychiatric disorders and advancing psychiatric practice.
© 2010, LLS SAS Dialogues Clin Neurosci.2010;12:533-545.
Keywords: depression; affect; emotion; grief; seeking; play; endophenotype; Address for correspondence:Department of Veterinary & Comparative Anatomy,
affective neuroscience Pharmacology and Physiology, College of Veterinary Medicine, Washington State
University Pullman, WA 99162, USA
Author affiliations:Baily Endowed Chair for Animal Well-Being Science, Department (e-mail: [email protected])
of Veterinary & Comparative Anatomy, Pharmacology and Physiology, College of
Veterinary Medicine, Washington State University Pullman, Washington, USA
Copyright © 2010 LLS SAS. All rights reserved 533 www.dialogues-cns.org
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But what systems are they? Here, arguments for the ipate key survival needs. They mediate what philoso-
critical importance of brain systems that integrate the phers have called “intentions-in-action” (Table I).
distress and despair of separation-distress (overactiv- Until we understand the neurobiological nature of basic
ity of basic PANIC/GRIEF networks) and the dimin- emotional feelings within the human BrainMind, our
ished arousal of SEEKING networks that constitute understanding of psychiatric disorders will remain woe-
dysphoria will be presented. Excessive arousal of fully incomplete. Because of striking cross-species
SEEKING urges may contribute substantially to homologies in mammalian primary-process emotional
mania and psychostimulant addictions, leading to systems, animal models may provide optimal guidance
excessive elation/euphoria, arising from excessive for deciphering brain affective mechanisms that also
appetitive dopamine SEEKING urges, which can pro- operate in our species. This review will delve into vari-
mote unwise life choices.1 (Capitalizations highlight ous levels of emotional control, especially the first:
the need for a specialized vocabulary when discussing (cid:129)Primary-processemotional feelings within mammalian
the evolutionary foundations of the mind. Vernacular brains—namely the experienced aspects of the uncon-
terms have excess meanings, and thus will not suffice ditioned emotional brain systems (ie, “instinctual” inte-
for clear discourse). Thus, drug addictions share some grative BrainMind systems) in action. From a philo-
important affective features with depression; for sophical point of view, they control
instance, the dysphoric feelings that accompany both “intentions-in-action.”
addictive drug withdrawal and depression which (cid:129)Secondary emotional processesthat arise from simple
reflect diminished SEEKING urges.2Studies in psy- emotional learning, such as classical and operant con-
chology and neuroscience, as well as in psychiatric syn- ditioning that has been well studied in animal models,
dromes, indicate that there are many distinct emo- especially FEAR conditioning.
tional feelings within mammalian brains and minds (cid:129)Tertiary-processemotions are the intrapsychic rumina-
(henceforth BrainMind, a monistic term). We are just tions and thoughts about one’s lot in life. Such higher-
beginning to understand the underlying innate, genet- order affective-cognitions that promote “intentions-to-
ically determined, and epigenetically refined aspects act” and are elaborated by medial-frontal regions,
of emotional feelings. which can only be well studied in humans (Table I).
Emotional nomenclature can be confusing. Here pri- It is among the inherited subcortical primary-process
mary-process (ie, basic or primordial) emotional net- instinctual tools for living that the foundations of human
works are defined in terms of neural and behavioral cri- emotional lives reside, and neurochemical imbalances
teria. Basic emotional networks can be defined by six there can lead to persistent affective imbalances of psy-
criteria: chiatric significance.3Also, it is reasonable to currently
(cid:129)They generate characteristic behavioral-instinctual
1. Primary-process, basic-primordial affects(sub-neocortical)
action patterns
i) Emotional affects(emotion action systems;
(cid:129)They are initially activated by a limited set of uncon-
intentions-in-actions)
ditional stimuli
ii) Homeostatic affects(hunger, thirst, etc via brain-body
(cid:129)The resulting arousals outlast precipitating circum-
interoceptors)
stances
iii)Sensory affects(sensorially triggered pleasurable-
(cid:129)Emotional arousals gate/regulate various sensory
displeasurable feelings)
inputs into the brain
2. Secondary-process emotions (learning via basal ganglia)
(cid:129)They control learning and help program higher brain
i) Classical conditioning
cognitive activities
ii) Instrumental and operant conditioning
(cid:129)With maturation, higher brain mechanisms come to
iii)Emotional habits
regulate emotional arousals.
3. Tertiary affects and neocortical “awareness” functions
Affects are the subjectively experienced aspects of emo-
i) Cognitive executive functions: thoughts and planning
tions, commonly called feelings. Critical evidence now
ii) Emotional ruminations and regulations
indicates that primary-process emotional affects are
iii)“Free-will” or intention-to-act
mammalian/human birthrights that arise directly from
genetically encoded emotional action circuits that antic- Table I. Levels of control in brain emotion-affective processing.
