Mesocorticolimbic System
What was the key finding from Olds and Milner's 1954 study?
Brain stimulation activates neurons in the ventral tegmental area, which are midbrain dopamine neurons that form most of the mesolimbic and mesocortical projections involved in reward
True or False. DA neurons are projection neurons
True. All cell bodies are located in the midbrain send axons to many brain regions
Ventral tegmental area is the heart of the mesolimbic DA system. Where does it send DA axons to?
It sends DA axons via the medial forebrain bundle to limbic regions such as PFC, amygdala and nucleus accumbens regions of the ventral striatum.
What are three ways to test level of motivation?
1. Progressive ratio
-To measure instrumental costs you make the reward progressively harder to get
2. Difficult vs easy instrumental responding
-Have a difficult task to get good reward or and easy task for regular food -- getting sucrose after a hard task vs getting regular chow easily. If you increase DA the animal is more likely to work hard to get the reward, if you decrease DA the animal doesn't work as hard to get the reward and is more likely to eat the chow.
3. T-maze barrier
-The animal has the option to jump a 30cm barrier to recieve a good reward or have free access to regular food
Compare instrumental vs consummatory phase
Instrumental Phase:
DA dependent
Approach/ avoidance behaviours--'seeking part,' how willing the animal is to get the reward
Consummatory phase
DA independent
Direct interaction with the goal stimulus