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Chapter 4

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Dan Dolderman

Chapter 4 The brain and Consciousness Epilepsy: debilitating affliction in which seizures, uncontrolled storms of electrical activity begin in some part of brain and spread Penfield’s patient undergone surgery, deactivating some regions reactivated regions closely connected to that region Egyptians: viewed heart as more important Later realized brain was essential for central functioning- idea comes from those with brain injury (roman gladiators)  Early 1900, Franz Gall and Johann Spurzheim proposed theory of phrenology based on idea that assessing personality traits and mental abilities by measuring bumps on the human skull  Pierre Fluorens believe brain function as one unit  Expt on bird and rodent by removing part of their brain and obs effect on behaviour  Karl Lashley used same method to identify where learning occurs  Conceded specific brain regions involved in motor control and sensory experiences  All parts of brain contributed to mental ability (Equipotentiality)  Theory discredited this day b/c brain function as parts  Paul Broca  Performed autopsy on Mr. Leborgne before death, a patient only able to say word “tan” but understand language  Lesion in left language production  Left frontal region known as Broca’s area  Brain Imaging techniques available now! What are the basic brain structures and their functions?  How brain is adaptive  First nervous system was very brief  Today’s brain is best viewed as a collection of interacting neuronal circuits that have accumulated and developed throughout human evolution  Through process of adapting to environment, brain more specialized at performing different tasks The spinal cord is capable of autonomous function  Spinal cord is a rope of neural tissue runs inside hollows of vertebrae from pelvis up to base of skull  Segmented  Contain gray matter and white matter  Grey matter are cell bodies of neurons  White matter are axons and fatty sheath  Gray and white also in brain  Sensory info from body enter spinal cord and passed up to brain  Spinal cord take action on its own Strech reflex  Spinal reflex  Conversion of sensation in to action by neurons reflex present throughout skeletal musculature and to maintain joint position  All muscles have stretch receptors inside them to sense changes in length  Receptors are dendritic tips of receptor neurons whose cell bodies located in spinal Cord, stetching muscle cause receptor neurons connected to it to fire  Stretching the muscle causes the stretch receptor neurons to fire, which causes the motor neurons to increase their firing, which contracts the muscles The brainstem houses the basic programs of survival  Spinal cord continues into brainstem, which houses most basic programs of survival Brainstem  House basic programs of survival: breathing, swallowing…  Perform similar functions for head as spinal cord for body  House reflexes eg. Gagging  Has nerve connecting it to skin and muscle of head and sense organs  Use reflexes of spinal cord to produce useful behaviour  Stimulating brainstem disconnected to rest of brain can allow animal to start walking Reticular formation (part of brainstem)  Network of neurons in brainstem project up into cerebral cortex and affect arousal  Induce and terminating stages of sleep  Brainstem without brain can still walk around and show basic normal behaviour Cerebellum is essential for movement (empathy and motor)  Little brain  Protuberance connected to back of brainstem  Supplementary brain  Lesion to different parts of cerebellum produce different effects  Cellular organization identical throughout  Important for proper motor function  Damage to little nodes at bottom cause balance problems  Damage to ridge running up its back affects walking  Damage to bulging lobes on either side cause loss of limb coordination  Allows independent and unconscious skills (eg. Ride bike and thinking what to eat for lunch)  Cognitive process eg. Making plans, rmb events, emotion  Activation of cerebellum when people experience pain or loved on experience pain  Involved in experience of empathy  Disorder: ataxia- clumsiness and loss of motor coordination, lack of emotional response  Damage to cerebellum: change in personality, mental disorder Subcortical structures control basic drives and emotions  Forebrain above brainstem and crebellum: 2 hemispheres  Forebrain has cerebral cortex, below is subcortical regions (lie under cortex)  Include hypothalamus, thalamus, hippocampus, amygdala, basal ganglia  Limbic system (border between brain stem/cerebellum and cerebral cortex)  Basic drives and emotions Hypothalamus  Master regulatory structure, indispensable to organism’s survival  Regulate vital function eg. Body temp, bp..  