biolpsy_06

Lecture Overview

• Topic: Phylogeny and Ontogeny of the Brain

• Instructor: Dr. Richárd Reichardt

• Email: reichardt.richard@ppk.elte.hu

Theory of Evolution

• 19th Century: Darwin proposes natural selection as the mechanism for species evolution.

• Religious Conflict: The theory conflicts with major religious beliefs.

• Scientific Validity: The term ‘theory’ does not diminish the scientific validity of an idea.

• Importance: The theory of evolution is a foundational concept in modern biology.

Natural Selection

• Variability: Presence of attribute variability allows certain variants to be advantageous in their environment.

• Impact: Advantageous characteristics influence reproductive success and attribute distribution in future generations.

Behavioral Traits and Selection

• Behavioral Selection: Behaviors can also undergo natural selection.

• Baldwin Effect: Behavioral plasticity is beneficial; the ability to learn has adaptive advantages.

Selection for Behavioral Traits

• Raven Example:

  • Reluctant Ravens: More cautious ravens that avoid novelty may have lower reproductive success.

  • Proactive Ravens: Ravens that approach novel objects quickly tend to increase their diet and reproductive success.

Biological Basis of Behavioral Variability

• Novelty Seeking: Linked to the brain's reward system.

• Individual Differences: Questions arise regarding what biological factors and genes influence novelty-seeking behavior.

Evolution of the Nervous System

• Basic Structure: Comparison of nervous systems across various phyla (e.g., Echinodermata, Mollusca, Cnidaria).

• Human Nervous System: Neural ring, brain, spinal cord, and ganglia represent basic evolutionary forms of the nervous system.

Homology of Traits

• Common Ancestor: Living species share a common ancestor, with recent common ancestry seen in humans and chimpanzees compared to humans and rats.

Evolution of Brain and Cognition

• Brain Complexity: Simple brain size measures do not accurately predict cognitive ability.

• Encephalization Factor:

  • Metric: Brain weight relative to body weight (body weight^0.69).

  • Significance: Indicates how the brain size compares to expected norms based on body size.

Encephalization Factor Correlation

• Prediction of Cognitive Ability:

  • Data on brain weights across species shows the relationship between brain size and cognitive ability.

• Chart Overview: Comparison of brain weights from shrew to elephant illustrating the encephalization factor.

Human Brain Development

• Postnatal Growth: Human brain development continues significantly after birth, leading to a substantial increase in brain size.

Cultural Evolution

• Human Impact: Societal structures and traditions evolve similarly to biological processes of natural selection, termed cultural evolution.

Development of the Human Body

• Starting Point: Development begins as a single cell (zygotic stage).

• Cell Count: Human body evolves to consist of approximately 724 trillion cells, with about 11.5% being nerve cells.

Embryonic Development

• Critical Timing:

  • Zygote division starts within 12 hours post-fertilization.

  • Distinct cellular layers form after a week, leading to the creation of the neural tube responsible for nervous system development.

Cell Fate During Development

• Predetermined Fate: In simpler organisms like C. elegans, cell fate is predetermined; more complex organisms rely on local interactions during development.

Fetal Alcohol Syndrome (FAS)

• Developmental Risks: Regular alcohol use during pregnancy can lead to FAS, impacting behavior and learning abilities due to disrupted development.

Development Stages of the Nervous System

• Stages of Background Development:

  • Neural tube cell division and migration to determine specific regions.

  • Neuron differentiation and synaptic formation shape brain connectivity.

Chemoaffinity Hypothesis

• Axonal Guidance: Proposes that chemical concentrations guide the pathways for growing axons, supported by experiments demonstrating non-spatial effects on neural connections.

Neural Darwinism in Development

• Neurotrophic Factors: Neurotrophins, such as NGF and BDNF, play critical roles in regulating neuronal survival, especially in the brain.

Myelination

• Continued Myelination: Neural pathway myelination persists into adulthood; particularly associated with maturation of the prefrontal cortex and related behaviors.

Human Brain Development Timeline

• Development Overview: Key structural divisions of the developing brain from neural tube to adult brain structures.

Plasticity of the Nervous System

• Lifelong Plasticity: The nervous system retains certain plasticity throughout life, although this can be diminished in conditions like Alzheimer’s disease.

Conclusion

• Thank You: Instructor expresses gratitude for attention and preview of the next class's topic, "Homeostatic Regulation."