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Evolution and The Brain.ppt

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Evolution and The Brain.ppt Powered By Docstoc
					Journey to the Center of
       the Brain

      Created for SPICE by
      Catherine Marcinkiewcz and Sean Sand
Anatomy of the Brain
• The vertebrate brain has three
  main parts which evolved in
  different stages

• Forebrain – Newest part of the
  brain; mammals only
• Midbrain – Vertebrates only
• Hindbrain – Oldest part of the
  brain
What does it do?
•    Forebrain – performs all of the “higher
     functions” of the brain
•    The forebrain has two main components

                       Forebrain


             Neocortex            Limbic System


    1.   Planning                  1. Emotional/sensory processing
    2.   Thinking and reasoning    2. Learning and memory
    3.   Sensory processing
The Neocortex
  The new kid on the block
     The Neocortex
•    Neocortex is divided into
     four lobes

1.   Frontal lobe
2.   Parietal lobe
                        Neocortex
3.   Temporal lobe
4.   Occipital lobe
                                       Image by Freelance Illustration and Graphics

                                          The Human Brain
•    Cerebellum
                      Hindbrain and Midbrain
•    Brain stem
Different lobes do different jobs
• The four lobes process different types of information

• Frontal lobe – assimilates information relayed from “lower”
  brain areas concerned with movement. Plans and executes
  complex movements. Also an integral part of personality

• Parietal lobe – higher processing of sensory information from
  other brain areas and the spinal cord. Orientation in 3-
  dimensional space. Proprioception.

• Temporal lobe – processes auditory information. Concerned
  with the production of speech and understanding spoken
  language (and music)

• Occipital lobe – Visual processing
Damage to the brain
• The case of Phineas Gage

• 25-year old foreman who suffered severe
  brain trauma when a tamping iron penetrated
  his skull

• Survived the injury and could even speak
  shortly after the accident!
• Profound changes in personality and
  demeanor

• Once a highly-respected and responsible
  foreman, Gage now became “irreverent,
  profane, and unreliable”. He no longer
  followed through with plans and had little
  respect for his friends and colleagues.

• “He was no longer Gage”
The Limbic
 System
 The Emotional Brain
What is the limbic system?

• Lies underneath the neocortex
• Homeostatic and visceral functions
  integrated with behavior
• Regulates emotion, behavior and
  long-term memory
• Pleasure, fear and rage
• Olfactory associations
Some Limbic Functions
• Reward: Septum (medial forebrain bundle) and
  hypothalamus (appetite & satiety).

• Punishment: PVN of hypothalamus (stress circuits),
  anterior cingulate cortex

• Rage/Emotion/Sex: If cortex is removed, animal is
  easily enraged. Why?
 When the rat turns a wheel, it receives an
 electrical stimulus to the medial forebrain
 bundle, which is rewarding. The rat will
 continue to do this indefinitely and pass up
 food, sex, and other “natural” rewards for
 the artificial stimulus.
Hypothalamus
• Function: Homeostasis (i.e. hunger, thirst, pain,
  pleasure, sex drive and aggression)
• Stress response: stimulates hypothalamus-
  pituitary-adrenal (HPA) axis to release cortisol
• Cortisol regulates breathing, pulse, blood
  pressure and arousal in response to stress
• Note proximity to other parts of the limbic
  system, like the hippocampus and amygdala
 Hippocampus
• Lies underneath the temporal lobe
• Encodes “short-term” memories into long-
  term memories
• Damage: Inability to form new long-term
  memories
• Long term memories are eventually
  stored in the cortex
• Mammilary bodies transmit information
  from hippocampus to cortex
  Cingulate Cortex
• Lies just above the corpus
  callosum
• Relay station for the thalamus to
  “talk to” the hippocampus
• Focusing attention on emotional
  events
• Memories linked to smells and pain
   Amygdala
• Lower end of the hippocampus on
  either side of the thalamus
• Stimulate → Fear, aggression
• Removed → Tame and indifferent
• Fear conditioning
                       A little boy named Albert was fond of white animals,
                       including rats. One day, a scientist by the name of
                       James Watson made a loud, unpleasant noise with a
                       hammer while Albert was looking at a white rat. He
                       cried and seemed very frightened. Now every time
                       Albert sees a rat, even when there is no noise, he
                       starts to cry. What happened?
                       Albert’s amygdala has learned to associate white
                       rats with loud noises. Since he is afraid of loud
                       noises, he is now afraid of rats by association. This
                       is called “fear conditioning”
The Brain Stem
    Midbrain and Hindbrain
The Brain Stem
•   In humans, the brain controls the basic
    functions of the body

•   Brain stem – respiration (breathing), heart
    beat, digestion and circadian rhythm
    (sleep cycle)

•   Evolved hundreds of millions
    (100,000,000) years ago and is the
    “oldest”, most primitive part of the brain

•   Necessary for survival in animals, from
    reptiles to humans
                                                  From http://www.Miketheheadlesschicken.org

•   Amazingly, chickens can survive without a
    head, as long as their brainstem is still
    intact!
The Cerebellum
                                  Human cerebellum
• Balance and coordination

• Procedural learning – motor
  skills such as riding a bike

• Relatively small in the human
  brain compared to other
  animals such as the rat           Rat cerebellum


• Part of the hindbrain

• Extension of the brain stem

				
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posted:12/21/2012
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