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Evolution of Social Brains
Rayna M. HarrisGraduate Researcher, Hans Hofmann’s Lab
rayna.harris@utexas.eduraynamharris@github.io
Comparative Animal Physiology (BIO 361T)April 7, 2016
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About me!Hallsville
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Brains are awesomely diverse and complex!
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Learning, memory, and the hippocampus
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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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“Endless forms most beautiful and wonderful”
Fish
Amphibians
Reptiles
Birds
Mammals
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Animal brains are very diverse as well!
Amphibians
Reptiles
Birds
Mammals
Fish
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Ecology can shape brain size!Somatosensory (touch) cortex Auditory (echolocation) cortexVisual cortex
“…the fittest succeed in adapting themselves best to their environment.”
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What else could give rise to the similarities and differences in animal brains?
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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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Do similar genes control brain development?
Amphibians
Reptiles
Birds
Mammals
Fish
O'Connell & Hofmann, 2011 & 2012
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Yes, similar genes control brain development!
Amphibians
Reptiles
Birds
Mammals
Fish
O'Connell & Hofmann, 2011a & 2012
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What decisions do animals (including humans) make?
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Some categories of decision makingFind foodFind mates Find shelter
Care for family
Fight competitors
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All animals face challengesand opportunities
O'Connell & Hofmann, 2011b
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Some brain regions regulate social behaviors
Dopaminergic Reward System Social Behavior NetworkSocial Decision Making Network
O'Connell & Hofmann, 2011a & 2012
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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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Yes, the same brain regions control behavior!
Mesolimbic Reward SystemNewman’s Social Behavior NetworkShared by both circuits
Fish
O'Connell & Hofmann, 2011a & 2012
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Do the same molecules control behavior in all animals?
Signaling Molecules Receptors
O'Connell & Hofmann, 2011a & 2012
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Some molecules are known to influence animal social behavior
Dopamine
Vasopressin
Testosterone Estradiol
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How conserved is gene activity in the same brain regions?
O'Connell & Hofmann 2012
Androgen receptorEstrogen receptorProgesterone receptor
Dopamine receptorVasopressin receptorOxytocin receptor
VasopressinOxytocin
Tyrosine hydroxylase
• 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?
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How conserved is gene activity in the same brain regions?
O'Connell & Hofmann 2012
Androgen receptorEstrogen receptorProgesterone receptor
Dopamine receptorVasopressin receptorOxytocin receptor
VasopressinOxytocin
Tyrosine hydroxylase
• What are the most striking similarities and differences in gene expression between the striatum and the proptic area
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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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Social animals use similar neuromolecular networks to generate similar behaviors
Fish
Amphibians
Reptiles
Birds
Mammals
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If all brains are made of the same parts, how what gives rise to diversity in behavior?
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Differences in decision makingFind foodFind mates Find shelter
Care for family
Fight competitors
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How does diversity in mating system arise?
Neuromolecular networks that regulates mating system
MonogamyPolygamy
Oldfield et al. 2013
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Herichthys cichlid fishesHerichthys cyanoguttatus
Texas CichlidHerichthys minckleyi
Cuatro Cienegas Cichlid
Oldfield et al. 2013
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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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This experiment integratesecology, 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
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11-ketotestosterone is higher in haremic males
Monogamous Haremic
High testosterone often leads to:
• Decreased paternal care
• Increased Aggression
Oldfield et al. 2013
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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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Diversity in social behavior is a result of quantitative differences in neuromolecular
activity
Fish
Birds
Mammals
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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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AcknowledgementsHans Hofmann Lab
The University of Texas at Austin
rayna.harris@utexas.edu
raynamharris@github.io
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