Chapter 5 Flashcards
What are the three major systems of the motivation control system of the brain?
- Learning and memory system;
- Motor loop;
- Homeostatic Input.
What are the areas involved in the learning and memory system?
(Hippocampus and amygdala)
Cortex
What are the areas involved in the motor loop?
(Thalamus)
(Basal ganglia)
(Cortex)
What are the areas of the reinforcement system?
(Nucleus accumbens)
(Ventral tegmental area).
These combined are the mesolimbic dopamine system.
What area does homeostatic input influence?
The tegmental area.
What area does sensory input influence?
The Thalamus.
Where does the motor output come from?
The cortex.
What areas does the Hippocampus and Amygdala together influence?
The Cortex and Nucleus accumbens.
What does the Cortex influence?
(Hippocampus and Amgydala)
Motor output
Nucleus accumbens
Basal ganglia.
What areas does the Thalamus influence?
The cortex
What areas does the Basal ganglia influence?
Thalamus
What areas oes the Nucleus accumbens influence?
Basal ganglia
Ventral tegmental area
What areas does the ventral tegmental area influence?
Nucleus accumbens
What is addiction?
Abuse or dependence upon a drug.
DSM IV defines two stages:
Substance dependence: the need to use increased doses of the drug, withdrawal symptoms, unsuccessful attempts to cut down on dug use, and continued use in spite of the drugs harmful effects (needs three or more within 12 month period for diagnosis).
Substance abuse: more extreme, includes failure to fulfill major obligations at one’s job, at school, or family; recurrent problems with the legal issues; and persistent social or personal problems (need only one symptom for diagnosis).
What are the two necessary components of any system that controls motivation?
Must be able to energize or activate behviour
And it must be able to direct that behviour toward a particular goal and make sure the organism acts appropriately to obtain that goal.
Guided missile analogy: Needs a rocket motor to make it go, and must have guidance system that directs it to the right place.
Organism has a need: e.g., hunger - this is the rocket moor The guidance system is more complicated, but we are attracted to specific targets which have incentive (e.g., taste of sugar).
Describe activation within the motivation control system.
Activation arises when there is an imbalance or deficiency in some internal system, such as when the organism is hungry, this input stimulates the ventral tegmental area in the hindbrain. Axons from the ventral tegmental area are connected to the nucleus accumbens, and the ventral tegmental area stimulates the nucleus accumbens by releasing dopamine at its synapses. This makes up the mesolimbic dopamine system, which is the reinforcement system of the motivation control system.
Cells in the nucleus accumbens send axons back to the ventral tegmental area where they release an opioid like peptide neurotransmitter, forming a circuit.
The nucleus accumbens also sends axons to the basal ganglia, which, with parts of the cortex, belong to the motor loop.
Activation of the mesolimbic dopamine system for hunger will stimulate the motor system which causes a general increase in the activity of the organism.
How does the output of the nucleus accumbens affect the motor loop?
The output of the nuclleus accumbens normallly provides continuous inhibition of the motor system. When dopamine is released in the nucleus accumbens, it actually inhibits the inhibitory output to the motor system. This has the same effect s stimulating the motor system.
Explain how the motivation control system guides an organism.
The motivation control system receives sensory information about the environment. This information is processed by the thalamus and cortex, and then sent to the amygdala and hippocampuus which make up the learning and memory system. This system holds information about previously experienced stimuli, past actions and their outcomes.
With the aid of these memories it is determined whether these external stimuli are biologically significant (e.g., food, or a lever that ,when pressed leads to the presentation of food).
Behaviour is activated and directed so that the organism approaches objects in the environment and performs acts that have resulted in the restoration of homeostatic balance in the past. In this way, the motivation control system enhances survival.
What areas make up the learning and memory system and what does it do?
Hippocampus and amygdala - Holds information about previously experienced stimuli, past actions, and their outcomes.
Explain the reward learning hypothesis of dopamine function.
Learning and memory circuitry provides the basis for this hypothesis. Dopamine is implicated in the acquisition of operantly conditioned response-reward actions, classically conditioned stimulus-reward associations, and the coding of predictions about reward availability based on the presence of conditioned stimuli, that is, the guidance system.
How does the motivation reward system evolved?
Evolved so that an organism will be able to show maximum flexibility in a very wide variety of environmental conditions, thus ensuring its survival and increasing its chances of that it will pass its genes (including the genes that create this neural circuitry) along to another generation.
How does the motivation control system (MCS) work?
A need state occurs (e.g., hunger), it is detected by the MCS and the mesolimbic system is activated (Nucleus accumbens and ventral tegmental area = reinforcement system = mesolimbic system). This causes an increase in general activity. In the absence of any previous learning or relevant salient stimuli, this activity ensures that the animal will move around its environment and maybe find food accidentally.
Information associated with the discovery of food is stored in the cortex and hippocampus - incentive salience is given to stimuli that lead to this discovery (salience = stimuli will grab organisms attention in the future, incentive = animal will be attracted to them).
