PSB3340 Chapter 1 & Evolution of the CNS

Behavioral neuroscience

study of neural bases of behavior and mental processes

Nerve

collection of wiring portion, i.e axons aka nerve fibers, of many neurons

Neurological vs psychiatric/psychological disorders

Neurological disorders pinpoint the root cause, i.e. what is going wrong, in the nervous system. Psychiatric disorders—we are not sure what’s going wrong in the underlying biology and neurological side of the brain.

History of Behavioral Neuroscience: Ancient Egypt

Brain wasn’t considered important—kept important organs in jars (hearts, lungs, etc) for after life

History of Behavioral Neuroscience: Aristotle

Thought that brain cooled down the heart’s passions (brain unimportant) and heart regulated emotions/decisions

History of Behavioral Neuroscience: Galen

Gladiator doctor in Rome. Noticed behavior changes when people have severe head injuries, once they recovered. Those with heart injuries often died immediately.

History of Behavioral Neuroscience: Rene Descartes

Thought brain was irrelevant; believed body operated as a hydraulic system, with ventricles through which fluid flowed; animals only behave reflexively because they lack a soul

Dualism

Humans have a soul (nonmaterial), which is located in the pineal gland and allows for free will, and a hydraulic/machine-like body

History of Behavioral Neuroscience: Thomas Willis

Introduced empirical evidence that convinced Western world that the brain was responsible for coordinating/controlling behavior

History of Behavioral Neuroscience: Luigi Galvani

Found that delivering electric current to a recently deceased frog caused its leg to contract—no machine or brain, even, required for this

History of Behavioral Neuroscience: Johannes Muller’s Doctrine of Specific Nerve Energies

Different sensations in body are due to specific types of nerve energies produced by different nerves that are in charge of different sensations. Issues: can’t have a dedicated nerve for each type of sensation and nerve energies, APs, produced by all neurons are identical

History of Behavioral Neuroscience: Herman von Helmholtz

Electrical conduction in nerves is much slower, 25-28 m/s, compared to electrical wires

History of Behavioral Neuroscience: Phineas Gage

Lost part of his frontal cortex in a railroad accident. Suffered with seizures and loss of emotional control. Other than that, all other functions remained fine.

History of Behavioral Neuroscience: Santiago Ramon y Cajal

established the neuron doctrine

Neuron doctrine

brain is made up of billions of individual cells (neurons)—it’s not one big, continuous cell

somatic intervention

Alter a structure or function of the brain (e.g. excise part of the brain) to see how behavior changes

Behavioral intervention

Alter a behavior to see how the body/brain structure or function is changed

What happens if we can’t manipulate and can only observe the variable of interest?

This occurs often in controlled experiments and in humans. Instead, we measure associations—such as correlation. Correlation doesn’t equal causation!

Broca’s area

In front left side of the brain with a circumscribed function of ability to speak

Wernicke’s area

In posterior left side of the brain with circumscribed function of comprehending speech and language

Phrenology

bumps on the skull reflected enlargements of brain regions responsible for certain behavioral traits

Lobotomy

psychosurgical procedure used to treat mental illnesses such as schizophrenia, bipolar disorder, and epilepsy

Functional specialization vs phrenology

Almost the entire brain is active to some extent when performing any task. Specialized areas are part of the brain that are most active during certain tasks, i.e. more blood is rushing to that part of the brain. However, there are a limited number of areas that are essential for a specific function. Our brains are always active

Reductionism

breaking down a system into its smaller parts in order to understand it (e.g. looking at things from an atomic level; studying rats, simpler organism)

How do ethical considerations impact research?

Researchers study simpler nervous systems and other vertebrates and/or invertebrates, such as rats. Much of what we know about molecular/synaptic basis of memory comes from Eric Kandel’s study of Aplysia, type of large sea snail.

Levels of analysis

scope of experimental procedures consisting of social interactions, organ, neural systems, brain region, circuit, cellular, synaptic, and molecular levels

Monism

the modern view and says that the mind is produced by the brain

Important features of our view of the brain

Brain is monist (i.e. ultimate source of thoughts, feelings, actions), product of evolution, and has plasticity

Trial and error Natural selection analogy

Natural selection is reproduction/survival of the fittest and each generation is a trial where individuals less suited to their ecological niche reproduce less.

Mutations

Random changes in the genes, contributing to random changes in the genetic pool. Often, they have a low chance of success but every now and then, one will be successful in the long-term.

What shapes the phenotype?

Phenotype is constantly changing and a sum of the genotype, environment, and experience

Epigenetics

study of changes in an organism caused by a modification in gene expression (as a result of experience and the environment, without altering the genetic code (nature)

Why are identical twins not 100% indentical?

Epigenetics and mutations throughout life can lead to slight variations

Directional vs stabilizing vs disruptive selection

Directional: move to one extreme; stabilizing: move towards middle trait; disruptive: favor both extremes

Divergent evolution

descent from a common ancestor

Convergent evolution

similar traits due to chance and environment only

Homology

similar characteristics due to shared ancestor

Homoplasy

similar characteristics not derived from a common ancestor but rather derived from individual environments (e.g. tail bone in dogs and humans)

Analogous

traits with a similar function without a shared genetic background (e.g. wings in birds and insects)

Artifical selection

can occur rapidly as it is the selective breeding of plants and animals to encourage certain traits (e.g. dachshund were bred to fit into badger holes; seedless watermelon)

How has the human brain evolved in recent evolutionary history?

Expansion of the human brain volume has not been equal across all areas. The forebrain, including cerebral cortex, expanded the most and is associated with higher order functions like memory and complex thoughts.

How many layers are in the cerebral cortex?

6-layered (among all warm-blooded vertebrates)

Higher and lower regions of the brain and their functions

Cortical (cortex): abstract and concrete thought, complex thinking and functioning. Limbic: attachment, sexual behavior, emotional reactivity, motor regulation. Midbrain: arousal, appetite/satiety, sleep. Brainstem: reflexive or unconscious tasks, blood pressure, heart rate, body temperature

Larger brains are associated with

Tool use (simple), communication, learning—including social learning, adaptability, longer gestation (development in the wom) time, difficult birthing, more dependenc eon parents

Ontogeny

the developmental history of an individual organism, i.e. the process by which an individual changes in the course of its lifetime

Evolutionary psychology

Studies how natural selection has shaped behavior (phylogeny)

Phylogeny

Studies relationships among different groups of organisms and gives evolutionary history of a species