Download Basic Brain Structure and Function

Brain Structure and Function
“If the human brain were so
simple that we could
understand it, we would be so
simple that we couldn’t”
-Emerson Pugh, The Biological Origin of Human
Values (1977)
Phineas Gage
• September 13th, 1848
• Phineas 25 years old
• Rutland & Burlington Railroad, Cavendish,
VT
• Paving the way for new RR tracks
• “Tamping Iron”
– 1.25in x 3ft
Phineas Gage
• Accident
– Quick Recovery
• Months later: “No longer Gage”
– Before: capable, efficient, best foreman, well-balanced
mind
– After: extravagant, anti-social, liar, grossly profane
• Stint with P.T Barnum
• Died 12 years later
• Watch Clip
Evolution of the Brain
Reptilian  Paleomammalian  Neomammalian
The Brain
• Brainstem
–responsible for
automatic survival
functions
• Medulla
–controls heartbeat
and breathing
Parts of the Brain
THALAMUS
 Relays
messages
amygdala
hippocampus
pituitary
CEREBELLUM
 Coordination
and balance
BRAINSTEM  Heart
rate and breathing
Reticular Formation
•Widespread connections
•Arousal of the brain as
a whole
•Reticular activating
system (RAS)
•Maintains
consciousness and
alertness
•Functions in sleep and
arousal from sleep
The Cerebellum
–helps coordinate
voluntary
movement and
balance
The Limbic System
• Hypothalamus, pituitary,
amygdala, and hippocampus
all deal with basic drives,
emotions, and memory
• Hippocampus  Memory
processing
• Amygdala  Aggression
(fight) and fear (flight)
• Hypothalamus  Hunger,
thirst, body temperature,
pleasure; regulates pituitary
gland (hormones)
The Limbic System
 Hypothalamus
 neural structure lying
below (hypo) the
thalamus; directs several
maintenance activities
 eating
 drinking
 body temperature
 helps govern the
endocrine system via the
pituitary gland
 linked to emotion
 (show video)
The Limbic System
Show self stimulation clip
The Limbic System
• Amygdala
–two almondshaped neural
clusters that are
components of
the limbic system
and are linked to
emotion and fear
August 1st, 1966
Charles Whitman
The Brain
• Thalamus
– the brain’s sensory
switchboard, located
on top of the
brainstem
– it directs messages to
the sensory receiving
areas in the cortex
and transmits replies
to the cerebellum and
medulla
The Cerebral Cortex
• Cerebral Cortex
–the body’s
ultimate control
and information
processing
center
The lobes of the cerebral hemispheres
The lobes of the cerebral hemispheres
Planning, decision
making speech
Sensory
Auditory
Vision
The Cerebral Cortex
• Frontal Lobes
– involved in speaking and
muscle movements and in
making plans and judgments
– the “executive”
• Parietal Lobes
– include the sensory cortex
The Cerebral Cortex
• Occipital Lobes
– include the visual areas, which
receive visual information from the
opposite visual field
• Temporal Lobes
– include the auditory areas, each of
which receives auditory information
primarily from the opposite ear
The Cerebral Cortex
•
•
•
•
Frontal (Forehead to top)  Motor Cortex
Parietal (Top to rear)  Sensory Cortex
Occipital (Back)  Visual Cortex
Temporal (Above ears)  Auditory Cortex
Motor/Sensory Cortex
• Contralateral
• Homunculus
• Unequal
representation
Sensory Areas – Sensory Homunculus
Figure 13.10
The Cerebral Cortex
 Aphasia
 impairment of language, usually caused by left
hemisphere damage either to Broca’s area
(impairing speaking) or to Wernicke’s area
(impairing understanding) –see clips
 Broca’s Area
 an area of the left frontal lobe that directs the
muscle movements involved in speech
 Wernicke’s Area
 an area of the left temporal lobe involved in
language comprehension and expression
Language Areas
• Broca 
Expression
• Wernicke 
Comprehension
and reception
• Aphasias
LEFT HEMISPHERE
Paul Broca [1800s]
• Suggested localization
Techniques to examine functions
of the brain
1. Remove part of
the brain & see
what effect it has
on behavior
2. Examine humans
who have suffered
brain damage
3. Stimulate the
brain
4. Record brain
activity
Brain Lateralization
Our Divided Brains
• Corpus collosum –
large bundle of
neural fibers
(myelinated axons,
or white matter)
connecting the two
hemispheres
Hemispheric Specialization
LEFT
RIGHT
Symbolic thinking
(Language)
Detail
Literal meaning
Spatial perception
Overall picture
Context,
metaphor
Contra-lateral
division of labor
• Right hemisphere
controls left side of
body and visual field
• Left hemisphere
controls right side of
body and visual field
Split Brain Patients
• Epileptic patients had corpus callosum cut
to reduce seizures in the brain
• Lives largely unaffected, seizures reduced
• Affected abilities related to naming objects
in the left visual field
Brain Plasticity
Brain Plasticity
• The ability of the brain to
reorganize neural pathways
based on new experiences
• Persistent functional changes in
the brain represent new
knowledge
• Age dependent component
• Brain injuries
Environmental influences on
neuroplasticity
Impoverished environment
Enriched environment
Sensation and Perception
Sensation
• The process by which the central
nervous system receives input from
the environment via sensory neurons
• Bottom up processing
Perception
• The process by which the brain
interprets and organizes sensory
information
• Top-down processing
The psychophysics of sensation
• Absolute threshold  the minimum
stimulation needed to detect a stimulus with
50% accuracy
• Subliminal stimulation  below the
absolute threshold for conscious awareness
– May affect behavior without conscious
awareness
• Sensory adaptation/habituation 
diminished sensitivity to an unchanging
stimulus
The five major senses
• Vision – electromagnetic
– Occipital lobe
• Hearing – mechanical
– Temporal lobe
• Touch – mechanical
– Sensory cortex
• Taste – chemical
– Gustatory insular cortex
• Smell – chemical
– Olfactory bulb
– Orbitofrontal cortex
– Vomeronasal organ?
