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Primer on the brain revised

  1. 1. A Primer on the Brain and its Functions Dr. Stan Kutcher Katie Radchuck Jillian Soh Sun Life Financial Chair in Adolescent Mental Health Dalhousie University IWK Health Centre
  2. 2. The Human Brain: A Brief Tour The brain is a remarkable organ, controlling everything from heart rate to digestion to sexual functioning, and everything in-between! It produces our thoughts and speech, and allows us to create works of art – complex activities which help define our humanity.
  3. 3. The Human Brain: A Brief Tour The human brain weighs approximately 1100-1200 grams, or around 2.5 pounds. Your body and organs are made up of cells, and the brain is no different. Neurons are a type of nerve cell which form networks in your brain to relay information. Glial cells tend to provide support to the brain (nourishment, mechanical support, immune response, etc.). DID YOU KNOW? The brain contains an estimated 100 BILLION nerve cells, more cells than there are stars in the Milky Way galaxy. That‟s not all, glial cells are thought to outnumber the nerve cells by as many as 10 to 50 times! Source: Encyclopedia Britannica. Astronomy. 2000
  4. 4. The Human Brain: A Brief Tour Neurons are cells specialized to send and receive information. Generally, a neuron is made up of three basic parts: Dendrites: consisting of many branches, this is the area where the cell receives information Soma (Cell Body): contains the cell nucleus, which acts like a blueprint for the production of proteins and other materials that keeps the cell running smoothly Axon: carries information received by the dendrites, sometimes over long distances, to other cells. The axon is sometimes covered in myelin sheaths, another type of cell that speeds up the signal.
  5. 5. What’s This “Information” Anyway? In the same way humans use sounds to talk to one another and share information, neurons use both electricity and chemicals to talk to each other. These chemical messengers are called neurotransmitters. Just a few examples of neurotransmitters: (Glutamate) (Dopamine) (Serotonin) (Epinephrine/ (Acetylcholine) Adrenaline) Photo credit (CC 2.0): Anselm Hook
  6. 6. What’s This “Information” Anyway? These neurotransmitters play a major role in the brain and heavily influence consciousness, emotions, and behavior. In a group of people, if someone is whispering their ideas may not be heard. In the same way, too little of a neurotransmitter may cause communication failures between brain areas, affecting how we think, feel, and act. Photo credit (CC 2.0): Anselm Hook
  7. 7. What’s This “Information” Anyway? You can see then, how important communication is in the brain. If it is disrupted, either through chemical imbalances or problems with the neurons themselves, this may contribute to brain dysfunction and mental illness. Photo credit (CC 2.0): Anselm Hook
  8. 8. The Human Brain: A Brief Tour Two basic layers of the brain can be seen with the naked eye. There is the outer layer, known as grey matter, as well as the inner layer, known as white matter. The gray matter is made up of densely packed neuronal bodies, whose long axons make up the white matter. Remember how axons are sometimes covered in myelin sheaths? This myelin is quite fatty, giving the tissue a white-ish color.
  9. 9. Grey matter, containing the cell bodies, is where all the thinking happens. This is your brain‟s processing centre. White matter, containing those long axons, are like a super highway. They transport information to different parts of your brain. Photo credit (CC 2.0): facemepls, MSVG
  10. 10. The Central and Peripheral Nervous System The brain, along with your spinal cord, makes up your body‟s Central Nervous System (CNS). From the spinal cord extend nerve cells that receive sensory information (such as the roughness and heat of the beach) and transmit that to the brain. These outside nerves make up the Peripheral Nervous System (PNS). It‟s a two-way street, The brain can also send signals through the spinal cord and PNS to control the movement of your limbs and trunk.
