PSYCH361 Chapter Notes - Chapter 4: John Hughlings Jackson, Swiss Army Knife, Triune Brain
11 Feb 2020
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PSYCH 361 – Test 2 Summary Notes
Textbook Chapter 4 (Brain Function)
• Soft tissues that comprise the nervous system do not leave records such as fossils the way hard tissues do,
making it difficult to study cellular structures across evolutionary time
o Alternatives includes studying existing organisms known to be modern decedents of earlier
organisms, changes in the brain as it increased in size, and changes in genetic structure across
species
• The brain has 4 lobes: frontal, parietal, occipital, and temporal
• The outer shell of the brain is made of grey matter, underneath are axon which transfer information
through the brain and are padded with myelin sheaths or white matter
• The brain’s neocortex has a six layered structure and includes regions for sensory, motor, and higher
cognitive processing while the allocortex is older and includes the hippocampus, olfactory cortex, etc.
• If the observed similarities of two living species are due to shared evolutionary history (a common
ancestor) it is homologous, otherwise it is analogous (independently evolved)
• John Hughlings Jackson proposed three levels of the brain for vegetative/motor/higher cortical processes
and two principles:
o Hierarchical integration – the levels of the brain interact with each other such that higher levels
restrict or inhibit lower levels
o Encephalization – over evolutionary time, special-purpose control systems are taken over by
general-purpose control system (newer systems control older systems)
• Paul MacLean’s idea of the triune brain suggests that we can process information in 3 independent but
not autonomous ways:
o The reptilian brain for breathing, temperature regulation, sleep-wake cycles, olfaction, and
instinctive motor processes
o The paleomammalian brain for the limbic system and emotional processes
o The neomammalian brain for the neocortex and thalamic structures including problem solving,
executive control, and linguistic functions to orient the self to the external world
• Blindsight (when individuals report they cannot see an object but can accurately guess it’s location) and
hemispheric lateralization (humans’ right brain specializes in spatial processing and left in language) show
humans can process information outside of conscious awareness
• The brain’s default network comprises of the neural networks active during internal processing
• Having a larger brain provides the evolutionary advantage of being able to connect information
processing with time (which eventually led to a sense of self in humans) but requires more energy and a
longer period of dependency to support development
• The mental module model (or “Swiss army knife” model) suggests that the brain contains modules
devoted to specific tasks and requires a new module to support a new cognitive ability, while the
alternative model suggests increased abilities come with a global increase in neurons and their
interconnectedness which allows for greater information processing
• Humans males have larger brains than females with a difference in grey/white matter and cerebrospinal
fluid between hemispheres supporting more lateralization
• As primates evolved, there has been a shift from relying on the olfactory system to the visual system (the
olfactory bulb is smaller and simpler in humans than other primates)
Document Summary
The brain has 4 lobes: frontal, parietal, occipital, and temporal. The outer shell of the brain is made of grey matter, underneath are axon which transfer information through the brain and are padded with myelin sheaths or white matter. The brain"s neocortex has a six layered structure and includes regions for sensory, motor, and higher cognitive processing while the allocortex is older and includes the hippocampus, olfactory cortex, etc. If the observed similarities of two living species are due to shared evolutionary history (a common ancestor) it is homologous, otherwise it is analogous (independently evolved)
