noradrenaline, arousal, decisions and anxiety Flashcards
noradrenaline
- tyrosine- same for DA and NA
- L-DOPA
- dopamine
- NA
additional synthesis step in the adrenal gland results in the hormone adrenaline (drives effects in the body)
NA
Thalamus, hypothalamus, amygdala. Sympathetic nerv system, arousal, anxiety, exploitation vs exploration (about how the brain focuses its attention and decides on an behavior), reward and addiction, memory consolidation.
Locus Ceruleus- neuron firing
- highest rates rapidly follow a transient noxious or extremely positive stimulus/event
- silent during REM sleep
high LC and NA
- fight, flight, freeze or fornicate
- state od hyperarousal adapted for evolutionary important situation where individual or sexual fitness is involved
states that high levels of LC and NA bring
- stress: often experienced when LC/NA activity is sustained due to environmental factors
- anxiety; excessive, uncontrolled and often irrational worry
panic attacks: brief intense episodes believed to reflect spikes of LC/NA activity triggered by random events, internal thoughts - decn making and adaptive behavior
stress and arousal
stress response involves intricate interaction between the brain and body
- optimal performance require balance, function is impaired with tool little or too much stress
NA function beyond arousal
- at moderate levels of LC activity, noradrenaline acts to consolidate decisions
- adaptive behavior represents the trade-off between exploiting known sources of reward and exploring the environment for alternative sources of reward
exploitation vs exploration
- both learned associations between making decision between something wanted right now and waiting for something rewarding
NA and behavioral selection
- NA involved in coding for representations in the brain which represent different behaviors.
- competition play out, burst of NA release ‘tips of balance’ in favor of winning (increases strength) of activating and inhibiting signals
- competition resolved selection completed
- the more important or arousing one of the alternatives is the bigger the burst of LC neurons and the more NA released
LC neurons and behavioral selection
- after they fire the neurons are inhibited allowing the selected behavior to be ‘exploited’
LC neurons and high arousal
- the larger the response of neurons in the LC, the more NA released and the longer the following period of inhibition
- in highly arousing situations the chosen focus of attention dominates them for longer- so the distracting alternatives are inhibited
LC neurons during low arousal
- in the absence of recent decisions or arousing events the baseline levels of firing increase and more NA is released throughout the brain.
- increased NA promotes a switch to a new decision, promoting ‘exploration’ of alternative behaviors
LC-NA and performance
- low levels of LC activity and NA release= tired, vague and poor performance
high levels of LC activity and NA release: restless, stressed and poor performance - optimal performance requires moderate activity with large intermittent bursts
ambiguity and perceptual competition
- In the case of perception there is a need to balance our perception.
- Role of noradrenaline in behavioral processes
NA and the pupil
- in the dark, dialation reflects NA levels,
- is there any relationship between pupil diameter and timing of perceptual switch?
