Lecture 25: The Neurobiology of Love & Attachment Flashcards
1
Q
neurobiological view of attachment
A
- There is no single attachment system dedicated exclusively to the formation of social bonds
- Rather, a set of more general purpose affective-emotional systems for which attachments emerge with learning
(ex. Separation distress, Felt security and social pleasure, Motivation to seek out & engage with close others)
2
Q
Affective neuroscience
A
a branch of neuroscience focused on understanding emotions in humans & other mammals
3
Q
Emotions
A
complex psychological states involving physiological changes, subjective experience, and behaviours/expression
4
Q
Affect
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the subjective experience of emotion
5
Q
Key assumptions of affective neuroscience
A
- Emotions & associated feelings evolved to serve specific purposes in relation to biologically significant and life-challenging situations
- Felt aspects of emotional systems (affects) serve 3 key adaptive purposes
6
Q
3 adaptive purposes of affect
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- Highlight survival & reproductive issues in the environment
- Motivate behaviour for survival & reproduction
- Aid in memory construction through reinforcement
7
Q
current neurobiological research
A
- Much of the research pertains to animals
- May not generalize perfectly to humans
- Ex. humans appear to lack dedicated neural machinery for detecting pheromones
8
Q
social pain
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- Distress we experience when important social ties are threatened or lost
- Often, we use physical pain words to describe such experiences
- This tendency is cross-cultural
- The propensity to feel social pain may be rooted in separation distress children experience when separated from the caregiver; generalized to maintaining other social relationships given the benefits of group living
9
Q
evolution of social pain
A
- May have evolved from general pain mechanisms
- Pain serves an important adaptive purpose: it captures our attention & demands action
- Individuals with congenital insensitivity to pain are highly susceptible to physical injury have reduced life spans (often die in childhood)
- For highly vulnerable infants, being left alone is a life-or-death situation
- Experiences of social pain motivate behaviour to re-establish proximity with caregiver
10
Q
two components of pain
A
- sensory component
- affective/motivational components
11
Q
sensory component of pain
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- Specific information about what’s happening
- What, where, how intense is it?
- Involves the somatosensory cortex
12
Q
affective/motivational component of pain
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- The aversiveness of the experience & motivation to stop it
- The alarm component
- Involves a different set of neural regions (ex. Dorsal anterior cingulate cortex (dACC) anterior insula (AI))
- Activation in some areas (ex. dACC) may trigger physiological stress response
13
Q
social pain in the brain
A
- Increased activation in the affective pain regions (ex. dACC, AI) during various kinds of social pain experiences, like
1. Reminders of deceased for bereaved individuals
2. Reminders of ex-partners for those who had been recently dumped
3. Social exclusion: Strength of the activation is correlated with feelings of rejection/exclusion - Interestingly, some studies have observed activation in the somatosensory cortex as well
14
Q
interoception
A
- Ability to perceive signals originating within the body
- Ex. breathing, hunger, thirst
- Crucial for being able to maintain a steady internal state
15
Q
insula
A
- Plays a key role in processing signals originating in the body & imbuing them with emotional & motivational significance
- Ex. may interpret signals of sympathetic nervous system activation as anxiety
16
Q
types of mechanoreceptors in the skin
A
fast-conducting & slow-conducting mechanoreceptors
17
Q
fast-conducting mechanoreceptors
A
allow for fine discrimination
18
Q
slow-conducting mechanoreceptors
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- Respond to low-pressure, low-velocity tactile stimulation (ex. Slow and light stroking)
- This type of stimulation is typically found in intimate affiliative interactions and is experienced as subjectively pleasant
- Signal travels directly to the insula (may serve an all-clear signal)
19
Q
felt security
A
- Once contact with caregiver is regained, experience strong feelings of pleasure & comfort
- Reinforces the attachment bond
- In adulthood, symbolic proximity-seeking may be sufficient to restore the sense of comfort & security
- Some parallels to the literature on physical pain & placebos: cognitive factors like mere expectation of pain relief can alleviate pain
20
Q
pain relief as a reward
A
- Relief from pain (i.e. omission/reduction of an aversive event/punishment) is more than simply an attenuation of pain; it is rewarding & pleasurable