  11. 11. The CNS and PNS It takes around11.5 milliseconds to transmit a signal from the tip of your toe to your brain. This may seem pretty fast but in some cases – like when accidentally putting your hand on a hot stovetop – this delay is too long and would cause your hand to burn. Instead of sending a signal all the way to the brain and waiting for a return signal to move your hand away, a network of cells within the spinal cord receive the sensory information, then pass it on to motor neurons, which are cells that control your muscles. Bypassing the brain like this is called a reflex. Your muscle will contract causing you to pull away from the hot stovetop – it is only after a short delay that your brain catches up and realizes your hand hurts! Photo credit (CC 2.0): Ndecam
  12. 12. The CNS and PNS Speaking of signal transmission speeds, some nerve fibers transmit signals faster than others. Usually it depends on whether they are myelinated or not (remember that myelin speeds up transmission!). Think about when you stub your toe. You definitely feel it right away since the touch signals reach your brain almost instantaneously. However it‟ll take a few seconds before the pain signal will reach your brain, and when it does – YEOWCH! Photo credit (CC 2.0): Ndecam
  13. 13. So now we know what the brain is made of. We know that different parts of the brain communicate with one another using neurotransmitters, and this communication can extend down the spinal cord to the rest of your body. But what does the brain actually DO and HOW does it do it? Photo credit (CC 2.0): perpetualplum
  14. 14. There are 6 functions of the Brain 1. Thinking & Cognition 2. Emotion & Feeling 3. Signaling (being responsive and reacting to the environment) 4. Perception & Sensing 5. Physical Functions 6. Behavior
  15. 15. Thinking and Cognition Thinking & Cognition includes all of our internal mental processes and functions Higher Cognitive Functions Communicating Processing Arithmetic Reading Insight Focusing Planning Attending Judgement Memory Comprehension Contemplation
  16. 16. Thinking & Cognition Overview FACT SHEET Location: Frontal Lobes Neural Pathways: 2-way connection between Your frontal lobes are responsible cortical and limbic areas for the majority of your conscious Main Neurotransmitters: thought. This area works closely with Dopamine, serotonin, and the limbic system, a section deep adrenaline within the brain responsible for mood, emotion, and storage of memories.
  17. 17. Thinking & Cognition The Limbic System The limbic system includes several brain structures: the amygdala, hippocampus, anterior thalamic nuclei, and limbic cortex. The hippocampus, responsible mainly for the storage of long-term memory, is one of the first places affected by Alzheimer’s Disease.
  18. 18. Thinking & Cognition Attention Your frontal lobes also include an area called the prefrontal cortex, which controls many of your cognitive abilities, such as attention. However, this area of the brain changes drastically during adolescence, and is one of the last brain areas to mature completely!
  19. 19. Thinking & Cognition Attention Is your attention drifting right now? Don’t worry! Scientists have measured attention in adolescents, and have discovered that performance increases with age. So that means… Yes, attentional capacity might improve as you and your brain matures! Anderson et al. (2001)
  20. 20. Thinking & Cognition Phineas Gage We know that some parts of the brain are specialized for certain tasks. An injury to specific, limited parts of the brain can help scientists know for sure what that part of the brain is responsible for. Take for example the case of poor Phineas Gage. Photo credit: From the collection of Jack and Beverly Wilgus.
  21. 21. Thinking & Cognition In 1848, Phineas was a young man working on clearing out some rock for the construction of a railroad. An explosive was set off accidentally, thrusting a large iron rod under Phineas‟ left cheek bone and out the top of his head. The force of the explosion was so severe that the rod completely left Phineas to land 90 feet away, taking with it most of the left frontal lobe. Photo credit (CC 2.0): Kevin Dooley
  22. 22. Thinking & Cognition His recovery was long and at some points bleak, but he eventually regained his memory and physical strength. He suffered no motor or speech impairments, however a startling change had occurred with his personality and behavior. Photo credit (CC 2.0): Kevin Dooley
  23. 23. Thinking & Cognition He became rash, where before he was mellow. He used to be a good worker, but now his colleagues could not handle his temper. He had trouble forming and executing plans, didn‟t think before he acted, and often made choices Photo credit (CC 2.0): Kevin Dooley against his best interests.
