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, wellbalanced mind
– After: extravagant, anti-social, liar, grossly
profane
• Stint with P.T Barnum
• Died 12 years later
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
The Limbic System
• Amygdala
–two almondshaped neural
clusters that are
components of
the limbic system
and are linked to
emotion and fear
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