- Pleasure of relief is derived from the violation of negative expectancy
- `Pessimists (who generally hold more negative expectations) experience greater dread of adverse event & greater relief when the adverse event is avoided
21
Q
endogenous opioid system
A
system of opioid receptors & their respective ligands (chemical messengers that bind to a receptor)
22
Q
μ-opioid receptors
A
- Bind drugs like morphine & heroin, mediate their analgesic & rewarding effects
- Normally bind internally produced (endogenous) chemical messengers like β-endorphin
- Play an important role in pain relief, placebo effects, hedonic responses to rewards like food
23
Q
Brain opioid theory of social attachment (BOTSA)
A
- Opioids mediate attachment through dual mechanisms
- Declining levels of opioids during separation contribute to social pain/separation distress
- Increasing levels of opioids during reunion contribute to feelings of reward & comfort
24
Q
receptor agonist
A
chemical substance that binds to & activates a certain receptor
25
receptor antagonist
- Chemical substance that binds to & blocks a certain receptor, thereby blocking or dampening normal biological responses
- Seeing how typical behavioural responses change after the administration of an antagonist allows us to infer the neurochemical mechanisms behind the typical response
- Naloxone & naltrexone are common opioid receptor antagonists
26
BOTSA Hypothesis 1
if separation distress reflects state of endogenous opioid withdrawal, stimulation of opioid activity should diminish behavioural manifestations of separation distress (e.g., distress vocalizations (DVs), clinging)
27
pharmacological approach to BOTSA hypothesis 1
activation of μ-opioid receptor agonists like morphine or β-endorphin reduce DVs & proximity-seeking behaviour like clinging in variety of non-human animals species
28
brain-stimulation approach to BOTSA Hypothesis 1
- Electric stimulation of the periventricular gray (PVG) produces the release of β-endorphin, physical analgesia, and the reduction of DVs in isolated guinea pigs.
- Both analgesia & reduction in DVs can be reversed with the administration of an opioid receptor antagonist (naloxone)
29
BOTSA hypothesis 2a
social contact leads to the release of endogenous opioids
30
evidence for BOTSA hypothesis 2a
Large increases in cerebrospinal fluid concentration of β-endorphin following grooming in monkeys
31
BOTSA hypothesis 2b
If this release of endogenous opioids mediates (drives) the comforting effects of social contact, should be able to block the comforting effects of social contact by blocking endogenous opioids
32
evidence for BOTSA Hypothesis 2b
Young animals treated with opioid receptor antagonists like naltrexone continue to cry & cling to mom even after reunion
33
further BOTSA animal evidence
- Further evidence that opioids mediate the formation of attachment bonds
- Genetic knock-down of the μ-opioid receptor in mouse pups causes deficits in attachment
- Oprm - - pups emit fewer separation distress calls relative to wild-type controls (oprm + +)
- Do not develop preference for the mother’s olfactory cues (in contrast to wild-type controls)
- Attachment & separation distress go hand-in-hand: the pain of separation is the price we pay for attachment
34
indirect evidence for BOTSA in human research
- Social contact decreases physical pain in real-life (e.g., heel lance in infants, labour) and experimental settings
- Even viewing picture of a loved one decreases pain during lab task
- However, not clear if this is opioid-mediated
35
imaging evidence for BOTSA in human research
When thinking of an experience of social loss, deactivation of opioid neurotransmission in regions to pain affect
36
pharmacological evidence for BOTSA in human research
- Naltrexone (vs. placebo control) decreases feelings of warmth & connection participants experience while reading affectionate notes from close others or looking at their photographs. Also decrease activity in the left ventral striatum (reward-related region of the brain) while looking at pictures of close others
- Participants received naltrexone or placebo before completing a self-disclosure task. There was no effect on feelings of closeness toward partner, but blocked the increases in positive affect and self-esteem that placebo participants experienced after the task. This suggests that opioids may contribute to positive feelings we experience in different kinds of affiliative situations
37
OPRM1 A118G
linked to variation in both physical pain sensitivity & rejection sensitivity (the G allele being the sensitive variant)
38
genetic evidence for BOTSA in human research
- Couples filled out a questionnaire after each interaction they had over a period of 3 weeks
- Found that individuals carrying at least 1 copy of the G allele reported steeper declines in felt security when their partner behaved more coldly or hurtfully towards them than usual
