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Brain Constituents

Brain Constituents. Kevin O’Doherty. 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?.

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Brain Constituents

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  1. Brain Constituents Kevin O’Doherty

  2. 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

  3. What does it do? • Forebrain – performs all of the “higher functions” of the brain • The forebrain has two main components • Planning • Thinking and reasoning • Sensory processing 1. Emotional/sensory processing 2. Learning and memory

  4. The Neocortex The new kid on the block

  5. The Neocortex • Neocortex is divided into four lobes • Frontal lobe • Parietal lobe • Temporal lobe • Occipital lobe • Cerebellum • Brain stem Neocortex Image by Freelance Illustration and Graphics The Human Brain Hindbrain and Midbrain

  6. Different lobes do different jobs • The four lobes of Neo-Cortex 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. • Temporal lobe – processes auditory information. Concerned with the production of speech and understanding spoken language (and music)…relevance for our development of language????? • Occipital lobe – Visual processing

  7. 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”

  8. The Limbic System The Emotional Brain

  9. What is the limbic system? • Lies underneath the neocortex • Homeostatic (maintains equilibrum) and visceral functions (deep feelings) integrated with behavior • Regulates emotion, behavior and long-term memory • Pleasure, fear and rage • Olfactory associations (sense of smell)

  10. Some Limbic Functions • Reward: Septum (medial forebrain bundle) and hypothalamus (appetite & satiety). • Punishment: (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.

  11. 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 (Whenever the body is put under stress, it will respond by producing cortisol which increases the blood sugar level, suppresses the immune system and promotes fat, protein and carbohydrate metabolism)

  12. 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 • Brain damage cases evidence

  13. Amygdala • Lower end of the hippocampus on either side of the thalamus • Stimulate → Fear, aggression • Removed → Tame and indifferent (Why?) • 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”

  14. The Brain Stem Midbrain and Hindbrain

  15. 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 Amazingly, chickens can survive without a head, as long as their brainstem is still intact! From http://www.Miketheheadlesschicken.org

  16. 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 • Part of the hindbrain • Extension of the brain stem Rat cerebellum

  17. Question to Consider • Given the amazing ability of our brains to think, be creative, problem solve and plan for the future…what might that future hold for us as a species? (be constructive!)

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