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postulate that the secondary and tertiary emotional lev- Historical perspectives and the role of
els of organization remain critically linked to the dynam- animal models in biological psychiatry
ics of primary processes, which serve as a foundation for
diverse higher psychological functions. Twentieth-century thinking about psychiatric issues can
The mammalian brain is clearly an organ where evolu- be divided into two phases: the first half of the century
tionary layering remains evident at both the anatomical focused heavily on emotional and related psychological
and chemical levels, and striking cross-species homolo- complexities, especially through Freud-inspired psycho-
gies exist in the more ancient primary-process neural analytic theory. Because of the immaturity of neuro-
regions.4In contrast, higher brain functions, which are science, this eventually led to the study of the mind with-
much harder to study in preclinical models, are more dis- out a brain—a top-down speculative perspective with
tinct across species. Such neuroevolutionary facts allow little scientific basis. The second half of the century, after
us to envision primary emotional processes in humans the discovery of several highly effective psychiatric med-
that are homologous across mammals, permitting animal ications, was framed more in a Krapelinian context—
models to effectively illuminate how primordial emo- psychiatric diagnostic categories were linked to diverse
tional feelings—ancestral states of consciousness— brain mechanisms, which were studied objectively. This
emerge from human brain activities.5 In addition, has now led to abundant ruthless reductionism, where
advances in understanding subcortical emotional brain mental (experienced) aspects of brain functions are
organization, especially its evolutionary roots, can illu- inadequately considered in the genesis of psychiatric dis-
minate certain higher tertiary-process BrainMind func- orders, especially when preclinical models are used to
tions, permitted by massive encephalization in primates. clarify underlying principles. This has led to the increas-
Here, some of the cross-species primary-process emo- ing study of living brains without feelings—without a
tional systems that help us decipher the foundations of mind. This is ontologically unsatisfactory.
emotions in normal human mental life, as well as psy- The above traditions can now be blended, illuminating
chiatric conditions, will be described.6However, first it how our ancestral affective BrainMind contributes to
should be noted that there are historical forces at work and often causes psychiatric problems. But the absence
that are delaying such integration. of a general solution to how emotional feelings are cre-
Many still believe in James-Lange's 125-year-old con- ated in the brain continues to impede development of
jecture that emotional feelings reflect neocortical neuroscientifically coherent psychiatric nosologies
“readout” of bodily autonomic arousals. For a sam- (reflected in the current discussions regarding DSM-5
pling of such opinions from prominent investigators definitions). Detailed understanding of primary emo-
see the video of Charlie Rose’s 8th Brain Series on tional systems in animal models may yield psychologi-
May 26, 2010.7 Regrettably, this time-honored theo- cally relevant endophenotypes for psychiatry.10
retical vision has essentially no consistent support. However, preclinical models pose major problems, as
However, evidence that affective feelings arise directly emphasized by the past director of NIMH, Steve
from medial subcortical networks is consistent and Hyman,11who highlighted three dilemmas of current
substantial.8The primary-process networks for emo- research in facilitating more coherent future nosologies
tional instincts run from midbrain periaqueductal gray (eg, DSM-5). They were (my commentary in italics):
(PAG) regions to medial diencephalon to various basal (cid:129)“The difficulty of characterizing the circuitry and
ganglia nuclei (amygdala, bed nucleus of the stria ter- mechanisms that underlie higher brain functions.”
minalis, nucleus accumbens, etc) that interact with Regrettably Hyman largely neglected the emotional dif-
paleocortical brain functions (eg, cingulate, insular, as ficulties that arise from imbalanced lower emotional-
well as medial- and orbitofrontal cortices) and more affective brain functions that can be studied in animals.
indirectly with certain neocortical regions to provide (cid:129)The “complexity of the genetic and developmental
integration with higher cognitive activities. The sub- underpinnings of normal and abnormal behavioral
cortical locus of affect generation strongly suggests variation” that prevents integration between diagnos-
that the foundational principles of human emotions tic labels and brain pathophysiology. This is surely so,
can be understood by studying these brain structures but many current emotion-free genetic-psychiatric link-
and functions in other animals.9 age studies are providing few insights. Perhaps more the-
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oretically focused studies that include affective issues can tertiary processes) with no compelling strategy for
lead to faster progress.12 unraveling primary-process emotional networks. To this
(cid:129)The “unsatisfactory nature of current animal models day, abundant “battles” are waged between psychologists
of mental disorders.” The key problem here may be our who espouse “basic emotion” views in human research
relative unwillingness to discuss the nature of affective and those who prefer dimensional views. The “basic
experience in animals, which prevents development of emotion” approaches posit a variety of distinct, inher-
preclinical brain emotional-network models that could ited brain emotional systems; the “dimensional” views
better clarify primary-affective issues. envision distinct emotions simply to reflect verbal label-
The rest of this article will highlight: (i) how emotional ing of locations in some type of continuous affective
states can be understood neuroscientifically through ani- space that is defined by two continuous axes: generalized
mal models; and (ii) how such knowledge can impact forms of: (i) low and high arousal; and (ii) positive and
clinical practice in biological psychiatry, with a focus on negative valence.
