Task 5 - limbic system Flashcards
emotions vs feelings
- automatic, largely unconscious behavioral and cognitive responses
- > triggered when brain detects positive/negative charged significant stimulus
-feelings: conscious perception of emotional states
Physiological changes
- changes in activity of the visceral motor (autonomic) system
- increase/decrease in heart rate, cutaneous blood flow (blushing or turning pale), piloerection, sweating, gastrointestinal motility
- > changes in sympathateic, parasymoathetic and enteric components of visceral system
visceral motor system
- controls involuntary functions mediated by the activity of smooth muscle fibers, cardiac muscle fibers, and glands
- 2 divisions: the sympathetic and parasympathetic subsystems
sympathetic division of visceral motor system
-mobilizes the body’s resources (metabolic and others) for dealing with challenges of one sort or another
parasympathetic division of visceral motor system
-predominates during states of relative quiescence, so that energy sources previously expended can be restored
responses of autonomic nervous system are specific
- different patterns of activation characterise different situations their associated emotional states
- each pattern of facial muscle activity (instructed) causes different visceral motor activity
->responses are stronger the closer the facial expression resembles an actual emotional expression (then also accompanied by subjective experience)
2 systems of integration of emotional behaviour
-2 distinct systems:
1) Volitional movement:
- classical motor areas of voluntary somatic motor control
- cortex + brainstem
- basal ganglia, cerebellum
2) Emotional expression:
- from medial + ventral forebrain -> terminate on visceral motor centers in reticular formation + somatic motor neuron pools (also receive info from volitional centres)
- > runs in parallel to volitional motor system
Facial expression fake vs real
Fake:
- voluntary contraction of facial muscles
- pyramidal smile: driven by motor cortex which communicates with brainstem + spinal cord via pyramidal tract
real:
- spontaneous emotional smile (Duchenne smile)
- motivated by motor areas in anterior cingulate gyrus
- access facial muscles via muli-synaptic extrapyramidal pathways through reticular formation
-> depending on which one is lesioned, you can either not produce an actual or a fake smile
Limbic system
- orbital and medial PFC
- ventral party of basal ganglia
- mediodorsal nucleus of the thalamus
- amygdala
- parahippocampal gyrus
- cingulate cortex
- hypothalamus
Amygdala location
- complex mass of grey matter buried in anterior-medial temporal lobe
- rostral to hippocampus
Amygdala - 3 major subdivisions and functions
1) medial group of nuclei
2) basal-lateral group
3) central group
Klüver - Bucy syndrome
- abnormal behavior seen in monkeys after removal of much of limbic system (medial temporal lobe, amygdala included)
- didn’t show fear in response to aversive stimuli anymore
- first reasoning: interruption of pathways explained by Papez
- later: demonstrated that removal of Amygdala alone was enough
-Downer removed amygdala on only one side
- amygdala gets somatic sensory info from both sides of the body
- BUT klüver-bucy symptoms only seen when monkeys saw with eye on side of the lesion
LeDoux conditioned fear experiments
-Medial geniculate nucleus in hypothalamus necessary for development of conditioned fear response (of a tone)
- responses were elicited when connections of auditory cortex to MGN were severed
- > there has to be a direct pathway
- if MGN to Amygdala was also severed -> no fear response anymore
- > amygdala establishes associations between neutral stimuli and stimuli with reinforcement value
Basal-lateral Amygdala
- major connections with PFC and hippocampus
- memory
central and anterior Amygdala
-major connections with hypothalamus
brainstem
- > important role in expression of emotional behaviour
- > by influencing activity in both somatic and visceral motor efferent systems
Connection Amygdala cortex
function
- to modulate attention, perception, memory and decision making
- amygdala influences selection and initiation of behaviors aimed at obtaining rewards and avoiding punishment
- accounts for subjective feelings of emotional states as they need cognitive self-awareness
amygdala and orbital + medial frontal lobes
- associate info from sensory modalities and integrate those
- influence content retrieved from memory and help shape mental response plans parallel to amygdala
- amygdala -> thalamus -> orbital and medial frontal lobes
endocrine system
-responsible for secretion and regulation of hormones into the bloodstream that affect bodily tissues and brain
Early theories - William James’s peripheral feedback theory
- emotional stimuli processed in sensory systems
- > transmitted to motor cortex
- > produce emotional responses in body
- > feedback signals to cortex (info about body responses)
- > cortical processing of this sensory feedback is the ‘feeling’
Early theories - Cannon-Bard central theory
- emotions explained by processes within CNS
- sensory info to thalamus
- > to hypothalamus and cerebral cortex
- > hypothalamus evaluates emotional qualities of stimulus -> connections to spinal cord and brainstem -> gives rise to emotional response
-> from thalamus also to cortex -> conscious feelings
early theories - Papez circuit
- extended canon-bard theory
- added cingulate cortex (receives hypothalamic output and creates feelings)
- output of hypothalamus -> anterior thalamus -> cingulate
- output of cingulate -> hippocampus -> hypothalamus
very basic function thalamus
- relay station for sensory info (sight, hearing, taste, touch)
- > emotions are contingent on things you see/hear etc.
