W2L1: Dopamine and Desire

dopamine: pathways

projects locally at basal forebrain: Ventral Tegmental Area (VTA) and Substantial Nigra (SN)

dopamine: function

reward system, influences motivation, learning, movement, mood, satisfaction

dopamine: pathways: VTA

Ventral Tegmental Area responsible for motivation, emotional response, reward, desire, addiction

dopamine: pathways: substantial nigra

responsible for motor control

dopamine: synthesis

get dopamine from tyrosine, amino acid converted into L-DOPA and then converted to dopamine in brains (one step away from noradrenaline)

dopamine: tyrosine

amino acid found in food (cheese, nuts, avocados)

dopamine: synthesis: L-DOPA

can boost dopamine by giving people this drug (often given to people with Parkinson’s disease)

dopamine: L-DOPA presctiprion: Parkinson’s

Upregulates natural L-DOPA so that in conjunction with enzymes end up producing more dopamine to compensate for cell loss occurring in substantia niagra that happens during Parkinson's

Parkinson’s

caused by death of dopamine cells in substantia nigra

Parkinson’s: L-DOPA: don’t use

not recommended for people with psychosis because it can lead to neuroleptic sensitivity because of role dopamine plays in underpinning and driving psychotic symptoms

dopamine: reward prediction error: unexpected reward

dopamine neurone become more active and release burst of dopamine

dopamine: reward prediction error: repeatedly given reward after stimulus

reward will be expected and no dopamine will be released with reward but will now be released at time of stimulus presentation

dopamine: reward prediction error: if reward is expected but not provided

dopamine neurons will be suppressed

dopamine: value-modulated attentional capture task (VMAC)

designed to measure propensity to learned reward-related cues at expense of adaptive functioning/goals

dopamine: value-modulated attentional capture task (VMAC): findings

the more points given to a task the worse the performance because attention is captured by high value reward cue rather than the task itself

dopamine: cognitive control and reward

dopamine codes both goal reward and effortful costs and aversive feeling of cognitive effort reflects opportunity cost

dopamine: cognitive effort and reward

task persistence is justifiable only while progress outpaces accruing costs

gambling

brains are bad at encoding real value of things - easier to encode positive unexpected high wins (not able to balance cost-benefit ration of what is capitalised)

drug addiction

chronic relapsing disorder which consists of a compulsive pattern of drug-seeking and drug-taking behaviour

drug addiction: crux

about reward-anticipation - huge rush when anticipating/ craving drugs (even when performing act of taking becomes less rewarding over time feeling of anticipation have power)

dopamine: drugs: cocaine

blocks reuptake of presynaptic neurotransmitter transmitter (excess dopamine in synaptic cleft which continues stimulating post-synaptic neuron)

dopamine: drugs: amphetamines (ice and speed)

reverses uptake transporter actively expelling dopamine and noradrenaline out of neuron which prevents dopamine uptake

dopamine: drugs: amphetamines: cell death

because neurotransmitters are being flushed out and prevented from reuptake (over excitation and toxic processes)

drugs: addictive nature

how quickly you receive a reward after any reward cues (when reward is much later than cues it isn’t as addictive)

dopamine: drugs: levels released

more dopamine released greater the high produced by drugs like cocaine and ice

drugs: addiction and free will: cognitive control

“top down” control is reduced by impaired function of prefrontal cortex (PFC) caused by excessive dopamine (can’t provide homeostatic control and are overwhelmed - bottom up excitation)