depression. The study of primary-process brain mechanisms of emo-
tions, best pursued in animal models, provides a bridge
Emotion theory—old beliefs and new realities that can help settle such debates. A primary-
process/basic emotion view may prevail in many sub-
Primary-process emotion approaches to the BrainMind cortical regions, and constructivist/dimensional
are not well represented in modern psychology, psychi- approaches may effectively parse higher emotional con-
atry, or even neuroscience. The most widely acknowl- cepts as processed by the neocortex (Table I). In other
edged theory of emotional feelings remains the James- words, such debates may simply reflect investigators
Lange conjecture (see above) that advanced the working at different levels of control.
counterintuitive idea of life-challenging situations (ie, The Affective Neuroscience3strategy relies on preclinical
when inadvertently confronted by a grizzly bear in the evidence for the existence of a variety of primary-
woods) resulting first in various bodily symptoms of process emotional networks in mammalian brains. These
autonomic arousal, and emotional experiences follow- networks are identified by distinct emotional behaviors
ing only after bodily arousals are “read out” by higher evoked with highly localized electrical stimulation of the
cognitive processes. This has promoted the misleading brain (ESB) sites which exist almost exclusively in sub-
belief that emotions are just a subset of cognitive cortical regions. Such instinct-generating sites also gen-
process. If one defines cognitive processes as neural han- erate emotional feelings, as monitored by “reward” and
dling of incoming sensory stimuli, a disciplined distinc- “punishment” attributes. In other words, animals care
tion can be made between cognitive and primary- whether such emotional states are evoked. The likeli-
process emotional processes, with the former consisting hood that there are just singular types of “good” and
of externally sourced information processing and the lat- “bad” feelings (positive and negative valence) among
ter being internal state-control processes, as done here. the subcortical affective networks is unlikely; humans
When one moves to higher levels of processing, sec- report a variety of emotional feelings that generally cor-
ondary (learning), and tertiary processes (thought) lev- respond to the types of emotional actions evoked in ani-
els of analysis, cognitive and emotional issues do get mals.14Also, a single primordial dimension of arousal
more conflated. must be questioned: the psychological feeling of emo-
Another bias impeding progress is the fact that many tional intensity is regulated by many systems—eg, acetyl-
psychologists believe that emotions arise not from brain choline, dopamine, glutamate, histamine, norepinephrine,
evolution but from social-developmental learning based serotonin, and various neuropeptides—leaving open the
on primal gradients (dimensions) of arousal and possibility of distinct types of arousal in lower regions of
valence.13This “experimental convenience”—namely a the brain. Perhaps at a tertiary-process conceptual (neo-
convenient conceptual way to study human emotions cortical) level, we do conflate feelings into positive and
verbally—goes back to the 19th-century work of negative—“good” and “bad”—categories, but that is a
Wilhelm Wundt, but it has never been firmly connected heuristic simplification (a Wittgensteinian “word game”)
to neuroscientific facts. Such dimensional approaches promoted by our thinking processes. But can the neo-
effectively focus on the diverse languages of emotion (ie, cortex generate emotional feelings on its own?
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No scientist who has worked on primary-process brain ration-distress/GRIEF may have arisen from earlier
emotional systems has ever subscribed to the James- physical pain systems of the brain.23
Lange conjecture that affective feelings are only experi-
enced when unconscious sensory information about The primary-process emotional-affective
bodily arousals reaches the neocortex. Beside Walter networks of mammalian brains
Cannon’s seminal critique,15abundant modern findings
contradict that view: Brain research supports the existence of at least seven
(cid:129)The emotional-behavioral coherence of organisms is primary-process (basic) emotional systems—SEEKING,
fully formed in subneocortical regions of the brain— RAGE, FEAR, LUST, CARE, GRIEF (formerly
eg, just consider that physical PLAY, the most complex PANIC), and PLAY—concentrated in ancient subcorti-
basic social emotion, persists after neodecortication.16 cal regions of all mammalian brains.
