- The document discusses the evolution of social brains in animals from different perspectives including differences in brain regions, genes, molecules, and behaviors between species. - Key findings include that similar brain regions regulate social behaviors across species, including the mesolimbic reward system and social behavior network, and that similar genes and molecules like dopamine and vasopressin influence social behaviors in all animals. - Differences in behaviors between species arise from quantitative differences in the activity of these shared neuromolecular systems, influenced by ecology and other factors, giving rise to diversity in mating systems and other social decisions.

1. Evolution of Social Brains
Rayna M. Harris
Graduate Researcher, Hans Hofmann’s Lab
rayna.harris@utexas.edu
raynamharris@github.io
Comparative Animal Physiology (BIO 361T)
April 7, 2016 1

2. About me!
Hallsville
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3. Brains are awesomely diverse and complex!
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4. Learning, memory,
and the hippocampus
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5. Evolution of Social Brains
• Bird, frog, fish, reptile, and mammal brains
• Brain regions and molecules that regulate aggressive and mating behavior
• Differences in mating systems
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6. “Endless forms most beautiful and wonderful”
Fish
Amphibians
Reptiles
Birds
Mammals
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7. Animal brains are very diverse as well!
Amphibians
Reptiles
Birds
Mammals
Fish
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8. Ecology can shape brain size!
Somatosensory (touch) cortex
Auditory (echolocation) cortex
Visual cortex
“…the fittest succeed in adapting themselves best to their environment.”
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9. What else could give rise to the similarities
and differences in animal brains?
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10. Hox genes control body development in
all animals!
Hox Genes Developing embryos Adults
Rodents
Nobel Prize: 1995:
Lewis, Nüsslein-Volhard,
and Wieschaus
Flies
Fish
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11. Do similar genes control brain development?
Amphibians
Reptiles
Birds
Mammals
Fish
O'Connell & Hofmann, 2011 & 2012
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12. Yes, similar genes control brain development!
Amphibians
Reptiles
Birds
Mammals
Fish
O'Connell & Hofmann, 2011a & 2012
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13. What decisions do animals (including
humans) make?
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14. Some categories of decision making
Find foodFind mates Find shelter
Care for family
Fight competitors
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15. All animals face challengesand opportunities
O'Connell & Hofmann, 2011b
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16. Some brain regions regulate social behaviors
Dopaminergic Reward System Social Behavior NetworkSocial Decision Making Network
O'Connell & Hofmann, 2011a & 2012
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17. Do the same brain regions control
social behavior in all animals?
Fish
Amphibians
Reptiles
Birds
Mammals
O'Connell & Hofmann, 2011a & 2012
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18. Yes, the same brain regions
control behavior!
Mesolimbic Reward System
Newman’s Social Behavior Network
Shared by both circuits
Fish
O'Connell & Hofmann, 2011a & 2012
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19. Do the same molecules control behavior in all animals?
Signaling
Molecules Receptors
O'Connell & Hofmann, 2011a & 2012
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20. Some molecules are known to influence animal
social behavior
Dopamine
Vasopressin
Testosterone Estradiol
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21. How conserved is gene activity in the same brain
regions?
O'Connell & Hofmann 2012
Androgen receptor
Estrogen receptor
Progesterone receptor
Dopamine receptor
Vasopressin receptor
Oxytocin receptor
Vasopressin
Oxytocin
Tyrosine hydroxylase
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• Which molecules in the striatum
are present in all species
examined?
• Which molecules in the striatum
are absent in all species
examined?
• Which two pairs of species are
more similar to each other than
to the rest?

22. How conserved is gene activity in the same brain
regions?
O'Connell & Hofmann 2012
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Androgen receptor
Estrogen receptor
Progesterone receptor
Dopamine receptor
Vasopressin receptor
Oxytocin receptor
Vasopressin
Oxytocin
Tyrosine hydroxylase
• What are the most striking similarities and differences in gene expression
between the striatum and the proptic area

23. How conserved is gene activity in the same brain
regions?
Where signals are received is well
conserved
Where signals are produced is less
conserved.
12 brain regions * 10 genes = 120 rows
O'Connell & Hofmann 2012
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24. Social animals use similar neuromolecular networks
to generate similar behaviors
Fish
Amphibians
Reptiles
Birds
Mammals
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25. If all brains are made of the same parts, how
what gives rise to diversity in behavior?
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26. Differences in decision making
Find foodFind mates Find shelter
Care for family
Fight competitors
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27. How does diversity in mating system arise?
Neuromolecular networks that regulates mating system
Monogamy
Polygamy
Oldfield et al. 2013
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28. Herichthys cichlid fishes
Herichthys cyanoguttatus
Texas Cichlid
Herichthys minckleyi
Cuatro Cienegas Cichlid
Oldfield et al. 2013
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29. Does behavior change when levels of these
neurochemical change?
• V1aR, OTR, D1, D2
• ER, PR, AR
Dopamine
Arginine Vasopressin
Testosterone Estradiol
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30. This experiment integrates
ecology, endocrinology, and molecular biology
1. Catch fish in Shoal Creek 2. Collect blood 3. Dissect brains
4. Quantify hormone levels 5. Extract RNA 6. Quantify gene expression
Oldfield et al. 2013 30

31. 11-ketotestosterone is higher in haremic males
Monogamous Haremic
High testosterone often
leads to:
• Decreased paternal
care
• Increased Aggression
Oldfield et al. 2013 31

32. Vasopressin Receptor activity is higher in the
hypothalamus of haremic males
Monogamous Haremic
High vasopresin receptor is often
associated with
• Increased aggression
• Increased territory size
• Important for social behavior
Oldfield et al. 2013
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33. Diversity in social behavior is a result of quantitative
differences in neuromolecular activity
Fish
Birds
Mammals
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34. Links to the four papers discussed
• O’Connell LA, Hofmann HA (2011a) The vertebrate mesolimbic
reward system and social behavior network: A comparative synthesis.
Journal of Comparative Neurology. 519:3599-639. PDF
• O'Connell LA, Hofmann, HA (2011b) Genes, hormones, and circuits:
An integrative approach to study the evolution of social behavior.
Frontiers in Neuroendocrinology 32:320–335. PDF
• O'Connell LA & Hofmann HA (2012) Evolution of a Vertebrate Social
Decision-Making Network. Science 336, 1154-1157. PDF
• Oldfield RG, Harris RM, Hendrickson DA, Hofmann HA (2013)
Arginine Vasotocin and Androgen Pathways are Associated with
Mating System Variation in North American Cichlid Fishes. Hormones
and Behavior 64, 44–52. PDF
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35. Acknowledgements
Hans Hofmann Lab
The University of Texas at Austin
rayna.harris@utexas.edu
raynamharris@github.io
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