The sixth sense
And the seventh…and eighth…and ninth…
• Vestibular  balance and motion
– Inner ear
• Proprioceptive  relative position of body
parts
– Parietal lobe
• Temperature  heat
– Thermoreceptors throughout the body, sensory cortex
• Nociception  pain
– Nociceptors throughout the body, sensory cortex
Thresholds of the five major senses
The Retina
The retina at the
back of the eye
is actually part
of the brain!
Rods –
brightness
Cones – color
Functions of Olfaction
• Many animals are macrosmatic
– having a keen sense of smell that is
necessary for survival
• Humans are microsmatic
– a less keen sense of smell that is not
crucial to survive
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Identifying Odors
• Humans can discriminate among 100,000
odors but they cannot label them accurately
– This appears to be caused by an inability
to retrieve the name from memory, from a
lack of sensitivity
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Structure of the Olfactory System
• Olfactory mucosa is located
at the top of the nasal cavity
glomeruli
– Odorants are carried
along the mucosa
coming in contact with
the sensory neurons
Sensory
neurons
– Cilia of these neurons
contain the receptors
receptors
– Humans have about 350
types of receptors.
– Signals are carried to the
glomeruli in the
olfactory bulb
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Activating the Olfactory Bulb
• Olfactory mucosa is divided into 4 zones
– Each zone contains a variety of different receptors
– Specific types of receptors are found in only one zone
– Odorants tend to activate neurons within a particular
zone
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Patterns of activation in the rat olfactory bulb (Linster, et
al., 2001)
• 2-deoxyglucose (2DG)
technique
– 2DG, which contains
glucose, is ingested into
an animal
– Animal is exposed to
different chemicals
– Neural activation is
measured by amount of
radioactivity present
• This technique shows the
pattern of neural activation is
Figure 15.10 These molecules have the same
related to both chemical
chemical formula, but the molecular group at the
structure and to perception
bottom is rotated to a different position.
The black arrows indicate that the two forms of
liminone activate similar areas in the olfactory
bulb.
The pattern of activation on the OB is related
to functional groups and structures of the
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chemicals as well as their perceived odors
Pheromones
•
•
•
In many animals, the sense of smell is used for
communication. For example, insects such as ants and
termites and vertebrates such as dogs and cats
communicate with each other by secreting and detecting
odorous signals called pheromones – especially to signal
sexual receptivity, danger, territorial boundaries, and food
sources.
We humans seem to use the sense of smell primarily in
conjunction with taste to seek and sample food, but some
evidence exists to suggest that people may also use sexual
pheromones as well as pheromones that help us identify
family members by smell.
For more information:
– Video on PBS called “Sweaty T-Shirts and Human Mate
Choice” for an evolutionary perspective on pheromones
Functions of Taste
• Sweetness is usually associated with
substances that have nutritive value
• Bitter is usually associated with substances
that are potentially harmful
• Salty taste indicates the presence of sodium
• However, there is not a perfect connection
between tastes and function of substances
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Basic Taste Qualities
• Five basic taste qualities:
– Salty
– Sour
– Sweet
– Bitter
– Umami - described as meaty, brothy or
savory and associated with MSG
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Five Distinct Tastes:
• Five Distinct Tastes:
– Each of these tastes developed as survival
functions, according to evolutionary
psychology.
• Sweet - energy source
• Sour – potentially toxic acid
• Bitter – potential poisons
• Salty – sodium essential to physiological
processes
• Umami – proteins to grow and repair tissue
A Theory Debunked
• Since 1942, tongue maps like this one were
widely published and touted as an accurate
portrayal of where certain taste receptors
were located.
– Wine glasses are even designed around this idea.
• The notion that the tongue is mapped into
four areas—sweet, sour, salty and bitter—is
wrong. There are five basic tastes
identified so far, and the entire tongue
can sense all of these tastes more or less
equally.
• The tongue map is easy enough to prove
wrong at home.
– Place salt on the tip of your tongue. You'll
taste salt.
– For reasons unknown, scientists never
bothered to dispute this inconvenient
truth until 1974, and even today, many
textbooks still publish pictures of the
tongue map.
• Remarkably, more is known about vision and
hearing, far more complicated senses, than
taste.
Human Tongue (from wikipedia)
The surface of the tongue is
very bumpy: many ridges
and valleys.
This structure is called
Papillae (singular:
papilla)
There are 4 types of
papillae:
Filiform, Fungiform,
Circmvallate, foliate
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Tongue
circumvllate
• papillae:
– Filiform - shaped
like cones and
located over entire
surface
– Fungiform - shaped
like mushrooms and
found on sides and
tip
– Foliate - series of
folds on back and
sides
– Circumvallate shaped like flat
mounds in a trench
located at back
foliate
filiform
fungiform
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Structure of the Taste System - continued
• Taste buds are located in
papallae except for filiform
– Tongue contains
approximately 10,000
taste buds
– Each taste bud has taste
cells with tips that extend
into the taste pore
– Transduction occurs
when chemicals contact
the receptor sites on the
tips
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