  24. 24. Thinking & Cognition Phineas Gage Although the front left portion of his brain was destroyed, Phineas was still able to function well. He could walk and talk, since the brain areas responsible for that wasn‟t affected. However, the frontal lobes are responsible for judgment, planning, and defining your personality. All of these changed after his brain injury. Photo credit: From the collection of Jack and Beverly Wilgus.
  25. 25. Thinking & Cognition Speech and Comprehension Your brain also has specific areas dedicated to speech and language comprehension. Broca’s Area Mainly responsible for language production. People who have damage to this area are still able to understand language, and know what they want to say, they just can‟t „get it out‟. Wernicke’s Area Mainly responsible for language comprehension. People who have damage to this area can still produce speech but it tends to have no meaning. This is known as „word salad‟: Example: “Colorless green ideas sleep furiously.”
  26. 26. Emotion is the ability to experience feelings and to express those feelings to others.  Happy  Sad  Anxious  Excited  Depressed  Worried  Calm  Guilty  Fearful  Peaceful  Ashamed  Nervous  Content  Angry  Panicky  Serene  Irritated  Inferior  Joyful  Annoyed  Inadequate  Pleased  Resentful  Lonely  Carefree  Frustrated  Discouraged We can also call our emotions and feelings “MOODS”
  27. 27. Emotion & Feelings Overview FACT SHEET Location: Prefrontal Regulating your emotions is yet cortex, amygdala another complex thing your brain has Main Neurotransmitters: to do. Your prefrontal cortex Serotonin and dopamine produces cognitive emotions (“thinking with you head”) while the amygdala produces instinctive emotions (“thinking with your heart”). Serotonin and dopamine and two very important neurotransmitters needed to regulate your emotional state.
  28. 28. Emotion & Feelings Neural Correlates Different parts of your brain are active depending on what type of emotion you are feeling. For example, the top brain scan shows which areas of our brain are active when we feel sadness. The bottom brain scan shows which areas of our brain are active when we feel happiness. The brain really does create all of our emotions.
  29. 29. Emotions & Feelings Serotonin and Mood Since the brain produces much of what we feel, when something goes wrong with the brain our emotions can get messed up. Clinical depression is characterized by a persistent, intense negative mood, which affects a person‟s normal life. Photo credit (CC 2.0): Alejandro Cordon
  30. 30. Emotions & Feelings Serotonin and Mood Research has found that serotonin is important for communication between the prefrontal cortex and amygdala areas of the brain. Remember how those two areas are important for regulating emotions? Photo credit (CC 2.0): Alejandro Cordon
  31. 31. Emotions & Feelings Serotonin and Mood Some people with major depression don‟t have a good connection between the prefrontal cortex and amygdala. By increasing the amount of serotonin in the brain with drugs, this connection can be strengthened and help people regain a better mood. Photo credit (CC 2.0): Alejandro Cordon
  32. 32. Signaling is the brain’s way of responding to a perceived threat, danger, or stress from the environment. Photo credit (CC 2.0): GE Healthcare
  33. 33. Signaling Overview FACT SHEET Location: Your brain is constantly alert, taking Cortex, thalamus, amygda note of your surroundings. When it la, hippocampus perceives a danger, such as an Main Neurotransmitters: oncoming car, the brain begins a Adrenalin, serotonin physiologic cascade with the help of neurotransmitters like adrenalin and serotonin. Your heart rate and alertness go up, more blood is pumped to your muscles, and your senses become sharper. Your brain then makes a decision whether to run from the danger, or stay and fight it.
