brain structure and function
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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 13 th , 1848 Phineas 25 years old - PowerPoint PPT PresentationTRANSCRIPT
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Brain Structure and Function
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“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)
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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
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• 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
Phineas Gage
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Evolution of the Brain
Reptilian Paleomammalian Neomammalian
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The Brain• Brainstem
–responsible for automatic survival functions
• Medulla–controls heartbeat
and breathing
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BRAINSTEM Heart rate and breathing
CEREBELLUM Coordination
and balance
Parts of the Brain
amygdala
pituitary
hippocampusTHALAMUS
Relays messages
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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
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The Cerebellum
–helps coordinate voluntary movement and balance
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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)
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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
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The Limbic System
• Amygdala –two almond-
shaped neural clusters that are components of the limbic system and are linked to emotion and fear
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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
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The Cerebral Cortex
• Cerebral Cortex –the body’s
ultimate control and information processing center
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The lobes of the cerebral hemispheres
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The lobes of the cerebral hemispheres
Planning, decision making speech
Sensory
AuditoryVision
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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
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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
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The Cerebral Cortex
• Frontal (Forehead to top) Motor Cortex• Parietal (Top to rear) Sensory Cortex• Occipital (Back) Visual Cortex• Temporal (Above ears) Auditory Cortex
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Motor/Sensory Cortex
• Contralateral• Homunculus• Unequal
representation
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Sensory Areas – Sensory Homunculus
Figure 13.10
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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
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Language Areas
• Broca Expression
• Wernicke Comprehensionand reception
• AphasiasLEFT HEMISPHERE
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Paul Broca [1800s]
• Suggested localization
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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
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3. Stimulate the brain
4. Record brain activity
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Brain Lateralization
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Our Divided Brains
• Corpus collosum – large bundle of neural fibers (myelinated axons, or white matter) connecting the two hemispheres
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Hemispheric Specialization
LEFT
Symbolic thinking(Language)DetailLiteral meaning
RIGHT
Spatial perceptionOverall pictureContext, metaphor
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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
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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
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Brain Plasticity
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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
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Environmental influences on neuroplasticity
Impoverished environment
Enriched environment
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Sensation and Perception
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Sensation
• The process by which the central nervous system receives input from the environment via sensory neurons
• Bottom up processing
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Perception
• The process by which the brain interprets and organizes sensory information
• Top-down processing
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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
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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?
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The sixth sense
• 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
And the seventh…and eighth…and ninth…
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Thresholds of the five major senses
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The Retina
The retina at the back of the eye is actually part of the brain!
Rods – brightnessCones – color