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Chapter 4

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

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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
-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
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
Amygdala: EMOTION, overrules instinct, emotional/sexual arousal, plays special role in stimuli that makes
Basal ganglia: initiate PLANNED MOVEMENT, damagedParkinson’s (tremors/rigidity) or Huntington’s
(jerky movements)
- nucleus accumbens: structure responsible for REWARD
Epilepsyheightened response of hippocampus and amygdale, is MOST COMMON neurological disorder (1-
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
Change in the strength of connections underlies learning
-when make new memory, physical changes being made in brain, these changes are most likely
not in the brain’s gross wiring or arrangement, but simply in the strength of preexisting
-Hebbian learning: “fire together, wire together”
-another possible method: growth of entirely new connections
otakes longer, MAJOR factor in recovery from injury
-new neurons ARE produced in adult brain, process known as neurogenesis
oThere appears to be a fair amount of neurogenesis in the HIPPOCAMPUS
oMemories are retained within the hippocampus initially but are eventually transferred to the
cortex, with the hippocampus being continuously overwritten.
oe.g. stressful experiences interfere with neurogenesis during development and adulthood
odominant animals show greater increases in new neurons than subordinate ones
oit is possible that neurogenesis underlies the entire basis of neural plasticity
oneurogenesis may be able to reverse the loss of neurons and slow down the rate of decline as
we age
Cortical maps
-maps in cerebral cortex change in response to their activity
-more cortical tissue is devoted to body to body parts that receive more sensation or that are used
-If finger repetitively stimulated, finger’s cortical representation will expand. But NOT when
-phantom limbs: intense sensation that amputated body part still exists
The Brain can recover from injury
Reorganization of brain in response to brain damage
-Lesion in cortex surrounding gray matter assumes function of damaged area
-Some remapping occurs immediately and continues for years, involves all levels of nervous
-Reorganization more prevalent in children than adults
-Epilepsy children radical hemispherectomyremoval of one entire cerebral hemisphere
regain use of
-Stem cells are “master” cells that not only are able to regenerate themselves, but also have the
capacity to develop into any type of tissue
-being used for degenerative diseases (park’s, huntington’s)
oObtained from human fetal tissue, ethical dilemmas
The Hemispheres can be separated
-Corpus callosum: a fibre of axons that transmits info between the two cerebral hemispheres of
the brain
-if cut out, two halves of the forebrain isolated, hemispheres connected only at the back of the
brainstem, hence only indirectly: split brain
-Roger Sperry: just as brain had split in two, so had the mind. (Epilepsy)
-Most obvious thing about the split-brain patients was how normal they were
Left brain: language, interpreter mechanism
Right brain: spatial relationships
The mind is a subjective interpreter
-The left brain tends to compress its experience into a comprehensible story and reconstruct
remembered details based on the gist of the story.
-The right brain seems simply to experience the world and remember things in a manner less
distorted by narrative interpretation
Can we study consciousness?
-The mind is physically distinct from the brain, this view of consciousness, called dualism, posits a
clear separation between what we call mind and the brain. As an alternative to dualism,
materialism is based on the belief that the brain and mind are inseparable, that the brain directly
enables the mind. According to materialism, it is the activity of neurons in the brain that produces
the contents of consciousness, such as cognition and perception
-the unique perspective each of us has on our own conscious experience