Drives thirst, hunger, aggression, lust  Receives input from everywhere and influence everywhere  Induce motivational drive and behaviours to satisfy need  Controls pituitary gland which controls all other glands and processes as development, ovulation, lactation  Govern sexual and reproductive development and behaviours  Hypothalamic organization difference between men and women, influence sexual orientation  Fetal masculinization  Anterior hypothalamus smaller for homosexual man=heterosexual women Thalamus  Gateway to cortex  Incoming sensory info go through thalamus before reaching cortex  Smell is exception, direct route to cortex bypassing thalamus  Role in attention  Shuts during sleep Hippocampus and amygdala  Memory and emotion  Hippocampus  Storage of new memory  Change in size with increased use  Involved in how we rmb arrangement of places and objects in space and how streets laid out…  Study of taxi driver, large hippocampus  Volume of gray matter in taxi driver correlated with number of yrs of experience as driver  Hippocampus increase volume to store more  Amygdala  In front of hippocampus  Associate things with emotion eg. Food disgusting  FEAR CONDITIONING  Intensifies memory during emotional arousal eg. Scary membrane seared into memory  Responding to stimuli that elicit fear  Evaluating emotional significance of facial expression  Strong response to fearful faces  Processing sexual arousal when sees stimuli Basal ganglia  Planning and producing movement  Receive input from cerebral cortex and project to motor center of brainstem, buy thalamus, back to motor planning area  Damage: parkinsons, huntingtons jerky movements, learning of movements  Learning of habits eg. Look across road  Nucleus accumben important for experiencing reward  Activated more when viewing attractive things Cerebral cortex underlies complex mental acitivity  Enormous in human  Thoughts, detailed perception, consciousness  Think before act  Source of complex culture and communication  Each hemisphere has 4 lobes: occipital, parietal, temporal, frontal  bridge of millions of axons called corpus callosum connect two hemisphere occipital lobe  sense of vision  primary visual cortex: visual info projected, for cerebral cortex  left eye gets info from right sides of visual world, right eye gets from left  secondary visual area process colour, motion, forms.. parietal lobe  sense of touch AND SPACE  primary somatosensory cortex (bodily sense)  left hemisphere receive touch info from right body  somatosensory homunculus (little man) distorted because more sensitive areas of body such as face and finger have more cortical area devoted to them  spatial relationship between us and objects  damage to right parietal region=hemineglect  failure to notice things on their left side  expts done temporal lobe  primary auditory cortex, for hearing  secondary auditory area for further processing of what we hear eg. Decode words and sentence  visual area for recognizing detailed objects such as faces  memory, contain hippocampal formation and amygdala  dr. pendield stimulated this area in his patient to recall past experience  intersection of temporal and occipital cortices=fusiform face area  more active when looking at faces  damage results in can’t recognize people  but can recognize objects just not people frontal lobes  planning and movement  primary motor cortex  project to spinal cord to move muscle of body  left hemi controls right arm  auxiliary motor areas responsible for complex movEments  rest of frontal lobe not for movement= prefrontal cortex (30% of brain)  directing and maintaining attention  big  area in center are behind eyes, called orbiofrontal cortex  for personality, emotion, impulse control  part of limbic system HOW DOES THE BRAIN change  continually changing – plasticity  plasticity decreases with age  predictable development pattern with different structures and ability progressing at diff rates and maturing at diff points in life  brain connection refined with every exp in live Interplay of genes and environment wires the brain  baby’s vision development before ability to see in stereo  but environment still a factor and can affect DNA’s activity Chemical signals guide growing connections  transplanted early take on identity appropriate to new location, organism develops normally  cells transplanted later grow connections with old location  connection produced by growing axons detection of particular chemicals that tell them where to go and where not to  neurons in one region look for particular chemical and neuron in another are producing them  axon grow toward or away from in or decreasing conc of chemicals- chemical gradient Experiencing fine tunes neural connections  detailed connections governed by experience  critical periods are times in which certain experiences must occur for development to proceed normally  enhanced conditions can approximate rat’s life in wild compared to lab rats The brain rewires itself throughout life  change in the strength of connections underlies learning  hebbian learning: fire together, wire together  changes increases strength of preexisting connections  repeating behaviour make us tend to perform it automatically  growth of entirely new connections  was believed adults produce no new cells, but GAGE demonstrated new neurons produced (neurogenesis)  fair amount of neurogenesis in hippocampus  hippocampus send to cortex and hippo overwritten with new info  social environment influence: dominant animals have greater increase in new neurons Changes in distort cortical maps  wiring in brain affected by overuse and under-use  monkey’s finger stimulated, cortical representation expands, same with driver  amputated arm respond when touched on their cheek when eyes closed  brain had not reorganized in response to injury The brain can recover from Injury  remapping immediately after lesion in cortex, grey matter assumes function of damaged area  young children recover faster, radical hemispherectomy, removal of one entire hemisphere ok in children, but results in paralysis in adults  transplantation of stem cell into brain to repair damage  treatment for Parkinson, hungtinton  challenge is to get newly i
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