week 12 Flashcards
Define Anxiety
An adaptive state of increased apprehension that helps an animal avoid potential danger, and it is associated with muscle tension and vigilance
An cautious or avoidant behaviours
Includes panic
Define Fear
Emotional response to real or perceived imminent threat
What does fear include?
surges of autonomic arousal necessary for fight or flight
Thoughts of immediate danger, and escape behaviours
What is anxiety related to?
Fear
It is not the same
What is anxiety a umbrella term for?
A variety of disorders
within DSM-5
What are the manifestations of anxiety disorder?
Both psychological and physical
What are examples of potential stressors?
- Failures
- Personal losses
- Frightening events
- Time precursors
- Insults
When the potential stressors are perceived as a threat, what is it subdivided into?
- Bodily effects
2. Upsetting thoughts
What are examples of bodily effects?
- Autonomic emergency response
- Shallow breathing
- Pounding heart
- Tense muscles
- Digestive problems
- Sleep disturbances
- Fatigue
- Psychosomatic illness
What are examples of upsetting thoughts?
- Anger
- Fears
- Preoccupations
- Self-doubts
- Negative self-talk
- Repeated ‘‘danger’’ thoughts
- Worry about body reactions and health
What does bodily effects and upsetting thoughts lead to?
Ineffective behaviour
What is an example of ineffective behaviour?
- Escape
- Avoidance
- Indecision
- Aggression
- Inflexible responses
- Poor judgement
- Inefficiency
- Drug use
What is ineffective behaviour’?
Behaviour you engage that has no actual purpose or produce no result
What is fear processing?
- Thalamus projects to amygdala
- Indirectly via the cortex (long pathway)
- Directly (short route)
- Amygdala connects hypothalamus: bodily manifestations of feat
- Output: run/freeze
Where is sensory stimulation interpreted in?
sensory thalamus
When do we respond very quickly to a stimulus?
When the stimulus evokes fear and bypasses the cortex
Engage in fear without thinking, simply start feeling very agitated
what are the main circuits involved in fear conditioning?
- sensory areas - process the conditioned and unconditioned stimuli
- certain regions of the amygdala that undergo plasticity
Where does fear reponse start in the brain?
Amygdala
What is amygdala dedicated to detecting?
Emotional salience of the stimuli
What does amygdala activate?
Areas involved in preparation for motor function involved in fight or flight
Triggers the release of stress hormone and sympathetic nervous system
leads to bodily changes that prepare us to be more efficient in a danger
What brain regions is closely connected to amygdala and what are their roles?
- Hippocampus
- Prefrontal cortex
Help brain interpret the perceived threat
Involved in higher processing of context
Where does the conditioned stimulus flow from?
The lateral amygdala to the central nucleus of the amygdala
What controls defensive behaviour i.e. freezing?
Pathways from central nucleus of amygdala to downstream areas
what does the hypothalamus ochestrate?
- Freezing or fleeing response and all the physical manifestation
where is amygdala located in?
Medial temporal lobe
composed of number of different nuclei
What is lateral nucleus?
primary nucleus input of the amygdala
It receives input from the thalamus and the cortex which provide it with information of the sensory stimuli the animal is experiencing
What is the primary output nuclei of the amygdala?
Central medial nucleus
Projects to a number of different structures
Where does the central medial nucleus project to?
- Paraventricular nucleus of the hypothalamus and triggers release of stress hormone cortisol
- Lateral hypothalamus - stimulating the autonomic nervous system
- Periaqueductal grey matter - which in mice causes fear behaviours such as freezing
What happens when the downstream targets are coordinated?
The amygdala is able to produce many of the physiological changes associated with feeling of fear:
- Increased heart rate
- Sweating
- Dilation of the pupils
What is fear conditioning?
When an animal learns to fear something
What happens in a typical fear conditioning experiment?
- A mouse is given an unconditioned stimulus which is inherently negative such as a painful foot shock
- causes a natural unconditioned response - the expression of fear
- Also uses a neutral stimulus e.g. a sound which on its own produces no fear
- When the neutral and unconditioned stimuli are presented , the animal learns the association between the sound and the shock
- A neutral stimulus of the sound is then able to cause the fear behaviour itself without the shock
What is related to fear conditioning?
The concept of fear extinction
When does extinction occur?
When the conditioned stimulus of the tone is presented repeatedly without the unconditioned stimulus of the foot shock
The animal gradually learns that the sound no longer predicts a shock
The association is broken and the fear behaviour is no longer displayed
What is amygdala thought to be?
Primary area of the brain responsible for fear conditioning
How does amygdala participate in fear conditioning?
- The unconditioned stimulus of the foot shock travels to the spinal cord to the thalamus and cortex
- Which both project to the lateral nucleus of the amygdala
- The synaptic input from the unconditioned stimulus of the shock is strong enough to excite lateral amygdala neurons
- Activation of neurons in the central medial nucleus and produces a fear response
What happens when the neuron encoding the shock and the neuron encoding the sound fire together?
Synaptic plasticity occurs
This strengthens the synapse between the incoming neuron carrying information about the neutral stimulus of the sound and the lateral amygdala neurons
What does the lateral amygdala neuron do?
Excite central medial nucleus and produces feeling and fear
What are the neuroanatomical regions involved in anxiety disorders?
- Amygdala: the central fear centre
- Locus Coeruleus: Norepinphrine secretion - stimulated by active HPA axis
- Septohippocampal GABAERGIC system
Amygdala: The central fear centre
- Crucial for fear conditioning
2. Lesion in humans demonstrated pivotal for storage and processing of emotional memories
Locus coeruleus: Norephinephrine secretion
LC stimulation generates panic attack
LC blockade decreases panic attacks
Septohippocampal GABAERGIC system
- Mediate anxiety and vigilance
- High concentration of GABAergic neurons and receptors
- Directly connected to LC
What does the stimulation of the stress response engage?
Locus Coeruleus
Generating excessive response to a fear stimulus
Within a non-clinical population, where will there be differences in?
presentation of certain phenotypes