39
implications of opioid research
Opioid drugs may be a substitute for unmet belonging needs
40
oxytocin
- A neurochemical messenger that plays a key role in parturition & lactation, is released during copulation
- Also postulated to play an important role in social behaviour & bonding
- Has received more research attention (in humans) than opioids, but their precise function still remains unclear
41
oxytocin research in animals
- Early evidence indicating that oxytocin may play a role in social bonding came from the comparison of two closely related species with very different social structures
- Prairie voles: typically form pair bonds after mating, exhibit biparental care
- Montane voles: live in isolation, no evidence of pair bonding
- Different responses to separation in infancy: prairie voles respond with DVs and stress hormone secretion; montane voles do not exhibit behavioural/physiological reaction
- Prairie voles have high density of oxytocin receptors in regions related to reward & reinforcement (nucleus accumbens), whereas montone voles have few receptors in these areas
- Can facilitate partner bonding in prairie voles by injecting exogenous oxytocin (even if the voles have not mated)
- Oxytocin receptor antagonist blocks partner preference formation following matin in prairie vole
42
initial oxytocin research in humans
- First study to examine social effects of oxytocin in humans found that intranasal oxytocin increases trust during an economic trust game
- A subsequent flurry of research found many prosocial effects:
emotional recognition & empathy, generosity & cooperation, more positive communication behaviours during couple conflict discussions, increases in social motivation
43
subsequent oxytocin research in humans
- As research accumulated, it became clear that the effects of oxytocin are not always consistent
- Some studies found no effects, very small effects, or negative/antisocial effects
- Ex. oxytocin actually decreases trust towards out-group members ad those with clinically high levels of rejection sensitivity (borderline personality disorder)
- Effects of oxytocin may depend on interpersonal & intrapersonal context
44
Social salience hypothesis
oxytocin may focus attention on social cues
45
evidence for the social salience hypothesis
- Oxytocin has been found to increase gaze to the eye region & lead to changes in functional connectivity among brain regions indicative of the heightened attention
- In mice, oxytocin enables maternal care behaviour (pup retrieval) by fine-tuning neurons in the auditory cortex so pup distress calls become more salient
46
psychological/behavioural effects of increased social salience
- Psychological/behavioural effects of increased social salience will depend on contextual factors
- Might magnify prosociality when dealing with close or trusted others
- But, diminish prosociality when the situation or the individual’s disposition biases them to construe social information negatively
- Ex. oxytocin administration makes individuals low in attachment anxiety remember their mom as more caring & close; opposite effect for individuals high in attachment anxiety
47
fMRI passion study
- fMRI study of early-stage intense romantic love (dating 7 months on average)
- While in the scanner, they viewed photos of a loved and familiar acquaintance
- Activation of the ventral tegmental area and related regions that receive projections from this area
- Part of the dopamine reward pathway
- Note: fMRI does not allow for measuring activity of a specific neurotransmitter, but other research has found increased dopamine release in these regions in response to rewards like money
48
replicating fMRI passion study
- Finding since replicated cross-culturally and with same-sex couples
- Also replicated in long-term marriages who reported being still “madly in love” with their spouses
- Replicated using stronger control condition (close, long-term friend)
- Activity in the VTA correlates with feelings of passionate love
- But, not with scores on friendship-based love scale
49
dopamine
- Commonly described as a “reward neurochemistry”
- Contributes to the incentive/motivation to pursue rewards
(wanting vs. liking distinction)
- Unlike opioids, does not appear to mediate the pleasure of sensation
- At the affective level, this may be experienced as anticipatory exhilaration, eagerness, and euphoria
- Allows animals to pursue various rewards important for survival
- Responds to incentives in the environment and imbalances in homeostatic needs
- May contribute to the experience of passionate, romantic love; but likely also plays a role in attachment figures and care behaviour
50
case of Leonard L
- Childhood encephalitis led to a destruction of dopamine brain circuits
- After being treated with L-DOPA (precursor of dopamine), able to experience a sense of engagement with the world, energy, and excitement
