Emotion, Motivation, and Anxiety: Brain Mechanisms and ... · PDF fileEmotion, Motivation, and...

Click here to load reader

  • date post

    29-Jun-2018
  • Category

    Documents

  • view

    218
  • download

    0

Embed Size (px)

Transcript of Emotion, Motivation, and Anxiety: Brain Mechanisms and ... · PDF fileEmotion, Motivation, and...

  • Emotion, Motivation, and Anxiety: Brain Mechanismsand Psychophysiology

    Peter J. Lang, Margaret M. Bradley, and Bruce N. Cuthbert

    The organization of response systems in emotion isfounded on two basic motive systems, appetitive anddefensive. The subcortical and deep cortical structuresthat determine primary motivated behavior are similaracross mammalian species. Animal research has illumi-nated these neural systems and defined their reflex out-puts. Although motivated behavior is more complex andvaried in humans, the simpler underlying response pat-terns persist in affective expression. These basic phenom-ena are elucidated here in the context of affective percep-tion. Thus, the research examines human beings watchinguniquely human stimuliprimarily picture media (butalso words and sounds) that prompt emotional arousalshowing how the underlying motivational structure isapparent in the organization of visceral and behavioralresponses, in the priming of simple reflexes, and in thereentrant processing of these symbolic representations inthe sensory cortex. Implications of the work for under-standing pathological emotional states are discussed,emphasizing research on psychopathy and the anxietydisorders. Biol Psychiatry 1998;44:12481263 1998Society of Biological Psychiatry

    Key Words: Emotion, anxiety, brain mechanisms, moti-vation, fear

    Introduction

    The aims of this paper are twofold. First, a theoreticalmodel of emotion is presented that is founded on basicexperiments from both the animal and human researchlaboratories. In this view, emotions are held to be productsof Darwinian evolution. Expressed emotions developedfrom primitive actions that facilitated the survival ofspecies and individuals. In man, the evolved affects arebest characterized as motivationally tuned states of readi-ness. The second aim of this paper is to show how thisapproach generates a useful technology, facilitating par-ticularly the study of human anxiety disorders. Applica-

    tions are described that can aid in the differential diagnosisof anxiety. Research is presented, showing that psycho-physiological analyses conducted during initial patientevaluation can help predict success in therapy.

    The Motivational Organization of Emotion

    Patterns of emotional expression are highly varied. Theo-rists have compiled categorical lists that include as manyas eight (Plutchik 1962) or 10 (Izard 1977) so-calledprimary affective states, augmented by various blends.Verbal reports of affects can have a great richness andsubtlety of discrimination, with hundreds of emotionallydescriptive words available in natural language lexicons. Itis proposed here, however, that the evolutionary founda-tion of emotion has a simpler, two-factor motivationalorganization. That is, affects are organized by brainsystems that adaptively respond to two basic types ofstimulation, appetitive or aversive. This biphasic organi-zation of emotion has been proposed by many theorists.Konorski (1967), for example, developed a model basedon a typology of unconditioned reflexes and their biolog-ical, motivational roles. Exteroceptive reflexes were eitherpreservative (e.g., ingestion, copulation, nurture of prog-eny) or protective (e.g., withdrawal from or rejection ofnoxious agents). Preservative emotions include such af-fects as sexual passion, joy, and nurturance; fear and angerare representative of protective affects. Dickinson andDearing (1979) further developed Konorskis dichotomyinto two opponent motivational systems, aversive andattractive, each activated by a different, but equally widerange of unconditioned stimuli, determining perceptualmotor patterns and the course of learning.

    The view that affects might be organized by overarch-ing motivational factors has also been suggested byresearchers studying subjective reports of emotion, begin-ning with Wundts (Wundt 1896) mental chemistry.Contemporary studies of natural language categories(Shaver et al, 1987; Ortony et al 1988) suggest thatemotional knowledge is hierarchically organized, and thatthe superordinate division is between positivity (pleasantstates: love, joy) and negativity (unpleasant states: anger,sadness, fear). Osgood and his associates (e.g., Osgood et

    From the NIMH Center for the Study of Emotion and Attention, University ofFlorida, Gainesville, Florida.

    Address reprint requests to Peter J. Lang, PhD, Box 100165 HSC, University ofFlorida, Gainesville, FL, 32610.

    Received April 16, 1998; revised August 10, 1998; accepted August 21, 1998.

