PSY100H1 Chapter Notes - Chapter 4: Spinal Cord, Cerebellum, Sleep Deprivation

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26 Mar 2012
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Chapter 4 – The Brain and Consciousness
Phrenology: based on idea of functional localization, assess personality traits/mental abilities by measuring
bumps on skull
- Franz Gall and Johann Spurzheim
oFlourens (critic) thought that brain worked as single unit
oKarl Lashley: believed in equipotentiality: all parts of the cortex contributed equally to
mental abilities
We know today that brain is a patchwork of highly specialized areas
Broca’s area: first strong evidence supporting a specialized brain
- the left frontal region of the brain that is crucial to the production of language
Mind is adaptive: Brain’s specialized mechanisms regulate breathing, food intake, sexual behavior,
bodily fluids & sensory systems, some basic roles have changed little over evolution, e.g. breathing
Spinal cord
-Part of CNS, a rope of neural tissue that runs from pelvis to base of skull
-Segmented into 2 tissue types:
ogrey matter, dominated by cell bodies of neurons
owhite matter, mostly axons and myelin sheaths
odistinguishable in brain as well
relays info, also controls spinal reflex: conversion of sensation to action (e.g.
stretch reflex)
Thickens into brainstem
-Houses the most basic roles of survival: breathing, swallowing, vomiting, urination, orgasm.
-Because it is a continuation of spinal cord, performs for head similar to what spinal cord does for
rest of body
oComplement of reflexes analogous to spinal reflexes.
E.g. gagging
-Has nerves connecting to skin and muscles of head and specialized sensory organs of head like
eyes and ears.
-Includes reticular formation: large network of neurons within brainstem involved in general
arousal (behavioral, sleep-wake cycles). It is also involved in inducing and terminating the
different stages of sleep
Cerebellum
-large convoluted protuberance at the back of the brainstem that is essential for coordinated
movement & balance
-“Little Brain”, needed for motor function, motor learning, functional imaging, ataxia: clumsiness
ABOVE cerebellum and brain stem is the Forebrain
-two cerebral hemispheres
ocerebral cortex
osubcortical regions
hypothalamus
thalamus
hippocampus
amygdale
basal ganglia
many of these part of limbic system—separating the evolutionary order
(brainstem, cerebellum) and new (cerebral cortex)
include basic drives, eating, drinking, emotions
Subcortical regions
Hypothalamus: REGULATION of body, controls pituitary glands i.e. hormones (master gland), smaller in
women/gay men
Thalamus: GATWAY to brain, receives all income sensory info except smell, shuts gate during sleep, some
role in attention
Hippocampus: MEMORY, creates new interconnections within cortex (grey matter expands from each new
experience)
Amygdala: EMOTION, overrules instinct, emotional/sexual arousal, plays special role in stimuli that makes
FEAR
Basal ganglia: initiate PLANNED MOVEMENT, damagedParkinson’s (tremors/rigidity) or Huntington’s
(jerky movements)
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- nucleus accumbens: structure responsible for REWARD
Epilepsyheightened response of hippocampus and amygdale, is MOST COMMON neurological disorder (1-
3%)
Celebral Cortex: outer layer of brain tissue that forms the convoluted surface of the brain
-site of all thoughts, detailed perceptions, consciousness (everything that makes us human)
-is the source of our complex culture and communication, allowing us to understand other people
and to follow the rules of society
-ability to think before we act
-EACH hemisphere has four lobes
oOccipital: vision (back bottom)
oParietal: touch, spatial relations (back, top)
primary somatosensory cortex, runs from top of brain down the side
the left hemisphere receives touch info from the right side of the body, and vice versa
somatosensory homunculus: distorted because more sensitive areas of body, e.g.
face and fingers, have greater area
oTemporal: hearing, memory (mid, bottom)
oFrontal: thought, planning movement (top, front)
INTERSECTION of temporal and occipital cortices is fusiform face area.
-Name comes b/c more active when look at faces (other regions of temporal cortex are active
when looking at objects)
Frontal lobes
-Planning and movement
-Prefrontal cortex
oespecially prominent in humans, important for attention, working memory, decision making,
appropriate social behaviour, and personality
oNot anatomically fully mature until early adulthood
o30% of brain in humans
oRational, directed activity
-area in center of prefrontal cortex just behind eyes is orbitofrontal cortex
opersonality, emotion, impulse control
opart of limbic system
odamage: easily distracted, improper social behavior
-Lobotomy: deliberately damaging frontal lobes in treating mental patients. Made them
emotionally flat and lethargic, easier to deal with in mental hospitals
How Does the Brain Change?
-brain is MALLEABLE, constantly changing
-plasticity: property of brain that allows it to change as a result of experience, drugs, or injury
-brain follows predictable development pattern
Chemical signals guide growing connections
- neural tissue that is transplanted early completely transforms into whatever type is appropriate for its
new location
obut as time passes, cells become more committed to their identities, growing connections as if
they hadn’t been moved
-connections of brain produced by growing axons’ detection of particular chemicals telling them where
to go
-Neurons in one region are looking for particular chemicals, and neurons in another are
producing them
-Axons grow toward or away from increasing or decreasing concentrations of signaling
chemicals: chemical gradients
- This method creates specific connections within cerebral cortex
Experience forms detailed connections
Critical period: time in which certain experiences must occur for normal brain development
-adult cats that are deprived of eyes for a period (eye patch) don’t lose sight, whereas kittens DO
lose sight
The brain rewires itself throughout life
Although plasticity decreases with age, the brain retains the ability to rewire itself throughout life. This is the
biological basis of learning
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