Emotions
Refer to cognitive + behavioral responses that are largely
a) automatic
b) unconscious
–> triggered when the brain detects a positively/negatively charged significant stimulus
Regulatory mechanisms of emotions are mostly mediated by … ?
- Amygdala
- Striatum
- Hypothalamus
- Brain stem
Feelings
Refer to the conscious perceptions of emotional states
Emotionally competent stimuli
Refer to Stimuli that are naturally significant to trigger emotions
–> other objects/events acquire their significance through association with those
In which way can be said that the responses of autonomic NS are specific ?
There are different patterns of ANS activity that correspond to different situations + their associated emotional states
How is the neural activity relayed ?
- Forebrain
- Hypothalamus
- ARAS
James peripheral feedback theory
Suggests that feelings come about when the bodily expression of that emotional response enters consciousness
–> only involvement of the cortex, but later re-movement of it showed that you can still feel emotions
Cannon + bards central theory of emotions
Suggests that sensory info is processed in the thalamus
- Sent to
a) hypothalamus
- -> to produce emotional responses
b) cerebral cortex
- -> to produce conscious feelings
Bard experiment
Involved cutting out cerebral hemispheres out of monkey, where a sham rage (rage with absence of aggressor) only occurred when the caudal hypothalamus was lesioned
- Hypothalamus is critical for coordination of somatic + visceral motor components of emotional behavior
- Subjective experience of emotion depends on the cortex, whereas the expression of coordinated behaviors doesn’t
=> Hypothalamus is responsible for the brains evaluation of the emotional significance of stimuli + reactions that depend on this appraisal
Circuit of papez
- Hypothalamus
- -> mammilary bodies - Thalamus
- -> anterior thalamic nuclei - Cingulate cortex
- -> here the signals are converged to produce feelings - Hippocampus
- -> parahippocampal Region - Hypothalamus
McLean later fond the “visceral brain” that was later renamed the limbic system
Included amygdala to the circuit + the subcortical regions that are connected to it
–> thought the hippocampus was the point of convergence
Why did McLean think that emotional responses involved relatively primitive circuits ?
Because, he saw emotional responses as essential for survival
–> then realized that emotional states + cognitive processes involve distinct circuits that can functionally be relatively independent
Klüver-Bucy syndrome
Refers to abnormal/non-emotional behavior seen in monkey after the removal of most of limbic system, then later just amygdala
–> no fear in response to aversive stimuli
How was the Klüver-Bucy syndrome explained ?
Previously:
Circuit of papez was interrupted
Now:
Removal of amygdala is enough to elicit this
LeDoux conducted conditioned fear experiments.
What were his main findings ?
- MGN in hypothalamus is necessary for the development of conditioned fear response
- Response is still there when connectivity to the auditory cortex was cut, so there had to be a direct pathway
- Amygdala establishes the association between neutral stimuli + stimuli with reinforcement value
- -> LTP
Neural circuit of fear conditioning
- Sensory input reaches lateral nucleus indirectly + directly
- Amygdala + cortex are activated simultaneously
–> so amygdala can process info before we can consciously feel it
How are unconditioned (innate) fear responses processed in the brain ?
Are mediated by the olfactory system to the medial amygdala
–> relies on odors
Name the input vs output source of the neural circuit of fear conditioning
- Lateral nucleus (input source)
- -> receives info about CS from thalamus - Central nucleus (output source)
- -> project to hypothalamus
Does simply telling about a CS or watching someone else, enough to elicit a subsequent fear response ?
Yes, as
- Amygdala is involved in implicit learning
- Hippocampus is involved in explicit learning
Role of the orbital + medial frontal lobes
Associates info from the sensory modalities + integrates those
–> influence the content that was retrieved from memory to shape a mental response plan parallel to the amygdala
The amygdala has additional varieties of connections to cortical areas to be able to modulate
a) attention
b) perception
c) memory
d) decision making
Name these connections.
- a) amygdala
b) thalamus
c) orbital + medial frontal lobes - a) amygdala
b) Basal ganglia
- -> which receives info from the PFC
=> amygdala influences the selection + initiation of behaviors and obtains rewards vs avoids punishment
Volitional movement
Involve the classical motor areas of the voluntary somatic motor control
–> cortex –> brainstem
Emotional expression
Involves the descending projections from medial + ventral forebrain
- Termine on visceral motor centres in
a) reticular formation
b) somatic motor neuron pools
- -> also receive info from volitional centre
Reticular formation
Receives info from + projects to
a) somatic
b) autonomic
effector systems in brainstem + spinal cord