  34. 34. Signaling Fight or Flight Sensory Perception (Ears, eyes, smell, taste, touch) + Internal Signals When faced with DANGER, your 5 senses perceive it and sends a signal to the BRAIN Your brain initiates a Physiologic Cascade  Heart Rate  Alertness  Perception Now you are ready to  Tension FIGHT or FLEE for your safety and protection Photo credit (CC 2.0): Mangpages, Phillipe Put
  35. 35. Signaling Anxiety Sensory Perception (Ears, eyes, smell, taste, touch) + Internal Signals Anxiety happens when the brain believes there is danger, but there isn‟t any Your brain initiates a Physiologic This Cascade produces  Heart Rate feelings of  Alertness ANXIETY  Perception  Tension Photo credit (CC 2.0): Mangpages, flequi
  36. 36. Signaling Anxiety Normal anxiety happens to all of us. A situation Which causes can trigger it: feelings of anxiety: First date Preparing for an exam Apprehension Performing at a concert Nervousness Giving a speech Tension Moving from home Edginess Climbing a tall ladder Nausea Etc. Sweating Trembling
  37. 37. Signaling Anxiety Normal anxiety: Is transient, which means that it will go away after a while Does not significantly interfere with a person‟s well-being Does not prevent a person from achieving their goals
  38. 38. Signaling Anxiety Some people suffer from pathologic anxiety. A situation, or nothing Which causes can trigger it: intense anxiety: Feels like a heart attack First date Feels like you‟re dying Preparing for an exam Feels like you‟re going Performing at a concert crazy or having a Giving a speech nervous breakdown Moving from home Climbing a tall ladder This happens when there is a dysfunction in the NOTHING! signaling mechanisms.
  39. 39. Signaling Anxiety Pathological anxiety: Is persistent, meaning symptoms stay around for a lot longer than they should Is excessive, intense, and inappropriate to the situation – feeling like you are having a heart attack before giving a speech is not how the brain should react Leads to impairment in a person‟s everyday life, where they may avoid people and act withdrawn in an attempt to avoid trigger situations
  40. 40. Perception is the way your five senses work with your brain to take in your surroundings. Photo credit (CC 2.0): Mohamed Malik
  41. 41. Perception & Sensing Overview We have five senses that work together to give awareness of our environment: See Hear Smell Taste Touch
  42. 42. Perception & Sensing Vision For us to see, light must enter into our pupils and hit the retina lining the back of the eye. Cones are cells in the retina that give us our color vision, while rods are cells that give us black and white (night) vision. The optic nerve carries the signal through the lateral geniculate nucleus to the back of the brain, the primary visual cortex.
  43. 43. Perception & Sensing Vision The primary visual cortex transmits the signal to two different areas of the brain: Temporal lobes Responsible for object recognition, “what” the object is Conscious processing Parietal Lobes Responsible for object location, “where” the object is Unconscious processing of the relationship between the object and your body
  44. 44. Perception & Sensing Vision: Blindsight People who sustain damage to their temporal lobes may develop a condition known as blindsight. Since the temporal lobes are responsible for the conscious processing of vision, they would not be able to „see‟ normally, and would be considered legally blind. However, their unconscious, spatial processing has not been damaged, so even though they may not be able to identify objects in a room they can walk around tables and chairs without bumping into them. They can follow objects with their fingers and may even be able to catch a ball thrown at them. Photo credit (CC 2.0): Jim Simonson
  45. 45. Perception & Sensing Hearing Many tiny hairs in your inner ear vibrate to sounds in the environment. Those vibrations are felt by cells in the ear and the signal is transferred along the brain to eventually reach the primary auditory cortex. DID YOU KNOW? As people age, their ability to hear very low and high frequency noises diminishes. An anti-loitering alarm was developed that plays a high-pitched, annoying noise that only teenagers can hear. Talk about discrimination!
