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Aggression, Serotonin, and Gene-Environment Interactions in Monkeys by Stephen J. Suomi

Aggression, Serotonin, and Gene-Environment Interactions in Monkeys by Stephen J. Suomi. Chris DeGrood. Nature or Nurture?. What shapes us as individuals, the genes we were given by our parents or the the way we were raised? Attachment has its basis in biology. Rhesus Monkeys.

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Aggression, Serotonin, and Gene-Environment Interactions in Monkeys by Stephen J. Suomi

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  1. Aggression, Serotonin, and Gene-Environment Interactions in Monkeysby Stephen J. Suomi Chris DeGrood

  2. Nature or Nurture? • What shapes us as individuals, the genes we were given by our parents or the the way we were raised? • Attachment has its basis in biology

  3. Rhesus Monkeys • Factors unique to rhesus monkeys and humans: • Mothers are directly able to reduce fear through social contact and soothing behaviors • Use mother as a ‘secure base’

  4. Monkey Neonates • Display 4-5 universal “Component Instinctual Responses” (Bowlby) • Sucking • Clinging • Crying • Following • Smiling

  5. Mothers of Neonates • Provide • Essential nourishment • Physical and psychological warmth • Protection from elements, potential predators, and other members of the social group • Infant-Mother Attachment • Only mother shares prenatal environment uniquely attuned to circadian rhythm and other biological rhythms • Neonates are continuously exposed to mothers odor, taste (nursing), and relative warmth

  6. Monkey Development • By the 2nd month of life • Monkey uses its mother as a secure base for exploration • Mother is responsible for maintaining close contact • Within 2-3 months • Social fear develops, and infant is now responsible for maintaining close contact • “functionally and developmentally equivalent to human infant 9-month stranger anxiety”; (cf. Sackett, 1966; Suomi & Harlow, 1976) • Puberty • Males leave family, form ‘gangs’ • Females become more involved with family

  7. Social Attachment Bond Forms • For a male it will last at least until puberty • For a female it will last as long as both mother and daughter survive • Monkeys with less than optimal attachment have reduced exploratory behavior

  8. High-Reactive Sub-Group • 15-20% of both wild and captive population • Respond with fear and anxiety • Within first few weeks of life: • Unusually high and stable heart rates • Dramatic increase in CNS metabolism of norepinephrine • Leave mothers later • Explore physical and social environments less • Tended to be shy around peers • “Increasing evidence that these features are highly heritable”

  9. High-Impulsive Sub-Group • 5-10% of both wild and captive population • In social interactions play often escalates into aggressive exchanges, and more often than not they are damaged • Difficulty moderating behavioral responses to peers • Have deficits in visual orienting during first month of life • “Exhibit chronically low rates of brain metabolism of serotonin…” (cf. Coccaro & Murphy, 1990) • Consistently have lower CSF concentrations of 5-HIAA • Difficult attachment relationships with mother • Conflicts intensify during weaning

  10. Maternal Style vs. Infant Temperament • Low ranking mothers are more restrictive of exploration • High ranking mothers have a “laissez-faire” attitude • Change in social hierarchy or a food supply shortage may also make the mother more restrictive

  11. Peer-Reared Monkeys • More extreme reactions to social separation • Behavioral • Adrenocortical • Noradrenergic • Consistently lower CSF concentrations of 5-HIAA than mother reared counterparts • Resemble impulsive mother-reared monkeys in the wild both behaviorally and by decreased serotonergic functioning • Required higher ketamine doses for anesthesia • Higher rates of whole-brain glucose metabolism under isoflurane anesthesia (detected by PET scan) • Larger alcohol consumption & tolerance

  12. Serotonin Transporter Availability • Mediates Serotonin reuptake • Polymorphism • S/S – low qty. 5-HTT • S/L – medium qty. • L/L – high qty. 5-HTT • Among peer reared subjects, short allele had much lower 5-HIAA concentration

  13. Foster Mom Experiment • Infants • High-Reactive • Normal-Reactive • Mother • Unusually nurturent • Normal nurturent

  14. Foster Mom Experiment • High-Reactive + Control  expected social problems and behavioral responses • Ended up on bottom of hierarchy • High-Reactive + Nurturent  “Behaviorally Precocious” • Rose to top positions in hierarchy • Left mothers earlier • Explored environment more • Less behavioral disturbance during weaning than either infant group with the control mother

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