(Animal rummaging for food in the woods analogy)
In the future, when the animal gets hungry and the nucleus accumbens is stimulated by the ventral tegmental area, general activity will increase, but now the stones in the stream bed will draw the animal’s attention, it will be attracted to the and consequently find food.
The stones, the streambed, and the act of turning over the stones then acquire more incentive salience. These stimuli will then have the power to activate the nucleus accumbens, so the organism will tend to approach and spend time there, even if it is not hungry.
How do stimuli lose their incentive salience?
If there is a drought the water will dry up and no food will be under the rocks. After turning over a number of rocks and not finding any food, the behaviour will extinguish, the stream bed will lose its reinforcing and incentive value, and the activation caused by the huger would drive the animal to seek food in other places.
Explain the role of dopamine in the Motivation control system.
Surge of dopamine in the nucleus accumbens is clearly correlated with changes in the animal’s behaviour caused by reinforcement, but how does it guide behaviour?
Mice genetically manipulated to have no dopamine and mice genetically manipulated to have excess dopamine learn the same as normal mice. So dopamine surge is not responsible for acquiring the stimulus-reward association.
Dopamine may contribute to learning indirectly, through the enhancement of attention, motivation, rehearsal and memory consolidation rather than a direct “teaching” role. The dopamine surge may be a consequence, rather than a cause, of associative learning and reward prediction.
How does dopamine play into reinforcement?
Incentive motivation. Stimuli associated with reinforcement are said to have acquired incentive salience; they are easily noticed, they capture the attention of the organism, elicit wanting, and motivate approach.
In the presence of these salient stimuli, the hippocampus, amygdala and prefrontal cortex stimulate the mesolimbic dopamine system via the nucleus accumbens. The nucleus accumbens then activates the motor loop via the basal ganglia. The motor output that results will be directed toward the significant stimulus (the food or lever), guide by sensory inpute received via the thalamus. Because behaviour is directed toward the significant stimulus, in a Skinner box, the lever will be pressed and the food will be eaten; in the natural environment, the rocks will be turned over and the grubs will be eaten. This outcome will then be stored in the learning and memory system and used to modify behaviour in the future, ether when the need arises or the appropriate environmental stimuli are present.
Explain the role of “liking” in reinforcement.
..
Describe the correlation between human and other animals self administration.
Thousands of studies have examined drug taking behaviour of animals and humans. Operant procedures can be used for both animal and human subjects. However, due to ethical reasons, only already addicted volunteers can participate in human studies.
Humans: Do tasks (such as exercise) to earn tokens that you can “spend” on a dose of drug.
However, some procedures allow other human volunteers. Volunteers report to lab every morning and are asked to swallow a capsule of a particular colour. On alternate days, they take a capsule of a different colour. Usually, one colour is a drug and the other a placebo. When they have been exposed to both, they are asked to choose which one they want to take. If the drug is a reinforcer, it will be chosen more often than the placebo. This procedure has the advantage of not being carried out in an artificial laboratory environment, but a considerable aount of precision is lost.
Explain the similarities between human and non-human self administration.
Type of drug: Comparisons of human and nonhuman behaviour in controlled studies have made it quite clear that there is a great deal of similarity between species. Lab animals will choose many of the same drugs that humans do.
However, some drugs have aversive properties that animals will try to escape from the drug infusion.
Pattern: Humans and nonhumans appear to self-administer similar drugs, but the patterns of their self-administration are also very similar.
What is positive reinforcement? How do you prove a drug is a positive reinforcer?
A positive reinforcer is any stimulus that increases the frequency of a behaviour it is contingent upon.
Provide rat with two levers: one gives no drug, the other gives drug on continuous reinforcement schedule.
Lever with drug pressed 8 - 12 times per hour, other lever not pressed at all.
Lever pressing for drug extinguishes if saline is administered instead of drug upon lever pressing.
What are the problems with the positive reinforcement model?
The positive reinforcement model:
Many addictive drugs have effects that are punishing enough to make an organism stop using them E.g., when a monkey is given unlimited access to cocaine it will often refuse to eat or sleep. Ultimately the monkey will die, and will mutilate itself in the process.
Many addicts will receive treatment to end their drug use. “If addictive drug use is on balance positively reinforcing, then why would a user ever want to stop?”
How do we explain the problems of the positive reinforcement model?
One of the reasons why positive reinforcing stimuli continue to control behaviour, in spite of punishing effects, is that they are immediately experienced after behaviour, whereas the punishing and painful effects are often delayed.
If a reinforcer is delayed, its ability to control behaviour is diminished.
Thus, if alcohol produces pleasure within minutes, and a hangover hours later, the pleasure, rather than the hangover, will be more likely to determine whether the person will drink again.
What is the circularity problem of positive reinforcement model?
Provides circular explanation of drug use. If we say that a drug is a positive reinforcer because it will increase a behaviour upon which it is contingent, then we cannot explain drug use by saying that a drug is a positive reinforcer.