  46. 46. Perception & Sensing Smell Smell exists as tiny molecular odorants that travel up your nose to be detected by cells in the olfactory epithelium. This signal travels through the olfactory nerve to your brain, where the signal is processed by the olfactory cortex. Some of the signal makes it to the limbic system, where long-term, emotional memories are stored. This is why smells can sometimes help you remember strong memories, maybe of your home or childhood! Photo credit (CC 2.0): DrJimiGlide
  47. 47. Perception & Sensing Taste Taste buds which cover the surface of the tongue allows us to distinguish different flavors in our food. There are five basic tastes: Sweet Sour Salty Bitter Umami (savoury) Photo credit (CC 2.0): Zoe Shuttleworth
  48. 48. Perception & Sensing Taste Information from the taste buds travel up cranial nerves to reach the brain stem, where the signal is passed onwards to the primary gustatory cortex. DID YOU KNOW? Not everyone perceives food the same way! Some people have a lot more taste buds than average, and are known as „super tasters‟. Your genes determine whether you are a „super taster‟, „taster‟, or even a „non-taster‟. Super tasters tend to be very sensitive to different foods, especially bitter things like broccoli and coffee, and may be picky eaters. Tepper et al. 2009; Photo credit: Zoe Shuttleworth
  49. 49. Perception & Sensing Touch Your body is full of touch receptor cells near the surface of the skin. When activated, they send a signal up to your brain to let it know. Some areas of your body have many more touch receptors than others, and thus have a larger representation in the brain, in a place called the somatosensory cortex. Photo credit (CC 3.0): btarski
  50. 50. Perception & Sensing Touch A homunculus is a representation of what a human would look like if made in the same proportions as the brain area assigned to it. The hands and facial areas, especially the lips and tongue, are highly sensitive! Dr. Penfield, the famous Canadian neuroscientist (yes, the „burnt toast‟ guy!) came up with the homunculus by mapping limb locations to different areas of the brain.
  51. 51. Signaling is the brain’s way of responding to a perceived threat, danger, or stress from the environment. Your brain takes care of many different physical functions, such as digestion, breathing, c ontrolling your muscles, etc. Photo credit (CC 2.0): GE Healthcare
  52. 52. Physical Functions Voluntary Movement In the same way that different brain regions are assigned for sensing different areas of your body, different brain regions control different areas of your body. Places where fine motor control is needed, such as your hands and mouth (for producing speech and eating), take up a larger area in the brain! This place is called the motor cortex.
  53. 53. Physical Functions Voluntary Movement Your prefrontal cortex – which if you remember is where all your thinking happens – sends a signal to the motor cortex area assigned to a body part. This signal travels down the spinal cord to alpha motor neurons, which tell muscles to contract. This whole process allows us to produce thought- directed, voluntary movements. This entire complex arrangement is known as the somatic nervous system.
  54. 54. Physical Functions Involuntary Movement What about involuntary movement? Stuff you can‟t control consciously? Your heart needs to keep beating and your stomach needs to keep churning for you to stay alive. If you had to consciously think about every breath you took you probably would be too distracted to think about much else. This is where the autonomic (from „automatic‟) nervous system comes in. Photo credit (CC 2.0): David DeHetre
  55. 55. Physical Functions Involuntary Movement Your autonomic system is basically in charge of all your internal organs, and controls what they do unconsciously (although some things, like your breathing, can be taken over by the conscious mind). It is divided into two parts: the Sympathetic Nervous System, and the Parasympathetic Nervous System.
  56. 56. Physical Functions Involuntary Movement Sympathetic Nervous System Remember how signaling and anxiety works? Your sympathetic nervous system controls that „fight or flight‟ mechanism (makes the heart pump faster, inhibits digestion, raises blood pressure, etc.). It also maintains equilibrium, or homeostasis. Stuff like making sure your body temperature is just right, and balancing your blood sugar levels. Photo credit (CC 2.0): Mark Robinson
  57. 57. Physical Functions Involuntary Movement Parasympathetic Nervous System While the sympathetic nervous system is most active when you‟re stressed, the parasympathetic nervous system works when you are resting, so it‟s known as the „rest and digest‟ system. Think of it working in the opposite direction, instead of speeding up your heart rate it slows it down. It lowers your blood pressure. Since, at rest, your body can expend energy to relax and eat, much more saliva is produced.
  58. 58. Behavior is simply the way we act, usually in response to our environment. It includes everything from running to joking, from reading to Photo credit (CC 2.0): Jamie Davis working.