(cid:129)Both the emotional-behavioral and affective (reward In sum, affective neuroscientific analysis of basic emo-
and punishment) aspects of ESB are most readily tions is based on several highly replicable facts: (i)
obtained, with the lowest current levels, from the most Coherent emotional-instinctual behaviors can be
ancient midbrain regions (PAG or central gray) rather aroused by electrically stimulating very specific subcor-
than from higher emotional regions (eg, amygdala, cin- tical regions of the brain; (ii) Wherever one evokes emo-
gulate, and frontal cortices).17 tional action patterns with ESB, there are accompany-
(cid:129)Cognitive working-memory fields concentrated in dor- ing affective experiences. Again, the gold standard for
solateral frontal cortical regions have a “seesaw” rela- this assertion is the fact that the brain stimulations can
tionship with subcortical emotional-affective systems, serve as “rewards” when positive-emotions are
so that their activities are commonly reciprocally aroused—eg, SEEKING, LUST, CARE, and aspects of
related.18 PLAY. When negative emotions are aroused—RAGE,
(cid:129)Human brain imaging of intense emotional experi- FEAR, GRIEF—animals escape the stimulation; (iii)
ences (anger, fear, sadness, and joy) “light up” subcor- The above behavioral and affective changes are rarely,
tical brain regions, homologous in all mammals.19 if ever, evoked from higher prefrontal neocortical
The second point above is critical. There is a remarkable regions, suggesting that higher brain areas may not have
correspondence between ESB sites yielding emotional the appropriate circuitry to generate affective experi-
action patterns (the various distinct instinctual-behav- ences, although the neocortex can clearly regulate (eg,
ioral profiles, described below for each of seven primary inhibit) emotional arousals and, no doubt, prompt emo-
emotional processes) and their capacity to sustain “rein- tional feelings by dwelling on life problems.
forced” learning in animals and intense emotional feel- The emotional primes are summarized in several mono-
ings in humans. Accordingly, we can use a dual-aspect graphs, with another appearing soon.24 Thumbnail
monismstrategy to study emotional feelings—ie, ESB descriptions are provided below, with one key reference
evoked RAGE behaviors reflect angry-type feelings for each.
(animals turn off such ESB20), while evoked PLAY
behaviors reflect joyful-type feelings—ESB evoking The SEEKING/desire system
play-vocalizations sustain self-stimulation reward,21etc.
(In physics, a related “dual-aspect” strategy—concurrent This extensive network confluent with the medial fore-
acceptance of “wave” and “particle” descriptions of elec- brain bundle (MFB) is traditionally called the “brain
tromagnetic radiation—is needed to make sense of reward system.” In fact, this is a general-purpose appet-
available data). In the present view, the affective states itive motivational system that is essential for animals to
generated by primordial brain emotional networks may acquire all resource needs for survival, and it probably
have been among the first experiences that existed in helps most other emotional systems to operate effec-
brain evolution. Without them, higher consciousness tively. It is a major source of life “energy”, sometimes
(frontal neocortical executive functions) may not have called “libido.” In pure form, it provokes intense and
evolved.22In evolutionary terms, all primal emotional enthusiastic exploration and appetitive anticipatory
systems are rooted in yet deeper and more ancient excitement/learning. When fully aroused, SEEKING25
processes. For example, the psychological pain of sepa- fills the mind with interest and motivates organisms to
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effortlessly search for the things they need, crave, and arousal of this brain system; ESB of the above brain
desire. In humans, this system generates and sustains regions can evoke sudden, intense anger attacks, with no
curiosity from the mundane to our highest intellectual external provocation. Key chemistries which arouse this
pursuits. This system becomes underactive during addic- system are the neuropeptide Substance P and glutamate,
tive drug withdrawal, chronic stress, and sickness, and while endogenous opioids and γ-aminobutyric acid
with accompanying feelings of depression. Overactivity (GABA) inhibit the system. A prediction is that gluta-
of this system can promote excessive and impulsive mate and Substance P receptor antagonists (eg, aprepi-
behaviors, along with psychotic delusions and manic tant) may help control human anger. Additional medi-
thoughts. All antipsychotics reduce arousability of this cines to control RAGE could presumably be developed
“reality-creating” mechanism of the brain. The term through further detailed understanding of RAGE cir-
“reality-creating” is used to highlight the fact that this cuitry.
