Pain and pleasure

Question 1

Opioids and pleasure

Answer 1

• Opioids produce a sense of euphoria, pleasure because they are interacting with the brain’s reward centers
• The pain reducing effect of opioids may be related to this increase of pleasure (because pleasure is the opposite of pain)

Question 2

According to Aristotle, _______ drives out pain

Answer 2

Pleasure

Question 3

2 dimensions to pleasure

Answer 3

1. Liking
2. Wanting or Desire

Question 4

Desire or wanting

Answer 4

• In pursuit of a reward that you have not yet obtained (wanting state)
• Associated with dopamine release in the frontal lobe
• This dopamine release helps you do what is needed to obtain the reward : increase of motivation, energy

Question 5

Liking

Answer 5

• When you get the reward, you immediately experience pleasure
• related to the release of opioids in hedonic hotspots.
• Usually short-lived, before moving on to next reward

Question 6

Motivation-Decision Model of Pain

Answer 6

• Explains how pain and pleasure interact in the brain
• The central nervous system makes a decision over what is more important than pain, and inhibits pain if there is something more important

Question 7

Neurons in the brain stem that can inhibit pain based on pleasure

Answer 7

OFF neurons are activated by opioids such as morphine and will inhibit the transmission of pain at the level of the spinal cord

Question 8

Neurons that increase pain

Answer 8

ON neurons are activated by opioids antagonists like naloxone, and will increase pain.

Question 9

Motivation-Decision Model of Pain circuit

Answer 9

Circuit where brain stem has descending projections to the spinal cord to gate the transmission of nociceptive inputs : opioids are also involved in shutting off or opening that circuit as a function of whatever is more important than pain at a given moment.

Question 10

Flow

Answer 10

State of intense focus and absorption in an activity, where a person is fully immersed in the task at hand and loses track of time and their surroundings.
- “effortless” focused attention usually doing an activity you both like and are good at

Question 11

Video games and pain reduction

Answer 11

• Regardless of preferred or least preferred game, video game is much more efficient at reducing pain compared to the two back or left right task : effect on both pain intensity ratings and pain unpleasantness rating.
• On pain and pleasantness, we seem to have an advantage for playing the preferred games compared to the least preferred games.

Question 12

Video games, flow state and pain reduction

Answer 12

the advantage of playing video games was mediated by self ratings of flow, suggesting that the reason why video games are more efficient at reducing pain is because they induce more flow (associated with high dopamine state, in pursuit of reward).

Question 13

Effect of passion on pain

Answer 13

engaging in a meaningful activity can cause great pain reduction through the brain’s endogenous pain modulatory system.
E.g. expert playing chess will get more pain reduction than a chess player

Question 14

Preferred music and pain reduction

Answer 14

• Preferred music is much more efficient at reducing pain compared to experimenter selected music.
• Fits with the idea that if you really like an activity and it is important to you, your brain is going to decide that there is something more important in the environment compared to your pain : the net result will be to inhibit pain.

Question 15

Descending pathways use neurotransmitters that are important for motivation and emotion : ________, ________, ________

Answer 15

Noradrenaline, serotonin, dopamine

Question 16

Pain is a ______ (something we FEEL) just like color

Answer 16

Qualia

Question 17

Nociception is ______ unlike pain

Answer 17

Objective

Question 18

Stress induced analgesia is an example of ________ without ________

Answer 18

Nociception without pain

Question 19

Stress induced analgesia

Answer 19

Pain will be inhibited by something even more aversive and important than pain : when your life is threatened
E.g. wounded soldiers walking to the infirmary during WWII

Question 20

Stress induced analgesia is related to the release of …

Answer 20

Noradrenaline, the stress hormone at the level of the spinal cord

Question 21

Phantom limb pain is an example of _______ without _______

Answer 21

Pain without nociception

Question 22

Phantom limb pain

Answer 22

• pain that people experience in a missing limb (no nociceptive input)

Question 23

Other example of pain without nociception

Answer 23

A man fell on a nail, but the nail had only gone between his toes, the foot was entirely uninjured
- The multisensory information was so convincing that it triggered the pain response without any nociceptive stimulus

Question 24

3 dimensions of pain according to Melzack

Answer 24

1. Sensory dimension
2. Affective motivational dimension
3. Cognitive and evaluative dimension

Question 25

Sensory dimension

Answer 25

- Location of the pain and its intensity - Sensory qualities : burning, stinging, etc.

Question 26

Affective motivational dimension

Answer 26

- Pain is unpleasant. - When you feel pain, you're motivated to do something to stop the pain.

