Pavlovian Learning & Conditioning in Real Life

• Pavlovian Learning & Conditioning

  Learned associations between stimuli and responses
• Three applications/implications of Pavlovian conditioning in everyday life


  • Learned taste/smell aversions as a consequence of clinical treatments and how they can be avoided
  • Learned contribution to drug tolerance and how it contributes to overdoses amongst users
  • Learned suppression and enhancement of immune system function
• Side-effects of therapy


  1. Cancer patient enters hospital for chemotherapy treatment and eats a meal

  2. They receive their treatment and subsequently feel sick and nauseous

  3. They may develop an aversion to some of the foods they ate at lunchtime

  4. Over repeated chemotherapy sessions, the acquired aversions may extend to many common foods

  5. Characteristics of taste/smell aversion learning suggest a method for dealing with the appetite loss
• Anticipatory nausea and vomiting (ANV)


  Nausea and vomiting that occurs before any chemotherapeutic agent has been administered to the patient
• ANV


  CS, US, CR, UR
• Drug tolerance


  The finding that over repeated administrations, the effects of a drug get progressively smaller
• Development of drug tolerance


  1. Physiological changes

  2. Pavlovian learning
• Drugs that tolerance can develop for


  • Insulin
  • Amphetamines
  • Alcohol
  • Opiates
  • Benzodiazepines
• Compensatory CR


  A CR that counteracts the effect of the drug, leading to tolerance
• As the CR develops

  Tolerance to the drug develops
• Larger and larger doses are needed to produce the same effect as tolerance develops
• A person used to taking a drug in certain locations


  Develops a tolerance partly due to the CR evoked by the situational stimuli (CSs)
• If CSs are not present (new situation)


  The CR will be reduced or absent, so the effect of a dose will be greater
• A significant contributory factor to accidental overdoses is the reduction in the compensatory CR when the drug is taken in an unfamiliar situation
• Conditional immunosuppression


  A learned immunosuppression effect where the immune system is suppressed in response to stimuli associated with drug administration
• Conditional immunosuppression


  1. US: drug (e.g. cyclophosphamide)

  2. UR: immunosuppression

  3. CS: stimuli associated with drug administration

  4. CR: immunosuppression
• Benefits of conditional immunosuppression


  • Avoidance of side-effects: drugs with side-effects need only be used until the learned effect is established
  • Cost savings: some immunosuppressive drugs are very expensive
• Conditional immune enhancement is also possible using drugs that enhance immune function
• Placebo effect


  The beneficial effect in a patient following a treatment that arises from the patient's expectations concerning the treatment rather than from the treatment itself
• Conditional immune suppression and enhancement contribute to some instances of the placebo effect
• Placebo


  Something administered or otherwise presented to a person/ animal as a treatment or part of a treatment procedure that has no demonstrable effect on health and is often intended to be 'fake' (e.g., a pill that contains no active ingredient or a 'sham' treatment such as sham surgery)
• Placebo effect


  A remarkable phenomenon in which a placebo -- a fake treatment, an inactive substance like sugar, distilled water, or saline solution -- can sometimes improve a patient's condition simply because the person has the expectation that it will be helpful
• Placebo effect


  The beneficial effect in a patient following a particular treatment that arises from the patient's expectations concerning the treatment rather than from the treatment itself
• Placebo effect


  A positive therapeutic effect claimed by a patient after receiving a placebo believed by him to be an active drug
• These definitions include the implicit assumption that there can only be one explanation of the placebo effect (if it is real) and that is belief/expectation
• Placebo effect


  A person's (or animal's) health-related response to a placebo that is positive (i.e., a benefit to health)
• Types of placebo effects


  • An objectively measureable effect on the body's function or condition (e.g., a patient recovers from a condition more quickly, heals faster, etc.)
  • A psychological effect that is not accompanied by any measurable improvement in function or condition (e.g., a person reports feeling better or having less pain, but there is no measurable change in their physical condition)
• In order for a placebo effect to be a Conditioned Response (CR), it is necessary that there be a prior history of treatment that has led to the acquisition of that CR
• It will also typically be necessary for the CR to be beneficial (given that placebo effects are normally beneficial), so CRs like hyperalgesia would not typically be considered
• A person's history of medication and treatment can act like a Pavlovian conditioning procedure: treatment/medicine (US) is presented in a pared fashion with a variety of other contextual stimuli (CSs), e.g., the therapist, a pill, a syringe
• Research investigating the relationship between mind, brain and immune function is called psychoneuroimmunology
• Pavlovian conditioning


  The acquisition of a new stimulus-response relationship
• Pavlovian memory


  The CS comes to elicit a response (CR) that it didn't elicit prior to training
• The increased strength (or the new connectivity) represents the memory formed by the learning process
• Unconditional reflex


  Mediated by a brainstem pathway from receptors in the cornea to the muscles that close the eyelids
• There's nothing in the unconditional reflex circuit that can mediate the conditional response (blink in response to the tone CS)
• The required link (reflex pathway)

  1. Auditory receptors transmit signals to neurons in the brainstem auditory nuclei

  2. Neurons in the pontine nuclei project to the cerebellar cortex and to nuclei within the cerebellum

  3. Neurons in the interposed nuclei project to the red nucleus in the brainstem

  4. Neurons in the red nucleus project to the eye-lid motor nuclei
• In order for this link to be established, information about the predictive relationship between the CS and the US must be available somewhere in the CNS
• Sensory information about the two stimuli is brought together in the cerebellum and the predictive relationship between them is detected in the cerebellum