CBWL 1 – Evolution & Function of the nervous system
Evolution & historical perspectives on mind & brain
Why is the brain so important?
The brain’s primary function is to produce behavior. To do so, it must:
• receive information about the world;
• integrate information to create a sensory reality;
• make a constant stream of predictions about what to expect;
• produce commands to control the movement of muscles.
The make up of the nervous system altogether allows the brain to do so.
What is Behavior?
• Relatively Fixed Behaviors
- Dependent on heredity
• Relatively Flexible Behaviors
- Dependent on learning
• Complexity of behavior varies considerably in different species
depending on complexity of nervous system
Philosophy of brain and behavior: Aristotle and Mentalism
Mentalism
• An explanation of behavior as a function of the nonmaterial
mind
• Ancient Greece: Aristotle
- Psyche or soul: Synonym for mind; an entity once
proposed to be the source of human behavior, that lives
after death
Philosophy of brain and behavior: Descartes and Dualism
Dualism
• Both a nonmaterial mind and the material body contribute to behavior
• Mind directs rational behavior
• Body and brain direct all other behavior via mechanical and physical principles
- Examples: sensation, movement, and digestion
• Mind is connected to the body through the pineal gland of the brain
• Mind–Body Problem
- Difficult / impossible to explain a nonmaterial mind in command of a material body
Philosophy of brain and behavior: Darwin and Materialism
Materialism
• Behavior can be explained as a function of the nervous system without considering the
mind as a separate substance
• Related to evolutionary theory of Charles Darwin
Darwin’s Concept of Natural Selection:
• Differential success in the reproduction (i.e., passing on your genes) of different
characteristics / behavior (phenotypes) results from the interaction of organisms with
their environment!!
• Traits / behavior that increase reproductive success and chances of survival will be
passed on to offspring
• Competition is a key concept
,Evolutions of Animals having Nervous Systems
Humans have got a relatively large brain compared to their body weight. There is probably a
relation between this fact and the fact that we, humans, can show complex behavior.
Neuroplasticity
• The brain is plastic:
- Neural tissue has the capacity to adapt to the world by changing how its functions are
organized
- Because the brain can adapt to the world, different species could develop
- Neuroplasticity is seen both in the developing brain and in adaptations of brain
structure following injury
Epigenetics
• Study of differences in gene expression related to environment and experience
• Epigenetic factors do not change your genes, but they do influence how your genes
operate
• Epigenetic changes can persist throughout a lifetime, and the cumulative effects can
make dramatic differences in how your genes work and how likely a species is to
pass on its genes → evolution
,Plastic Patterns of Neural Organization:
Phenotypic Plasticity
An individual’s genotype (genetic makeup) interacts with the environment to elicit a specific
phenotype from a large repertoire of possibilities
Studying Brain and Behavior in Modern Humans
The brain – and especially the cortex – is highly flexible
- That means that humans can live VERY different life styles in VERY different
environments, with equal skill and success. That also means that individual
differences in brain organization are huge! The average brain does not exist!
Anatomical & functional divisions of the nervous system
Central nervous system
Brain
Overview of the structure of the brain
- Forebrain: major structure of the brain, consisting of two almost identical hemispheres
(left and right). Prominent in mammals and birds, responsible for most higher order
conscious behaviors
- Cerebellum: “little brain”. Involved in the coordination of motor and cognitive
processes
- Brainstem: central structures of the brain, including the hindbrain, midbrain, thalamus
& hypothalamus. Source of behavior in simpler animals, responsible for most of our
unconscious behaviors
- Spinal cord: consists of nerves that carry incoming and outgoing messages between
the brain and the rest of the body including reflexes
Forebrain:
- Cerebral / Neo cortex
The cerebral cortex is a thin sheet
composed of 6 layers of nerve cells folded
many times to fit inside the skull,
responsible for regulating various mental
activities
- Allocortex Cortex
Evolutionary older part of cortex consisting
of 3 or 4 layers of nerve cells present in
structures of the limbic system (cingulate cortex,
hippocampus, amygdala), as well as structures related to
the olfactory system.
Cingulate cortex:
Controlling motivational states, attention, and self-
monitoring
, Orientation
“Brain–Body Orientation” illustrates brain-structure location from the frame of reference of the
face
“Anatomical Orientation” illustrates the direction of a cut, or section, through the brain (part A)
from the perspective of a viewer (part B)
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