system appears to generate causal convictions about the
nature of the world from the perception of correlated The FEAR/anxiety system
events (for a full discussion see Chapter 8 of Affective
Neuroscience3). The evolved FEAR27 circuit helps to unconditionally
Neuroanatomically, SEEKING circuitry corresponds to protect animals from pain and destruction. FEAR-ESB
the extensive medial forebrain bundle and major leads animals to flee, whereas much weaker stimulation
dopamine-driven, self-stimulation “reward” circuitry elicits a freezing response. Humans stimulated in these
coursing from ventral midbrain to nucleus accumbens same brain regions report being engulfed by an intense
and medial frontal cortex, where it can promote frontal free-floating anxiety that appears to have no environ-
cortical functions related to planning and foresight. mental cause. Key chemistries that regulate this system
Rather than being a “pleasure or reinforcement system,” are Neuropeptide Y and corticotrophin releasing factor
SEEKING coaxes animals to acquire resources needed (CRF); anti-anxiety agents such as the benzodiazepines
for survival. It promotes learning by mediating antici- inhibit this system by facilitating GABA transmission.
patory eagerness, partly by coding predictive relation-
ships between events. It promotes a sense of engaged The LUST/sexual systems
purpose in both humans and animals, and is diminished
in depression and the dysphoria of withdrawal from Sexual LUST,28mediated by specific brain circuits and
addictive drugs. This is further highlighted by the simple chemistries, distinct for males and females, is aroused by
fact that bilateral lesions of the system produce pro- male and female sex hormones, which control many brain
found amotivational states in animals (all appetitive chemistries including two “social neuropeptides”—oxy-
behaviors are diminished) and the elevated threshold for tocin transmission is promoted by estrogen in females
self-stimulation reward probably reflects the dysphoria and vasopressin transmission by testosterone in males.
state. These brain chemistries help create gender-specific sex-
ual tendencies. Oxytocin promotes sexual readiness in
The RAGE/anger system females, as well as trust and confidence, and vasopressin
promotes assertiveness, and perhaps jealous behaviors, in
When SEEKING is thwarted, RAGE26is aroused. Anger males. Distinct male and female sexual tendencies are
is provoked by curtailing animals’ freedom of action. promoted by these steroid hormones early in life, with
RAGE is a reliably provoked ESB of a neural network sexual activation by gonadal hormones at puberty.
extending from the medial amygdala and hypothalamus Because brain and bodily sex characteristics are inde-
to the dorsal PAG. RAGE lies close to and interacts with pendently organized, it is possible for animals that are
trans-diencephalic FEAR systems, highlighting the externally male to have female-typical sexual urges and,
implicit source of classic “fight-flight” terminology. It others with female external characteristics to have male-
invigorates aggressive behaviors when animals are irri- typical sexual urges. The dopamine-driven SEEKING
tated or restrained, and also helps animals defend them- system participates in the search for sexual rewards just
selves by arousing FEAR in their opponents. Human as for all other types of rewards, including those relevant
anger may get much of its psychic energy from the for the other social-emotional systems described below.
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The CARE/maternal nurturance system assertive actions are consistently accompanied by positive
affect—an intense social joy—signaled in rats by making
Brain evolution has provided safeguards to assure that abundant high frequency (~50 kHz) chirping sounds,
parents (usually the mother) take care of offspring. resembling laughter. One key function of social play is to
Some of the chemistries of sexuality, for instance oxy- learn social rules and refine social interactions.
tocin, have been evolutionarily redeployed to mediate Subcortically concentrated PLAY31urges may promote the
maternal care—nurturance and social bonding—sug- epigenetic construction of higher social brain functions,
gesting there is an intimate evolutionary relationship including empathy. Further studies of this system may lead
between female sexual rewards and maternal motiva- to the discovery of positive affect promoting neuro-
tions.29The shifting hormonal tides at the end of preg- chemistries that may be useful in treating depression.32
nancy (declining progesterone, and increasing estrogen, These seven emotional networks provide psychiatric
prolactin, and oxytocin) invigorate maternal urges days research with various endophenotypes important for
before the young are born. This collection of hormonal advancing psychiatric understanding of affective order
and associated neurochemical changes also help assure and disorder. For preclinical modeling, these emotional
strong maternal bonds with offspring. systems provide a variety of affectively important
BrainMind networks to guide not only psychiatrically
The GRIEF/separation distress system relevant research, but as already highlighted, the devel-
opment of more specifically acting psychiatric medicines.
This system was initially called the PANIC system, but To highlight one concrete possibility, there will follow a
few understood the intent of that primary-process ter- brief focus on how such systems may help us understand
minology, so we shifted to the more comprehensible ter- the genesis and better treatment of depression.
tiary-process term of GRIEF30(highlighting once more
terminological problems in emotion research: what are
the differences between the tertiary-level emotions of Emotional networks and depression
bereavement, grief, and mourning, for instance?). In any
event, young socially dependent animals have powerful A key research question for affective disorders is why
emotional systems to solicit nurturance. They exhibit depression feels so bad. Specifically, which negative
intense crying when lost, alerting caretakers to attend to affect generating networks within mammalian brains
their offspring. ESB mapping of this separation-distress helps generate depressive pain that leads to chronic
system has highlighted circuitry running from dorsal despair?
