Transcript 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 Hindbrain
• Brainstem
– responsible for
automatic survival
functions
• Medulla
– Involved in vital
functions and controls
heartbeat, blood
pressure and breathing
The Pons
-located in the front of the medulla and is
involved in regulating body movement,
attention, sleep, and alertness
Cerebellum
-looks like the larger part of the brain, the
cerebrum (under which it rests).
-Involved in balance and coordination.
Parts of the Brain
THALAMUS
 Relays
messages
amygdala
hippocampus
pituitary
CEREBELLUM
 Coordination
and balance
BRAINSTEM  Heart
rate and breathing
The Cerebellum again
–helps coordinate
voluntary
movement and
balance
The Midbrain: 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 Forebrain
• Four key parts of the Forebrain:
– The Thalamus
– The Hypothalamus
– The Limbic system
-- The Cerebrum
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 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
 Hypothalamus
 neural structure lying below
(hypo) the thalamus; directs
several maintenance
activities
 eating
 drinking
 body temperature
 Storage of nutrients
 helps govern the endocrine
system via the pituitary gland
 linked to emotion
 Also involved in hunger,
thirst, sexual behavior caring
for offspring.
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
Cerebrum
• The crowing glory of the brain!
• Only in human beings does the cerebrum
make up such a large part of the brain.
• The surface of the cerebrum is made up of
wrinkled ridges and valleys called the
cerebral cortex.
The Cerebral Cortex
• Cerebral Cortex
– the body’s ultimate
control and
information
processing center
– The cerebral cortex
makes up the main
information
processing lobes of
the brain.
The Corpus Callosum
• The structure
that connects
the two
hemispheres
of the brain is
called the
corpus
callosum
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
How?
• 1. Electroencephalogram
(EEG)
– A device that records
the electric activity of
the brain
2. Cat Scans
--a moving ring passes
X-ray beams around
and through the head.
Radiation is measured
by computers to piece
together threedimensional view of the
brain
3. MRIs (magnetic resonance imaging)
--a person lies in a very powerful magnetic field.
Then radio waves give off extra energy. That
energy Is measured at different angles and then
those images are transmitted to a computer.
*More clear than a CAT scan.
4. PET scans,(positron emissional tomography)
and fMRIs (functional MRIs) enable researchers
to catch the brain at work.
In PET scans a person is injected with radioactive
sugar and as the sugar reaches the brain, more
of it is used in areas of the brain that is more
active.
• 5. fMRIs can show which parts of the brain
are more active when we perform different
activities such as listening to music,
playing chess, using language, or working
out a math problem
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