Motivation and Reward 2 Flashcards
(37 cards)
Reward directed activity depends on what ?
predictability of stimulus
Phasic activity of A8,A9 and A10 neurons is increases by ?
surprising rewards
phasic activity of DA neurons is decreased by ?
omission of predicted rewards
Prediction error
difference between the reward obtained
and the reward that was predicted
If reward occurs unpredictably after a certain action
is prediction error pos or neg ? does learning occur ?
prediction error is positive and learning occurs
if reward is predicted, prediction error is ?
0 = no learning
nucleus accumbens is the primary target for which DA neurons ?
VTA A10
also recieves from motor pathway, hippo c and amygdala
nuc accumbens is divided into two sections ?
lateral “core” (extension of striatum)
medial “shell” limbic- like
Afferent connections to nuc accumbens ?
basolateral amygdala, PFC, hippocampus, VTA
Efferent connections to core ?
core -> through dorsal pallidum, STN and SN -> motor thalamus ->premotor cortex
Efferent connections to the shell ?
shell -> subcortical limbic regions including LH,
VTA, ventral pallidum
nuc Accumbens integrates
motor, limbic and reward predicting info
motor - BG
limbic - amygdala
reward predicting info - VTA
Role of nucleus accumbens in unconditioned reward
Wise (1978) – ‘Anhedonia hypothesis’: DA projections to NAc mediates hedonic aspects of rewarding stimuli
Berridge & Robinson (1998) – DA in NAc mediates incentive salience of rewards ie. promotes motivational aspects of goal-directed behaviour
Ikemoto & Panksepp (1999) - DA in NAc enables responses to novel events, discerning of meaning of external stimuli
Salamone et al (2003) – DA in NAc is required to overcome larger response costs to obtain rewards
Recent studies- fast, phasic changes in DA release in NAc dynamically modulate a variety of reward-directed behaviours
Role of nucleus accumbens in conditioned reward
Setlow et al (2003) - As animals learned to associate (pair) olfactory cues with rewarding sucrose, the cues evoked phasic responses in an increasing number of NAc neurones
Roitman et al (2005) - NAc neurones developed responses to reward-predictive audiovisual cues in operant conditioning task
Ability of conditioned stimuli to evoke changes in NAc neuronal activity increases with increasing strength of stimulus-reward associations
Following pairing, the CS evokes stronger excitation in
individual cells than does the reward itself
associative learning processes is mediated by ?
are mediated by DA transmission in the core
primary reinforcement (reward value) is mediated by ?
is mediated by DA transmission in the shell
lesions or antagonist in what part of the nuc accumbens impairs conditioned approach behaviour ?
core
Role of ventral pallidium in reward ?
Part of BG
NAc projections to ventral pallidum
translate limbic motivation signals into motor output (‘Limbic -motor integration’)
Lesions of ventral pallidum
(without damaging LHA) impair motivation for ?
eating.
Also, lesions replace normal ‘liking’ for sucrose with ‘disliking’
necessary for liking component towards food
Three dissociable components of reward?
‘Liking’ (hedonic impact)
‘Wanting’ (incentive salience)
Learning (predictive associations)
Where are the hedonic hotspots ?
NAc shell and posterior ventral pallidum
DA anatagonism. how does it affect liking and wanting ?
reduces wnating but liking (amphetamines have the opposite affect.)
when rats are described as sign trackers ?
they pay more attention to the lever in order to get food - predictability focused
Goal trackers?
pay more attention to the food tray - wanting focused
