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MODULE 2 - Coggle Diagram

- - - - a temporary interruption in the tonic firing of cholinergic interneurons in a response to a cue that is important in a behavioural context
      - tonic ACh release inhibits the release of phasic dopamine so prevents LTP but the PAUSE response removes this block and amplifies phasic dopamine release -> LTP
    - - phasic dopamine inhibits ACh by turning on D2 receptors on cholinergic neurons
      - there is overactivity of cholinergic system in PD (which we know has loss of dopamine)
      - during reward conditoning, phasic dopamine strengthens excitatory synapses onto cholinergic interneurons
      - continued expression of the pause response in cholinergic interneurons requires dopamine
      - phasic dopamine release is amplified during a pause
      - the pause response is thought to be a temporal window during which corticostriatal synapses can be modifed by DA
      - a pause releases the ACh block on LTD mechanisms
      - a pause releases the block on dopamine release and amplifies phasic dopamine -> LTP
    - - cholinergic interneuron releases ACh onto muscarinic M1 receptor which inhibits L-type calcium channel. calcium cannot enter cell it blocks LTD
    - - tonic dopamine activates D2 receptors on cholinergic interneurons which reduces the ACh release. this means the L-type calcium ion channel is not blocked allowing calcium to enter the cell. Calcium can then work on endocannbinoid production which will signal to presynaptic to limit glutamate production which is LTD
- - - - reinforcement: learning the strategy in a given situation that maximises the chance of a successful outcome. process of strengthening associations between a stimulus and a response
        
        THORNDIKES RULE: movement thats been reinforced is more likely to be selected
        
        can be stored as an option for later selection
        
        reinforcement helps us bias our selection towards the strategy in a similar situation in future
      - how to bias / reinforce selection?
        
        DOPAMINE
        
        evidence:
        
        can measure dopamine in striatum in response to rewarding stimuli
        
        dopamine cells are activated to fire by rewarding stimuli
        
        electrical stimulation of dopamine pathways is rewarding = rats will self-administer electrical and optical simulation of dopamine pathways
        
        drugs which block dopamine receptors reduce the effectiveness of rewards - press lever less after receiving D1 antagonist
        
        loss of dopamine in PD results in a loss of habitual behaviour which has been established through reinforcement learning
        
        LTP
        
        phasic dopamine
        
        must be 2 seconds after salient stimuli
        
        amplifies the channels neural input by increasing the value of a stimulus in the cortex
        
        glutamate depolarises cell so that the mg+ ion blocking the NMDA channel unblocks. this lets calcium through to the cell. phasic dopamine enters cell increasing levels of cAMP. cAMP and Ca2+ together phosphorylate the AMPA receptor. This means that with the next wave of glutamate a higher current will be produced and this is LTP
        
        postsynaptic
      - selection: the most appropriate movement , sensation, idea based on experience
- - - - sensorimotor claibration / skill =
      - structure = very uniform over its entire surface
      - re-entrant loop = structure of origin -> pons -> cerebellum -> thalamus -> structure of origin
    - - re-entrant loop with entorhinal cortex
      - emotional, episodic, spatial
    - - selection of most appropriate movement, sensation, idea, memory based on experience
      - reinforcement learning of the strategy ina. givne situaiton that maximises the chance of a successful outcome
      - re-entrant loop: cortex - striatum (BG input) - pallidum/nigra (BG output) - thalamus