  59. 59. Behavior Overview Teens don‟t „get‟ their parents. What‟s with all the rules and restrictions? And parents don‟t like the things teens do – they always seem to be experimenting and taking unnecessary risks. This seeming rift between teens and adults has a lot to do with behavior, and behavior has a lot to do with the brain. Photo credit (CC 2.0): Ollie Crafoord
  60. 60. One example of a behavioral difference is Behavior motivation. Motivation is your drive to do Motivation stuff – like studying hard to do well on a test, or finishing a marathon, or beating one more level of a video game. Photo credit (CC 2.0): shirokazin
  61. 61. Behavior Motivation Motivation is influenced heavily by the reward pathway in the brain. A reward doesn‟t have to be something physical, it can be getting a good mark or a positive feeling. Drug addiction causes your brain to constantly seek out that positive „feeling‟, and your brain becomes dependant on it as a reward. The danger comes when that feeling can only be achieved by drugs! Photo credit (CC 2.0): Ollie Crafoord
  62. 62. Behavior Motivation In teens, the reward pathway of the brain is stronger than in adults. Also, the cognitive parts of the brain that think about things logically and weighs the pros and cons are not as developed in teens. This means teens may be motivated to try riskier behaviors and be more impulsive than adults would be, and are more prone to push beyond their limits and boundaries without weighing consequences (Smith et al., 2011).
  63. 63. Behavior This isn‟t always a bad thing. Motivation Since the brain matures in this way, young people can be extremely passionate about the things they care about, they work hard to achieve things that are important to them. They open their eyes to the world and have new experiences, and become better people for it. It‟s all about the choices you make. Photo credit (CC 2.0): James Tosh
  64. 64. So now we know the six basic functions of the brain, but how does such a complex organ develop? NewScientist (2009) suggests that there are 5 different „ages‟ of the brain: 1. Gestation 2. Childhood 3. Adolescence 4. Adulthood 5. Old Age Photo credit (CC 2.0): Neil Conway
  65. 65. Gestation Overview Gestation is the stage of development where you are still in your mom‟s womb. It is this time where your brain undergoes initial development, and your cells differentiate to create your first neurons (this process is called neurogenesis). Neurogenesis is a hot topic right now, because while people are really good at making new neurons when they are fetuses, it gets much harder when they are adults. If we learn how to create new neurons where we want them, we may be able to help people with brain diseases and spinal cord injuries.
  66. 66. Childhood Overview Childhood is the stage where our brains probably undergo the biggest changes. It is this time where we learn language, how to store memories, and how to think. Timeline: 6 years: 2-3 months: 18 months: apply logic and trust, understands cortex develops develop a sense of self personal thought process 6-12 months: 3-4 years: frontal lobe sense that other people develops have minds too
  67. 67. Adolescence Overview Adolescence is the teenage years. It is around this time that your brain areas start to fully mature and develop. Your sensory and motor areas are the first to mature, which is why teens can be „sensation seekers‟. Your prefrontal cortex matures last, which helps in decision making, emotional control, and temper. Most teens pass through these years without severe or prolonged difficulties, but 15% of teens will experience significant mental health problems during their adolescent years.
  68. 68. Adolescence Overview Adolescence is the time where your brain gets rid of neural pathways that it doesn‟t need. When you‟re young, you have a high volume of gray matter in your brain. During adolescence, this gray matter is pruned away. This is thought to make the brain more efficient. What gets removed depends a lot on usage. It‟s really „use it or lose it!‟ It is important to keep your brain active and healthy during these years.
  69. 69. Adulthood Overview You‟ve finally made it to your adult years! People‟s brains peak around the age of 22. This is when they can process things the fastest and learn new things easier. When you hit 27 years, your brain will progressively start to decline. However, adults are excellent at crystallized intelligence, or wisdom, which is the ability to use and apply everything you‟ve learned up till now. You can keep your brain sharp and slow down that decline by being mentally and physically active.
  70. 70. Old Age Overview In your golden years, you brain is in the most danger of deteriorating. Death of brain cells in the hippocampus area can lead to memory loss. Again, by keeping fit and eating healthy, you can stimulate brain cell growth and slow this decline. The elderly are more prone to diseases such as Alzheimer’s – plaques and tangles are seen in the brain wrapped around cells responsible for memory and retrieval. Parkinson’s is another disease which mainly affects the elderly, and is caused by the death of cells responsible for movement.
