Synaptopathies and Inclusive Fitness Theory

Central Thesis:
- Both conditions arise from unique aspects of human intelligence.
### Research Findings:
- Recent research highlights behavioral traits of autism or schizophrenia observed in non-human primates are rare.
- Experiment specifics: Comparison of RNA from over a million cells across three brain regions in six mammalian species: mice, marmosets, rhesus macaques, gorillas, chimpanzees, and humans.

Common types of brain cells remained relatively unchanged across species.
Exception: Neocortical neurons have transformed significantly in humans.
- Definition: Neocortical neurons are structures in mammals responsible for high-order functions including cognition, reasoning, and language.
Implications of Neocortical Neuron Changes:
- Genetic changes in this region correlate with conditions like autism and schizophrenia.
- Hypothesis: Changes may have contributed to enhanced capacities for language and complex thinking but also increased the likelihood of neurodevelopmental conditions.
- Quote: "Our results suggest that some of the same genetic changes that make the human brain unique also made humans more neurodiverse." - Alexander Starr, Stanford University.

Definition: Autism and schizophrenia are classified as Synaptopathies, diseases characterized by disruptions in the synaptome.
Human Synapse Proteome:
- A highly complex collection of proteins altered by numerous gene mutations linked to over 100 brain diseases, including many psychiatric, neurological, and developmental disorders.
- Synaptic Diseases: These are defined as synaptopathies that stem from both Mendelian and complex genetic mechanisms.
Classification: Proposes a new brain disease classification system based on molecular etiology and pathogenesis.
Variability: Mutations in synaptic proteins result in a wide range of brain diseases, with Autism and Schizophrenia being primarily disorders of synaptic dysfunction.

The organization of the synapse proteome involves receptors that must be anchored; nothing is floating.
Impact of Mutations: Mutations can affect different levels of synapse hierarchy, leading to various disorders.

Timeline: Significant evolutionary milestones include:
- First life > 4 billion years ago (Mya)
- Vertebrate genome evolution characterized by:
- Paralog diversification
- Two complete genome duplications
Invertebrate Development: Focusing on cell adhesion processes influencing pre- and postsynaptic assembly.
Complexity in Evolution: As organisms evolve, the complexity of genomes and their components increases.

Function: They are adhesion molecules vital for connecting pre- and postsynaptic cells and organizing synapses.
- Modifications of these proteins lead to diseases, demonstrating a convergence of multiple mutations that can lead to conditions like schizophrenia and autism.
Polygenic Overlap: Suggests a shared genetic origin for these disorders highlighting the influence of specific proteins or supercomplexes.

Definition of Endophenotypes: At the synaptic level, they contribute to models of psychiatric disease pathogenesis, affecting synaptic function based on which brain region is affected.
Epigenetic Influence: Epigenetic markers can be removed or modified, indicating that changes aren't static.

Impact of inclusive fitness emphasizes the evolution of social behavior.
- Hamilton’s Contribution: Shifted the concept of selection from the individual to the gene level, termed the ‘gene's eye view’ in natural selection, presented in popular literature like "The Selfish Gene".
Theories on Social Behavior: Includes reciprocal altruism and all-inclusive fitness, suggesting that some behaviors can be genetically dictated and pass on through generations if capable of being detected and selected.

Studies Highlighted: Knafo et al. (2008) identified human genetic polymorphisms influencing decision-making in economic games, demonstrating evolutionary conservation related to social bonding mechanisms in rodents.

Definition of Game Theory: This concept explores strategic interactions and decision-making dynamics within social contexts. A key example is the Prisoner's Dilemma, emphasizing cooperative versus non-cooperative behavior.

Outcome Matrix:
- Prisoners face choices that affect sentencing based on mutual actions (either confess or remain silent), illustrating strategic decision-making under dilemmas.

The Dictator Game: Allocates funds with variance related to genetic factors, specifically the arginine vasopressin 1a receptor RS3 promoter region.
Results Show: Variation in RS3 length correlates with altruistic behavior linked to social decision-making.

Understand the distinctions between opposite psychiatric spectrum conditions (psychotic vs. autism) concerning brain development and function.
Discuss the proposed molecular mechanisms explaining these conditions relative to social behavior circuits and genetics, focusing on imprinting and copy number variants.
Grasp the principles behind inclusive fitness theory and its implications on human behavior.
Analyze how game theory can elucidate human interactions, focusing on a particularly impactful gene involved in altruism and its parallels with other species.