PAG to anterior cingulate, and it is aroused by glutamate Although all the affective networks of the mammalian
and CRF and inhibited by endogenous opioids, oxytocin, brain can be influenced by depression—from diminished
and prolactin—the major social-attachment, social- CARE and PLAY to elevated FEAR and RAGE—the
bonding chemistries of the mammalian brain. These neu- “painfulness” of depressive affect may be engendered
rochemicals are foundational for the secure attachments most persistently (i) by sustained overactivity of GRIEF,
that are so essential for future mental health and happi- which promotes a downward cascade toward chronic
ness. It is still worth considering that panic attacks may despair, following a theoretical view originally formu-
reflect sudden endogenous spontaneous loss of feelings lated by John Bowlby.33This promotes (ii) the sustained
of security (acute separation-distress) rather than sud- dysphoria of depression which may be due largely to
den FEAR. We predict that these circuits are tonically abnormally low activity of the reward-SEEKING sys-
aroused during human grief and sadness, feelings that tem. For an extensive discussion, along with expert com-
accompany low brain opioid activity. mentaries, see ref 34.
This vision allows investigators to focus on specific net-
The PLAY/rough-and-tumble, physical social- work analyses as opposed to the nonspecific stress mod-
engagement system els most commonly employed. Many stressors are used
to evoke depressive phenotypes in animals—ranging
Young animals have strong urges for physical play—run- from physical restraint and various punishments to
ning, chasing, pouncing, and wrestling. These “aggressive”- intense psychological losses such as enforced maternal
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or social isolation and social defeat in adult aggressive about the crucial role of separation distress—the acute
encounters.35Few models specifically modify or monitor “protest” or “panic” responses to social loss, especially
activities of specific emotional networks such as GRIEF in young animals—allows neuroscience to clarify the
and SEEKING. Rather, they typically use very general “painfulness” of social loss. The GRIEF system of sev-
outcome measures—timidity during exploration (eg, eral species has been mapped to similar brain regions
center crosses in open fields), various diminished plea- (Figure 1), and this may be a key to the acute psycho-
sure responses (eg, diminished sexuality and consump- logical pain of social loss. Indeed, the higher reaches of
tion of sweets) and varieties of learned helplessness (eg, this system in the anterior cingulate are targeted in
diminished struggling when placed into water). For recent deep brain stimulation (DBS) initiatives for treat-
extensive summaries of such models, see the whole issue ment-resistant depressions.38 A focus on the neuro-
of Neuroscience & Biobehavioral Reviewsdevoted to this chemical controls in this system provides other options
topic (2006, vol 29). for medicinal development. Likewise, facilitation of
As a result, existing research typically focuses on general SEEKING urges should further facilitate recovery,
brain consequences of stress—from changing brain nor- whether by joyful life activities, pharmacological stimu-
epinephrine and serotonin dynamics to many other brain lation of SEEKING reserves, or even DBS of the
changes.36However, such general brain chemical changes nucleus accumbens and MFB.39
may not specificallyclarify the morbid mood of depression. Opioids that activate mu receptors are especially effective
The amines regulate rather general brain functions that in reducing arousal of GRIEF/separation distress in ani-
influence all emotions and related cognitive processes. We mals.42Each of the above neurochemical controls (eg, opi-
now need strategies that aim to study the more specific oids and oxytocin) provides novel options to reduce the
affective changes that characterize depression. This psychic pain of depression in ways that are currently not
requires a specific emotional network approach. clinically used. Indeed, reasonably safe opioids, such as
Primary-process emotional-systems analyses provide ultra-low-dose buprenorphine, are very effective antide-
preclinical models where specific types of affective pressants for individuals who have obtained no relief from
change can be manipulated and studied, and new treat- standard antidepressants.43 Similarly, drugs that inhibit
ments can be developed based on the neurochemical CRF and glutamate, the key neurochemistries that pro-
characteristics of the relevant circuits. For instance, the mote separation calls (vocalizations made when young ani-
separation-distress/GRIEF “protest” gateway to depres-
sion may engender “psychological pain” that can cascade
toward “despair” and sustained clinical depression.30,34
The entry to despair may reflect diminished SEEKING
urges, promoting lack of initiative and lethargy, thereby
further amplifying dysphoria. Thus, primary-process
affective neuroscience is beginning to highlight distinct
emotional networks that may specifically help explain
why depression feels bad. This suggests potential bene-
fits of relatively safe mu-opioid agonists, such as the
mixed agonist-antagonists buprenorphine, and kappa
antagonists for treating depression (see below).
