Unit 2. REWARD
Unit 2. REWARD
1.
Nature of motivational systems
2.
Reward neural system
3.
Motivation and addiction
Pixabay.com
The concept of motivation is a useful summary concept for how an individual’s
past history and current state interact to modulate goal-directed activity.
Eating, drinking, having sex, and displaying maternal behavior are all activities
that are essential for the survival of the individual and the species. In the course
of evolution, natural selection has associated strong feelings of satisfaction with
these behaviors that meet such basic needs.
Motivational Systems
Neurobiological processes that direct the body to look for stimuli or
situations that ensure its survival and well-being at a specific time
(adaptation: biological importance)
Motivational State
Internal conditions (physiological factors, including neuronal) that
direct a behavior, orienting the body towards a goal or incentive
Impulse that initiates, guides and maintains the behavior, to reach the desired goal or
objective
Hunger
Ingest
Food
Objective (incentive):
Stimuli or situations that exist in the external environment, towards which
motivated behavior is directed
- They are usually associated with pleasure (or reward) and are called
“Reward stimuli”
The ultimate goal of motivated behaviors is satisfying specific needs
They form part of the regulatory processes of homeostasis
Maintenance of equilibrium and of internal stability (the
organism must actively maintain)
But... there is not always a homeostatic imbalance or internal deficit:
External triggering stimuli (incentives) have appetizing
and reinforcing properties
Incentive Motivation
MOTIVATION
Regulator / Homeostatic
To regulate internal balance
(homeostasis)
No Regulator / Incentive
Aimed at external stimuli with
incentive properties
(hedonism, anticipate the reward)
Regulator / Homeostatic
Motivational state
No Regulator / Incentive
Interaction
Incentive
Motivated behavior
• Strong motivation increases the attractiveness of a weak incentive
• Attractive incentives tend to increase the strength of a motivation
Unit 2. REWARD
1.
Nature of motivational systems
2.
Reward neural system
3.
Motivation and addiction
Pixabay.com
How does your brain help you find a goal?
How does your brain help you pursue that goal?
A veritable reward circuit evolved to encourage these
behaviors. Subsequently, this circuit expanded to encourage
us to repeat other pleasurable experiences that we learn in
the course of our lives.
1. VENTRAL TEGMENTAL AREA
This midbrain area produces dopamine and
forms part of one of four major dopamine
pathways in the brain. Affected by drugs
including nicotine, alcohol and opioids (eg
heroin).
2. NUCLEUS ACCUMBENS
A small region in the forebrain with ancient
evolutionary origins, which helps regulate
survival drives like food and thirst. Affected
by drugs including cocaine, amphetamine,
cannabinoids (eg cannabis) and opioids (eg
heroin).
https://bigpictureeducation.com/brains-reward-system
3. PREFRONTAL CORTEX
Part of the frontal lobe that is involved in
many cognitive functions, including
memory, language, planning and decision
making.
3 DOPAMINERGIC PATHWAYS
Functions of the reward system
1- Mesolimbic DA system (VTA / ACC)
ALLOWS DETECTION OF the presence of the REWARD stimulus and
associated stimulus
Reward prediction and "salience"
(novelty, unexpected
reinforcement, effort...)
Functions of the reward system
2- The Mesocortical DA System is also involved
Allows assessment of aspects related to reinforcement (planning strategies,
estimation of cost / benefit to achieve a goal, adequacy of behavior...)
Functions of the reward system
3- The Nigro-Striatum DA System (SN dorsal striatum)
Striatum (caudate, putamen)
SN
Allows automatic motor behavior, by habit to achieve reinforcement
ACC, CPF
dopamina
ATV
Dopamine provides predictive value (detection)
and gives meaning (assessment) to stimuli, with
positive and negative reinforcing value ("desire")
Endogenous opioids
(encephalins and
endorphins) provide the hedonic value of the
reward
Other NT (GABA, glutamate...)
Reward Error Prediction
ATV neurons respond according to the
discrepancy between the reward and its
prediction (prediction error).
-
Unexpected reinforcement +
•
Reinforcement predicted no response
•
Default of prediction -
- The neurons of the nucleus Acc increase the
DA when there is a discrepancy between the
expected reinforcement (expectation) and
the received (occurrence).
Satisfaction = Result - Expectations
Sistemas MOTIVATIONAL SYSTEMS
REWARD-REINFORCEMENT
LEARNING AND MEMORY
Motivation, drive, expectance
Increase Opioids Acc
Cognitive control (making decisions,
planning)
Volkow et al., 2003
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