very basic function hypothalamus
- regulating autonomous NS (fight ,flight, freeze)
- hunger, thirst, sleep, sex
- > activation leads to motivational states (leading to eating, drinking etc)
non-limbic arousal (reticular)
- evoked by stimulating ascending reticular activating system (ARAS) in brainstem
- leads to arousal we experience when we encounter a novel/unexpected stimulus
- orienting response to novelty
- habituation with repeated stimulation
- input of mixed sensory nature
Limbic system arousal
- accompanied by increases in motivation and strong negative/positive affect
- negative effect = central grey area (=pariaqueductal grey)
- positive affect = VTA (ends dopaminergic neural projections to both the limbic and cortical areas )
- resistant tp habituation
- input: dominated by visceral sensory structures (=limbic areas)
-
Anxiety disorders
- stress response when central nucleus of amygdala is active
- > hyperactivity of Amygdala
- > diminished activity of hippocampus
- > both receive highly processed info from the neocortex
Stress response
- characterized by:
1. Avoidance behavior
2. Increased vigilance (Wachsamkeit) and arousal
3. Activation of the sympathetic division of the ANS
4. Release of cortisol from the adrenal glands
The hypothalamic-pituitary-adrenal axis and stress
- HPA regulates secretion of cortisol from adrenal gland in response to stress
- paraventricular nucleus of Hypothalamus releases CRH (corticotropin-releasing hormone)
- > arrives at anterior pituitary gland
- > releases ACTH (adrenocorticotropic hormone)
- > travels to adrenal gland above kidney
- > cortisol release
When CRH is overexpressed in genetically engineered mice…
…animals display increased anxiety-like behavior
regulation of the HPA axis by amygdala
- sensory info enters basolateral amygdala
- > central nucleus becomes active
- > activates paraventricular nucleus of hypothalamus
regulation of HPA axis by hippocampus
- hippocampus contains glucocorticoid receptors -> respond to cortisol released from adrenal gland (in response to ACTH)
- > inhibits CRH release when circulating cortisol levels get too high
Affective Disorders - short description
- mood disorders
- major depression
- bipolar disorder
Affective disorder - monoamine hypothesis
- mood is tied to levels of released monoamine neurotransmitters in the brain
- depression is consequence of deficit in one of these diffuse modulatory systems
evidence against it: antidepressants take a long time to work
Affective disorder - diathesis-stress hypothesis
- HPA-axis is main sight for genetic and environmental influences -> converge to cause mood disorders
- diathesis: term for predisposition for a certain disease
-must be a genetic predisposition or early childhood abuse/neglect -> you won’t develop enough receptors
cat experiment canon bart
- removed different parts of cortex
- if hypothalamus removed from brainstem -> no shamrage (emotional response)
-if forebrain desected -> still connection between hypothalamus and brainstem -> normal shamrage
LTP amygdala
…
Nieuwenhuys model
-2 circuits : 1 more around amygdala -> emotion 1 more around hippocampus -> memory
- hypothalamus: autonomous motor system, instinctive movements, creates motivational states
- hippocampus: memory
- extended amygdala: motivational states, emotions
- role of olfaction
lateral amygdala
-input from sensory info from hypothalamus and cortex
default mode network
- trennung von freund -> man denkt immer dran (aktives default mode network)
- > wenn man sich ablenkt (default node network schaltet sich aus)
- hippocampal dienceohalic circuit -> episodic memory, spatial orientation (in papez circuit, cingulate cortex )
- temporo amygdala orbitofrontal network (inhibiton, monitoring,
