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19 Apr 2012
Visceral motor system is pre-dominant motor output for emotion
Emotion mediates many of the autonomic functions (both parasympathetic and sympathetic innervation)
Researchers can measure things about emotion by measuring variables associated with output for visceral motor system
Stimulation of emotional system exhibits high degree of situational specificity (i.e diff ppl in same situations show similar emotional responses and visceral motor responses)
however difficult to apply this to general population b/c patterns of activation for one indvl not necessarily the same to another indvl
recognition that there is reciprocity in rship btwn outward expression of emotion and autonomic activity
experiment: trick ppl into posing faces recognized as anger/disgust/happiness/fear/sadness/surprise results in changes in autonomic activity normally associated with that action. Doesn’t
work with pain or terror
used a technique for electrical stimulation (Galvonic stimulation) that directly causes muscle contractions
puts electrodes on various muscles on the face and record results
2: bilateral stimulation of the two cheekbone muscles = characteristic smiling (lower face) but upper face has no changes (compare this to 3, a spontaneous smile)
this experiment led to the theory that diff regions of the brain control the expression of the muscles of the upper and lower face during natural face expressions
4: no discomfort despite looking in pain
two indp systems control mvmnts used for facial expressions
• volitional: controlled by descending pyramidal projections from motor cortex and brainstem. Synapse on motor neuron pools in facial nucleus
damage: lose voluntary control over ability to regulate facial muscles
Neural systems for emotional expression
Damage: can control facial muscles voluntarily, but cannot control involuntarily (i.e. no spontaneous smile from a joke)
Left (damage to volitional mvmnt)
Cannot move left side of mouth
Nearly symmetrical spontaneous smile
Right (damage to neural system for emotional expression)
Can smile voluntarily
Despite finding joke funny, cannot spontaneously smile
Lesions that interrupt communication btwn hypothalamus and cortex cause “sham” rage
Stimulating certain parts of hypothalamus induces same “shame” rage, presumably b/c disrupting normal circuitry control btwn cortex and hypothalamus
Hypothalamic control is mediated by diffuse system of neurons that runs through the brainstem, called the reticular formation
Typically divided into two parts
raustral (mesencephalic + rostral pontinue reticular formation) modulates forebrain activity
caudal (caudal pontine + medually reticular formation) involved in premotor coordination of both lower somatic and visceral neuron pools
somatic motor system (non-volitional) and visceral motor system co-modulated by reticular formation
limbic system
Papez circuit thought to be primary loop of anatomical brains structures controlling emotion (initial beliefs, which have since been changed)
Many structures anatomically connected in the limbic system don’t have specific functions in emotion
Update to beliefs: hypothalamus still involved, now also include orbital and medial prefrontal cortex, amygdala, and larger parts of cingulate gyrus
Role of amygdala was discovered by accident by Kluver and Bucy. By removing bilateral medial temporal lobes (destroyed many structures involved in emotional processing) observed Kluver-
Bucy syndrome:
visual agnosia without blindness (monkeys didn’t recognize normal objects
Bizarre oral behaviors: put things in their mouths
Marked changes in emotional behavior
These symptoms similar to ppl with damage to medial temporal lobes
The emotional symptoms often seen when damage to amygdala occurs
Behavior of animal dpded on eye used to see
Ipsilateral to lesion: similar behavior to Kluver-Bucy syndrome
Contralateral to lesion: normal, fearful, aggressive behavior
Touch animal to either side: normal (thus somatic sensory info still contacted good amygdala, but visual info access dpded on side of body)
Initially when brain imaging techniques, provided support for amygdala for specialized ‘fear area’ of the brain
Urbach-Wiethe disease: these subjects have specific destruction of amygdala and related structures, but sparred remainder of brain
Rings show missing amydala
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