    1998 Society of Biological Psychiatry 0006-3223/98/$19.00PII S0006-3223(98)00275-3

  • al 1957), using the semantic differential, earlier showedthat emotional descriptors were primarily distributed alonga bipolar dimension of affective valenceranging fromattraction and pleasure to aversion and displeasure. Adimension of activationfrom calm to arousedalsoaccounted for substantial variance. Similar conclusionshave been drawn by other investigators based on verbalreports (e.g., Mehrabian and Russell 1974; Russell 1980;Tellegen 1985), as well as facial expressions (Schlosberg1952).

    The view taken here merges these lines of theoreticaldevelopment. It is postulated that two motivational sys-tems exist in the brain, appetitive and defensive, and thateach can vary in terms of activation or arousal. That is,arousal is not viewed here as having a separate substrate,but rather as representing intensity of activation (metabol-ic and neural) of either the appetitive or aversive system,or the coactivation of both systems (see also Cacioppo andBernston 1994). The varying emotional states, observedand reported, reflect these basic motive systems. That is,the motive system determines the general behavioralstrategy, defense or appetitive acquisition. The specificsomatic and autonomic patterns of affective respondingare tactical, in that they are formed by the behavioralcontext. To give an example from the observation ofanimals, if a caged rat is subjected to electric shock on thefoot pads, the defense system is engaged. It is then likelyto 1) flee if an exit is available (fear), or 2) attack acagemate if one is present (anger). If shocks are repeatedrandomly and uncontrollably it will 3) first cower help-lessly and then become dull and unresponsive (depres-sion). Although emotions may come in many forms,shaped by genetics and learning to fit the demands of localcontext, their fundamental organization is motivational.Thus, their primary description is in terms of affectivevalence (i.e., appetitive or aversive) and arousal (intensityof activation).

    Patterns of Human Emotion

    The behavior of very primitive organisms can be whollycharacterized by two responses: direct approach to appet-itive stimuli and withdrawal from aversive stimuli (seeSchneirla 1959). This modest behavioral repertoire cannot,however, implement the many subgoals of human beingsnor effectively deal with the perceptually rich, complexenvironment in which we live. Elaborate instrumental acts,behavioral delay, and response inhibition have evolved,complicating the path of simple bidirectional goal-relatedbehavior. Thus, emotional behaviors in humans are moreadaptive and creative, and less predictable than those ofless evolved species.

    In human beings, the presumed indices of emotional

    expression include responses in three reactive systems(Lang 1978): 1) expressive and evaluative language; 2)physiological changes mediated by the somatic and auto-nomic systems; and 3) behavioral sequelae, such aspatterns of avoidance or performance deficits. This is thedatabase of emotion, and a theory of emotion has to copewith its breadth and diversity. The task is not simple.Correlations among emotion indices, within and betweensystems, are generally quite modest (e.g., Lang 1968;Mandler et al 1961), and the patterns of response can varyconsiderably within subjects and across different contextsof stimulation (Lacey 1958; Lacey and Lacey 1970).Analysis is further complicated by the fact that, whereashuman emotions appear to have derived from primitiveactions, the defining response may never actually occur;the bosss insult may incite hostility, but the angry blow iswithheld. In this sense, emotions are often dispositions toaction, with an accompanying physiology of preparationthat is not discharged.

    As noted previously, affective expression is in great parta tactical response to contextual demands. Thus, responsepatterns in emotion have often proven unreliable, reflect-ing variability in stimuli and methods across experiments.If procedures are held constant, however, and standardemotional stimuli are used, tactical features can be speci-fied and emotions underlying strategic framework ofappetite and defense should be highlighted. We haveextensively tested this hypothesis in such a standardcontextviewing emotional picturesas a method forinvestigating emotion in the laboratory.

    Emotion and Perception

    Over the past 10 years, we have developed a set ofcalibrated picture stimuli to use in the scientific study ofemotion. There are currently over 600 pictures in theInternational Affective Picture System (IAPS; Lang, Brad-ley, & Cuthbert, 1997), which includes normative ratingsof the pleasure and arousal associated with each picture,obtained from groups of naive subjects. A representativesample of IAPS pictures, distributed in the two-dimen-sional affective space formed by covarying pleasure andarousal ratings, is presented in Figure 1. The overallboomerang-shaped distribution of these picture stimuliindicates two arms that extend from a common calm,nonaffective base toward either the high-arousal pleasantor the high-arousal unpleasant quadrant. This organizationis consistent with an underlying bimotivational structure:two systems of appetitive and aversive motivation thateach vary along a dimension of arousal. Despi