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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

BOX 3.1

Definitions
Classical conditioning
Also called Pavlovian conditioning after Pavlov’s experiments with dogs, in which
stimuli such as the sound of a bell, repeatedly paired with food presentation,
eventually came to elicit salivation in the dogs in the absence of the food. Classical
conditioning is the simplest form of learning to make new responses to stimuli
and to learn about relationships between stimuli. It is a form of learning in which
a previously neutral stimulus (conditioned stimulus) gains power over behaviour
through association with a biologically relevant stimulus (unconditioned stimulus),
and can elicit the same behavioural or physiological response (unconditioned
response) as the unconditioned stimulus. The response to the conditioned stimulus
is called the conditioned response.
Conditioned response
In classical (or Pavlovian) conditioning, a response elicited by a previously neutral
stimulus, which occurs as a result of pairing the neutral stimulus with an
unconditioned stimulus.
Conditioned stimulus
In classical conditioning, the previously neutral stimulus which comes to elicit a
conditioned response.
Cognition
The process of knowing, including attending, remembering, reasoning etc., as
well as the content of these processes, such as concepts and memories.
Craving
Drug craving is the desire for the previously-experienced effects of a psychoactive
substance. This desire can become compelling and can increase in the presence
of both internal and external cues, particularly with perceived substance availability.
It is characterized by an increased likelihood of drug-seeking behaviour and, in
humans, of drug-related thoughts.
Dependence
A cluster of cognitive, behavioural, and physiological symptoms indicating that
the individual continues the use of the substance despite significant substance-
related problems.
Emotion
A complex phenomenon, including physiological arousal, feelings, cognitive
processes, and behavioural reactions, made in response to a situation perceived
to be personally significant.
Habit
A behaviour performed automatically in response to specific stimuli, independently
from its outcome.

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