An affective neuroscientific perspective on
why depression feels so bad
Figure 1. Human and animal sadness and animal separation-distress/GRIEF
systems. Animal data comes from mapping of separation dis-
As noted already, John Bowlby first emphasized that tress circuits with localized electrical stimulation in guinea pigs40
and human data from PET imaging of affective states by
depressive affects are related to the experiences of social
Damasio’s group.41AC, anterior cingulate; VS, ventral striatum;
attachments and social loss. This is, epidemiologically,
dPOA, dorsal preoptic area; BN, bed nucleus of the stria ter-
now a well-supported conclusion.37 Bowlby’s insight minalis; DMT, dorsomedial thalamus; PAG, periaqueductal gray
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Neuroscience of the emotional BrainMind - Panksepp Dialogues in Clinical Neuroscience - Vol 12 .No. 4 .2010
mals are separated from mothers or siblings, ie, GRIEF), Thus, although negative affective changes in the opioid-
have yielded promising antidepressant effects.44,45 and oxytocin-driven attachment and affectional systems
In sum, GRIEF circuitry evolved from general pain may be the pivotal precipitants of psychological pain that
mechanisms, well over a hundred million years ago is the entry point for a depressive cascade, it may be
(birds possess a homologous system). This emotional sys- diminished SEEKING that pushes the system into a sus-
tem forges social bonds and dependencies between tained clinically significant dysphoria. This scenario does
infants and caretakers, and probably regulates adult not exclude the potential contribution of other biogenic
social relationships and solidarity. The affective conse- amine imbalances in depression—changes in overall
quences of severed attachment bonds make adults suf- brain arousal can reinforce the above affective changes.
fer in a distinct way, commonly called grief, but this is not Because of the affective complexity and diversity of
yet clinical depression. depression, many variants on these basic themes can be
envisioned, yielding many subtypes of depression. It
Separation distress is only would be premature to try to relate the emotional primes
the gateway to depression to the various subtypes—anxious, agitated, etc—but to
simply indicate that FEAR overactivity may contribute
The acute GRIEF response may need to be supple- to anxious forms, while the GRIEF separation-distress
mented by other neuroaffective changes before individ- system might contribute more to melancholic forms,
uals cascade into sustained depressive lassitude and while selectively diminished SEEKING may contribute
despair. Cytokines that promote sickness feelings (eg, to those forms where agitation is not prevalent.
Interleukin 1) and endogenous inflammatory cascades The critical point is that detailed clarification of dedi-
have been proposed as possible causal vectors; both may cated emotional-affective circuits in mammalian brain
operate, in part, by diminishing SEEKING arousals.46A should allow us eventually to invest in more direct affec-
sustained depressive phenotype may arise when dimin- tive strategies to understand and treat depression as well
ished SEEKING urges allow the behavioral manifesta- as other psychiatric disorders accompanied by imbal-
tions of GRIEF (the “protest” phase of separation dis- anced affective states.10 This may be a substantial
tress) to diminish. This need not mean that the advance over generalized stress models, for it is easier to
intrapsychic pain of GRIEF also disappears. Indeed, if envision how to focus on changes in specific brain emo-
the psychic pain is sustained, the dysphoria of dimin- tional circuits rather than more global stress-induced
ished SEEKING could further elevate negative affect. brain changes. Affective circuit perspectives also coax us
Thus, depressive affect may start with psychological pain to consider the potential benefits of strengthening vari-
(GRIEF, with concurrent SEEKING arousal) followed ous positive emotional systems to promote affective
by “giving up” (consisting of sustained psychic pain, homeostasis. For instance, therapeutic approaches that
accompanied by the lethargic anhedonia of diminished promote the positive hedonics of social CARE and
SEEKING). PLAY systems may increase treatment options that
Diminished brain reward in preclinical models of could yield better outcomes than existing therapies.