Question 27

Cognitive and evaluative dimension

Answer 27

When in pain, your cognitive system is recruited to process the meaning, cause of the pain and future actions

Question 28

If pain is multidimensional, it must be also complex in its _______ representation according to Melzack

Answer 28

Brain

Question 29

neurosignature

Answer 29

Proposal by Melzack that pain is a specific pattern of brain activity

Question 30

Neuromatrix

Answer 30

The neurosignature emerges in regions of the brain with state of the body representations (probably somatosensory cortex, maybe others) : the neuromatrix

Question 31

From the neuromatrix, many _______ states can emerge; pain is one of them

Answer 31

Somatic

Question 32

From the thalamus, the nociceptive signal will be distributed to these 2 brain regions,

Answer 32

1. Somatosensory cortices 2. Anterior Cingulate Cortex (ACC) and Insula

Question 33

Somatosensory cortices

Answer 33

Linked to the sensory dimension - primary somatosensory cortex - secondary somatosensory cortex

Question 34

Anterior Cingulate Cortex (ACC) and Insula

Answer 34

Linked to the affective dimension (pleasantness) - In the frontal lobe - Dorsodorsal posterior insula and anterior insula

Question 35

Primary somatosensory cortex lesion

Answer 35

Deficit in the sensory dimension of pain : identifying stimulus and describing its sensory properties on the opposite side of the body from the lesion in the cortex BUT : the emotional dimension of pain remains, e.g. vague unpleasantness coming from the opposite side of the body that is not attached to any sensation

Question 36

Percentage of people with phantom limb pain

Answer 36

60% to 80% of patients experience painful phantom sensations. - Only in 5% to 10% of patients, the pain is severe.

Question 37

When does phantom limb pain appear ?

Answer 37

Pain appears in the first days/weeks after amputation. The pain is intermittent and tends to decrease over time.

Question 38

Why is phantom limb pain almost completely absent in infants ?

Answer 38

Brain plasticity is higher in infants : the somatosensory cortex has not yet set in very strongly

Question 39

Phantom limb pain is proportional to the degree of ...

Answer 39

functional reorganization in the primary somatosensory cortex

Question 40

deafferentiation in phantom limb pain

Answer 40

Following amputation, a large part of the primary somatosensory cortex that is left deafferented: it receives no input

Question 41

Functional reorganization

Answer 41

The several representation of the adjacent body parts (e.g. shoulder and head for arm + forearm amputation) will invade the region of the somatosensory cortex that has been left empty following the amputation.

Question 42

How does functional reorganization create pain ?

Answer 42

With functional reorganization, stimulating the head for example will produce activity in a region of the brain that used to represent the hand, creating confusion in the brain which reacts by generating a painful sensation

Question 43

Goal of treatment against phantom limb pain

Answer 43

Providing multisensory information to trick the brain into believing the missing body part is still there

Question 44

Mirror therapy

Answer 44

Mirror between missing limb and remaining limb so that when patient looks in the mirror, he has the illusion that his missing limb is still there : get visual, proprioceptive feedback that missing limb is still there even if the brain is not perceiving anything sensory - mirror therapy is more effective than mental visualization at reducing pain

Question 45

Prosthesis and phantom limb pain

Answer 45

- A prosthesis gives the brain the illusion that the limb is still there - Usually a prosthesis makes the patient less likely to develop phantom limb pain

Question 46

Anterior cingulate cortex

Answer 46

- Region of the brain involved in fear, negative feelings, cognitive control (e.g. increasing attention) : multipurpose - Associated with the affective dimension of pain

Question 47

Anterior cingulate cortex lesion

Answer 47

- Opposite dissociation compared to primary somatosensory cortex lesion - Patient will still report feeling a quite strong sensation, but it will not be felt as unpleasant, not aversive

Question 48

What's the difference between the consequences of an anterior cingulate cortex lesion and congenital insensitivity to pain ?

Answer 48

- A person with ACC lesion has nociceptive fibers, and his primary somatosensory cortex is perceiving the pain, but he does not have the unpleasantness feeling - He can feel the strength of the sensation unlike people with congenital insensitivity to pain

Question 49

Cingulotomy

Answer 49

- Lesioning the anterior singular cortex to treat pain - Done as a last resort for patients in palliative care - Not ideal because this part of the brain is important for other functions, and usually pain comes back after a while

Question 50

Hypnosis as pain relief

Answer 50

Suggestions targeting the affective dimension of pain reduced the interior cingulate cortex activity :pain unpleasantness is reduced just like in cingulotomy (no impact on sensory aspect of pain, only pleasantness)

Question 51

Neural pain signature

Answer 51

- More sensitive to nociceptive pain (from increasing intensity of a nociceptive stimulis) - Includes anterior cingulate, the thalamus, etc.

Question 52

Stimulus intensity independent pain signature

Answer 52

- To predict a fluctuation in perceived intensity pain ratings that weren't explained by the intensity of the stimulus - more associated with the cognitive evaluative dimension of pain.

Question 53

The combination of these two signals can predict how much pain the patient is experiencing

Answer 53

Neural pain signature and stimulus intensity independent pain signature

Question 54

Amount of variance explained by the map of activity with neurosignatures

Answer 54

For 1 stimulus : the explained variance in pain rating for one single stimulation is low (but still significant) because of noise For the average of many painful stimuli : can get up to 80% of variance explained - Classification accuracy is even better With a simple classification task : - 2 maps of brain activity, have to decide which one has the most pain in it - Accuracy is very close to 100%.

Question 55

Stimulus intensity independent pain signature (sips) neurofeedback

Answer 55

- Found that the decrease in pain that people experienced was proportional to their capacity to modulate the Sips, but only in the down regulation group - Had a ceiling effect on the up regulation, but able to get people to change the activity of their brains and it had an impact on their perception of pain.