Problem 5 Flashcards
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
Forced smile
Involves the voluntary contraction of the facial muscles
–> pyramidal smile, driven by motor cortex which communicates with brain stem + spinal cord via pyramidal tract
Spontaneous emotional smile/
Duchenne smile
Is motivated by the motor areas in the anterior cingulate gyrus
–> facial muscles are accessed via multi synaptic extrapyramidal pathways through the reticular formation
What does the activation of the hypothalamus generate ?
Motivational states + their associated affects
–> eating, drinking
Central patterns controllers
Are cell groups that generate motivational states
–> connect to the midbrain + spinal cord to control the generation of actual movement (primitive actions)
Non-limbic system arousal
Is evoked by stimulating the ARAS in the brainstem
–> leads to arousal when we encounter novel/unexpected stimuli
BUT: Habituation with repeated exposure
Limbic system arousal
Is evoked by increased motivation + strong negative/positive affect, by receiving input by visceral sensory structures
a) negative affect
- -> central grey area
b) positive affect
- -> VTA
BUT: resistant to habituation
Name the structures of the limbic system.
- Cortex
- Limbic cortex
- Olfactory system
- Intermediate level
- -> amygdala + hippocampus - Hypothalamus
The more an animal depends on learning to develop its full potential of meaningful behaviors, the more it is affected by a removal of the hypothalamic + forebrain regions.
Why is that ?
Forebrain is important in linking species typical action patterns
–> learning instinctive movements
Memory subsystems
- EM division
- -> circuit of papez - Spatial memory/orientation division
- -> parahippocampal circuit
Emotional subsystem
- a) amygdala
b) stia terminalis
c) septal nuclei + pre-opic nucleus of hypothalamus - Main output channel
- Nuclei are responsible for emotional expression
Olfactory system
Includes the
- Primary olfactory cortex
- Amygdala
- Hippocampus
–> which are closely connected within the uncut
BUT: input of odors occurs via amygdala to categories objects/events
Limbic cortex
Is the high end side, involved with the cortex + voluntary behavior
Cortex
Includes the default mode network
–> affect related, has 2 subcortical networks
a) hippocampal-diencephalic circuit
b) Temporo-amygdala-orbitofrontal network
=> PCC + ACC are connected via the dorsal cingulum, are active during “resting state”
Hippocampal-diencephalic circuit
Connects the memory subsystem via the cingulum with the PCC
–> PCC is first major medial hub of default mode network
Temporo-amygdala-orbitofrontal network
Connects the amygdala via the orbitoinsular cortex with ACC
–> ACC is the second major hub of default mode network
AND: Integrates the visceral + emotional states with cognition + behavior
Anxiety disorder
Stress response occurs when the central nucleus of amygdala is active
–> inappropriate response –> HPA-axis hyperactive –> degeneration of hippocampus
VICIOUS CYCLE
Monoamine hypothesis
Affective disorder
Mood is tied to levels of released monoamines in the brain
–> depression results from a deficit on one of the diffuse modulatory systems
Diathesis-stress hypothesis
Suggest that the HPA-axis is the main site of where genetic + environmental influences converge to cause mood disorders
Diathesis
Having a predisposition for a certain disease
What does the limbic lobe consist of ?
Parahippocampal region + cingulate gyrus
–> cingulum connects it (white matter)
Where does hebbian learning take place ?
Lateral nucleus
–> US and CS converge on here
What do lesions of the amygdala lead to ?
No implicit learning of US + CS, so no emotional learning and physiological learning
–> BUT: declarative memory of it
