Emotions - theories and neural circuits

physiological psych

Emotion

a subjective mental state usually accompanied by distinctive behaviors and involuntary physiological changes

emotional states often activate the autonomic nervous system

• sympathetic nervous system

• parasympathetic nervous system

• sympathetic nervous system

“fight or flight” system; activates the body for action

parasympathetic nervous system

prepares the body to relax and recuperate (support rest, digestion, recovery)

different emotion theories

• james-lang theory

• cannon bard theory

James-Lang theorey

the emotions we feel are caused by bodily changes; emotion differ due to different physiological responses

• but there is NO distinctive autonomic pattern for each emotion (many share profiles)

Cannon-Bard theorey

emotions we feel, and bodily changes appear simultaneous. The cerebral cortex decides on the emotional response and also activates the sympathetic response

we use situation to label the emotions

schachter’s cogntive attribution model

• emotional labels (ex: anger, fear, joy) are attributed to relatively nonspecific feelings of physiological arousal

• which emotion we experience depends on cognitive systems that assess the context

• but there is evidence that patterns of autonomic activity differ between some emotions

individual response stereotypy

people differ in emotional reactivity and physiological responses to emotional situations; evident even in infants

• response patterns are remarkably consistent throughout life

• infants will exceptionally strong reactions to stimuli (“high reactives”) were more likely to have increased phobias or fear responses later in life

PLUTCHIK suggests 8 different emotions, in 4 pair of opposites

• joy/sadness

• affection/disgust

• anger/fear

• expectation / surprise

• but researchers do not yet agree ab the number of basic emotions. one clue may come from the number of facial expressions we have

EKMAN says there are 8 distinctive expressions:

• anger

• sadness

• happiness

• fear

• disgust

• surprise

• contempt

• embarrassment

• these different emotions can be detected in facial expressions that are similar across cultures

specialized neural mechanism mediate the experience and expression of emotions

2 categories of facial muscles:

• superficial facial muscles - attach to facial skin

• deep facial muscles - attach to skeletal structures in the head

• facial muscles are innervated by cranial nerves: the FACIAL NERVE (VII) and the motor branch of the trigeminal nerve (V)

facial feedback hypothesis

sensory feedback from our facial expressions can affect our mood. example, forcing a smile can make you feel happier

electrical stimulation of the brain can be used to study the neuroanatomy of emotion

brain self-stimulation = animals perform a task to receive electrical stimulation to their brain - also works in humans

brain sites that respond to self-stimulation have been mapped

medial forebrain bundle

tract that rises from the midbrain through the hypothalamus- contains many sites for self stimulation

the nucleus accumbens

invovlved in the DOPAMINERGIC CIRCUIT, is an important target for the medial forebrain budnle, and stimulating the nucleus accumbens is considered pleasurable

brain lesions affect emotions

DECORTICATE RAGE= a sudden intense rage in dogs with their cortex removed, suggesting that the cortex inhibits rage

the papez circuit = interconnected brain regions with the limbic system; damaged in some patient with emotional changes

Klüver–Bucy syndrome

characterized by reduction of fear and anxiety, oral tendencies, hypersexuality; results from bilateral removal of large portions of temporal lobe.
• Further studies identified the amygdala as a key structure in the mediation of fear

Amygdala lesions abolish fear

Interconnections within the amygdala are important for fear associations.

Fear-associated behaviors are similar in many different species

Fear conditioning

a previously neutral stimulus is repeatedly paired with an unpleasant
experience, causing the subject to act fearful in response to the previously neutral stimulus.
• Fear conditioning studies allowed researchers to develop a map of the neural circuitry of
emotional learning.

The amygdala is also crucial for appetitive learning

positive reactions to attractive stimuli.

The amygdala is thought to help form associations between emotional responses and
specific memories of stimuli that are stored elsewhere in the brain.

Sensory information from the thalamus that goes directly to the
amygdala bypasses conscious processing and allows for immediate emotional reactions (the low road)

2 roads : High road and Observational fear learning

High road

information is routed through the cortex, allowing conscious processing (low road would be fight or flight)

Observational fear learning

fear of potentially harmful stimuli is learned through social transmission

Learned fears are slow to extinguish

During extinction training, activity in the prefrontal cortex, which projects to the amygadala, is necessary

Mice missing one type of cannabinoid receptors

have a harder time extinguishing fear responses, suggesting cannabinoid signaling is important for fear extinction

Neural mechanisms of fear conditioning are thought to play a role in posttrumatic stress disorder (PTSD)

people with bilateral damage to their amygdalas show little to no fear in response to external threats

but they do feel fear in response to epinephrine and hypoxia. the brain must rely on other systems for internal threats

stopped here.

different emotions activate different brain regions

brain imaging studies show a unique network of brain areas is responsible for the emotion of love

Emotions are associated with bilateral changes in insula, amygdala, caudate, putamen,
cingulate cortex and prefrontal cortex activity

Brain activation during sadness, happiness, fear, and anger show involvement of several brain regions

• same brain region may participate in different emotions

• Physiological responses preceded the awareness of feeling an emotion

• these studies confirm there is no simple, one-to-one relation between a specific emotion and activity of a brain region.

Aggression has different meanings; the primary focus here is
physical aggression and violence between individuals

Intermale aggression

aggr. between males of same species

Human males are more likely than females to commit murder; more aggressive behavior between boys in early childhood; suggests testosterone plays a role

Androgens seem to increase aggression in other species; decreasing circulating androgens by castration usually reduces intermale aggressive behavior

But the correlation in humans is less clear.

• Two confounding variables affect testosterone levels:
experience and dominance

There is a negative correlation between serotonin and aggression:

The most aggressive monkeys in a free ranging colony had the lowest levels of
serotonin.

Mice lacking a serotonin receptor are hyperaggressive

Balance between GABA (inhibitory) and glutamate (excitatory) appears to be
important in aggressive responses. A drug that enhances GABA transmission
reduces aggressive behavior.

____, ____, and _______ control aggression and social behavior

Vasopressin, oxytocin, and endogenous opioids

The ______ in mice appears to act as a trigger for aggression.

ventromedial hypothalamus

Emotional dyscontrol syndrome

behavior disorder that may be the result of temporal lobe disorders

Psychopaths

intelligent
people with superficial charm
who have poor selfcontrol, a
grandiose sense of self-worth,
and little or no feeling of remorse.
• Most lead normal lives but
some commit very violent acts

psychopaths don’t react as negatively to words about violence as controls do and show
blunted responses to aversive cues associated with fear conditioning.
• Imaging studies suggest that psychopaths have reduced size and activity of the prefrontal cortex, which may impair their ability to control impulsive behavior

Stress

is any circumstance that upsets homeostatic balance

Alarm reaction

initial response to stress

“Fight or flight” system: hypothalamus activates the sympathetic nervous system
which stimulates the adrenal medulla to release epinephrine and norepinephrine

These hormones increase heart rate and breathing; prepare body for action

The hypothalamus also stimulates the anterior pituitary to release a hormone that
causes the adrenal cortex to release adrenal steroids such as cortisol

These hormones act more slowly but also prepare the body for action by releasing
stores of energy

Hormonal responses to stress were studied in military recruits learning to parachute

slide 25

tbd see if this is covered in class on fri