Pavlovian-instrumental transfer (PIT) is a

psychological Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries betw ...

phenomenon that occurs when a

conditioned stimulus Classical conditioning (also known as Pavlovian or respondent conditioning) is a behavioral procedure in which a biologically potent stimulus (e.g. food) is paired with a previously neutral stimulus (e.g. a triangle). It also refers to the learn ...

(CS, also known as a "cue") that has been associated with

rewarding The reward system (the mesocorticolimbic circuit) is a group of neural structures responsible for incentive salience (i.e., "wanting"; desire or craving for a reward and motivation), associative learning (primarily positive reinforcement and class ...

or aversive stimuli via

classical conditioning Classical conditioning (also known as Pavlovian or respondent conditioning) is a behavioral procedure in which a biologically potent stimulus (e.g. food) is paired with a previously neutral stimulus (e.g. a triangle). It also refers to the lear ...

alters motivational salience and

operant behavior Operant conditioning, also called instrumental conditioning, is a learning process where behaviors are modified through the association of stimuli with reinforcement or punishment. In it, operants—behaviors that affect one's environment—are c ...

. Two distinct forms of Pavlovian-instrumental transfer have been identified in humans and other animals – specific PIT and general PIT – with unique neural substrates mediating each type. In relation to rewarding stimuli, specific PIT occurs when a CS is associated with a specific rewarding stimulus through classical conditioning and subsequent exposure to the CS enhances an operant response that is directed toward the same reward with which it was paired (i.e., it promotes approach behavior). General PIT occurs when a CS is paired with one reward and it enhances an operant response that is directed toward a different rewarding stimulus. An example of specific PIT, as described by a neuroscience review from 2013 on Pavlovian-instrumental transfer, is as follows: "in a typical experimental scenario a rat is trained to associate a sound (CS) with the delivery of food. Later, the rat undergoes an instrumental training where it learns to press a lever to get some food (without the sound being present). Finally, the rat is presented again with the opportunity to press the lever, this time both in the presence and absence of the sound. The results show that the rat will press the lever more in the presence of the sound than without, even if the sound has not been previously paired with lever pressing. The Pavlovian sound-food association learned in the first phase has somehow transferred to the instrumental situation, hence the name 'Pavlovian-instrumental transfer.'"

Specific and general transfer

In relation to rewarding stimuli, specific PIT occurs when a CS is associated with a specific rewarding stimulus through classical conditioning and subsequent exposure to the CS enhances an operant response that is directed toward the same reward with which it was paired (i.e., it promotes approach behavior). General PIT occurs when a CS is paired with one reward and it enhances an operant response that is directed toward a different rewarding stimulus. Neurobiological state factors (e.g.,

appetite Appetite is the desire to eat food items, usually due to hunger. Appealing foods can stimulate appetite even when hunger is absent, although appetite can be greatly reduced by satiety. Appetite exists in all higher life-forms, and serves to reg ...

and

satiety Satiety ( ) is a state or condition of fullness gratified beyond the point of satisfaction, the opposite of hunger. It is a state which induces meal termination.Hetherington, M.Sensory-specific satiety and its importance in meal termination ''Neuro ...

states, stress level, drug states such as

intoxication Intoxication — or poisoning, especially by an alcoholic or narcotic substance — may refer to: * Substance intoxication: ** Alcohol intoxication ** LSD intoxication ** Toxidrome ** Tobacco intoxication ** Cannabis intoxication ** Cocaine in ...

and

withdrawal Withdrawal means "an act of taking out" and may refer to: * Anchoresis (withdrawal from the world for religious or ethical reasons) * '' Coitus interruptus'' (the withdrawal method) * Drug withdrawal * Social withdrawal * Taking of money from ...

, etc.), and particularly the motivational state of an animal, strongly affect the amount of appetitive motivational salience (i.e.,

incentive salience Motivational salience is a cognitive process and a form of attention that ''motivates'' or propels an individual's behavior towards or away from a particular object, perceived event or outcome. Motivational salience regulates the intensity of be ...

) that a ''reward cue'' confers to an associated rewarding stimulus via Pavlovian-instrumental transfer. Acute stress amplifies the motivational salience that reward cues confer to rewarding stimuli through both specific and general PIT; however, chronic stress reduces the motivational impact reward cues. Specific PIT and general PIT also occur with aversive stimuli and are defined analogously. Specific PIT with an aversive stimulus occurs when a CS is paired with an aversive stimulus and subsequent exposure to the CS enhances an operant response that is directed away from the aversive stimulus with which it was paired (i.e., it promotes escape and avoidance behavior). General PIT with an aversive stimulus occurs when a CS is paired with one aversive stimulus and it enhances an operant response that is directed away from a different aversive stimulus.

Neural substrates

Based upon studies on rats that involved PIT with rewards, specific PIT is mediated by the

nucleus accumbens shell The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hypot ...

and basolateral amygdala, while general PIT is mediated by the

nucleus accumbens core The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hypot ...

and central amygdala. Studies on humans which employed neuroimaging during PIT experiments with rewards appear to be consistent with these findings.

Clinical significance

Addiction

Due to the effect of reward cues and Pavlovian-instrumental transfer on the amplification of incentive salience for rewarding stimuli, PIT is believed to be one of the mechanisms responsible for producing "cue-triggered wanting", or craving, for a drug that occurs when an individual with a

drug addiction Addiction is a neuropsychological disorder characterized by a persistent and intense urge to engage in certain behaviors, one of which is the usage of a drug, despite substantial harm and other negative consequences. Repetitive drug use oft ...

is exposed to drug cues even after long periods of abstinence. For example, anti-drug agencies previously used posters with images of

drug paraphernalia "Drug paraphernalia" is a term to denote any equipment, product or accessory that is intended or modified for making, using or concealing drugs, typically for recreational purposes. Drugs such as marijuana, cocaine, heroin, and methamphetami ...

– which is a type of drug cue – as an attempt to show the dangers of drug use. However, such posters are no longer used because of the effect of incentive salience in causing cravings and

relapse In internal medicine, relapse or recidivism is a recurrence of a past (typically medical) condition. For example, multiple sclerosis and malaria often exhibit peaks of activity and sometimes very long periods of dormancy, followed by relapse or ...

upon sight of the stimuli illustrated in the posters.

Dieting

The sight or smell of food which one has consumed and enjoyed in the past can elicit hunger (i.e., the motivation to eat) in humans, an effect which is presumably mediated through PIT. In PIT experiments with rats, the presentation of a conditioned stimulus which has been paired with food has been shown to increase instrumental actions that have been reinforced by food, such as pressing a lever which leads to the delivery of a food pellet.

Notes

References

{{reflist, 30em Addiction Behavioral concepts Behavioral neuroscience Behaviorism Cognition Cognitive psychology Experimental psychology Motivation