  71. 71. Old Age The chance of experiencing a stroke also increases Overview when you‟re older. A stroke occurs when the blood supply to the brain has been disturbed. A portion of your brain may lose its functioning (causing paralysis on one side of the body, loss of speech, etc.). Neuroplasticity is the brain‟s ability to rearrange neural pathways and repair itself. It used to be thought that this could only occur in very young people, but recent research has shown that neuroplasticity can still occur in older adults, even in the elderly. There‟s a lot of science being done now to see if we can enhance neuroplasticity to help treat stroke patients and speed up their recovery. Photo credit (CC 2.0): TheArches
  72. 72. Think upon this… We‟re using the Brain to study the Brain And there’s still a lot to learn! What you’ve read here is just the tip of our current knowledge, and our current knowledge is just the tip of what is going on in that spongy mass of tissue. As science advances, the brain will come to better understand itself. So keep learning! Photo credit (CC 2.0): dierk schaefer
  73. 73. Sun Life Financial Chair In Adolescent Mental Health For more information visit WWW.TEENMENTALHEALTH.ORG
  74. 74. References Daftarya, S.S., Pankseppb, J., Dongb, Y., and Saal, D.B. 2009. Stress- induced, glucocorticoid-dependent strengthening of glutamatergic synaptic transmission in midbrain dopamine neurons. Neuroscience Letters 452, 3: 273-276. Lenroot, R.K., Giedd, J.N. 2006. Brain development in children and adolescents: Insights from anatomical magnetic resonance imaging. Neuroscience and Biobehavioral Reviews. 30: 718-729. Sowell, E.R., Thompson, P.M., Holmes, C.J., Jernigan, T.L., Toga, A.W. 1999. In vivo evidence for post-adolescent brain maturation in frontal and striatal regions. Nature Neuroscience. 2: 859-861. Sowell, E.R., Thompson, P.M., Toga, A.W. 2001. Mapping continued brain growth and gray matter density reduction in dorsal frontal cortex: Inverse relationships during postadolescent brain maturation. The Journal of Neuroscience. 21: 8819-8829. Grant, J.E., Correia, S., Brennan-Krohn, T., Malloy, P.F., Laidlaw, D.H., Schulz, S.C. 2007. Frontal White Matter Integrity in Borderline Personality Disorder With Self- Injurious Behavior. Journal of Neuropsychiatry Clinical Neuroscience 19:383-390.
  75. 75. References Chambers, R.A., Taylor, J.R., Potenza, M.N. 2003. Developmental Neurocircuitry of Motivation in Adolescence: A Critical Period of Addiction Vulnerability. American Journal of Psychiatry 160:1041-1052. Firedel et al, 17 December 2008 / Accepted: 30 March 2009. Springer-Verlag 2009 The auditory cortex Andrew J. King and Jan W.H. Schnupp Current Biology Vol 17 No 7.2007 The five ages of the brain: 05 April 2009 by Graham Lawton, Caroline Williams, Helen Phillips, Anna Gosline, Helen Thomson, . NewScientist Magazine issue 2702 Romer, D. 2010. Adolescent risk taking, impulsitivity, and brain development: implications for prevention. Developmental Psychobiology 52:263-276. Smith, A. B., Halari, R., Giampetro, V., Brammer, M., Rubia, K. 2011. Developmental effects of reward on sustained attention networks. NeuroImage 56: 1693-1704. Tepper, B. J., Williams, T. Z. A., Burgess, J. R., Antalis, C. J., Mattes, R. D. 2009. Genetic variation in bitter taste and plasma markers of anti-oxidant status in college women. International Journal of Food Sciences and Nutrition 60:35-45. Overgaard, M. 2011. Visual experience and blindsight: a methodological review. Exp Brain Res 209: 473-479.

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