depressive states is well established,47but it is not yet To develop this last theme a little further, when we develop
clear how this happens. A promising candidate is ele- antidepressants that can rapidly and specifically promote
vated dynorphin activity along SEEKING circuitry. desired affective rebalancing, we might consider develop-
Indeed, dynorphin mediates the negative affect arising ing complementary psychotherapeutic approaches where
from loss in competitive social encounters.48Again, this clinicians explicitly seek to utilize the power of positive
suggest that severe depression may be optimally coun- affective systems of clients’ brains. For instance, the “power
teracted by medicines that reduce both social-loss of PLAY” in adult psychotherapy remains largely unused,
induced psychic pain and depleted SEEKING resources; although preclinical benefits for childhood problems such
low-dose buprenorphine can counteract both through its as excessive impulsivity have been documented.49
mu-opioid agonist and kappa-receptor antagonism Considering that PLAY can promote the expression of
effects. Addictive tendencies are markedly reduced since various neurotrophins like brain-derived neurotrophic fac-
higher doses block mu receptors which blunt opioid tol- tor,50and insulin-like growth factor 1,32it is to be expected
erance and escalating addictive dosing. that playful interactions, just like exercise, may have anti-
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C l i n i c a l r e s e a r c h
depressant effects, and the resulting neuroplasticities may specific emotional processes to simulate psychiatric disor-
reinforce better and longer-lasting psychotherapeutic ben- ders and to also have outcome measures that are not so
efits. Affective neuroscientific thinking suggests many general (eg, gross locomotor activity, swimming, and other
other new avenues for medicinal developments since all stress-provoked changes that cannot be easily linked to
primary-process emotional systems seem to have unique specific brain affective circuits). By using an affective neu-
neuropeptidergic controls.51 roscience approach, we can now monitor affective states
by the ethological-emotional patterns of animals, especially
Summary: the promise of diverse emotional vocalizations that can be used as direct
new therapeutic approaches “self-reports” of changes in affective states.53,54Also, even
though preclinical models can tell us a great deal about
In the above context, it would not only be of interest to brain emotional and stress-induced changes that cannot
explore novel psychotherapeutic approaches that might be harvested in other ways, we must recognize that such
specifically influence endogenous neurochemical controls approaches cannot penetrate the tertiary-process cogni-
of the other affective networks of mammalian brains, but tive complexities that make human emotional life so rich
clinicians may seek to estimate the primary-process emo- and full of conflicts and devilishly complex vicissitudes.
tional strengths and weaknesses of clients so as to better However, what a cross-species affective neuroscience strat-
envision the major emotional forces that may have egy does provide is a better and more precise focus on the
become imbalanced in major forms of emotional distress. diverse forms of affective distress and euphoria that can
Of course, primary processes in humans can only be esti- arise from the basic emotional circuits of all mammalian
mated through tertiary-process verbal reports. Although brains, leading to concrete hypotheses of how each system
there are shortcomings in such approaches, we have may contribute to higher mental processes. For such a dis-
developed the Affective Neuroscience Personality Scales cussion of RAGE circuitry, see ref 55 and the relations of
to provide a tool whereby clinicians may better estimate GRIEF and SEEKING systems for further understand-
the primary-process emotional traits in normal as well as ing of addictions,54,56,57and depression.34,58-60Such issues are
psychiatric patients.52 central for many psychiatric concerns.
A better understanding of the emotional endophenotypes A final issue that deserves attention is how such view-
discussed here may help guide clinicians to deal more points may relate to psychiatric disorder susceptibility
strategically with the raw and troublesome feelings of their issues. One general principle might be that better evalu-
clients, and give them clearer explanations of the sources ation of basic emotional personality traits may provide
of their distress. This may be beneficial for many patients. a tool for analyzing such relationships.52Although it is
The approach also provides new avenues, yet to be devel- premature to reach any conclusions, we hypothesize that
oped, that better recruit the personal affective resources heightened constitutional sensitivity of GRIEF systems
of clients to promote healing. Therapists who can work and endogenous underactivity of SEEKING urges
effectively with the basic emotions—reframing and recon- would facilitate the emergence of depression in response
textualizing hurtful memories so they can be reconsoli- to stressors. To evaluate this, we have generated genetic
dated in the context of positive feelings—may be able to lines of animals that exhibit high and low positive affect
promote more lasting therapeutic change than those that based on heritability of emotional vocalizations.61
seek to remain more strictly at cognitive levels of inter- Preliminary work suggests that the high positive affect
action. This is not to minimize the ability of cognitive animals may be resistant to depression while low ones
processes to reframe stressful life events and to regulate may be more susceptible to depression.62Related work
negative emotionality through the analysis of life options, has been pursued at the genetic level by others.63
but to suggest that more direct work with the nature of Once we have a clear scientific understanding of the pri-
affects is a perspective that remains underdeveloped. mary emotional processes of mammalian brains, we may
In conclusion, affective neuroscience also has implications be able to employ the concept of endophenotypes more
for the future development of animal models of psychiatric effectively than it is currently used.10Such foundational
disorders. Currently preclinical models are rather deficient, knowledge may serve as a useful roadmap for gathering
as highlighted by Steven Hyman (see above).11What has knowledge useful for the next generation of progress in
been lacking so far is a more direct focus on manipulating biological psychiatry. ❏
542